Mixed metal hydroxides for thickening water or hydrophylic fluids.

DESCRIPTION

This invention concerns the thickening of water or hydrophilic fluids by using stratified mixed metal hydroxides.

There are various reasons for thickening water, aqueous solutions, hydrophilic fluids, and the like, such as for use as water-based, water-based fluids, fire suppression (fire extinguishing) fluids, oilfield drilling fluids , food additives, hydraulics, water-based paints or coatings, separation and release solutions, and other applications in which the thickening of a liquid or a solution is beneficial.

Water thickening agents, such as guar gum and polyacrylamide, are not stable against high-shear hydrothermal treatment, at temperatures above about 121 ° C, oxidation, attack by bacteria, and salts. To compensate for and solve some of these problems, additives such as bactericides and antioxidants are sometimes required.

Thickening agents or viscosifying agents for aqueous materials, such as drilling fluids, which involve a certain form of hydrated aluminum compound, are described, for example, in US Patents 4,240,915; 4,349,443; 4,366,070; 4,389,319; 4,428,845; 4,431,550; 4,447,841; 4,473,479 and 4,486,318. Patents describing other forms of aluminum compounds for the same purpose are, for example, US patents. 4,240,924; 4,353,804; 4,411,800 and 4,473,480. Similar patents, which describe other types of viscosifying agents, are, for example, US patents. 4,255,268; 4,264,455; 4,312,765; 4,363,736; and 4,474,667.

The above patents deal with the formation of hydrated aluminum compounds in situ. The main disadvantages of such a procedure are:

(1) The resulting thickened fluid contains copious amounts of reaction salts. This may be undesirable in many situations. For example, in applications such as paints, metalworking fluids, or water-based hydroaulic fluids, the presence of a salt could cause serious corrosion problems. In the case of oilfield drilling fluids, many performance enhancing additives do not work well if a salt is present. Therefore, it is desirable to drill in fresh water (again), if possible.

(2) The reactions described in the cited patents are carried out in situ (for example, in the mud pit of a derrick), in codings such that the reaction cannot be adequately contracted and the properties of the resulting thickener can be unpredictable.

Other problems, which arise with the use of Al (OH) 3 as a gelling agent for various procedures, are the following:

one. It is known that Al (OH) 3 gels change detrimentally over time, unless certain anions such as carbonate or citrate are present.

two. The rheology of Al (OH) 3 is not too constant with variable pH values. For example, a suspension of Al (OH) 3 can be very thick and uniform at pH 6, but at pH 10, which the drilling industry prefers, the suspension crumbles and Al (OH) 3 settles out of the suspension . This creates significant problems, since most of the drilling operations are carried out at pH values ​​within the range of 9 to 10.5

A historically popular thickening agent, especially in a drilling mud, has been made of mineral clays, such as bentonite clay, often used together with other agents or densifiers, such as Fe2O3, BaSO4 and others. Variations from one batch to another batch of bentonite clay, and ion and temperature sensitivities, have resulted in erratic results and often an adjustment of the formulation is required during use; This hinders drilling operations.

Certain forms of crystalline stratified mixed metal hydroxides are described, for example, in US Pat. 4,477,367; 4,446,201 and 4,392,979; in which various compounds of Li, Mg, Cu, Zn, Mn, Fe, Co and Ni form part of the stratified crystalline structure. Other stratified compounds are described, for example, in US Pat. 2,395,931; 2,413,184; 3,300,577 and 3,567,472. These compounds are prepared through various reactions, including coprecipitations, intercalations, digestions with acids and digestions with bases.

In the drilling of oil wells, drilling fluids or “sludge” perform several functions:

one. Eliminate drilling debris from the well.

two. They cool the drill bit.

3. They provide hydrostatic pressure to balance the pressure of the formation.

Four. They control the penetration of fluids into the formation and protect this formation.

In order to perform some of these functions, it is necessary for the fluid to have a pseudoplastic rheology. There are various shear zones in the borehole of a well and the fluid should have varying viscosities in these areas. In the ring or ring between the drill pipe and the formation, the shear regime is approximately 100 to 1,000 sec^-1. In the mud pit, the shear regime is less than 30 sec^-1. In order to carry drilling solids with low shear rates, a fluid must have an important viscosity. However, if the fluid has

000 647 a high viscosity next to the drilling auger, a significant amount of energy is lost to pump the fluid. Therefore, a good drilling fluid should be dilutable by shear. It is very important that the fluid maintains this rheology throughout the drilling process. However, many unfavorable conditions, which typically inhibit the performance performance of existing drilling fluids are the presence of various cations (such as calcium and magnesium), fluctuating concentrations of salts, high temperatures, oxidation conditions and the presence of bacteria .

Some of the commercially accepted gelling agents, which are used in water-based drilling fluids, are polymers such as xanthan gum, guar gum and polyacrylamides. Non-polymeric gelling agents are typically clays such as bentonite and attapulgite. Each of these gelling agents has its own limitations. The polymers typically have instability against various salts, are susceptible to oxidation and attack by bacteria, degrade under extensive shear, and are thermally stable only at temperatures of about 120 to 150 ° C. The clay-type gelling agent, mine popular, is bentonite. Bentonite is severely affected by polyvalent cations and is limited to approximately 100 C, unless certain diluents are incorporated. However, bentonite cannot be oxidized under hydrothermal conditions, and is stable in a liquid vehicle against high shear conditions.

The present invention creates a new gelling component of a process fluid, for example a drilling fluid, a drilling mud, a fracturing fluid (frac), a sealing fluid, a terminating fluid, and the like, or other fluid thixotropic; said gelling agent, also called thickening agent, comprises a mixed metal stratified hydroxide of the empirical formula.

LimDdT (OH) (m + 2d + 3 + na) A_toⁿ.qH2O (I) where m is from zero to about 1;

D represents divalent metal ions;

d is from zero to about 4;

T represents trivalent metal ions;

A represents monovalent or polyvalent aions, or negative valence radicals other than OH ions^-;

a is the number of ions of A;

n is the valence of A;

na is from zero to about -3;

q is from zero to about 6;

(m + d) is greater than zero; and (m + 2d + 3 + na) is equal to or greater than 3.

