Low temperature coated particles for use as proppants or in gravel packs, methods for making and using the same

Low Temperature Coated Particles for Use as Proppants or in Gravel Packs, Methods for Making and Using the Same

Background of the invention

This disclosure relates to coated particles and methods for preparing and using them. Specifically, this disclosure relates to coated particles used as proppant materials or in gravel packs and which are prepared by coating a particle with liquid phenol-formaldehyde resole at ambient temperature, applying a powder, such as novolak powder or resole powder, to the coated particle and mixing Until dry at low temperature. If desired, the particles can be used in coated sand applications for use in the foundry industry.

The term "proppant" refers to a particulate material that is injected into fractures in subterranean formations surrounding oil wells, gas wells, water wells, and other similar bore holes to provide support. To prop these fractures in the open position and allow gas or liquid to flow through the fracture into a bore hole or out of the formation. Propagation materials are usually used to support open fractures that form in subterranean formations such as oil and natural gas wells during hydraulic fracturing.

Uncoated and/or coated particles are often used as proppant packing materials to maintain open fractures formed by hydraulic fracturing of a subterranean formation, e.g., oil or gas bearing strata, or as gravel packs.

Typically, uncoated proppant materials are sand particles, ceramics, glass beads, walnut shells, etc., as are known in the art. Particles used for fracture reinforcement generally include sand or sintered ceramic particles. The advantage of sand is that it is cheap. Its disadvantages are that its resistance is relatively weak (high crushing values) and flow capacities are lower than sintered ceramic particles. Sintered ceramic particles are also used as support fillers. But ceramic particles have the disadvantage that calcination is performed at high temperatures, which leads to high energy costs. In addition, expensive raw materials are used.

Coated proppant materials comprise discrete particles coated with resin. Typically the separated particles are particles of sand, ceramics, glass beads, walnut shells, etc., as are known in the art. The encapsulating materials for the backing material are materials that have been previously treated or can be treated. Precured proppant materials include a substrate core and a backing layer of resin that is cured before being inserted into the subterranean formation. Curable proppant materials include a substrate core and a backing layer of resin that is cured prior to the bottom of the hole to form a compact proppant. Resin formulations are typically used for coatings that can be cured onto support material substrates (sand, ceramics, etc.) creating a coating with strong cross-linking on the surface substrates.

Propants coated with curable resin and proppant materials coated with precured resin are commercially available for use as proppant agents. The curable proppant includes a coating layer consisting of resin comprising resin that is usually at least partially, but not completely, cured. Conversely, any “pre-cured” proppant has a backing layer of cured resin. The terms "processed" and "processable" for the present description are defined by three tests previously used in the field.

A) Testing the adhesion point at a specific temperature: The coated material is placed on a rod heated to the melting point and the lowest temperature at which the coated material adheres to the rod heated to the melting point is determined. Typically, the “adhesion temperature” refers to the formation of greater than 176.67°C (350°F) to the cured material, depending on the resin system used.

b) Acetone extraction test: A method of extracting acetone, as described below, by dissolving the portion of resin in the coating that has not been cured.

c) Compressive strength test: Typically, the absence of bonding, or no coalescence of the coated particles, following compression in the wet state below 70.3 kg/cm2 at 93.33°C (200°F) for a prolonged period of up to 24 hours indicates a cured material.

However, unless otherwise indicated, the expressions processed and processable are defined by the acetone extraction test.

Props are generally used to increase oil and/or gas production by providing a conductive channel into the formation. Fracking of an underground formation is carried out for the purpose of increasing oil and/or gas production. Fracking occurs by injecting a viscous fracturing fluid or foam at a high pressure (henceforth referred to as injection pressure) into the well in order to form a fracture. A similar effect can be achieved by injecting a thin fluid (water containing low concentration of polymer) at a high injection rate. When a crack forms, a particulate material, referred to as a "proppant", is placed in the formation to keep the crack in an open buttressed state when the injection pressure is relieved. When a crack forms, proppant materials are carried into the crack by suspending them in an additional fluid or foam to fill the crack with a slurry that is the proppant in the fluid or foam. After stress relief, proppant grouting material serves to keep the cracks open. Thus the supported crack provides a highly conductive channel into the formation. The degree of activation achieved by hydraulic treatment of a fracture depends greatly on configuration variables, the fracture's permeability, the propped fracture length, the propped fracture height, and the fracture's propped width.

Gravel packing treatments are used in order to reduce the migration of unconsolidated formation sand/particles into the well bore. In gravel pack operations, coated and/or uncoated particles suspended in a carrier fluid are fed into a borehole in which the gravel pack is to be placed. The carrier fluid leaks into the subterranean zone and/or is returned to the surface while particles are left in the annular space between the production tubing string and casing or outside the casing in the subterranean zone adjacent to the wellbore.

Gravel pack operations usually include placing a gravel pack screen in the well bore and packing the surrounding annulus between the network and the well bore with particles. The mesh represented by a gravel pack is generally a type of filling aggregate used to consolidate and retain particles that are placed during the gravel packing process. A wide range of sizes and mesh designs are available to suit the characteristics of a particular wellbore, production fluid and subterranean formation sands. These gravel packs can be used to stabilize the formation while minimally impairing production. The gravel fill acts as a fill material to separate the formation sand from the producing fluids while allowing the produced oil and/or gas to flow into the well bore. The particles work to prevent formation sand from clogging the mesh or migrating with the producing fluids, and the mesh works to prevent fines (crushed particles) from escaping from the product to the surface and out of the well.

Gravel packing may also be used to protect the wall of the well bore in order to integrate production by using a tightly packed sediment from an aggregate that includes sand, gravel, or both between the wall of the hole and the production pipe. Thus, the time and costs required to place a steel casing can be eliminated. It extends from the surface to the production area, which may reach several thousand feet below the surface. Gravel packing is self-permeable to the desired hydrocarbon fluid and provides strengthening of the hole wall structure against internal collapse or erosion due to flow. These well completion systems are called "open well" completions. Both the device and process by which a packed deposit of gravel is placed between the bore hole wall and the production pipe are included within the definition of “open well gravel packing system.” Unfortunately, open-hole gravel grouting systems known from the prior art used for placing and grouting gravel along a hydrocarbon producing zone are accompanied by an unavoidable precipitation risk of borehole wall collapse due to fluctuations in borehole pressure along the producing zone. These pressure fluctuations are generated by surface circulations of downhole tools during direct circulation of fluid into the well and completion tubing string. Further discussion of gravel packs is provided by US Patent No. 6,382,319, which is incorporated herein by reference.

In some cases, hydraulic fracturing and gravel packing are combined into a single treatment process to provide stimulator production and gravel packing in the annular space to reduce formation sand production. Such treatments are often referred to as “filling and crushing” operations. In some cases, treatments are completed with a gravel-packed mesh assembly in place, and hydraulic fracturing treatment fluid is pumped through the annular space between the casing and the mesh. In such a case, hydraulic fracturing treatment usually ends with an off-grid condition that creates an annular gravel packing between the grid and casing. This allows both the hydraulic fracturing fluid and gravel pack to be applied in one operation.

In addition, sand control is another issue that must be considered when extracting hydrocarbons such as natural gas and crude oil from earth's subsurface formations, such as drill holes drilled in hydrocarbon-bearing production areas. The production of oil, gas, and water from unconsolidated or poorly consolidated formations is usually accompanied by the production of formation sand particles together with the productive fluids. The production of sand with well fluids creates serious problems such as corrosion of the production facilities located below the surface and on the surface, and the accumulation of sand in the well bore and separators located on the surface. Many methods, such as filling with gravel, nets, and reinforcement with plastic materials, have been used for several years with varying degrees of success. However, these methods suffer from many technical and cost limitations. Further discussion of sand control is provided by U.S. Patent No. 6,364,019, which is incorporated herein in its entirety by reference.

When hydrocarbon-bearing formations are “fractured” in the oilfield industry, the use of proppant materials to maintain the large surface area generated by the fracture has become a common practical application.

It is highly desirable that proppant particles have high performance and can be produced using highly efficient (economically attractive) processes.

It is also desirable to find coated particles that can be produced in remote locations, such as a field located at or near a well site.

General description of the invention

The present invention relates to free-flowing coated particles with a particle size range of 74-3360 microns (6 mesh to 200 mesh), each particle comprising:

Substrate chosen from the group consisting of:

A particulate substrate comprising an inorganic material and optionally an at least partially cured coating layer,

A composite particle comprising a particle of substantially uniform shape comprising a first portion of binder and filler particles is dispersed over the entirety of said first portion of binder, wherein said first portion is at least partially cured, and wherein the particle size of the filler particles varies 0.5 to 60 microns; And :

A hybrid particle comprising a composite layer placed on an inorganic particulate core, the composite layer comprising at least a partially cured organic coating and filler particles, wherein the particle size of the filler particles ranges from 0.5 to 60 micrometer; And :

A coating layer placed on the substrate, the coating layer comprising a continuous phase comprising a curable phenolic-formaldehyde resole resin and comprising reactive or unreacted powdered particles embedded in or attached to the continuous phase, wherein the powdered particles comprise at least one member Of the group consisting of resole resin is phenolic-formaldehyde, novolak resin is phenolic-formaldehyde, polyester, acrylic, and urethane.

Regarding the method of the present invention, it relates to a method for preparing free flowing coated particles with a particle size ranging from 74.3360 microns (6 mesh to 200 mesh), and comprising a substrate and a coating layer placed on the substrate, the coating layer comprising a continuous phase. Comprising a liquid resole resin that is a processable phenolic-formaldehyde and comprising powdered particles embedded in or attached to the continuous phase, wherein the reacted powdered particles comprise at least one member of The group consists of resole resin, which is phenolic-formaldehyde, and novolak resin, which is phenolic-formaldehyde, polyester, acrylic, and urethane. The method includes the following steps:

Mixing, at a temperature in the range of 10°C (50°F) to 65.5°C (150°F), the substrate with the liquid coating material to form a continuous phase resin coating that can be cured onto the substrate,

You choose the substrate from the group consisting of:

A particulate substrate comprising an inorganic material and optionally an at least partially cured coating layer,

A particulate substrate comprising an inorganic material and optionally an at least partially cured coating,

A composite particle comprising a particle of substantially uniform shape comprising a first portion of binder and filler particles dispersed over the entirety of said first portion of binder, wherein said first portion is at least partially cured, and wherein the particle size of the filler particles ranges from 0.5 to 60 microns; And

A hybrid particle comprising a composite layer placed on an inorganic particulate core, the composite layer comprising at least a partially cured organic coating layer and filler particles, wherein the particle size of the filler particles ranges from 0.5 to 60 microns; wherein the encapsulating material includes a resole resin that is a curable phenolic-formaldehyde;

Mixing crushed particles with a resin-coated substrate to embed them in or adhere to a continuous length resin coating.

The particles used in this method can be reactive or non-reactive.

The powdered particles reacting in the product and/or method are reactive with at least the continuous phase mentioned above. The use of reactive powders advantageously improves the non-exclusive compressive strength properties of the particle. Unreacted particles, for example, silica powder, are inert to the continuous phase.

The reactive powder particles typically include at least one member selected from the group consisting of re sole resin (phenolic-formaldehyde), novolak resin (phenolic-formaldehyde), polyester, acrylic, and urethane. This preparation method involves applying organic resins, at low temperatures, to substrates of sand and ceramics in cycles that take only minutes, resulting in high-performance coated particles for the oilfield (and foundry) industry. The powder is added to effectively dry the applied liquid coating layer and allow the coated particles to be separated from each other and free to flow.

The substrate is defined as the portion of the particle that is encapsulated by one or more outer coating layers of the present invention. The substrate can be present in the coated particles in an amount ranging from 80 to 99.5 weight percent (wt%), based on the total weight of the coated particles.

In one embodiment, wherein the outer coating is applied directly to a particle of sand or ceramic material, the substrate is present in an amount ranging from 95 to 99.5% by weight, based on the total weight of the coated particles.

Typically, the outer resin coating represents between 5 and 15% of the total particle weight.

In one embodiment, the outer coating is applied to a single inorganic particle. Typically, a particulate substrate containing inorganic material is a particulate substrate of sand or ceramic. A preferred inorganic substrate is sand 40/70. In embodiments using an inorganic particulate substrate coated with one or more coating layers comprising a continuous phase phenolic-formaldehyde resole resin and reactive powder particles, the free-flowing dry particle is preferably characterized by a loss on ignition (LOI) of 0.3 to 8, or 0.3 to 5, or 0.5 to 5%, or 0.75 to 4%. Unless otherwise stated, all percentages disclosed in this description are percentages by weight.

In embodiments using an organic particulate substrate, the free-flowing dry particle is preferably characterized by an LOI in the range of 0.3 to 5%, which does not include LOI that can be attributed to ignition of the organic particulate substrate.

In embodiments involving an encapsulated particle in which the substrate is a composite particle, then the LOI is the combination of the LOI of the composite substrate (usually in the range of 12-15% based on the total weight of the substrate, after curing) plus the LOI For a coating containing resin placed on a substrate (0.5 to 5% by weight based on the total weight of the coated particle). In these embodiments, the total LOI typically ranges from 12% to 20% (including the LOI attributable to the organic binder of the composite substrate and coating, but not including the LOI attributable to the filler of the composite substrate, if any). Typically, filler particles represent 70 to 90% by weight of the composite particle. Typically, the composite substrate represents 95 to 99.5% by weight of the encapsulated particle of this invention.