These mixed metal stratified hydroxides are preferably prepared by an instantaneous coprecipitation (of the "flash" English), in which soluble compounds, for example salts, of the metals, are intimately mixed (using agitation or mixing without shearing) with an alkaline material that supplies hydroxyl groups to form crystals of mixed metal hydrated oxides. Although the empirical formula appears to be similar to that of the compositions described above, a distinctive feature of the present composition is that the crystals are essentially of the monolayer type, or a layer of mixed metal hydroxide per unit cell. In a liquid vehicle, stain crystals are essentially "monodispersed," meaning that individual crystals are distinct layers of mixed metal hydroxide. It is believed that these monolayers, monodispersed crystals, are new.

In the above formula, the Li ion number was represented by the value of m and may be from zero to about 1, preferably from 0.5 to 0.75.

The metal D represents divalent metal ions and can be Mg, Ca, Ba, Sr, Mn, Fe, Co, Ni, Cu Zio, preferably Mg, Ca, Mn, Fe, Co, Ni, Cu or Zn, preferably Mg io Ca, or mixtures of these. The value of d, the number of D ions in the formula (I), can be from zero to about 4, preferably 1 to 3, most preferably about 1.

The quantity of (m + d) is greater than zero.

The metal T may be Al, Ga, Cr heard Fe, preferably Al heard Fe, preferably Al.

In the suffix (m + 2d + 3 + na), adding “na” is actually a negative number, since the valence of the anioin, n, is negative. The sum of a negative number results in a subtraction.

The anions A can be monovalent, divalent, trivalent or polyvalent, and they can be inorganic ions, such as halide, sulfate, nitrate, phosphate or carbonate ions, most preferably halide, sulfate, phosphate or carbonate, or they can be hydrophilic organic ions such as glycolate, lignosulfonate, polycarboxylate, or polyacrylate or its salts, such as sodium polyacrylate. These anions are often the same as the anions that were part of the precursors of metal compounds from which these new crystals are formed.

The compound of formula (I) is substantially balanced and is preferably neutral in charge. The term "substantially balanced" means that there is little net positive or negative charge for the compound.

The liquid that is gelled by the new mixed metal hydroxides, presently described, may be an aqueous liquid, such as water or an aqueous solution, or a hydrophilic organic material such as an alcohol or a ketone; also a dispersion or emulsion, which comprises an aqueous medium containing non-soluble ingredients (orgaine and / or inorganic) in dispersed form, can be gelled by use of the

000 647 gelling agent presently described. While the present gelling agent is found to be useful as a thickening agent for water-based metalworking fluids, fire extinguishing fluids, food additives, hydraulic fluids, lóatex type paints, separation and release fluids, lubricants, and others, especially where extreme pseudoplasticity is a desirable property, This is particularly useful when it is used as an additive to form thixotropic fluids for use in underground operations such as drilling fluids, drilling muds, fracturing fluids, sealing fluids, terminating fluids, and the like, especially drilling fluids, either to drill oil wells, water wells, or gas wells, including drilling at the bottom of the ocean.

The present invention also creates a process for preparing the formula compounds (I) by the operations of (a) preparing a solution of predetermined amounts of compounds that provide the desired predetermined amounts of Li, D, T and A ions;

(b) mixing said solution with an alkaline solution that provides a source of hydroxyl ions to cause coprecipitation of said Li, D and T metals, in the form of crystalline mixed metal compounds, containing, as anions, hydroxyl ions and A ions , said crystals being monodispersed and displaying single-layered unit cell structures, it is determined by cirstalographic analysis; and (c) in which said mixing operation is performed in such a way that an instantaneous, thorough and rapid precipitation is achieved, without the use of shear agitation.

The "instantaneous" precipitation technique, used to prepare the present gelling agents, greatly approximates a permanent regime reaction in which the ratio of reactant feeds (cations / anions), and other reaction conditions (for example, are substantially constant) , concentration, pH, temperature). Such constant conditions are achieved substantially by mixing or combining a dosed stream (or regularly fed portions) of the "cation solution" with a predetermined amount of the "anion solution"; The combined solutions comprise a mixture (containing reaction product in the form of a flocculus or flake), which is removed from the mixing zone or aoreal. In this way, each new portion of the cation solution "sees" a new portion of anion solution, none of these new portions having been involved in the mixing of the previous portions. In this way, substantially constant conditions of temperature, pH, and ratio of feed reactants are obtained and a homogeneous, more uniform product is obtained in terms of composition, with each new product portion having experienced the same reaction orders (and regimes) than any previous portion of the product. By performing the reaction in this manner, the formation of "floccules" is maximized, provided there is not enough shear agitation to break the flocculae.

This state reaction or permanent regime was in contrast to a non-permanent state or regime reaction in which the reaction conditions (such as temperature, pH, ratio of reactants) are variable rather than constant. For example, if you have a container that contains a cation solution to which a stream (or portions) of the anion solution is slowly added, the first piece of anion solution “sees” all cations, the second piece does not See so many cations but also see some reaction product. Each subsequent patch of anion solution "sees" a different amount of cations and product; the ratio of cations / anions that are being bound is changing throughout the process, leading, most likely, to a non-homogenous or non-uniform product as a result of having found different reactivity orders, or different reaction regimes throughout the course. of the addition of anions. Here, in said non-permanent state reaction, there is the probability that some of the subsequent anions may react with some of the product already formed, resulting in a mixture of products.

Theoretically it can be said that a uniform, absolutely constant product is prepared under absolutely constant conditions by reacting a molecule of one reactant with the required or stoichiometric molecular amount of the other reactant. Such absolutely constant conditions cannot be achieved in commercial practice, but one can substantially approximate those conditions using substantially permanent regime conditions, where the constant conditions are greatly approximated.

The temperature of the reaction mixture should, of course, be above that of freezing and not above that of boiling. Passing over the boil would require a closed pressure vessel to prevent evaporation of the liquid and this is generally unproductive, offering no additional benefit commensurate with the supplementary expense. It could be expected that a temperature below about 5 ° C would slow the reaction rate. An ambient temperature can be used within the range of approximately 15 to 40^°C, but hot temperatures, up to 80, can also be quite beneficial^°Like, not only to keep the initial compounds in solution but also to accelerate the regime with which the compounds react.

A mixture of the selected soluble metal compounds, especially the acid salts (for example chlorides, nitrates, sulfates, phosphates) is dissolved in an aqueous vehicle. The relationships of the metalic ions in the solution are predetermined to give the desired relationships4

000 647 days in the final product. The concentration limit of the metal compounds in the solution is governed, in part, by the saturation concentration of the least soluble of the metal compounds in the solution; any undissolved portion of the metal compounds may remain in the final product as a separate phase, which is not a serious problem, usually, if the concentration of said separated phase is a relatively small quantity in comparison to the soluble portions, and preferably it is not more than about 20 percent of the amount of soluble portions. Then the solution is quickly and intimately mixed with an alkaline source of OH ions^- while substantially shear agitation is avoided, thereby forming monodispersed crystals of mixed metal layered hydroxides. A convenient way to achieve said mixing is to circulate the various feed streams within a mixing tea, from which the mixture circulates, carrying the reaction product, including the stratified hydroxides of monodispersed mixed metals of formula (I) above. . Then, the mixture can be filtered, washed with fresh water to remove soluble foreign ions (such as Na ions⁺, HN₄⁺ and other soluble ions) that are not part of the desired product.

The particular transmission electron microscope, used to perform crystallographic analyzes of the stratified hydroxides of mixed target metals, was operated together with its maximum detection limits, this is with a resolution of approximately 8 angstroms. The monodispersed crystals were so thin, in relation to their diameter, that a certain curl of the monolayer crystals was found, making exact measurements of the thickness difficult, but reasonable estimates placed the thickness of the crystals within the range of 8 to 16 angstroms for various crystals During the drying process, a certain agglomeration of the crystals is evident, which is detected in the analysis, giving rise to particles containing a plurality of the structures of single-layer unit cells. Many non-agglomerated, flattened crystals are detectable in the analyzes. These monolayer unit cell crystals are in contrast to the 2-layer and 3-layer unit cell structures, cited, for example, in US Pat. 4,461,714.

A process for preparing the composition, but which is not exclusively the procedure, consists in reacting a solution of metal salts, such as magnesium and aluminum salts (salt concentrations are preferably less than about 2 molar and most preferably about 0.25 molar) with a source of hydroxide ion. Sodium hydroxide, for example, may be used, but amoanic hydroxide is preferred. The concentration and amounts of the base are at least sufficient to precipitate the mixed metal hydroxide compound. For ammonium hydroxide, the most preferable range is between 1 and 1.5 moles of OH^- per mole of Cl^-.

Precipitation should be done with little or no shear, so that the resulting flocculations or flakes are not destroyed. A method of achieving this consists in circulating two currents, the salt current and the base current, towards each other, so that they affect a convergence zone, of low shear, as it will be found in a tea. The reaction product is then filtered and washed, producing a filter cake with approximately 10 percent saolides. At this point, if the mixed metal stratified hydroxide composition has been carefully washed to reduce the concentration of dissolved salts to a relatively low point, for example, approximately 300 ppm or less, a singular and strange phenomenon occurs. Over a certain period of time, the filter cake goes from being a solid, solid material to becoming an opalescent or iridescent liquid, which effectively disperses light. If ionic material is added back to the dispersion, the viscosity increases dramatically and the dispersion gels. The "relaxation" regime is dependent on the concentrations of free ions in the dispersion and will not occur if the concentrations are too high. The effect of various ions on the relaxation process differs. For example, the relaxation process is more tolerant for monovalent ions, such as chloride ions, than for polyvalent ions, such as sulfate, carbonate or phosphate.

If the relaxed dispersion is dried, when the level of solids reaches approximately 20 to 25 percent, the material forms a translucent, hard and solid material, which is very cold. This can be crushed to form a powder, even if it has a concentration of approximately 80 percent water. This solid was not redispersed in water or other hydrophilic solvents. Even if shear is applied with a Waring Blender mixer or an ultrasonic cell breaker, solids cannot be made to form stable dispersions.

A fruiting method of drying the material consists in adding a certain amount of hydrophilic organic material, such as glycerol or polyglycol, to the relaxed dispersion, before drying. The material can be dried to about 5% water, or less and can still be redispersible. If this is done so, the resulting dry material will spontaneously disperse in water. If a salt is then added to this dispersion, the fluid accumulates viscosity in the same way that the product that has never been dried. This drying technique is ineffective if significant amounts of dissolved salts are present in the dispersion. In this case, a certain amount of dispersion may be possible, but the resulting fluid did not accumulate viscosity.

One of the distinctive characteristics of hydrated mixed metal oxides, which have been described in the present case, is the fact that when filtering, after instantaneous coprecipitation, a gel that is predominantly the liquid phase is left on the filter. crystalline hydrated oxides swollen by the liquid in such a way that these are not visible as a solid phase. The gel can be called a "semi-solution" or "quasi-solution" and this one has the

000 647 look and feel of a semi-solid wax. This is in contrast to the precipitates of hydrated oxides of the prior art, which are easily separated by filtration from the liquid as a solid material in the form of discrete particles. Apparently, the particular crystalline morphology obtained here allows or causes the embedding and retention of large amounts of liquid.

The gelling agent may also be composed of either pure mixed metal hydroxides or fossil mixtures of the stratified compounds with themselves or with other hydrated oxides of the D or T metals, such as, for example, hydrated alumina, hydrated magnesia, hydrated iron oxides, hydrated zinc oxide and hydrated chromium oxides.

In each of the subsequent examples, the mixed metal stratified hydroxide compound was prepared by coprecipitation. The compounds were filtered and then washed to produce a substantially pure material. This purified product was then dispersed in water to form the thickened fluid.

The following examples are given to illustrate certain embodiments, but the invention was not limited to the particular embodiments shown.

Example 1

A 0.25 molar solution of MgCl2.AlCl3 was prepared. This solution was then pumped through a peristotic pump into an arm of a tea. A 2.5 molar NH4OH solution was pumped into a second opposite arm of the tea, so that the two solutions converged in the tea. . The product spilled out of the third arm and into a wide-mouth glass (called precipitates). The flow rates of the two solutions were carefully adjusted so that the product of the coprecipitation reaction had a pH of approximately 9.5. In this situation this amounts to approximately 10-20% excess of NH4OH. The reactor product consisted of delicate floccula or flakes of MgAl (OH) 4.7Cl0.3 suspended in an aqueous solution of NH4Cl. The dispersion was then carefully poured into a Buchner funnel with an intermediate filter paper. The product was filtered and washed on the filter with water, to remove excess NH4Cl. After washing, the Cl concentration^- dissolved was approximately 300 ppm, measured by a specific ionic electrode of Cl^-. The filter cake, which resulted, was translucent, but not optically transparent.

The resulting cake had a concentration of approximately 9% solids by weight, determined by drying at 150 ° C for 16 hours. The cake had the consistency of a soft candle wax. The product was analyzed for Mg and Al. The Mg: Al ratio was found to be essentially 1: 1.