The composite substrate can comprise 10 to 90 weight percent (wt%), and typically 70 to 90 wt% inorganic filler materials based on the total weight of the composite substrate. In one embodiment, inorganic materials can be present in an amount ranging from 20 to 80 weight percent (wt%) based on the total weight of the composite substrate. In another embodiment, inorganic materials can be present in an amount ranging from 30 to 70 weight percent (wt%) based on the total weight of the composite substrate. In yet another embodiment, inorganic materials may be present in an amount ranging from 40 to 60 weight percent (wt%) based on the total weight of the composite substrate.

Typically, a composite particle has a sphericity of at least 0.7.

In models of an encapsulated particle in which the substrate is a hybrid particle (an inorganic particulate core comprising a composite layer of organic packing material and inorganic filling material), then the LOI is the sum of the LOI of the hybrid substrate (where usually This is in the range of 5 to 20% based on the total weight of the substrate, after curing) plus the LOI of the coating containing the resin placed on the substrate (0.5 to 5% by weight based on the total weight of the coated particle). In these models the total LOI ranges from 5.5% to 25% (including the LOI attributable to the organic binder of the hybrid substrate and coating). Typically, the cured or partially cured composite layer represents at least 25 to 40 wt% of the hybrid particle. Typically, the hybrid particle represents 95 to 99% by weight of the encapsulated particle of this invention.

The proportion of ingredients, order of addition and timing of addition and mixing are chosen to form such free-flowing particles. For example, if the powder is mixed with uncoated inorganic substrate particles before applying the liquid resole, then adequate encapsulation is not achieved. Also, the ratio of resole liquid and powder is chosen to achieve the correct encapsulation. Excessive powder results in excess loose powder (not well bound), and too much liquid resole delays drying and/or contributes to particle aggregates (lots of particles stuck together).

The present invention relates to a method for forming a proppant or gravel fill, which includes suspending the above-described free-flowing particles in a carrier barrier to form a suspension and attaching the suspension to a subterranean formation.

The present invention also relates to a proppant or gravel fill particle comprising a substrate comprising a coating layer of resole resin containing a reactive powder included in a coating of resin resole.

Coating the substrates of sand or ceramics with liquid resole resin (phenolic-formaldehyde) at room temperature, followed by the introduction of powdered novolak resin (phenolic-formaldehyde) (with or without curing agents such as hexamethylenetetramine) results in an encapsulated particle. With resin, free flowing, and high performance, it can be used as proppant grout material in oil field.

The coating layer, represented by liquid resin, is reactive with the reactive powder.

For example, the coating of the resole can be enhanced by curing the novolak powder and/or the powder can contain hexamethylenetetramine (HEXA) to help cure the coating of the resole. Typically, the reacted powder or unreacted powder has an average particle size of 74 microns (200 mesh) or smaller, or 53 microns (270 mesh) or smaller. For example, the typical particle size of powdered resin ranges from 1300 to 500 microns (15 to 35 mesh) with a small amount of fines present. The reactive powder preferably includes Novolak powder or Resole powder. In general, at least the majority of the powder found in or on the packaging layers includes reactive resin powder. Unreacted powders and reactive powders do not dissolve or do not dissolve appreciably in water-based and petroleum-based working fluids.

In the outer coating that can be processed, the typical ratio of liquid resole resin to powder (total reactive powder and optional inorganic powder) is 1:3. The ratio between liquid resole to powder outer coating is preferably 20-30. % of liquid resole and 70- 80% of powder. When this coating is placed on the substrate, some of the resole evaporates, so on a dry solids basis, we have 15-20% solids from the original resole and 80-75% solids from the powder. So, for example, for a particle containing a particulate inorganic substrate and an LOI of 3 wt%, the total powder on the final particle will be 80-85% 3% = 2.4 2.5 wt%. The liquid-to-powder ratio can change based on the surface area of ​​the particle to be covered and the reaction conditions. The conditions and weight ratios are determined in order to obtain the particles of the product obtained in this way dry and free flowing with little or no excess powder.

Treatable casing layers can be placed at/near the well site. In this process, machining operations can be a continuous addition to a moving layer of substrate. However, the production of coated particles by this process is within the scope of the invention whether they are pre-coated on the proppant in the sand packing unit or at various remote locations, such as part of a transitional convection/stripping furnace, at or near a well site. The process is also a fast and economical way to increase production capacity quickly and at low capital costs.

The present invention is distinctive because the method results in a processable coated particle that can bind to the bottom of the hole. Also, the current method can be performed in remote locations in a low-cost unit. It is also possible to save on transportation fees by reducing the costs related to transporting piles to the lowest level. Also, this process requiring little or no heating enables energy savings compared to comparable processes in which phenol-formaldehyde resins are heated to melt the coating to the substrate or in which heat is used to dry or cure the resin coating. Also, by avoiding heating, the present method minimizes emissions of volatile materials, which must be dealt with in a process in which phenol-formaldehyde resins are heated to fuse the coating to the substrate or in which heat is used to dry or cure the coating resin, to the greatest extent. .

Brief explanation of the drawings

Below a brief description of the figures will be given, where similar numbers indicate similar elements.

Figure 1: An example of an encapsulated particle comprising a solid inorganic or solid organic substrate on which a resole coating containing a reactive powder is deposited.

Figure 2 shows another embodiment of an encapsulated particle comprising a solid inorganic substrate upon which a resole encapsulating layer comprising novolak or resole powder and inorganic or inert organic fillers is deposited.

Figure 3: shows another example of an encapsulated particle including a substrate, where the substrate includes a composite particle, which is an assembly of inorganic particles and a binder, upon which a resole containing a reactive powder is placed.

Figure 4: Another embodiment of a coated particle comprising a substrate, wherein the substrate includes a hybrid particle including a composite layer placed on an inorganic particulate core, and the composite layer includes a cured organic coating layer and an inorganic filler placed On a resole coating containing a reactive powder.

Figure 5: Shows a photograph of particles from Sample A “as produced” in a laboratory, at 10x magnification.

Figure 6: Shows a photograph of particles from Sample B “as produced” in a laboratory, at 10x magnification.

Figure 7: Shows a photograph of a metal disc of sample B particles formed after performing a UCS test using a k pressure at 93.3°C, at 10x magnification.

Figure 8: Shows a photograph of particles from sample B after tensile testing in the hot state, at 10x magnification.

Figure 9: Shows a sample of unpowdered resole from a comparative example, at 12x magnification.

Figure 10: Shows a sample of the product produced using a process in which the arrangement of the coating and powder sample is reversed, compared to a comparative example, at 30x magnification.

Detailed description

As used herein, the expressions "first," "second," and the like do not suggest any order or importance, but rather they are used to distinguish one element from another, and the definite and indefinite expressions the, a, and an do not imply any. A restriction of quantity, but instead suggests the presence of at least one in the items indicated. Furthermore, all range values ​​disclosed herein include the endpoints or minimum and maximum limits of the range and may be combined independently.

The present proppant particle or gravel pack particle includes a particle substrate with a resole resin coating containing a reactive powder, for example, novolak or resole powder, within the resole resin coating.

Typically for proppant, gravel pack, or foundry sand, the individual particles of the fine substrate have a particle size in the US standard test sieve number range, 3360 74 microns (6 to 200 mesh), e.g. 400 841 microns ( 20 to 40 mesh). Typically for a proppant or gravel fill, the individual particles of the fine substrate have a particle size in the US standard test sieve number range, 2380 149 microns (8 to 100 mesh) or 841 177 microns (20 to 80 mesh), or preferably 400 210 microns (40 to 70 mesh). Typical independent particles of a particulate substrate have a diameter of 0.254 to 1.00 mm (0.01 to 0.04 in). Typically for foundry sand, the substrate is sand or ceramic material.

For example, substrates 2, 21, and 42 of Figures 1-4 can have average particle sizes ranging from 100 microns to 1400 microns, 300 microns to 600 microns, or 400 microns to 500 microns.

The organic coating layer applied to the substrate can be treated before being used as a proppant or gravel fill.

Figure 1 shows a representative example of an encapsulated particle 10 comprising a particulate substrate 2 upon which an organic coating layer 4 is applied. The particulate substrate 2 may comprise inorganic material and/or inorganic material. Substrate 2 preferably comprises a single inorganic particle. The organic coating 4 includes a resole polymer that can be processed as a continuous phase 6 and a reactive powder 8 embedded or adhered to the continuous phase 6. If desired, an unreactive powder, such as inert inorganic or inert organic filler particles, such as silica powder, may be used together with or in place of the reactive powder 8. Reactive powders are preferred because they can be Useful in improving the unconfined compressive strength of particle 10.

Figure 2 shows a closed particle 12, which is the model shown in Figure 1 and has been modified to also include inert inorganic or inert organic filling particles:

inert inorganic or inert organic filler particles 14 embedded in or attached to the continuous resole phase 6.

Figure 3 shows another embodiment of an encapsulated particle 20 comprising a substrate 21 and a coating layer 4 placed on the substrate 21. The substrate 21 includes an assembly of inorganic particles 22 and a binder. The coating layer 4 includes the reactive powder 8 and the continuous resole phase 6.

If desired, an unreactive powder of inert inorganic or inert organic filler particles, such as silica powder, may be used together with or in place of the reactive powder 8. Reactive powders can advantageously improve Unconfined compressive strength of particle 20.

Figure 4 shows another exemplary embodiment comprising an encapsulated particle 40 comprising a substrate 42 having an inorganic particle 44 in the form of a core and an at least partially cured encapsulating layer 46 comprising inorganic or organic filler particle ranges 48. An encapsulating layer 52 is placed on this substrate 42. The coating layer 52 includes a continuous processable resole phase 54 and a reactive resin powder 56.

If desired, an unreactive powder of inert inorganic or inert organic filler particles, such as silica powder, may be used together with or in place of the reactive powder 56. Reactive powders can advantageously improve Unconfined compressive strength of particle 40. Preferably, the powder 56 comprises a reactive novolak or resole. If desired, non-reactive powders (not shown), such as silica powder, may be provided in or on the coating 52. In general, the majority of the powder comprises at least in or on the coating layer 52 a reactive resin.

A- A substrate that is a single particle

As shown, for example, in Figures 1 and 2, the substrate may be a single particle. The substrate can be any of the organic or inorganic particulate solids commonly used as proppant, gravel fill, or sand control agents. For example, a particulate material is suitable, i.e., including sand, naturally occurring mineral fibers, such as zircon and mullite, ceramics, such as sintered bauxite or sintered alumina, and other non-ceramic refractory materials such as ground glass beads Or ground walnut shells. The substrate can have any desired shape such as spherical, oval, cubic, polygonal, or similar. It is generally desirable for substrates to be spherical in shape. Substrates can be porous or non-porous. Substrates do not melt at a temperature lower than 93.3°C (200°F) or 107.2°C (225°F); Typically, substrates do not melt at temperatures below 232.2°C (450°F) or 287.78°C (550°F). The substrate particles are rigid and resist deformation or can be deformable (deformation). Deformation differs from crushing in that the particle deteriorates. Optionally, the single-particle substrate may include at least a partially cured resin coating.

McDaniel et al.'s U.S. Patent Publication No. 0078682/2006, which is incorporated herein in its entirety by reference, also discloses particulate substrates, comprising silica and alumina with a silica to alumina weight ratio of 2.2 to 5 and a bulk density less than or equal to 1 gram per cm3, suitable for use as a single-particle substrate of the present invention.

Examples of other inorganic materials that can be used in a substrate are inorganic oxides, inorganic carbides, inorganic nitrides, inorganic hydroxides, inorganic oxides having hydroxide coatings, and carbonitrides inorganic carbonitrides, inorganic oxynitrides, inorganic borides, and inorganic borocarbides inorganic borocarbides, or the like, or a combination including at least one of the aforementioned inorganic substances.

Examples of suitable inorganic materials are metal oxides, metal carbides, metal nitrides, metal hydroxy, metal oxides having hydroxide coatings, metal carbonitrides, and metal oxynitrides. , metal borides, metal borocarbides, or the like, or a combination including at least one of The aforementioned inorganic materials.

The metallic cations used in the aforementioned inorganic materials may be derived from transition metals, alkali metals, alkaline earth metals, rare earth metals, or the like, or a combination that includes one of the following. Less than the previous metals.

Suitable inorganic oxides include:

silica (SiO2), alumina (Al2O3), titania (TiO2), zirconia (ZrO2), ceria (CeO2), manganese oxide (MnO2), zinc oxide (ZnO), iron oxides (eg, FeO, α-Fe2O3, γ- Fe2O3, Fe3O4, or the like), calcium oxide (CaO), manganese dioxide (MnO2 and Mn3O4),

Or a combination including at least one of the above inorganic oxides. Examples of suitable inorganic carbides include:

silicon carbide (SiC), titanium carbide (TiC), tantalum carbide (TaC), tungsten carbide (WC), hafnium carbide (HfC),

or the like, or a combination including at least one of the above carbides. Examples of suitable nitrides include silicon nitrides (Si3N4), titanium nitride (TiN) or the like, or a combination including at least one of the foregoing. Examples of suitable borides include:

lanthanum boride (LaB6), chromium borides (CrB and CrB2), molybdenum borides (MoB2, Mo2B5 and MoB), tungsten boride (W2B5)

or something similar, or a combination that includes at least one of the previous borides. Representative inorganic substrates are those containing silica and/or alumina.