The electronic micrograph analysis of the product revealed tiny inserts with diameters of 300 to 500 angstroms. The particles were so thin that, in some cases, they curled up. The thickness estimates of these particles are 8 to 16 angstroms. The maximum resolution in the microscope is approximately 8 angstroms. The theoretical thickness of a layer of crystalline MgAl (OH) 4.7 Cl0.3 is approximately 7.5 angstroms. These data strongly suggest that some of the particles have a thickness of one to two crystals. It should also be noted that in the process of preparing the sample for electron microscopy, the material was dried, which apparently caused a certain degree of agglomeration of the crystals.

After settling undisturbed for approximately 16 hours, the filter cake had the consistency of petroleum jelly. After about 48 hours, the material was a thixotropic liquid. The relaxation process continued for approximately 5 days. At the end of this period of time, the product was more viscous than water, but was pourable. A small amount of NaCl was added to a sample of the liquid and this gelled almost instantaneously.

An amount of glycerol that was equal to 17% by weight of the solids present in the dispersion was added to the product. When glycerol was added to the dispersion, the apparent viscosity decreased to approximately 1 centipoise. Then, the suspension was placed on a tray and dried in an oven for 16 hours. On a large scale, more efficient drying equipment, such as spray dryers or shelf dryers, was used. The product from the oven was a solid solid that could easily be crushed. It had a concentration of 95% by weight of solids, including glycerol. When the solid material was placed in water, it dispersed spontaneously in less than 5 minutes. Phosphate ions in the form of NaH2PO4 were added to the dispersion and increased viscosity in the same manner as it did before drying.

Example 2

Similarly, a solution of magnesium and aluminum chlorides, which had a composition of 4 mg per 1 aluminum, was reacted with NH4OH. The Mg3.2Al (OH) 8.4 Cl1 concentration was approximately 1 molar. The product was filtered and washed immediately. After approximately 24 hours, the filter cake had relaxed to give a very diluted fluid. The solids content of the fluid was approximately 10% and the bulk analysis of the solids indicated that the Mg: Al ratio was 3.2: 1.

Transmission electron microscopy was performed with the material and it was found that the product was formed by inserts having an average diameter of 500 angstroms (± 100 angstroms). Some of the crystals are placed on the artists, so that it is possible to estimate the thickness of the crystals. It is revealed that there are crystals that have only a thickness of approximately 10 angstroms. This suggests that the material was essentially monodispersed. The bibliography (Crystal Structures of Some Double Hydroxide Minerals Taylor,

HFW, Mineralogical Magazine, Volume 39, Number 304, December 1973) teaches that known magnesium and aluminum hydroxide compounds that have Mg: Al as high as 4: 1 ratios are in the class of compounds of 6

000 647 hydrotalcite nominees. The crystalline structure data, which has been accumulated in the literature, indicates that there are basically two types of hydrotalcite, one that has an axis distance of approximately 24 angstroms and another that has a c-axis distance of approximately 15 angstroms. Since the data disclosed here indicates that many of the crystals prepared in this example are mine thin in the direction c that the hydrotalcite, therefore the crystalline structure data indicates that the material must have a crystalline structure that is different from the hydrotalcite .

Example 3

A part of aqueous solution, containing 23.8% by weight of MgCl2.AlCl3, is diluted with 4 parts of deionized water and enough MgSO4 is added to provide a ratio calculated for Mg: Al of 4: 1. The solution, at room temperature, is rapidly and thoroughly mixed, without substantial shear forces, with a stoichiometric amount of NH4OH, thereby providing instant coprecipitation of Mg3.2Al (OH) 8.4Cl1. The reaction mixture is filtered, leaving a semi-solid wax gel on the filter, containing approximately 6% by weight of the coprecipitate. The gel is washed on the filter, with additional amounts of deionized water, to substantially remove foreign material, such as NH4OH, SO4^-2, and Cl^-. However, the final concentration of Cl^- It was greater than 0.02 molar. The filter cake is diluted with deionized water to prepare a 2.5% dispersion that, measured with a Brookfield viscometer, is approximately 556 times more viscous than water with low shear rates and is thixotropic. Enough BaSO4 was added to the aqueous suspension to increase the density to approximately 1198.3 kg / m³. BaSO4 was suspended well and did not settle for a period of 6 months.

Example 4

A similar experiment was performed in which the Mg: Al ratio was 1: 4. The product was washed until the content of Cl^- it was less than 110 ppm. After the addition of salt, this material was able to accumulate viscosity and withstand BaSO4 in suspension for extended periods of time.

Example A (for comparison)

MgSO4.7H2O was dissolved in sufficient water to prepare a 0.25 molar solution. This was then reacted with KOH to produce Mg (OH) 2 in a reaction tea. The product was filtered and washed to an essentially zero concentration of Cl^-. This fluid was then dispersed in water and found to be thixotropic. BaSO4 was then dispersed in the suspension and allowed to stand undisturbed for 6 months; BaSO4 was separated by sedimentation mostly from dispersion.

Example B (for comparison)

A 1 molar solution of Al2 (SO4) 3 was prepared and precipitated with NH4OH. The resulting product was washed thoroughly and resuspended to prepare a 2.5% dispersion. BaSO was added₄ to test the suspending characteristics of the suspension. The suspension was allowed to settle undisturbed for 6 months; BaSO4 was separated by sedimentation for the most part from dispersion.

Example 5

A 0.25 molar solution of MgCl2.AlCl3 was prepared. These solutions were reacted with NH4OH to precipitate a material having a Mg: Al ratio of 1: 1. The product was filtered and washed to a point where the concentration of Cl^- in the cake it was 2,800 ppm. Then, the product was dispersed in water forming a thixotropic suspension. Then, it densified to 1138,385 kg / m³ with BaSO4 and allowed to settle and settle for 6 months; there was very little sedimentation. There was a synoresis effect, in which the top 10% of the fluid was clear water, but there was only a density gradient of approximately 10% through the other 90% remnant of the fluid.

Example 6

100 ml of 1 molar solution of MgCl2. AlCl3 was diluted with 200 ml of deionized water and 14.7 grams of CaCl was added.₂. The resulting aqueous salt solution was then precipitated instantaneously with NH4OH at a reaction pH of

10. The suspension was filtered and washed. The resulting product was then dispersed in water and densified as described in previous examples. This suspension was also thixotropic. Example 7

A fairly large amount of MgAl (OH) 4.7Cl0.3 precipitated instantaneously was prepared, and washed. The following tests were then performed with fluids containing the gelling agent.

one. Rheology data.

two. Shear stability.

3. Dependence on time.

Four. Dependence on pH.