Examples of other suitable inorganic materials that can be used in a substrate are:

silica (sand), aeschynite (rare earth yttrium titanium niobium oxide hydroxide), anatase (titanium oxide), bindheimite (lead antimony oxide hydroxide), bixbyite (manganese iron oxide), brookite (titanium oxide), chrysoberyl (beryllium aluminum oxide), columbite (iron manganese niobium tantalum oxide), corundum (aluminum oxide), cuprite (copper oxide), euxenite (rare earth yttrium niobium tantalum titanium oxide), fergusonite (rare earth iron titanium oxide), hausmannite (manganese oxide), hematite (iron oxide), ilmenite (iron titanium oxide), perovskite (calcium titanium oxide), periclase (magnesium oxide), polycrase (rare earth yttrium titanium niobium tantalum oxide), pseudobrookite (iron titanium oxide),

And members of the pyrochlore group such as:

betafite (rare earths calcium sodium uranium titanium niobium tantalum oxide hydroxide), microlite (calcium sodium tantalum oxide hydroxide fluoride), pyrochlore (sodium calcium niobium oxide hydroxide fluoride),

or the like, or a combination including at least one member of the foregoing pyrochlore group; ramsdellite (manganese oxide), romanechite (hydrated barium manganese oxide), and members of the rutile group, such as:

cassiterite (tin oxide), plattnerite (lead oxide), pyrolusite (manganese oxide), rutile (titanium oxide), stishovite (silicon oxide),

or similar, or a combination including at least one member of the foregoing rutile group; And

members; samarskite-(Y) (rare earth yttrium iron titanium oxide), senarmontite (antimony oxide), members

And members of the spinel group, which is a hard, glassy metal, such as:

chromite (iron chromium oxide), franklinite (zinc manganese iron oxide), gahnite (zinc aluminum oxide), magnesiochromite (magnesium chromium oxide), magnetite (iron oxide), and spinel (magnesium aluminum oxide),

or the like, or a combination including at least one of the members of the foregoing spinel group; And

members; taaffeite (beryllium magnesium aluminum oxide), tantalite (iron manganese tantalum niobium oxide), tapiolite (iron manganese tantalum niobium oxide), uraninite (uranium oxide), valentinite (antimony oxide), zincite (zinc manganese oxide), hydroxides,

like :

brucite (magnesium hydroxide), gibbsite (aluminum hydroxide), goethite (iron oxide hydroxide), limonite (hydrated iron oxide hydroxide), manganite (manganese oxide hydroxide), psilomelane (barium manganese oxide hydroxide), romeite (calcium sodium iron manganese antimony titanium oxide hydroxide), stetefeldtite (silver antimony oxide hydroxide), stibiconite (antimony oxide hydroxide),

Or something similar, or a combination that includes at least one of the aforementioned inorganic materials.

Suitable examples of materials that are modified and used in a substrate are flaky clays (e.g., expanded vermiculite), exfoliated graphite, blown glass or swollen silica, hollow glass spheres, foamed glass spheres, and balls. An inert hollow filled with inert gas, foamed slag, sintered bauxite, sintered alumina, or the like, or a combination including one of the above. Representative inorganic substrates may be derived from sand, ground glass beads, sintered bauxite, sintered alumina, mineral fibers such as zircon and mullite, or the like, or a combination including one of the above inorganic substrates. Hollow glass balls can be obtained commercially from Diversified Proppants.

Suitable examples of organic materials used as a substrate are ground or crushed nut shells, ground or crushed seed shells, ground or crushed fruit kernels, treated wood, ground or crushed animal bones, or a combination including at least one of the naturally occurring fill materials. For example, suitable organic materials are naturally occurring organic fillers including crushed or ground walnuts, crushed or ground pecans, crushed or ground almonds, crushed or ground Ivory almonds, crushed or ground Brazil nuts, or a combination including At least one of the above types of almonds. Other examples of suitable organic materials are crushed and ground plum seeds, crushed and ground peach seeds, crushed and ground cherry seeds, crushed or ground olive trees, crushed or ground apricot seeds, ground or ground corncobs, and treated wood materials from oak, hickory, and wood. Walnut, poplar, and mahogany wood that has been processed by grinding or planing.

In another representative embodiment, the inorganic substrate has a bulk density of 0.6 to 1 g/cm3 and a bulk density of 1.3 to 2 g/cm3. Inorganic substrates exhibit a crush test percentage less than or equal to 20% when subjected to a crush test under a pressure of 140.63 kg/m2 (2000 psi) according to API RP 60. The inorganic substrate has a roundness of 0.6 to 0.9 and has a roundness of 0.6 to 0.9.

The substrate density can be chosen based on the application in which the backing material is to be used. It is desirable to select substrates that can give the proppant an apparent density of 1 to 4 g/cm3.

Bulk density is defined as the density of the entire proppant (i.e., the weight per unit volume of the total proppant including the inherent voids in the proppant). In one embodiment, the proppant has a bulk density of 1.4 to 1.9 g/cm3. In another embodiment, the substrate has a bulk density of 1.5 to 1.85 g/cm3.

In yet another embodiment, the substrate has a bulk density of 1.6 to 1.8 g/cm3. Substrates coated using this process, such as sand, have a bulk density of 2.65 g/cm3 and various images of ceramic materials have a density of 2.5-3.4 g/cm3.

B- A substrate is a composite particle

As shown in the example shown in Figure 3, referred to above, the substrate 21 may comprise a formable composite particle comprising a homogeneous particle comprising crushed filler particles 22 that are bonded together by a cured or at least partially cured binder. 24. Various embodiments of these composite particles are described in more detail below and in US Patent Nos. 6,406,789, 6,632,527, and 6,582,819 and US Patent Publication No. 2006/0078682 of McDaniel et al., all of which are incorporated in their entirety herein by reference.

In such a case, the individual particles that fuse to form the substrate can have average particle sizes ranging from 2 to 30 microns. In one embodiment, the particles that aggregate to form the substrate 21 can have average particle sizes of less than or equal to 28 microns, less than or equal to 25 microns, less than or equal to 20 microns, or less than or equal to 15 microns. Bimodal or higher particle size distributions can be used.

The filling material 21 may be particles or fibrous filling materials that generally have a characteristic ratio greater than 1. As used herein, "fibrous" filling materials accordingly may exist in the form of crushed filaments, needles, and rods. , tubes, strands, stretched sheets, thin sheets, ellipses, powdered fibers, nano-sized ultrafine fibers, nano-sized tubes, stretched tissues, and the like. When these filling materials are present in aggregate form, any aggregate having a characteristic determining ratio greater than 1 will satisfy the purpose of this invention. Examples of these filling materials that are well known in the field include those described in:

Plastic Additives Handbook, 5th Edition Hans Zweifel, Ed, Carl Hanser Verlag Publishers, Munich, 2001.

Non-exclusive examples of suitable fibrous fillers include short inorganic fibers, including processed mineral fibers such as those derived from mixtures comprising at least one of aluminum silicates, aluminum oxides, magnesium oxides, and calcium sulfate hemihydrate , boron fibers, ceramic fibers such as silicon carbide, and fibers derived from mixed oxides of aluminum, boron, and silicon sold under the trade name NEXTEL by 3M Co., St. Paul, MN, USA. Fibrous fillers also include single crystal fibers or “whiskers,” which include silicon carbide, alumina, boron carbide, iron, nickel, and copper. It may also include fibrous fillers such as glass fibres, basalt fibres, including textile glass fibers and quartz.

It also includes natural organic fibers such as sawdust obtained by crushing wood, and fibrous products such as cellulose, cotton, kenaf, hemp, cloth, cotton threads, felt, and natural cellulosic fabrics such as kraft paper. , cotton paper, glass fibers glass fiber containing paper, starch, cork powder, lignans, ground almond shells, corn, rice hulls, or the like, or a combination including at least one previously.

In addition, synthetic reinforcement fibers may be used in the composite substrate. These include organic materials capable of forming fibers such as:

phenolic fibers, polyethylene terephthalate, other polybutylene terephthalate, and:

polyesters, polyarylates, polyethylene, polyvinylalcohol, polytetrafluoroethylene, acrylic resins

Highly cohesive fibers with great thermal stability include organic polyamides, polyaramid fibers such as those available commercially from Du Pont de Nemours under the trade name KEVLAR, polybenzimidazole and polyimide fibers such as those available from Dow Chemical Co. under the trade names polyimide 2080 and PBZ, and polyphenylene. sulfide, polyether ether ketone, polyimide, polybenzoxazole, polyimide or aromatic polyimides, and the like. Combinations of any of the above-mentioned fibers can be used. Representative fibers are phenolic resin fibers.

In one example embodiment, phenolic resin fibers or glass fibers may be used as the fiber fill material in the composite substrate. Useful glass fibers can be formed from any type of glass composition that can be formed into fibers, including those prepared from glass compositions that can be formed into fibers, known by the common names E-glass, A-glass, C-glass, and D-glass. glass, R-glass, S-glass, as well as E-glass derivatives free of fluorine and/or boron. AR glass can be used for its alkali resistance. Commercially produced glass fibers generally have filament diameters of 4 to 35 microns, and the most commonly produced E-glass fibers, which have filament diameters of 9 to 30 microns, can be included in the composite substrate. Non-round fiber cross sections can also be used. The size of the glass fibers may or may not be specified. Size-specific glass fibers may be coated on at least a portion of their surfaces using a size-specific composition chosen to harmonize with the coating applied to the substrate. The size-specific formulation facilitates external wetting or wetting through the coating layer on the fiber strands and helps achieve the desired physical properties in the composite substrate.

Glass fibers should preferably be glass strands whose size has been previously determined. When preparing fiberglass, a number of wicks can be formed at the same time, then sized by a coating agent in a salt solution and then assembled into bundles known as strands. Alternatively, the braid itself can first be formed from the wicks and then sized. The amount of the composition specified for the size is generally that amount sufficient to bind the glass wicks into a continuous strand and ranges from 0.1 to 5% by weight, and more typically ranges from 0.1 to 2% by weight based on the weight of the fiberglass. Generally speaking, this quantity can be 1% by weight based on the weight of the glass fiber. Glass fibers can also be used in the form of strands cut into lengths of 6.35 mm or less, preferably 3.2 mm. It can also be longer than 6.35 mm if desired.

The fibers used in the composite substrate can be of lengths ranging from 6 to 3200 microns. In one embodiment, fiber lengths range from 10 to 1600 microns. In another embodiment, fiber lengths range from 10 to 800 microns. Representative fibers are shorter than the largest diameter of the composite substrate.

Fiber diameters (or, for fibers with a non-circular cross section, after assuming the diameter of a hypothetical circle with an area equal to the cross-sectional area of ​​the fibre) range from 1 to 20 microns. The specific feature ratio (length-to-diameter ratio) can range from 5 to 175. The fiber can be round, oval, square, rectangular, or have any other suitable cross-section. Fibers can be straight, curly, coiled, or a combination of the above.

A representative filling material used in organic packaging material is silica powder. Generally, silica powder has particle sizes less than or equal to 20 microns. In one embodiment, the silica powder has particle sizes less than or equal to 10 microns. In another embodiment, the silica powder has particle sizes less than or equal to 5 microns. An example of a commercially available silica powder is SIKRON SF 242, which is commercially available from Quarzwerke GmbH, Frechen, Germany.

C- The substrate is a hybrid particle

As shown in Figure 4, another type of substrate is a hybrid particle substrate 42 comprising an inorganic particle 44 that serves as a core and a cured or at least partially cured coating layer (composite layer) 46 which includes inorganic filling materials. Or organic filling materials 48. The organic coating 46 can be applied in a single layer or in several layers if desired.

The fill materials 48 in the composite layer 46 of the hybrid particle substrate 42 may be the same as the fill materials described above for the composite particle substrate.

Various embodiments of these hybrid particles are described in more detail in US Provisional Application No. 611350/60 filed on September 20, 2004, and US Patent Publication No. 0078682/2006-1a of McDaniel et al., which are fully incorporated herein. for reference.

In the representative embodiment shown in Figure 4, where a substrate consisting of encapsulated particles comprises a single particle, any representative inorganic synthetically produced substrate comprises one or more of:

Silica (SiO2), alumina (Al2O3), titanium dioxide (TiO2), ferric oxide (Fe2O3), calcium oxide (CaO), magnesium oxide (MgO), potassium dioxide (K2O) and sodium oxide (Na2O).

The inorganic substrate may also include sulfite ions, chloride ions, water, and carbon dioxide in trace amounts less than or equal to 2% by weight, based on the weight of the substrate.