5. Dependence on KCl.

6. Dependence on CaCl2.

7. Filtration data.

8. Densified fluids.

9. Thermal Stability

10. Stability of Na2SO3.

Theological Data

The rheological data, which are illustrated here, were obtained using a Fann 35 rotary viscometer. Unless stated otherwise, all data was obtained at 46^or C. Table 1 is a comparison of the plastic viscosity, of the point or elastic limit and of 10 second and 10 minute gel resistances for 19.95 kg / m³ MgAl (OH) 4.7Cl0.3, 42.75 kg / m³ of Aquagel (a benefited sodium bentonite sold by Bariod) and 57 kg / m³ from Aquagel. The most notable differences are found in the plastic viscosities and gel strengths. In the case of MgAl (OH) 4.7Cl0.3, the plastic viscosity is very

000 647 falls, being approximately one eighth of the value of the elóastico point. In the case of Aquagel samples, the plastic viscosity is higher than the diagnostic point. The gel resistances of MgAl (OH) 4.7Cl0.3 are almost equal, while those of Aquagel fluids are significantly different. These data indicate that the MgAl (OH) 4,7Cl0.3 fluid gels varied rapidly and did not continue to accumulate gel strength. It is said that said fluid produces "frail gels." Aquagel fluids gel more slowly and continue to accumulate gel resistance for a longer period of time, forming "progressive gels." Fróagiles gels are more desirable for the drilling of oil wells, since the fluid was not so strongly gelled that it cannot be easily broken.

TABLE 1

Rheological data

<td>A / C</td><td>Plastic viscosity (cp)</td><td>Point elastic (kg / 100m²)</td><td colspan="2">Gel resistors 10 sec 10 minutes. (kg / 100 m² )</td>

<td>TO</td><td> 2,5</td><td> 102,48</td><td> 46,36</td><td> 53,68</td>

<td>B</td><td> 7,8</td><td> 21,96</td><td> 8,784</td><td> 9,76</td>

<td>C</td><td> 15</td><td> 70,76</td><td> 14,64</td><td> 41,48</td>

where:

A / C is Agent / Concentration

A MgAl (OH) 4.7Cl0.3 19.95 kg / m³

B Aquagel * 42.75 kg / m³

C Aquagel * 57 kg / m³ (* Aquagel is used as a comparison.)

Table 2 tabulates the shear stress and shear rate data for a suspension of 19.95 kg / m³, prepared with MgAl (OH) 4.7Cl0.3. These data were generated using a capillary viscometer. The fluid is extremely dilutable by shear from approximately 1 sec.^-1 up to approximately 25,000 sec^-1, where he becomes Newtonian. This is topical of all water-based drilling fluids. The viscosity of this fluid with low shear rates is approximately 600 cp but, together with the drilling auger, the viscosity is only approximately 4.5 cp.

TABLE 2

CAPILLARY VISCOSIMETER DATA

<td>Shear regime (sec^-1)</td><td>Shear stress (Kg / 100 m²)</td><td>Viscosity (cp)</td>

<td> 10.35</td><td> 59.08</td><td> 597.40</td>

<td> 20.60</td><td> 80.56</td><td> 409.30</td>

<td> 40.95</td><td> 92.28</td><td> 235.85</td>

<td> 102.80</td><td> 114.25</td><td> 116.32</td>

TABLE 2 (continue)

<td>Shear regime (sec^-1)</td><td>Shear stress (kg / 100 m²)</td><td>Viscosity (cp)</td>

<td> 204.48</td><td> 130.36</td><td> 66.72</td>

<td> 393.00</td><td> 152.14</td><td> 40.52</td>

<td> 666.75</td><td> 179.67</td><td> 28.20</td>

<td> 981.00</td><td> 190.71</td><td> 20.35</td>

<td> 1257.50</td><td> 227.03</td><td> 18.90</td>

<td> 1720.00</td><td> 230.74</td><td> 14.04</td>

<td> 2527.60</td><td> 292.95</td><td> 12.13</td>

<td> 6551.60</td><td> 394.50</td><td> 6.30</td>

<td> 13694.20</td><td> 687.93</td><td> 5.26</td>

<td> 25552.40</td><td> 1098.55</td><td> 4.50</td>

<td> 61743.30</td><td> 2735.62</td><td> 4.64</td>

<td> 87019.00</td><td> 3961.11</td><td> 4.76</td>

Shear Stability Data

Table 3 tabulates the plastic viscosity, the elastic point and the gel strengths as a function of the shear time in a Waring Blender mixer. Except for some change in the first few minutes, the viscosity parameters remain fairly constant. Capillary viscometer data also indicates that MgAl (OH) 4.7Cl0.3 fluids are stable against shear, since they were passed three times through the capillary viscometer and no observable shear degradation occurred.

TABLE 3

STABILITY DATA AGAINST SHEARING

<td>TO</td><td>B</td><td>C</td><td colspan="2">D</td>

<td> 0.0</td><td> 3.0</td><td> 73.2</td><td> 63.44</td><td> 73.2</td>

<td> 10.0</td><td> 2.0</td><td> 39.04</td><td> 39.04</td><td> 34.16</td>

<td> 35.0</td><td> 2.0</td><td> 39.04</td><td> 39.04</td><td> 39.04</td>

<td> 75.0</td><td> 2.5</td><td> 53.68</td><td> 43.92</td><td> 48.8</td>

Being:

A: Shear time (min.)

B: Plastic viscosity (cp)

C: Elóastico point (kg / 100 m²)

D: Gel resistances 10 sec. 10 minutes. (kg / 100 m²)

Time dependence data

Table 4 lists the plastic viscosity, the diagnostic point and the gel strengths for a suspension of MgAl (OH) 4.7Cl0.3 of 19.95 kg / m³for a period of 2.5 days. These data indicate that there is a certain change in the elastic point during the first several days. However, the change is not considered to be important. The fluids from these tests were also allowed to settle for 3 months and the rheology was measured again in them. There were virtually no changes in fluids.

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TABLE 4

DEPENDENCY DATA REGARDING

WEATHER

<td>TO</td><td>B</td><td>C</td><td colspan="2">D</td>

<td> 0.0</td><td> 5.0</td><td> 26.84</td><td> 14.64</td><td> 29.28</td>

<td> 0.3</td><td> 5.0</td><td> 34.16</td><td> 17.08</td><td> 29.28</td>

<td> 1.0</td><td> 5.0</td><td> 34.16</td><td> 17.08</td><td> 28.304</td>

<td> 2.0</td><td> 5.0</td><td> 30.256</td><td> 17.08</td><td> 28.304</td>

<td> 2.5</td><td> 5.0</td><td> 29.28</td><td> 17.08</td><td> 26.84</td>

Being:

A: Time days

B: Plastic viscosity (cp)

C: Elastic point (kg / 100 m²)

D: Gel resistances 10 sec. 10 minutes.