Synthetically produced organic substrates may include thermoplastic polymers, thermosetting polymers, or a combination including a thermosetting polymer and a thermoset polymer. Examples of suitable organic materials that can be used as a substrate are polymer-producing materials (e.g. low molecular weight types such as monomers, dimers, trimers, or the like), oligomers, polymers, and copolymers such as block copolymers, star block copolymers, tertiary polymers, and random copolymers , variable copolymers, grafted copolymers, or the like; Branched polymeric compounds, ionic polymeric compounds, or the like, or a combination that includes at least one of the above. When the substrate includes a thermoset polymer, it is desirable for the organic material to undergo processing (crosslinking) by application of thermal energy, electromagnetic radiation, or a combination including at least one of the above. Primers may be used to induce treatment to begin. Other additional substances may also be used to enhance or control processing such as accelerators, inhibitors, or the like.

Examples of heat-setting polymers suitable for use in the cured (non-reactive) coating 46 of the substrate are compounds:

epoxies, acrylate resins, methacrylate resins, phenol-formaldehydes, epoxy-modified novolacs, furans, urea-aldehydes, melamine-aldehydes, polyester resins, alkyd resins, phenol formaldehyde novolacs, phenol formaldehyde resoles, phenol-aldehydes, resole and novolac resins, epoxy modified phenolics, polyacetals, polysiloxanes, polyurethanes,

or the like, or a combination including at least one of the aforementioned thermosetting polymers.

D- Powders and curable outer layer resins

The outer organic coating layer comprises a resole polymer that can be processed as a continuous phase and a reactive and/or unreactive powder. External organic coating means the outermost coating layer of continuous phase resin, which encases the particle and any powder contained in or emerging from the continuous phase.

It includes:

phenol formaldehyde resoles, phenol formaldehyde and furfuryl alcohol or furfuryl aldehyde resoles, or phenol formaldehyde resole resins

Which are replaced with alkylphenols or almond oil. This includes resole resins arising from solvents and water. Resole resins will be explained in more detail below. The resole resins representing the outer coating layer of the present invention are characterized as low-density liquid resins that can be coated on a substrate at low temperatures, ranging from 10°C (50°F) to 66°C (150°F), preferably from 21°C. °C (70°F) to 49°C (120°F), as also described elsewhere in this description, and showing potential or processing to full performance when placed in the subterranean formation. However, resins do not harden cold and can react at 65°C or lower without the use of additional heat. The component associated with the use of encapsulating resole resins is a feature that distinguishes these resole resins from cold hardening resins such as alkaline modified resole resins, which are described in US Patent Application No. 0078682/2006 1a. That of McDaniel et al.,. Alkaline-modified resole is manufactured by adding potassium hydroxide or sodium hydroxide to resole resin so that a large portion of the resin is converted into the alkaline salt of the resin, where it is possible to process it using esters without high temperature. The outer coating resins used in the present invention do not contain these alkaline salts. The resole resins in the outer coating are dormant but can be heat cured, for example using the high temperatures (in excess of 70°C, typically in excess of 80°C) found in any subterranean formation.

Reactive powders include one or more of the following: novolak (with or without hexamethylenetetramine), resole resins, polyesters with a hydroxy functional group (reacting with resole resins), polyacrylates with a hydroxy functional group (reacting with resole resins), and Function-oriented polyurethanes that react with resole resins, such as those with an amine function or a hydroxy function. Typically, the reacting powder has an average particle size of 74 microns (200 mesh) or smaller.

Non-reactive powders may be either inorganic or organic powders that do not chemically bond with the coating containing continuous phase resole resin. Examples of unreactive inorganic powders include silica powder, glass, or ground materials. Examples of unreacted organic powders include crushed walnut shells or other natural organic materials such as sawdust obtained by crushing wood, and fibrous products such as cellulose, cotton, kenaf, jute, cloth, hemp, felt, and fibres. Natural cellulosic fabrics such as kraft paper, cotton paper, paper containing fiberglass, starch, cork powder, lignin, ground walnut shells, corn, rice hulls, or the like. That, or a combination that includes at least one of the above. The unreacted powder typically has an average particle size of 74 microns (200 mesh) or smaller.

1-resole resins

One embodiment of the invention uses a coating layer comprising a phenol-aldehyde resole polymer in the form of a solution or dispersion. Resole resin can also be used in powder form to be embedded or adhered to the packaging layer containing Resole. The resole powder typically has an average particle size of 74 microns (200 mesh) or smaller and is extracted using a spray drying method to retain the reactivity of the resole.

Resole resin used for packaging is liquid when applied to the substrate and therefore has the appropriate molecular weight to be liquid. The typical average molecular weight of liquid resole ranges from 400 to 2000. The resin encapsulation is processable. Resole ranges used for encapsulation are supplied as a wet aqueous solution and are dried by the current process to an untreated (non-cross-linked) state.

The resole resin used for the powder is solid when applied to the coated substrate and therefore has the appropriate molecular weight to be solid. A typical molecular weight of solid resole ranges from 500 to 5000. Powdered resole is processable. Resole powder can be applied in an untreated state. It is preferable that the Resole powder be reactive towards itself and the adhesive of the liquid Resole (not cured when applied).

Resole resins are preferably resole resins containing less than 3% by weight of free phenol, and preferably less than 2% by weight of free phenol.

The resole resin represented by phenol-aldehyde has a molecular ratio of phenol-aldehyde ranging from 1:1 to 1:3, and typically from 1:1 to 1:1.95.

A preferred mode of preparing resole resin is to combine the phenol with an aldehyde source such as formaldehyde, acetaldehyde, propionaldehyde, furfural and benzaldehyde, or paraformaldehyde in the presence of an alkaline catalyst. During this reaction, aldehyde is present in molecular abundance. Preferably, the resole resin should have a phenol to formaldehyde molecular ratio of 1:1.1 to 1:1.6. A typical method for manufacturing resole resins is to place phenol in a reactor, add an alkaline catalyst, such as sodium hydroxide or calcium hydroxide, and an aldehyde, such as a 50 wt% solution of formaldehyde, and react the components at elevated temperature until the desired viscosity is reached or free formaldehyde is achieved. The water content is adjusted by distillation. Flexibility agents or plasticizers, such as bisphenol A or almond oil, may also be present to enhance the elasticity or plasticity of the binding material. Other known additives may also be present.

Resole resins Resole resins can be conventional or modified. The modified resole resins are disclosed in U.S. Patent No. 521,808, which is incorporated in its entirety herein by reference. These modified resole resins are prepared by reacting aldehyde with a mixture of an unsubstituted phenol and at least one phenolic substance selected from the group consisting of arylphenol, alkylphenol, alkoxyphenol, and aryloxyphenol. Modified resole resins include alkoxy-modified resole resins. Among the resole resins modified with alkoxy, resole resins modified with methoxy are preferred. However, the most preferred phenolic resole resin is modified resole resin containing orthobenzylic ether which is prepared by reaction of phenol and aldehyde in the presence of an aliphatic hydroxy compound containing two or more hydroxy groups per molecule. In a preferred modification of the process, the reaction is also performed in the presence of monohydric alcohol.

The phenol and aldehyde compounds suitable for the preparation of phenolic resins containing modified orthobenzylic ether are generally any phenol and aldehyde compounds that can be used in the preparation of phenolic resins. Ionic metal catalysts useful in the production of modified phenolic resins include divalent ion salts of Mn, Zn, Cd, Mg, Co, Ni, Fe, Pb, Ca, and Ba. Tetra alkoxy titanium compounds with the formula Ti(OR)4, where R is a 3-carbon alkyl group, are also useful catalysts for this reaction. A preferred catalyst is zinc acetate.

A molar excess of aldehyde per mole of phenol is used to prepare modified resole resins. It is preferable that the molar ratio of phenol to aldehyde be from 1:1.1 to 1:2.2. The reaction of phenol with aldehyde takes place in the presence of a divalent ionic metal catalyst at a pH of less than 7. To the reaction mixture, an aliphatic hydroxy compound containing two or more hydroxy groups per molecule is added. The hydroxy compound is added at a molar ratio of hydroxy compound to phenol of 0.0001:1 to 0.03:1.

Useful hydroxy compounds that contain two or more hydroxyl groups per molecule are those with a hydroxy number ranging from 200 to 1850. The hydroxy number is determined by the acetic anhydride method, and is expressed in terms of mg of KOH/g of hydroxy compound. Suitable hydroxy compounds include ethylene glycol, propylene glycol, 1,3-propanediol, diethylene glycol, triethylene glycol, glycerol, sorbitol and polyether polyols with hydroxy numbers greater than 400.

After adding an aliphatic hydroxy compound containing two or more hydroxyl groups per molecule to the reaction mixture, heat is continued until 80% to 98% of the aldehyde has reacted. It is possible to "encapsulate" the modified resole phenolic as an alkoxy-modified resole resin phenolic. In encapsulation, the hydroxy group is converted to an alkoxy group by conventional methods, which will become clear to those skilled in the art from the information contained in the disclosure.

The resoles also include a terpolymer of phenol, furfuryl alcohol (or furfural aldehyde), and furfuraldehyde.

A terpolymer of phenol, furfuryl alcohol and furfuraldehyde is prepared from the catalytic reaction of phenol, furfuryl alcohol and furfuraldehyde, where the catalyst is a water-soluble multivalent metal salt and where the reaction is carried out under essentially aqueous conditions. The water-soluble salts of multivalent metal ions that can be used as the catalyst in the present invention are less expensive than the organic solvent salts soluble in equal equivalents of the metal ion that are used in the process disclosed in Wuskell's U.S. Patent Application No. 4,255,554. The use of a water-soluble multivalent metal salt eliminates the need to control the pH for the reaction required using an acid catalyst. However, the reaction catalyzed by the multivalent metal salt must be carried out at a pH below 7. When uncontaminated phenol, formalin, furfuryl alcohol, and zinc or lead acetate are mixed in the appropriate proportions, the pH is always below 7.

The water-soluble multivalent metal salts used as catalysts to prepare this terpolymer include multivalent ions of:

manganese, zinc, cadmium, magnesium, cobalt, nickel, tin, copper, iron, lead, and calcium.

The preferred catalysts are zinc acetate or lead acetate, and mixtures thereof.

The terpolymer reaction can be carried out by initiating the reaction of furfuryl alcohol with aldehyde at a temperature of 85°C to 105°C, under atmospheric pressure, then adding phenol, and continuing the reaction until it reaches a viscosity of 100 to 10,000 cP, preferably 200 to 5000 cP, measured at a temperature of 25°C. However, the reaction can be carried out at higher temperatures of up to 140°C in pressurized reaction vessels, taking care to ensure that the reaction mixture does not boil under these high conditions. The reaction may also be carried out by starting the phenol with aldehyde, then adding furfuryl alcohol, and continuing the reaction until it reaches a viscosity of 100 to 10,000 cP, preferably 200 to 5,000 cP, measured at a temperature of 25°C. Alternatively, the reaction can be carried out by reacting phenol, furfuryl alcohol and furfuraldehyde together in the presence of water-soluble divalent metal salt catalysts. The resulting terpolymer of phenol, furfuraldehyde and furfuryl alcohol may be used as is or diluted with any suitable solvent, including furfuryl alcohol or water.

In general, the molar ratio of phenol to furfuryl alcohol can vary from 0.1:1 to 10:1, respectively. The molar ratio of furfuraldehyde to phenol + furfuryl alcohol can vary from 0.5 : 1 to 2 : 1, respectively, in moles of CH2O : phenol + furfuryl alcohol. The amount of catalyst can vary from 0.2% to 8% by weight of the total amount of phenol and furfuryl alcohol.

Although the reaction has been described in terms of furfuraldehyde, it is possible to use other aldehyde compounds with the general formula: R-CHO, where R is a hydrocarbon radical containing from 1 to 8 carbon atoms such as acetaldehyde, propionaldehyde, furfuraldehyde, paraformaldehyde, which is Low molecular weight solid polymer of formaldehyde, etc. The preferred form of formaldehyde is in an aqueous form such as formalin.

It is possible to use furfuryl alcohol or substituted furfuryl alcohol compounds with formula I:

<img file="SA2587B1_D0001.tif" />

Whereas, R3 can be an alkyl, aryl, alkenyl, alkylol, alkoxy, aryloxy, halogen, hydrogen, or hydroxy radical. The preferred compound is furfuryl alcohol.

In addition, although phenol is the preferred phenolic reactant, other substituted phenols can also be used, particularly phenols with formula II:

<img file="SA2587B1_D0002.tif" />

Whereas R4, R5, and R6 individually are hydrogen, hydrocarbon radicals, oxyhydrocarbon radicals, hydroxy radicals, or halogen radicals, and they have substitution such that there are either two ortho positions, or one ortho and para positions, or ortho and para positions do not have substitution. In general, the phenol compounds that can be used are those suitable for the preparation of phenolic resins. Some examples are:

o-cresol, m-cresol, p-cresol, octyl phenol, nonyl phenol, 3,5-dimethoxy phenol, p-tert-butylphenol, p-butoxyphenol, resorcinol, 3,5-xylenol, 3-5-diethylphenol, catechol , 3,5-dibutylphenol

And so on.

After being used as coatings, these ternary polymers can be treated with curing materials such as an acid catalyst such as ammonium chloride or ammonium sulfate. The ternary polymers were also disclosed in US Provisional Patent Application No. 385578/60, filed on June 5, 2002, and are incorporated herein by reference.