(kg / 100 m²)

PH effects

Table 5 lists the plastic viscosity, the elastic point and the gel strengths as a function of the pH. Below approximately pH 6 the elastic point decreases dramatically. The curve is flattened at approximately pH 11. Above this point, it rises very quickly. These results are good, since drilling operations are performed at a pH from about 9.5 to about 10.5.

TABLE 5

PH EFFECTS ON FRESH WATER SYSTEMS

<td rowspan="2">pH</td><td rowspan="2">Viscosity plastic (cp)</td><td rowspan="2">Point elastic (kg / 100 m² )</td><td colspan="2">Gel resistors</td>

<td>10 sec (kg / 100</td><td>10 minutes. m²)</td>

<td> 4.5</td><td> 3.0</td><td> 12.2</td><td> 12.2</td><td> 24.4</td>

<td> 7.0</td><td> 3.0</td><td> 107.36</td><td> 34.16</td><td> 34.16</td>

<td> 10.5</td><td> 3.0</td><td> 122</td><td> 97.6</td><td> 102.48</td>

<td> 12.0</td><td> 3.0</td><td> 268.4</td><td> 58.56</td><td> 58.56</td>

Table 6 tabulates the rheology parameters for a fluid composed of 35% CaCl2 and approximately 17.1 kg / m³ of MgAl (OH) 4.7Cl0.3 at pH 6 and at pH 8.5. Fundamentally there is no change in rheology.

TABLE 6 pH DATA *

<td></td><td>Viscosity</td><td>Point</td><td colspan="2">Gel resistors</td>

<td></td><td>plastic</td><td>elastic</td><td>10 sec</td><td>10 minutes.</td>

<td>pH</td><td>(cp)</td><td>(kg / 100 m² )</td><td colspan="2">(kg / 100 m² )</td>

<td> 6.0</td><td> 8.5</td><td> 68.32</td><td> 31.72</td><td> 41.48</td>

<td> 8.5</td><td> 8.0</td><td> 68.32</td><td> 39.04</td><td> 48.8</td>

* CaCl concentration₂ = 35%, fluid weight = 1318.13 kg / m³.

Stability data for KCl and CaCl2

KCl is frequently added in varying amounts to water-based drilling fluids for shale stabilization. Table 7 is an enumeration of the various rheological properties as a function of the concentration of KCl, from 0% to 27%. The experiment will be carried out starting with an aqueous dispersion of MgAl (OH)₄.₇Cl₀.₃ and adding certain amounts of KCl to the suspension. Increasing the concentrations of KCl had very little effect on the global rheology of the fluid. A similar experiment with CaCl2, table 8, where a drop in the elastic point between 0.25% and 27.7% was observed. There was also an increase in plastic viscosity. However, these changes are not of great magnitude. These data are important, since they indicate that fluctuations in the salts normally found will not have a detrimental effect on the properties of aqueous dispersions of MgAl (OH) 4.7Cl0.3. TABLE 7

KCl STABILITY DATA *

<td>TO</td><td>B</td><td>C</td><td colspan="2">D</td>

<td> 0.00</td><td> 4.5</td><td> 53.68</td><td> 36.6</td><td> 39.04</td>

<td> 0.25</td><td> 3.2</td><td> 41.48</td><td> 43.92</td><td> 36.6</td>

<td> 0.50</td><td> 3.2</td><td> 43.92</td><td> 29.28</td><td> 26.84</td>

<td> 1.00</td><td> 3.0</td><td> 48.8</td><td> 26.84</td><td> 26.84</td>

<td> 3.00</td><td> 2.5</td><td> 58.56</td><td> 26.84</td><td> 24.4</td>

<td> 10.0</td><td> 3.5</td><td> 48.8</td><td> 31.72</td><td> 26.84</td>

<td> 27.0</td><td> 3.2</td><td> 53.68</td><td> 31.72</td><td> 26.84</td>

Being:

A: KCl concentration (% by weight)

B: Plastic viscosity (cp)

C: Elastic point (kg / 100 m²)

D: Gel resistances 10 sec. 10 minutes.

(kg / 100 m²) ^* MgAl (OH) concentration 4.7Cl0.3 = 19.95 kg / m³.

TABLE 8

STABILITY DATA OF CaCl₂

<td>TO</td><td>B</td><td>C</td><td colspan="2">D</td>

<td> 0.35</td><td> 2.5</td><td> 102.48</td><td> 46.36</td><td> 53.68</td>

<td> 27.7</td><td> 6.5</td><td> 73.2</td><td> 41.48</td><td> 41.48</td>

<td> 35.0</td><td> 8.0</td><td> 73.2</td><td> 39.04</td><td> 48.8</td>

Being:

A: CaCl2 Cocentracioan (% by weight)

B: Plastic viscosity (cp)

C: Elastic point (kg / 100 m²)

D: Gel resistances 10 sec. 10 minutes. (kg / 100 m²)

Filtration data

Aqueous MgAl (OH) 4.7Cl0.3 dispersions exhibit very high fluid loss values

API Therefore, it is generally desirable to add agents to control fluid loss to a drilling fluid constituted around stratified mixed metal hydroxides. However, it has been found that the addition of commercially available fluid loss control agents, such as starch, polyacrylates, carboxymethyl cellulose, and the like, provides adequate control of fluid loss (loss less than 10 cm³ in 30 min. using an API fluid loss cell). The quantities required to give adequate control are approximately the amounts suggested by the manufacturers of the agents. Some of these data are listed in Table 9. As might be expected, the presence of perforation solids, such as shales, is also beneficial for the control of fluid loss. More than one fluid loss control agent can be used in a drilling fluid.

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TABLE 9

FILTRATION DATA *

Concentration control agents to produce a 12 cm API fluid loss³ or less (kg / m³)

<td colspan="2">Hydroxyethylcarboxyme-</td>

<td>tilcellulose Hydroxyethylcarboxymethylcellulose (viscosi-</td><td> 4.275</td>

<td>low dad)</td><td> 5.700</td>

<td>Corn starch</td><td> 17.100</td>

<td>Seodic Polyacrylate</td><td> 5.700</td>

^* 19.95 kg / m³ MgAl (OH) 4.7Cl0.3, 28.5 kg / m³of bentonite (simulated drilling solids). Densified fluids

Table 10 lists the rheological data for 27,075 and 42.75 kg / m³ of densified fluids with BaSO4. An unexpected result is that the plastic viscosity remains very low while there is a high elliptical point. This runs contrary to current theories concerning the viscosities of aqueous dispersions.