If required, the coating of the Resole or the Resole powder may contain a curing substance, for example hexamethylenetetramine.

2. Resins containing novolak polymer

One embodiment of the present invention uses a powder comprising phenol-aldehyde novolak polymer.

A novolak can be any novolak used with proppant materials. Novolak can be obtained by reacting a phenolic compound with an aldehyde in a strongly acidic pH region. Suitable acid catalysts include strong mineral acids such as sulfuric acid, phosphoric acid, and hydrochloric acid, as well as organic acid catalysts such as oxalic acid, or para toluenesulfonic acid. An alternative method for preparing novolak polymers is to react phenol with aldehyde in the presence of divalent inorganic salts such as zinc acetate, zinc borate, manganese salts, cobalt salts, etc. The choice of catalyst can be important to guide the production of novolak polymers that have different ratios of ortho or para substitution with an aldehyde on the phenolic ring, for example zinc acetate is preferably substituted at the ortho position. Novolak polymers rich in ortho substitution, i.e. high ortho novolak polymers, may be preferred due to the greater cross-linking activity subsequent to polymer development. High ortho novolak polymers were described by Knop and Pilato in Reference:

Phenolic Resins, p. 50-51 (1985) (Springer-Verlag) and is incorporated herein by reference. High ortho novolak polymers are defined as novolak compounds where at least 60% of the total resin ortho substitution and para substitution is an ortho substitution, and preferably at least 70% of this total substitution is an ortho substitution.

Novolak polymer typically contains phenol and aldehyde in a molar ratio ranging from 1:0.85 to 1:0.4. Any suitable aldehyde can be used for this purpose. The aldehyde can be formalin, paraformaldehyde, formaldehyde, acetaldehyde, furfural, benzaldehyde or other aldehyde sources. Furfuraldehyde itself is preferred.

Novolak resins are preferably low free phenolic novolak resins with less than 1 wt% and preferably less than 0.6 wt% free phenol.

The molecular weight of novolak will vary from 500 to 10,000, and preferably from 1,000 to 5,000 depending on its intended use. The molecular weight of novolak and other polymers in this description of the present invention is based on average molecular weight unless otherwise stated. It is particularly preferable to use high ortho novolak resins.

Novolak resin compositions typically include at least 10 weight percent novolak polymer, preferably at least 20 weight percent novolak polymer, and most preferably 50 to 70 weight percent novolak polymer. The remainder of the resin composition may include cross-linking agents, modifiers, or other appropriate components. The phenolic moiety of novolak polymer is chosen from phenol compounds with formula III or bisphenols with formula IV, respectively.

<img file="SA2587B1_D0003.tif" />

<img file="SA2587B1_D0004.tif" />

Whereas, R and R1 individually are an alkyl, aryl, aryl alkyl, or H. In Formula III, R and R1 are preferably meta to the corresponding hydroxy group on the corresponding aromatic ring. Unless otherwise specified, an alkyl is defined as having 1 to 6 carbon atoms, and aryl is defined as having 6 carbon atoms in its ring. In formula IV, An alkylidene is a divalent organic radical with the formula V;

<img file="SA2587B1_D0005.tif" />

V.

When When It is preferable that the halogen atom be fluorine or chlorine. In addition, it is preferable for the cycloalkylidene to be replaced with fluorine or chlorine on the cycloalkylidene moiety.

A typical phenol with formula III is a phenol alone. Typical formula IV bisphenols include bisphenol A, bisphenols C, bisphenols E, bisphenols F, bisphenols S, or bisphenols Z.

Novolak polymers may include any one of the phenols of Form III, the bisphenols of Form IV, or a combination of one or more of the phenols of Form III and/or one or more of the bisphenols of Form IV.

For practical purposes, novolak phenolic polymers do not harden by heat, but remain soluble and molten unless a hardener (cross-linking agent) is present. Hence, when curing novolak resin, a cross-linking agent is used that includes hexamethylenetetramine (HEXA), paraformaldehyde, oxazolidines, melamine resin, other aldehyde donors and/or resole polymers described above. Each of these cross-linking materials can be used alone or in combination with other cross-linking materials. The resole polymer may contain a phenol with or without substitution.

A powder composition of novolak resin according to this invention comprises 25 weight percent of HEXA and/or 90 weight percent of resole polymers based on the total weight of the coating composition. Where HEXA is the sole cross-linking agent, HEXA comprises 5/25 weight percent resin. Where the phenol-aldehyde resole polymer is the sole cross-linking agent, the resin contains from 20 to 90 weight percent of the resole polymer. The composition may also include combinations of these binders.

To prepare novolak phenolic polymers using one or more formula III phenols, the phenol is mixed with an acid catalyst and then heated. Next, an aldehyde, such as a 50 wt% solution of furfuraldehyde, is added to the hot phenol and the catalyst at high temperature. The water resulting from the reaction is removed by distillation to obtain molten novolak. The molten novolak is then cooled, disassembled and ground into powder.

To prepare novolak polymers using Formula IV bisphenols, the bisphenols are mixed with a solvent, such as n-butyl acetate, at high temperature. An acid catalyst such as oxalic acid or methanesulfonic acid is then added, mixed with bisphenols and then with an aldehyde, typically formaldehyde. The reactants are then refluxed. It is noted that the preparation of novolak resin occurs under acid or divalent metal (e.g. Zn, Mn) catalysis, where bisphenols are present in a greater equimolar amount relative to the aldehyde source. After reflux, the water is collected by azeotropic distillation using n-butyl acetate. After removing water and n-butyl acetate, the resin is broken down to obtain the resin products. Alternatively, polymers can be prepared using water as a solvent.

Novolak polymer can also optionally be modified by adding VINSOL, epoxy resins, bisphenols, waxes or other known resin additives. One of the stages of preparing a phenol novolak polymer modified by alkylphenols is to combine alkylphenols with phenol in a molar ratio higher than 0.05:1. This combination is reacted with a formaldehyde source under acid or divalent metal (such as Zn, Mn) catalysis. During this reaction, the combination of alkylphenols and phenol exists in molar excess relative to the furfuraldehyde present.

When needed, novolak polymers of phenol-aldehyde or novolak polymers of bisphenols-aldehyde can be modified by reacting these polymers with an additional amount of aldehyde using a basic catalyst. The typical stimuli used are:

sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide (or lime), ammonium hydroxide and amines.

In the case of phenol-aldehyde polymers or bisphenols-aldehyde polymers, the molar ratio of aldehyde added to the phenolic moiety, based on the monomer units of the phenolic moiety in Novolak, ranges from 0.4:1 over 3:1, and preferably from 0.8:1 to 2:1. . This results in the achievement of a crosslinkable (reactive) polymer with different chemical structures and generally greater molecular weights than resole polymers obtained by a one-step process involving initial mixing of bisphenol monomers and aldehyde using an alkaline catalyst in the same molar ratio as the mixture of aldehyde and bisphenols. Moreover, it is practically convenient to use different aldehyde compounds at different boilers of polymer preparation. These polymers can be used alone or with other polymers such as novolak from phenol-aldehyde, novolak from bisphenols-aldehyde, or combinations thereof, in the form of a cross-linking agent, or as a component of cross-linking agents, which can be used with typical cross-linking agents Others are like those described above for novolak polymers.

3. resins polyester

An embodiment according to the present invention uses a powder comprising a reactive polyester polymer.

The term "polyester", as used herein, includes both "homopolyesters" and "copolyesters" and refers to a synthetic polymer prepared by polycondensation of a bifunctional carboxylic acid with at least one bifunctional hydroxyl compound, such as a diol or a diol component. glycol. Typical polyesters are those containing unsaturated (vinyl) end groups that are processed through the use of peroxide catalysts. These polyesters can be blended with other monomers to incorporate a desired property. Polymerization catalysts such as benzoyl peroxide can also use metal catalysts to accelerate processing such as cobalt salts.

Specifically, powder polyesters include polyacrylates having a hydroxy functional group that reacts with the resole compounds. These useful polymers according to the invention include polyhydroxy polyesters. Polyhydroxy polyester polymers (functions of 2 or more) are produced from the reaction of polycarboxylic acids or anhydrides (typically isophthalic acid and...

phthalic acid or anhydride, maleic acid or anhydride, fumaric acid, sebacic acid, azelaic acid, adipic acid, trimellitic acid or anhydride

etc.) with polyhydroxy materials such as:

ethylene glycol, propylene glycol, neopentyl glycol, butylene glycol, 1,4-butanediol, hexylene glycol, 1,6-hexanediol,

And polyglycols such as: diethylene glycol or triethylene glycol, etc., and triols such as glycerine, trimethylol ethane, trimethylol propane, etc., and other highly functional alcohols such as pentaerythritol, sorbitol, mannitol and the like. Polyhydroxy polyesters are also described in US Patent Application No. 4920199 and are incorporated herein by reference.

4. acrylic polymers

The acrylate polymers for use in reactive powders according to the present invention are polymers commonly known as acrylics, polyacrylates, or acrylate polymers. Some acrylate monomers (polymer components) used to form acrylate polymers can be:

acrylic acid, butyl acrylate, 2-ethylhexyl acrylate, methyl acrylate, ethyl acrylate, acrylonitrile, n-butanol, methyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate and TMPTA.

The acrylate ion (CH2=CHCOO-) is an ion of acrylic acid. Acrylates are salts and esters of acrylic acid. They are also known as propenoates (since acrylic acid is also known as 2-propenoic acid). Acrylates contain vinyl groups, more specifically, two carbon atoms double bonded to each other, directly attached to the carbonyl carbo atom. Acrylates and methacrylates (methacrylic acid salts and esters) are common monomers in acrylate polymers. Spray dried acrylate polymer is also suitable. Specifically, the powder acrylates include polyacrylates having a hydroxy functional group or polyacrylates having an amine functional group, reacted with the resole compounds.

5. urethane resins

Polyurethanes resins are manufactured by mixing a polyisocyanate component, a polyhydroxy component or a polyamine component with a catalyst. Typically, the polyhydroxy component is a polyhydroxy phenolic component dissolved in a solvent. The polyamine component can be multifunctional, and is selected to produce reactive polyurethane that is also oligomerized. In general, solvents are mixtures of hydrocarbons and polar organic solvents such as organic esters. Examples of hydrocarbon solvents include aromatic hydrocarbons such as benzene, toluene, xylene and ethyl benzene, high-boiling aromatic hydrocarbon mixtures, heavy naphtha compounds, and the like.

a. The polyhydroxy component

The polyhydroxy component is generally a phenolic resole resin or alkoxy modified resole resin as described above.

B. isocyanates compounds

The component of isocyanates can be very diverse, comprising two or more functional groups. As defined herein, polyisocyanates include isocyanates with diisocyanates, triisocyanates, etc. Examples of useful isocyanates are polyisocyanates, such as:

Tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, and mixtures thereof, specifically crude mixtures thereof, are commercially available. Other typical polyisocyanates include:

methylene-bis-(4-phenyl isocyanate), n-hexyl diisocyanate, naphthalene-1,5-diisocyanate, cyclopentylene-1,3-diisocyanate, p-phenylene diisocyanate, tolylene-2,4,6-triisocyanate, and triphenylmethane. 4,4',4''-triisocyanate.

Higher isocyanates are provided by the liquid reaction products of (1) di-isocyanates, (2) polyols or polyamines, and the like. In addition, isothiocyanates and mixtures of isocyanates can be used. In addition, several commercially available impure and crude polyisocyanates were considered. According to the invention, it is particularly preferable to use polyaryl polyisocyanates having the following general formula VI:

Whereas, R is chosen from the group consisting of hydrogen, chlorine, bromine, and alkyl groups with 1 to 5 carbon atoms; The X is chosen from the group consisting of hydrogen, alkyl groups with 1 to 10 carbon atoms and phenyl; n has an average value that generally ranges from 0 to 3. The preferred polyisocyanates can vary in the specific system in which the powder is used.

The urethane compounds are disclosed in Geoffrey's U.S. Patent Application No. 5,733,952.

e. Addition materials

Additives are used in special cases to meet special requirements. Resin systems according to the invention can include a wide variety of additives.

The resin may include one or more additives such as a coupling agent, typically added to a liquid resin, such as silane, to promote adhesion of the coating to the substrate.

Such coupling agents, for example, include organic silane compounds known as coupling agents. Examples of useful coupling agents of this type include amino silanes, epoxy silanes, mercapto silanes, hydroxy silanes, and ureido silanes. In particular, it is preferable to use functional organic silanes as coupling agents to improve organic-inorganic interfacial adhesion. These functional organic silanes are characterized by having the following formula VII:

R13Si(OR14)3 VII,

Whereas R13 is a reactive organic function, and OR14 is an already changed alkoxy group such as OCH3 or OC2H5. Silanes with an amino functional group are particularly useful for coupling phenolic resins or furan resins to silica, an example of which is Union Carbide A1100 (gamma aminopropyltriethoxysilane). The silane may be pre-mixed with the resin or added to the mixture separately.

The organic coating may optionally include additives such as silicones, surfactants, wetting agents, dyes, pigments, and flow modifiers (e.g., flow control agents, flow enhancers). Hardeners, crosslinking agents, foaming agents, initiators, thermal stabilizers, and light stabilizers. Antioxidants, flame retardants, anti-drip agents, antiozonants, stabilizers, anti-corrosion additives, mold release agents, fillers, and anti-static agents. -static agents, waxes, etc., or a combination including at least one of the above.

Surfactants can be anionic, nonionic, cationic, amphoteric, or mixtures thereof. Certain surfactants can also act as flow control agents. Other additives include moisture-resistant additives or heat-resistant additives. Of course, additives can be added in combination or individually.

When needed, the organic coating can contain an anti-dust additive in the form of a thermoplastic elastomer to reduce dust for a particle that is the same except that it lacks the thermoplastic elastomer. Some anti-dust additives include copolymers of ethylene and butylacrylate (ENABLE from Exxon-Mobil). Other examples include Novolak polymers modified with NBR (rubber) and resoles that act as “impact modifiers.”

If necessary, the organic coating may include a shock modulator. A shock rate can impart elastic properties to the organic coating. Suitable shock modifiers include natural and synthetic elastomeric polymers, typically derived from monomers such as olefins (e.g., ethylene, propylene, 1-butene and 4‑methyl-1-pentene), alkenylaromatic monomers (e.g., styrene and α-methylstyrene), compounds conjugated dienes (such as butadiene, isoprene and chloroprene), vinylic carboxylic acids and their additives (such as vinyl acetate, acrylic acid, alkylacrylic acids, ethyl acrylate, methyl methacrylate and acrylonitrile). It includes homopolymers, random, block, diagonal block, grafted, core-shell copolymers, or a combination comprising at least one of the foregoing.

A particularly useful class of shock modifiers includes shock copolymers of AB (diblock) and ABA (triblock), and core- and shell-type grafted copolymers of alkenylaromatic and diene compounds, particularly those comprising styrene and either butadiene or isoprene blocks. The conjugated diene blocks can be partially or fully hydrogenated, can be represented as ethylene-propylene blocks and the like and have properties similar to those of olefin block copolymers. Examples of suitable triblock copolymers of this type are:

polystyrene-polybutadiene-polystyrene (SBS), hydrogenated polystyrene-polybutadiene-polystyrene (SEBS), polystyrene-polyisoprene-polystyrene (SIS), poly(α-methylstyrene) -polybutadiene-poly(α-methylstyrene) and poly(α-methylstyrene) -polyisoprene-poly(α-methylstyrene).

Particularly preferred triblock copolymers are commercially available as HYCAR from Novion, or Kraton D and Kraton G from Shell.

There are also suitable solidification modifiers such as core-shell grafted copolymers such as ionic unit resins, which can be partially or completely neutralized by metal ions. In general, core-shell graft copolymers have a core of dominant conjugated diene or cross-linked acrylate rubber and one or more polymerized shells, derived from monoalkenylaromatic and/or acrylic alone or in combination with other modifiers. Other shock modifiers include the types described above that include units with polar groups or active functional groups as well as multiple polymers such as:

Thiokol rubber, polysulfide rubber, polyurethane rubber, polyether rubber (as polypropylene oxide), epichlorohydrin rubber, ethylene-propylene rubber, thermoplastic polyester materials, thermoplastic ether-ester materials, and the like, as well as mixtures comprising any One of the above. A suitable shock rate among ionic unit resins is Surlyn, which is provided by Du Pont.

When multiple layers are used in an organic encapsulation layer, shock modifiers can be used in any of these layers. In general, it is desirable to use shock modifiers in the layer on the substrate. Shock rates may be used in amounts greater than or equal to 0.5, preferably greater than or equal to 1, and most preferably greater than or equal to 1.5% by weight based on the total weight of the organic coating layer. In general, it is recommended to use a shock modifier of less than or equal to 20, more preferably less than or equal to 15, and most preferably less than or equal to 10% by weight of the total weight of the organic coating layer.

And the. Manufacture of coated particles

To make a coated proppant, or particle for gravel pack, the appropriate substrate (e.g., single particle, composite particle, or hybrid particle), wet resin, and dry resin powder are mixed under conditions to provide a layer composition. Processable packaging. In embodiments using composite particles or hybrid particles as substrates, the organic material used in the outer coating layer may be the same or different from that used in the composite substrate or hybrid substrate, provided that the coating resin material is curable and Curing the resin composite substrate or hybrid substrate at least partially.

The substrates, together with the desired thermoset polymer or thermoset polymer product, are fed into a mixing device and mixed to form a suitable first mixture at a temperature ranging from 10°C (50°F) to 66°C (150°F), Preferably from 21°C (70°F) to 49°C (120°F). Thermosetting resole polymers or materials producing thermoset resole polymer are liquids at room temperature. The substrates are not normally preheated before being mixed with the liquid thermosetting polymer or the thermosetting polymer producing material. When mixed, the liquid thermoset resole polymer or the product of the thermoset resole polymer is applied to the substrates to form an organic coating. It is recommended to add a coupling agent to the mixture at some point before or while the substrate and liquid resin are mixed. Suitable coupling agents are described in this invention.

Mixing can be performed in a device that uses shear force, extensional force, compressive force, ultrasonic energy, electromagnetic energy, thermal energy, or a combination that includes at least one of the aforementioned forces and energies. It is implemented in processing equipment, where the aforementioned forces are applied by a single screw, multiple screws, or intermeshing co-rotating or counter-rotating screws. rotating screws, non-intermeshing co-rotating or counter rotating screws, reciprocating screws, screws with pins, barrels with pins, screen packs, rollers rolls A helical rotating device, or combination involving at least one of the aforementioned forces. Examples of mixing equipment include extruders such as single or twin screw extruders, Buss pastries, helicones, EIRICH mixers, WARING mixers, HENSCHEL mixers, Barber Green batch mixers, Ribbon mixers, or the like.

The non-reactive powder and/or reactive powder is then added to the first mixture of coated particles and mixed for sufficient time to form a free-flowing secondary mixture of resole-coated particles in which the non-reactive powder and/or reactive powder, preferably novolak or resole, is incorporated and adhered. With a coating layer. The amount of liquid resin coating and the amount of powder are chosen depending on the required amount of coating to be used. Typically, the amount of liquid and powder resin can change depending on the temperature and time of adding the different ingredients. The typical ratio can be adjusted to avoid extremes in processability, i.e. adherent particles on the one hand and dust-like particles on the other. Product performance can depend on the level of resin used for the liquid and powder resin combined as well as the resin and powder chosen.

When needed, one or more layers of liquid and powder resin can be used. Additional coatings can be used by coating the single resin particle and the powder with an additional liquid resin coating, then adding an additional portion of the powder to the additional liquid coating, and repeating this as needed. Preferably, sufficient resin should be used to achieve a loss on ignition (integrated by weight of coating layer) of 0.3 to 5 wt%, preferably 0.3 to 4 wt% due to one or more outer layers of the resole coating curable with reactive powder.

Typically silane is added to the sand in a mixer, then, after 10 to 20 seconds of adding silane, such as 15 seconds, liquid resole is added. Preliminary mixing between silane and resole can then be performed. For example, 7 to 10.4 grams of liquid resole (which is 65% solids) are used per 1,000 grams of sand substrate. After 30 to 60 seconds after adding the resole, the reactive powder is added.

It is preferable that the powder be added 60 seconds after the first silane, which is added 45 seconds after the liquid resole. However, these addition times are sensitive to mixing speed, ambient temperature, and mixer design. In a particularly useful example for coated particles produced under laboratory conditions (23C using a Hobart mixer), silane is added to the substrate and mixed for 15 minutes; Then add the liquid resole resin while mixing continues for an additional 45 seconds; Powder addition is then continued for an additional 240 seconds (300 seconds total cycle) before the free-flowing dry particles are terminated.

It is recommended to add a lubricant to the mixture at a point before the product “breaks down” into free-flowing particles. It is preferable that the lubricant be a liquid at the mixing temperature and have a high enough boiling point so that it is not lost during the mixing process. Suitable lubricants include liquid silicone such as Dow Corning Silicone 200, mineral oil, paraffin wax, petrolatum, cocamidopropyl-hydroysultaine (Chembetatine CAS) from Chemron Corp., Paso Robles CA, or the synthetic lubricant ACRAWAX CT, which is bis -stearamide from diamine, available from Glyco Chemicals, Inc., Greenwich, Connecticut). The amount of lubricant can range from 0.01 or 0.03% to 0.5% by weight depending on the weight of the particulate matter).

Additional low levels of non-reactive powders of organic or inorganic filling material such as silica flour, wood flour or talc can be added as curing aids after mixing the reactive powder with the coated substrates or simultaneously by mixing the reactive powder with the coated substrates. The non-reactive filler powders, if any, shall be less than 10% of the amount of reactive powders. Non-reactive organic or inorganic filling powders typically have average particle sizes of 2 to 30 micrometers.

Particles that have processable coatings are then extracted.

In an example of manufacturing coated particles, a mixture comprising the substrate, the thermosetting polymer or the product producing the thermosetting polymer to be used for the organic coating, novolak powder or resole powder and any optional additives is fed into a mixer such as an EIRICH mixer. Mixing is first performed at the first speed for a given time. Then, this mixing speed is changed. Changing the mixing speed promotes the formation of an organic coating around the substrate to create particles of the desired size (more specifically, 200 to 800 microns). To obtain a desired density of coated particles, process variables can be changed. For example, the amount of fill material or the amount of organic matter can be increased to change the density of the coated particles.

g. Particle variables

The following variables can be useful when determining particle properties in accordance with the invention.

1. Quantity of resin

The amount of resin can be determined by measuring the loss on ignition (LOI). Loss on ignition is typically determined in a two-hour furnace test, which begins with preconditioning a series of lidded crucibles in a furnace preheated to 927°C (1700°F). Then the crucible with the lid is placed in the furnace at a temperature of 927 degrees Celsius (1700 degrees Fahrenheit), and the furnace is allowed to be reheated again to a temperature of 927 degrees Celsius (1700 degrees Fahrenheit), and the temperature of the crucible crucible with the lid is kept at a temperature of 927 degrees Celsius (1700 degrees Fahrenheit) for 15 minutes. Crucibles with pre-conditioned lids are placed in a desiccator containing standard desiccant and allowed to cool to room temperature. The crucible with the prepared lid is then weighed, and 8 g of sand coated with resin is placed in the crucible. The crucible with lid and sample are then reweighed. The coated crucible and the sample are then placed in the oven at a temperature of 927°C (1700°F), and the oven is allowed to be reheated again to a temperature of 927°C (1700°F), and the temperature of the samples is maintained for two hours after the temperature is restored. Oven to 927°C (1700°F). The crucible with lid and sample are then transferred to the desiccator and allowed to cool to room temperature. The cooled lidded crucible containing the sample is then reweighed using an analytical balance. Loss on ignition is calculated for each sample by calculating the difference between the original and final sample weight.

2. Particle size

In general, an encapsulated particle has an average particle size of 200 to 2000 micrometers (70 mesh to 10 mesh). In one embodiment, the coated particle has an average particle size of 300 to 1000 micrometers (50 mesh to 18 mesh). In another embodiment, the coated particle has an average particle size of 350 to 650 micrometers (45 mesh to 28 mesh). Coated particles can have a bi-peak or higher distribution. Typically, reactive and/or non-reactive powder has an average particle size of 74 microns (200 mesh) 210 microns (70 mesh) or smaller.

3. Density

It is recommended that the coated particles have a bulk density of 0.75 to 0.95 g/cm3. In one embodiment, the coated particles have a bulk density of 0.8 to 0.9 g/cm3. In one embodiment, the coated particles have a bulk density of 1.7 to 3.6 g/cm3. The coated particle has a bulk density of 1 to 4 grams per cubic centimeter (g/cc) as determined by API RP 58 using isobutanol. In one embodiment, the coated particle has a bulk density of 1.1 to 3 g/cubic centimeter. In one embodiment, the coated particle has a bulk density of 1.15 to 2 g/cubic centimeter. In one embodiment, the coated particle has a bulk density of 1.6 to 3.6 g/cubic centimeter. It is possible to change the density by changing the density of the cores/substrates, by changing the filter selection, or by both.

4. Unlimited compressive strength

The compressive strength of uncured proppant material is defined as measured according to the following procedure, known as the unconfined compressive strength test or UCS test. In this test, a 2 wt% KCl solution (treated with a small amount of detergent to enhance wettability) is added to the proppant. The KCl and proppant solution (2.7 kg to 8.2 kg, typically 5.4 kg proppant per 3.78 L of KCl) are gently stirred to moisten the proppant. Dispersed air bubbles, if present, are removed. A wetting agent is used to remove bubbles when necessary. This slurry slurry (100 - 200 grams depending on density) is transferred to double stainless steel duplicate cylinders 31.75 mm OD 254 mm, equipped with valves above and below for liquid diffusion and gas pressure as required, a pressure gauge with a zero reading of 140.63 kg/m2, and a floating piston. To transfer pressure to the sample. Typically at least 3 sample blocks, preferably 6, are loaded to give a length greater than twice the diameter of the finished block. The lower valve opens while stress is applied, allowing fluid to drain from the slurry, and then closes while temperature is applied. The cylinder is connected to a nitrogen cylinder and a pressure of 70.3 kg/m2 is applied to the cylinder, sending it with sliding pistons to the sample. Then the upper valve is closed and the lower valve remains open. (As the test temperature approaches the fluid valve on the die, the bottom valve (fluid valve) closes. Closing the fluid valve quickly can generate sufficient pressure, while the cell is heating, to prevent/reduce the intended closing stress on the proppant mass. Delayed closing of the valve can allow a significant amount of fluid to be lost from the mass through evaporation or boiling.