It is normally thought that when a densifying material is added to an aqueous dispersion, the plastic viscosity has to increase dramatically. One possible explanation is that MgAl (OH) 4.7Cl0.3 may be acting as a lubricant in the system. The potential result of this property is that higher penetration regonomic densified fluids can be achieved than is currently possible.

TABLE 10

DENSIFIED FLUID DATA

<td>TO</td><td>B</td><td>C</td><td colspan="2">D</td>

<td> 1138.385</td><td> 3.0</td><td> 119.56</td><td> 53.68</td><td> 73.2</td>

<td> 1797.45</td><td> 4.0</td><td> 156.16</td><td> 68.32</td><td> 68.32</td>

Being:

A: Mud density (kg / m³)

B: Plastic viscosity (cp)

C: Elastic point (kg / 100 m²)

D: Gel resistances 10 sec. 10 minutes.

(kg / 100 m²)

Thermal stability data

Table 11 illustrates shear stress curves as a function of the shear regime at 22.8 kg / m³, before and after the esthetic esthetic treatment at 204^orC for 20 hours. The result of the test is that the rheological properties, measured at 46^orC, they were basically unchanged.

TABLE 11

THERMAL STABILITY DATA *

<td>TO</td><td>B</td><td>C</td><td colspan="2">D</td>

<td> 46^orC / 24 h.</td><td> 2.5</td><td> 102.48</td><td> 46.36</td><td> 53.68</td>

<td> 204^orC / 24 h.</td><td> 2.5</td><td> 97.60</td><td> 41.968</td><td> 48.8</td>

Being:

A: Thermic conditioning B: Plastic viscosity (cp)

C: Elastic point (kg / 100 m²)

D: Gel resistances 10 sec. 10 minutes.

(kg / 100 m²) ^* 19.95 kg / m³ of suspension in 3% NaCl Stability against Na2SO3

Na is commonly added₂SW₃ to aqueous drilling fluids in order to control corrosion by scanning oxygen. Table 12 shows the effect of adding 1,500 ppm of Na₂SW₃to an aqueous dispersion of MgAl (OH) 4.7Cl0.3. The effect is that the viscosity is generally increased. Topical levels of Na2SO3 are approximately 100 to 200 ppm.

TABLE 12

STABILITY AGAINST Na₂SW₃*

<td>TO</td><td>B</td><td>C</td><td colspan="2">D</td>

<td> 0.0</td><td> 2.0</td><td> 112.24</td><td> 39.04</td><td> 39.04</td>

<td> 1500.0</td><td> 4.0</td><td> 156.16</td><td> 39.04</td><td> 39.04</td>

Being:

A: Na2SO3 concentration (ppm)

B: Plastic viscosity (cp)

C: Elastic point (kg / 100 m²)

D: Gel resistances 10 sec. 10 minutes.

(kg / 100 m²) ^* 25.65 kg / m³ MgAl (OH) 4.7Cl0.3.

Example 8

A mixed monodispersed, very pure, low-salt, mixed-metal hydroxide mixed with the formula MgAl (OH) 4.7Cl0.3 was mixed in a concentration of 19.95 kg / m³ of aqueous solution, with various weight ratios of NaH2PO4.H2O and the viscosity properties were obtained with various shear rates (agitation RPM). These data and other rheological properties are shown in Table 13. All tests were done at ambient temperatures within the range of approximately 23-26^orC.

The addition of PO ions₄^-3 significantly increases viscosity. Similar, but less pronounced, results are obtained with other salts, such as NaCl, Na2CO3, CaCl2, and the like.

TABLE 13 RELATIONSHIP OF

Nah₂PO₄.H₂O / MgAl (OH)_{4 7}Cl_{0 3}

<td>_TO*</td><td> 0.0</td><td> 0.1</td><td> 0.2</td><td> 0.3</td><td> 0.4</td>

<td>A1</td><td> 5</td><td> 27.5</td><td> 28.5</td><td> 27</td><td> 27</td>

<td>^TO2</td><td> 3</td><td> 23</td><td> 24</td><td> 22.5</td><td> 23</td>

<td>^TO3</td><td> 2</td><td> 19</td><td> 20</td><td> 19.5</td><td> 20</td>

<td>A4</td><td> 1</td><td> 15.5</td><td> 16.5</td><td> 16</td><td> 17</td>

<td>^TO5</td><td> -</td><td> 10</td><td> 10.5</td><td> 10</td><td> 11.5</td>

<td>A6</td><td> -</td><td> 8.5</td><td> 7.5</td><td> 6</td><td> 7</td>

<td>A7</td><td> 2</td><td> 4.5</td><td> 4.5</td><td> 4.5</td><td> 4</td>

<td>^TO8</td><td> 4.88</td><td> 90.28</td><td> 95.16</td><td> 87.84</td><td> 92.72</td>

<td>A9</td><td> 0</td><td> 34.16</td><td> 31.72</td><td> 26.84</td><td> 31.72</td>

<td>^TO10</td><td> 0</td><td> 34.16</td><td> 31.72</td><td> 26.84</td><td> 31.72</td>

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TABLE 13 (continued) RELATIONSHIP OF

NaH2PO4.H2O / MgAl (OH) 4.7Cl0.3

<td>_TO*</td><td> 0.5</td><td> 0.6</td><td> 0.7</td><td> 0.8</td>

<td>A1</td><td> 25</td><td> 24.5</td><td> 21</td><td> 20</td>

<td>^TO2</td><td> 21.5</td><td> 20.5</td><td> 18</td><td> 16</td>

<td>^TO3</td><td> 19.5</td><td> 18</td><td> 15.5</td><td> 14</td>

<td>A4</td><td> 17.5</td><td> 15</td><td> 13.5</td><td> 12</td>

<td>^TO5</td><td> 12.5</td><td> 11</td><td> 10.5</td><td> 9</td>

<td>A6</td><td> 7.5</td><td> 7</td><td> 8</td><td> 7.5</td>

<td>A7</td><td> 3.5</td><td> 4</td><td> 3</td><td> 4</td>

<td>^TO8</td><td> 87.84</td><td> 80.52</td><td> 73.2</td><td> 58.56</td>

<td>A9</td><td> 31.72</td><td> 31.72</td><td> 29.28</td><td> 36.84</td>

<td>^TO10</td><td> 29.28</td><td> 26.84</td><td> 26.84</td><td> 26.84</td>

Being:

A: Essay

A1: 600 rpm

A2: 300 rpm

A3: 200 rpm

A4: 100 rpm

A5: 6rpm

A6: 3rpm

A7: Plastic viscosity, cp

A8: Elóastico point kg / 100 m²

A9: 10-sec gel, kg / 100m²

A10: Gel 10-min., Kg / 100 m²^* All measurements were made using a Fann viscometer.