The double cylinders containing the sample are transferred to an oven preheated to the desired set point, specifically 93.3°C, and remain in the oven for 24 hours. Stress and temperature are maintained during curing time. The stress should be kept at 10%. During the kiln curing process, the loose curable proppant particles become a cohesive mass. At the end of the 24 hours, the cylinders are removed, the pressure and fluid are quickly released, and the 25.4 mm (152.4 mm) contact mass sample is passed through the cylinder. The sample is allowed to cool, air-dried for 24 hours, and is cut (typically sawed) into compression blocks with a diameter:length (D:L) ratio of 1:5 or greater. Air drying is performed at a temperature below 49°C (120°F). Typically, both ends of each block are smoothed to create flat, parallel surfaces and cut to maintain a diameter:length ratio (D:L) of 1:2.5 or greater.

The pressure blocks are installed in a hydraulic press and a force is applied between two parallel trays at a rate of 1814.4 kg/min until the block breaks. For blocks with compressive strength less than 35.2 kg/m2, a loading rate of 45.36 kg/min is used. The force required to break the block is recorded, copies are documented, and the compressive strength of each specimen is calculated using the equation below. The average of the copies is used to determine the value of this resin-coated proppant sample.

(Fc, psi) = 4 x Fg / {(px d2) [0.88 + (0.24d/h)]}

whereas

Fc = compressive strength (kilograms/m)

Fg = hydraulic gauge reading (force in kilograms)

p = pi (3.14)

d = block diameter (millimeters)

d = block length (mm)

The compressive strength of the blocks is determined using a hydraulic press, more specifically, a Carver press, Model #3912, Wabash, Indiana. The typical compressive strength of proppant materials according to the present invention ranges from 3.5 to 210.9 kg/m2 as detailed below. It has also been noted that the compressive strength test can be used to indicate whether a coating has been cured or is capable of being cured. Lack of cohesion or cohesion of coated particles, following a wet pressure of 70.3 kg/m2 at 200°C for a period of 34 hours, is indicative of a cured material.

5. Roundness

It is desirable for the coated particle to have a roundness of 0.7 to 0.9. There is a preferred roundness of 0.8. It is recommended that the coated particle have a sphericity of 0.7 to 0.9 as measured using API RP 58 (USA Recommended Procedure 58).

6. acidity of water extracts

The present invention relates to an experimental procedure for measuring the acidity of aqueous extracts of a resin-coated proppant. This procedure is not a measure of the acid solubility of a resin-coated proppant, but rather a measure of the effect of aqueous extracts (from the coating layer) on the pH of the water (or pH of the fracturing fluid system).

The acidity test (as related to resin-coated proppant) is a measure of the acidity levels of aqueous extracts of resin-coated proppant. This test relates to the effect that a resin-coated proppant (and the extractable aqueous components contained in its coating) will have on the pH of the frac fluid system that will be used to transport the proppant into a hydraulically induced fracture.

This is determined as follows: Prepare a large batch, 1000 ml, of slowly boiling distilled or deionized water, using the first hot plate and the large beaker. The heat is adjusted for a constant low or slow boiling action. The temperature should be 100°C (212°F) depending on the peak. Set the temperature setting to high on the second hot plate. 50 g of resin-coated proppant is placed in the 250 ml graduated beaker. The flask loaded with resin-coated backing material is placed on the second hot plate. Quickly, boiling deionized (distilled) water is added to the 125 ml mark to the resin-coated proppant flask, and stirred once to remove air bubbles. The mixture is left to reach the boiling point, the required time ranges from 15 to 30 seconds. Continue boiling for 3 minutes. Place the beaker in an ice bath, then stir, until the water temperature reaches 21–27°C (70–80°F). The curable backing material coated with partially cured resin will harden to a solid block. It is necessary to break the mass with a spoon while the suspension is cooling. Stirring is done first using a spoon to break up the mass of the backing material coated with resin, then stirring using a thermometer. Stir sufficiently to reduce the time required for complete cooling while the water is in the ice bath at a temperature at least as high as that of the liquid in the beaker.

After cooling the suspension back to room temperature, deionized water is added back to the beaker, up to the 125 mL mark, to replace any water lost during boiling; Immediately, the pH of the water layer is measured using a standard pH meter. The initial pH is recorded to 0.05 units. While the pH is being measured, the pH electrode is not in the proppant layer. Using 0.1 p sodium hydroxide, the pH of the suspension is titrated to pH = 9. The volume of titrant, required to reach the pH endpoint, is recorded to the nearest 0.05 ml. The pH of the end point is recorded to the nearest 0.05 units.

7. Acetone extraction test

The acetone extraction test is another way to determine if a coating or coatings are curable. In the acetone extraction method, the untreated resin portion is dissolved. This test is performed by placing a pre-weighed, 50 g, dried sample of resin-coated particles (using a known resin coating content) in a Soxhlet loop, and refluxing the acetone condensate over the material for 2 hours. After drying the treated sample, the change in resin content is expressed as acetone extracts. Specifically, since uncured resin is soluble in acetone, and cured resin is not soluble in acetone, reflux of acetone condensate will only remove the uncured portion. By weighing the sample before and after acetone reflux and determining a percentage change, the degree of treatment is calculated. For example, the weight loss of a typical cured sand coated with resin can be only 5% of the firing loss of the sample. Hence, a sample with a combustion loss of 2 g could have an acetone extract of 0.1 g. In contrast, the weight loss of fully curable sand coated with resin will be the firing loss of the sample. Hence, for a sample with a combustion loss of 2 g, the removal of 2 g by acetone extraction will reflect that the sample is 100% processable.

8. Temperature adhesion point test

The temperature adhesion point test is another indicator of whether a coating is curable. This test is performed by placing a coated material on a heated melting point rod and determining the lowest temperature at which the coated material will adhere. A "adhesion temperature" greater than 176.67°C (350°F) at the hottest end of the rod typically indicates a cured material, depending on the resin system used. The melting point rod is made of a brass metal rod (45.7 cm long and 5 cm wide) and is equipped with an electric heating element at one end. From here, a temperature gradient can be determined along the length of the rod and the temperature along the rod is monitored using thermometers or thermocouples.

Using a funnel, a homogeneous strip of 100 g of resin-coated substrate, such as sand, is placed on the heated rod and cured for 60 minutes. The rod is then trimmed to shake off any uncured proppant. The melting point is the lowest temperature at which the resin-coated sand forms a continuous mass and does not fall off the rod when it is ground to 90 degrees. Typically, the cured coating has an adhesion temperature range of 65.5 to 148.9 °C (150 to 300 °F), such as 93.3 to 121.0 °C (200 to 250 °F).

9. Wettability of particles in water

Wetability is performed to determine the amount of selected surfactant(s) needed to wet the proppant(s) to determine the amount of surfactant(s) needed to reduce aeration/air intake to zero.

A dilute surfactant solution is prepared and placed in a 25 ml glass burette. A typical dilution factor is 1:100. However, many surfactants can be tested as is. Next, 200 mL of 2% KCl are added to 300 mL brazallius (tail-shaped) flasks (deionized H2O can be used). Set the beaker under a VARIAC or agitator with a built-in speed control so that the blade is one-quarter inch above the bottom. The flask should be held in position using a ring holder and a clamp. The buret is then set to the appropriate position, the agitator switch is set to the off position, and the speed control is set to its highest setting, so as not to expel the contents of the flask (sand into the water). The stirrer is started, and the appropriate amount of proppant to be tested is added.

Table A shows typical ranges for proppant loading:

Table A: Propant loading ranges

9 /ml

q/200 mL

0.24

48

0.48

96

0.72

144

0.96

192

1.2

240

1.44

288 Favorite

After that, stir for 5 seconds, then stop and observe the air bubbles adhering to the granular surfaces of the proppant material. If no bubbles are observed, the proppant is considered to be fully hydrated. If there are air bubbles, add 1/4 ml of surfactant, restart the stirrer for 10 seconds, and air bubbles adhering to the proppant surface are again observed. If bubbles are again observed, the surfactant addition step is then repeated, stirring and observing until most of the bubbles are gone, then the excess surfactant is reduced to 1/8 ml. When bubbles are no longer observed, the volume of surfactant needed to wet the proppant is recorded.

The test is repeated as follows to duplicate the conditions of use and procedure in the field.

Another water sample is prepared, and to the water the exact amount of diluted surfactant is added (determined using the first procedure when the proppant was fully wet). The flask is then placed under the stirrer, and the stirrer is started. The appropriate amount of backing material is added. Stirring is done for 10 seconds, then the stirrer is stopped. The relative amount of air bubbles on the proppant surfaces is observed and recorded. If there are any bubbles in this step, continue titrating as before until the bubbles disappear and no more surfactant is needed. The additional volume of surfactant is recorded.

Calculate the volume of surfactant needed to completely wet the proppant.

Vv, (name of surfactant), L/1000 L (gal/1000 gal) = 1000 ((Vsurf FD) / Vfluid) at X lbm prop/gal

VM, (name of surfactant), L/1000 L (gal/1000 gal) = 119.831 ((Vsurf FD) / Mprop) per lbm prop/gal

whereas :

Vv is the volume of surfactant to wet the proppant, l/1000 liters (gal/1000 gal) at X lbm prop/gal

VM is the volume of surfactant to wet the proppant, l/1000 liters (gal/1000 gal) at X lbm

FD is a diluting agent, a bulk surfactant/volume diluent, dimensionless

Vsurf = experimental volume of reduced surface tension, ml

Mprop = mass of the proppant material tested

Vfluid = volume of water in the proppant/water mixture, ml

10. Turbidity test

The particles are subjected to turbidity testing as follows. Weigh 15.0 g of deionized/distilled water, treated with 0.1% FSO surfactant, place 15 g in a clean sample cell (Hach catalog #21228 or equivalent) and replace the cell screw cap. The FSO is a duPont Fluorosurfactant Zonyl FSO. The outside of the hive is wiped with lint-free paper. It must be ensured that no air bubbles adhere to the cell walls. The cell is placed in a turbidimeter (HACH Model 2100P), and the turbidity is read in NTUs. 5 g of the sample to be measured is weighed and placed in the cell. Using a Vortex mixer (Thermolyne Maxi-Mix 1 or equivalent), the sample/water mixture was stirred for 10 seconds. Again, the outside of the cell is organized using lint-free paper. The sample/cell is placed back in the turbidimeter and the turbidity is read 30 seconds after finishing mixing with the Vortex mixer. Turbidity is recorded in NTUs for this sample as “dust content”.

It is preferred that particles according to the present invention achieve a turbidity measurement of less than 100 NTU after being exposed to a ball mill time for 30 minutes, and/or less than 200 NTU after being exposed to a ball mill time for 60 minutes, and/or less than 150 NTU after being exposed to a ball mill time With balls for 60 minutes. Coated particles generally have a turbidity less than or equal to 250 as measured using API RP 56.

H. Use of particles in the form of proppant

The particles, as described in this invention, comprise processable coating layers. Hence, it can be injected into a subterranean formation and the coating layers can cure in the subterranean formation. It may be injected into the subterranean formation as a sole proppant, in the form of a 100% proppant (in hydraulic fracturing) or as a partial replacement for existing commercially available ceramic and/or sand-based proppant, resin-coated or uncoated, or Combinations such as coated particles of 10 to 50 weight percent of proppant injected into the wall. For example, after initially pumping precured proppant or uncured proppant into a wall, a curable proppant (according to the present invention) can be placed in the fracture closest to the wellbore or fracture holes. This type of fracture treatment is carried out without stopping to change the backing material, and this process is known in the industry as “tail treatment”.

In the case of curable proppant materials, the method may include curing the curable resin composition by subjecting the resin composition to sufficient heat and pressure in the subterranean formation to cause crosslinking of the resins and hardening of the curable proppant material in accordance with the present invention. In some cases, an activator may be used to facilitate hardening of the curable proppant material. In another embodiment, using a curable resin composition on the proppant, the method further comprises a low-temperature acid-catalyzed cure at temperatures as low as 21.1°C (70°F). Low-temperature acid-catalyzed treatment is disclosed in U.S. Pat. No. 4,785,554, which is incorporated in its entirety herein by reference.

The curable encapsulated particles according to the invention are particularly useful whether the encapsulated particles are used alone as a proppant or together with other proppant as a tail end after use of an uncoated proppant, a pre-cured coated proppant or another curable proppant To be in the part of the fracture closest to the well bore.

i. Use encapsulated particles as gravel filler or sand control

It is known that the hole of an oil or gas well is provided with gravel packing around the drill holes. A further feature according to the invention is that these gravel fillers can be provided with encapsulated particles according to the present invention.

It is possible to supply coated particles in standard sizes known to gravel used in gravel fills. Typically, the particle strength requirements of a proppant used in fractures with fill material are greater than for gravel fillers. Gravel pack can work to control sand to prevent formation particles from flowing from the formation into the well bore.

In gravel packing operations, the coated particles can be suspended in a carrier fluid that is pumped into a borehole in which the gravel pack is placed. The carrier fluid in the subterranean zone seeps out and/or returns to the surface while the encapsulated particles are left in the subterranean zone. The resulting gravel pack acts as a filter to separate the formation sand from the produced fluids while allowing the produced oil and/or gas to flow into the well bore. Therefore, the method for creating a gravel fill involves suspending the coated particles in a carrier fluid to form a suspension; Pumping the suspension into a wellbore; The carrier fluid is drained to form a gravel filling. Once the injected particles are fixed in position, they cure to form a solid, permeable barrier that restricts sand movement.

As another example, coated particles can be used by filling a cylindrical structure with a particulate material containing resin as a proppant and inserting it into the well bore. Once placed in the desired position, the encapsulated particles act as a filter or barrier to prevent backflow of sand, other proppant materials, or subterranean formation particles. This is a great advantage in eliminating the backflow of particulate matter to the ground equipment at the surface. Here, pre-grouted barriers are used, in which sand/resin-coated porcelain is put through a curing process before the barrier assembly is placed in the well.

The following examples, which are intended to be exemplary, not limiting, illustrate compositions and methods of fabrication of some of the various embodiments of coated particles described herein.

Examples

The following examples serve to illustrate the present invention. Unless otherwise stated, all parts and percentages are by weight, and all screen mesh sizes are standard US screen sizes. In examples, the silane is Union Carbide Corporation A1100 adhesion enhancer. The proppant was coated with EX262E, a commercial phenol-formaldehyde resole resin manufactured by:

Hexion Specialty Chemicals, Inc., Louisville, Kentucky. The powder used with the support filler was a layer of SD909A (phenol-formaldehyde novolak powder) (using 15% hexamethylenetetramine), a commercial phenol-formaldehyde novolak manufactured by Hexion Specialty Chemicals, Inc., Louisville, Kentucky. The SD909A powder has a particle size range to pass the 74 micron 200 mesh barrier.

Example No. 1

The experiment was performed to determine the properties of an encapsulated particle in accordance with the present invention. The packaging cycle was as follows. 1000 g of CarboProp 12/18 ceramic particles of medium density at room temperature were added to a Hobart laboratory mixer. Then the mixer stirrer was turned on. Then 0.8 g of A1100 (aminopropyltriethoxysilane) was added, and the timer was started, (minute zero). After 30 s, 10 g of EX262E (liquid resole of phenol-formaldehyde) was added. When the timer was at 2 minutes, 18.4 g of novolak SD909A phenol-formaldehyde powder (using 15% hexamethylenetetramine) was added with continuous mixing (2.4% of the total organic layers on the particles). When the timer was at 12 minutes, the mass was free-flowing and was removed from the mixer. The product was then tested for 24 hours with a UCS bond strength test under conditions of pressure of 70.31 kg/m2 and temperature of 93.34 °C (200 °F), to obtain a pressure of 41.5 kg/m2.

Example No. 2

This experiment was carried out to determine the properties of an encapsulated particle in accordance with the present invention. The packaging cycle was as follows. 1000 g of CarboProp 12/18 ceramic particles of medium density at room temperature were added to a Hobart laboratory mixer. Then the mixer stirrer was turned on. Then 0.8 g of A1100 (aminopropyltriethoxysilane) was added, and the timer was started, (minute zero).

After 30 s, 10 g of EX262E (liquid resole of phenol-formaldehyde) was added. When the timer was at 2 min, 33.2 g of SD672D powder (novolak from phenol-formaldehyde, without hexamethylenetetramine) was added with continuous mixing (4% of the total organic layers on the particles); The SD672D powder had a particle size of +/- micron mesh. When the timer was at 12 minutes, the mass was free-flowing and was removed from the mixer. The product was then tested for 24 hours with a UCS bond strength test under conditions of pressure of 70.3 kg/m2 and temperature of 93.34°C (200°F) to obtain a pressure of 75.6 kg/m2.

Example No. 3

A curable resin layer was developed by adding 0.4 g of coupling agent (silane A-1100) to 1 kg of substrate with constant stirring. Liquid resole (OWR-262E), available from Hexion Specialty Chemicals, Inc., Louisville, Kentucky, was added at 15 s to the cycle after silane addition.

Novolak resin powder, FD900-A (with 7% hexamethylenetetramine used to prepare samples C, D, and G), or novolak resin powder, SD-909A, available from Hexion Specialty Chemicals, Inc., Louisville, Kentucky, was then added at min. 1 per cycle time.

The materials were mixed for an additional 4 minutes and discharged from the mixing device. Using the procedure described above, analyze changes in analytical properties during the evaluation of alternative resins, resin levels, particle sizes, and substrates. Therefore, the concentration of hexamethylenetetramine in novolak powder varied from 7 to 15% depending on the powder used in each formulation (see Tables 1, 2, and 3 for all analytical data).

Figure 5 is a photograph of a sample of particles prepared in the laboratory (as is) for Sample A at 10x magnification.

Figure 6 is a photograph of a sample of particles prepared in the laboratory (as is) for Sample B at 10x magnification.

Figure 7 is a photograph of a laboratory-prepared block of particles for Sample B at 10x magnification after an unlimited compressive strength test at a pressure of 70.3 kg/m2 (70.31 kg/m2).

Figure 8 is a laboratory-prepared particle sample of sample B at 10x magnification after hot tensile strength testing.

An agglomeration analysis was performed on a given material by placing 50 of the coated materials in a 1 kg cylindrical container and placing them in a preheated oven for 24 hours at temperatures ranging from 40.56 to 60.0°C and 105-140°F (see Tables 1, 2, and 3 for analysis data).

schedule

The property that was measured

Sample number

a

B

C

Dr

Sand, API micron size, normal

210/420

210/420

210/420

210/420

Addition of Ceran A-1100, wt = g / time = sec

0.4/zero

0.4/zero

0.4/zero

0.4/zero

Add resole

OWR 262E, w = g / time = sec

10.4/15

7/15

8.6/15

5.2/15

Add energy

SD-909A, w = g / time = sec

23/60

20/60

Add energy

FD-900A, weight = g / time = sec

21.5/60

11.5/60

Discharge, time = seconds

300

300

300

300

Resin content, loss on ignition, % by weight

2.98

2.14

2.46

1.19

Melting point (adhesion), Fahrenheit [Celsius]

204 [96]

214 [101]

Less than 185 [85]

Less than 185 [85]

Hot tensile strength, kilograms per square meter

44

Particle size distribution

8.4

3.1

American standard sieving number [mm]

30 [0.589]

0.1

0.1

zero

zero

40 [0.42]

6

7.7

6

7.5

45 [0.351]

10.2

10.5

22.2

24.2

50 [0.297]

38

34.9

48.8

48.7

60 [0.249]

25.5

24.5

14.6

13.9

70 [0.211]

17.9

19.6

7.6

5.6

80 [0.150]

2.3

2.6

0.8

0.1

Pan [less than 0.150]

zero

0.1

zero

zero

Total

100

100

100

100

In magnitude (-40 + 70) [-0.42 + 0.211]

91.6

89.5

93.2

92.4

Table 2

Sample number

a

B

C

Dr

Aker, NTU (FTU)

233

125

Unlimited compressive strength

Closing stress at 93°C (200°F), 24 hours in 2% KCl, 12 lbm/gal added under a pressure of 0 psi [0 MPa]

405 [2795]

210 [1449]

305 [2105]

85 [587]

Closing stress at 93°C (200°F), 24 hours in 2% KCl, 12 lbm/gal added under a pressure of 70.31 kgf/m2 [6.9 MPa]

1325 [9143]

508 [3505]

955 [66590]

231 [1594]

Closing stress at 93°C (200°F), 24 hours in 2% KCl, 12 lbm/gal added under a pressure of 0 psi [0 MPa]

103

41

Closing stress at 93°C (200°F), 24 hours in 2% KCl, 12 lbm/gal added under a pressure of 70.31 kgf/m2 [6.9 MPa]

146

81

Tendency to clump

At 40.5°C

Free flow

Free flow

At 51.67°C

Free flow

Free flow

At 60.0°C

Free flow

Free flow

Aggregates,% by weight

Encapsulation effectiveness,% by weight

100

100

100

100

pH of a water extract

Initial pH

8.9

8.8

NaOH 0.1 p to pH = 9

0.4

0.3

NaOH 0.1 p to pH = 10

4.6

4.4

Table 3

the sample

e

And

g

12/18 CarboProp

500 Jim

1000 Jim

1000 Jim

A-1100

0.4 g

0.4 g

0.4 g

OWR-262E

5 Jim

10.6 g

10.6 g

SD-909A

8.2 g

32.4 g

-

FD-900A

-

-

34.2 g

-

-

-

Melting point (adhesion) in degrees Celsius

Less than 85

Less than 85

Less than 85

Loss on ignition % by weight

2.14

3.80

3.75

UCS, pounds per square inch (1 K) at 93°C (200°F) per kg/m2

34.5

140.63

123

UCS, kg/m2 (atmospheric) at 93°C (200°F)

71.72

61.9

Hot tensile, psi

224

232

121

Initial pH

8.43

8.72

mM to pH = 9

0.9

0.7

mM to pH = 10

7.6

5.6

pH (slurry water)

7.79

8.13

Addition times to the cycle

Time = zero: Add a coupling factor

Time = 30 seconds: add resole

Time = 2 minutes: Add PF powder

Time = 12 minutes: unloading

SSS (starting sand temperature) = ambient temperature

The above data showed that by coating sand or ceramic substrates with a resole of:

phenol-formaldehyde at room temperature, then introducing a powdered novolak resin of phenol-formaldehyde (with or without the curing agent hexamethylenetetramine) results in a high-performance free-flowing resin-coated particle that can be used as a proppant in an oil field.

Example No. 4

This example shows that a delay in adding the powder (after silane and resole) causes the resole to dry out and causes the resole to lose its ability to hold powder. Adding Novolak powder at delay times shows the effect of free (non-adherent) powder in the substrate due to partial drying of the liquid resin as the cycle time progresses. After packing four separate batches with different addition times, each material is sieved through a 149 and 74 micron filter (100 and 200 mesh). The collected non-adherent powder was weighed on the pan. Table 4 lists powder addition times and shows the remaining unbound resin phenol formaldehyde powder resulting from each sample preparation. The other tenses in the addition tenses in the cycle are shown in Table 4.

7 g of liquid resole (OWR-262E), available from Specialty Chemicals, Inc., Louisville, Kentucky, was added at 15 s to the cycle after silane addition. However, the addition time of 20 g of powdered novolak resin (FD900-A), available from Hexion Specialty Chemicals, Inc., Louisville, Kentucky, was changed. In the first operating cycle, powder was added at 1 minute to the cycle time. In subsequent runs, the powder was added at a later time as shown in Table 4.

The results below show an increased amount of non-adherent powder when powder addition is delayed.

Table 4

Powder addition time

Residual non-adherent PF powder

1 minute

1.04 g

Minute 2

2.01 g

Minute 3

2.96 g

Minute 4

2.98 g

the components:

1000 g of raw sand

7 g of liquid resole OWR-262E

20 g of novolak resin powder FD900-A

Example No. 5

Additional packaging testing was performed. To determine the effects of reversing the process, more specifically, adding the powder to the sand substrate before resole the liquid. Powdered phenol formaldehyde was added at 15 s, then liquid resole was added at 60 s using the same cycle time of 300 s. The material was separated into three phases: resole aggregates plus sand; Non-adherent powder and partially poorly coated substrate.

Figure 9 (using 12x magnification) shows clumps (clumps) of resole and sand resulting from sieving a sample of a partially poorly coated substrate. Figure 9 shows a group of agglomerates containing a large amount of resin. This sample was tested for loss on ignition (LOI) and was found to have a combustion loss of 19.1% by weight. This indicates that liquid resin is ineffective in coating the particles in a homogeneous layer. Instead of encapsulating substrate particles, resole resin is concentrated as agglomerates of few grains and powdered resin.

Figure 10 (using 30x magnification) shows another sample of partially poorly coated substrate that was extracted “as is” and not sieved. Figure 10 shows a batch of powder that did not adhere to the substrate. This sample was tested for loss on ignition (LOI) and was found to have a combustion loss of 1.99% by weight. The presence of large amounts of non-adherent powder indicated an inability to achieve a homogeneous dry mixture and substrate before adding the liquid resin. Once liquid resin is added, it will clump like the clumps shown in Figure 9, resulting in a condition in which the surface of the substrate is not adhered to the remaining powder.

While the invention has been described by embodiment, those skilled in the art will understand that various changes can be made and equivalents can be used to replace elements therein without departing from the scope of the invention. In addition, various modifications can be used to adapt a specific case or substance to the information contained in the invention without departing from its essential scope. Accordingly, it is intended that the invention is not limited to the specific embodiments disclosed and considered the best mode conceived to implement this invention.