Example 9

A solution of 11.2 g of MgCl2 and 32.7 g of FeCl3 in 300 ml of deionized H2O is reacted with a stoichiometric amount of NH4OH, in such a way that a thorough, rapid mixing is achieved, without using shear agitation; this provides an instant precipitation of a compound that essentially adapts to the approximate Mg1.7Fe (OH) 6Cl0.4 formula after filtering and washing. A suspension with 2.5% of solids in water exhibits thixotropic rheology.

Example 10

Similar to Example 9, an aqueous solution of 31.7 g of AlCl3.6H2O, 16.96 g of CaCl2.2H2O and 500 ml of H2O is reacted with NH3.H2O. The suspended product,

CaAl (OH) 4.5Cl0.5 exhibits thixotropic rheology. Example 11

Similarly to Example 9, three samples are prepared in which aliquots of an aqueous solution of MgCl2. 23.8% AlCl 3 are mixed, respectively, with CaCl2, BaCl2, and ZnCl2. These solutions are precipitated instantaneously by reaction with NH₄OH to prepare, correspondingly, MgCa0.3Al (OH) 6Cl0.4,

MgBa0.3Al (OH) 6Cl0.4, and Mg0.3Zn0.3Al (OH) 6Cl0.4 The precipitates are filtered, washed and diluted to approximately 2.5% of solids; each roast dispersion formed demonstrates thixotropic rheology. Example 12

In a manner similar to that of Example 9, 0.125 moles of LiCl and 0.25 moles of AlCl 3 are dissolved in deionized H2O. The resulting solution is reacted with 0.88 moles of NH4OH, with little or no agitation. The product,

Li0.5Al (OH) 3.5, is filtered and washed. A diluted sample of 17.12 kg / m³ it exhibits pseudoplasic rheology and, after dispersing in it BaSO4 for extended periods of time.

Example 13

A sample of MgAl (OH) 4.7Cl0.3 prepared by instant precipitation was diluted to 19.95 kg / m³ (2% by weight on a MgAl (OH) basis₄.₇Cl₀.₃) and 4,275 kg / m intermingled³ NaH2PO4.H2O (0.4% by weight on a NaH2PO4.H2O basis). The fluid became immediately thick. The fluid was allowed to settle for 4 days and a series of diluted fluids were prepared having the following concentrations: 2.85 kg / m³, 5.7 kg / m³, 8.55 kg / m³, 11.4 kg / m³, 14.25 kg / m³ and 17.1 kg / m³. The following table 14 contains data of plastic viscosity and elliptical point for fluids.

TABLE 14

<td>Concentration in the mixture (kg / m³)</td><td>Point elastic (kg / 100 m² )</td><td>Viscosity plastic (cp)</td>

<td> 2.85</td><td> 4.88</td><td> 1</td>

<td> 5.70</td><td> 9.76</td><td> 1</td>

<td> 8.55</td><td> 43.92</td><td> 2</td>

<td> 11.40</td><td> 68.32</td><td> 2</td>

<td> 14.25</td><td> 87.84</td><td> 2</td>

<td> 17.1</td><td> 107.36</td><td> 3</td>

<td> 19.95</td><td> 136.64</td><td> 3</td>

Example 14

Quantities of 120.7 g of AlCl3.6H2O and 101.7 g of MgCl2.6H2O were dissolved in 4 liters of deionized water. 20 g of granules of NaOH were dissolved in 2 liters of deionized water. These two progenitor solutions were pumped against each other in a tea. The resulting flocs were collected, filtered and washed. The resulting product was used to prepare a fluid with 19.95 kg / m³ of MgAl (OH) 4.5Cl0.5 in water. The fluid was very thixotropic and able to withstand BaSO4 and drilling solids.

Example 15

A solution containing 0.5 molar MgCl2 and 0.25 molar AlCl3 was prepared in deionized water. This solution was pumped into a tea against an appropriate volume of 0.5 molar NH4OH. The pH of the reaction product was 9.5. The product was filtered and washed and the composition was checked. The approximate composition was found to be Mg1.81Al (OH) 5.88Cl0.74.2.2H2O. The product was used to prepare a 19.95 kg / m fluid³ which contained NaH2PO4. The fluid was thixotropic and capable of supporting BaSO4 and drilling solids.

Example 16

In a manner similar to Example 15, a solution containing 0.75 molar MgCl2 and 0.25 molar AlCl3 in deionized water was prepared. This solution was pumped into a tea against an appropriate volume of 0.5 molar NH4OH. The pH of the reaction product was 9.5. The product was filtered and washed and the composition checked. The approximate composition was found to be Mg2.58Al (OH) 7.14Cl1.01.2H2O. The product was used to prepare a 19.95 kg / m fluid³ which contained NaH2PO4. The fluid was ti11

000 647 xotropic and capable of supporting BaSO4 and drilling solids.

Example 17

In a manner similar to Example 15, a solution containing 1.5 molar MgCl2 and 0.25 molar AlCl3 in deionized water was prepared. This solution was pumped into a tea against an appropriate volume of 0.5 molar NH4OH. The pH of the reaction product was 9.5. The product was filtered and washed and the composition checked. The approximate composition was found to be Mg3.76Al (OH) 9.5Cl1.02.2H2O. The product was used to prepare a 19.95 kg / m fluid³ which contained NaH2PO4. The fluid was thixotropic and capable of supporting BaSO4 and drilling solids. Example 18

Li0.5Mg0.75Al (OH) 4.6Cl0.4 monolayer is prepared by mixing together 500 ml of 1 molar LiCl, 750 ml of 1 molar MgCl2 and 1 liter of 1 molar AlCl3, then instantaneously precipitating the monolayer crystals transporting a solution stream together with a stream of NH4OH, the precipitate being a follicle. After filtering and washing, a wax cake filter is obtained, which has approximately 4.23% solids by weight. The cake is diluted to 2% in water (that is, approximately 19.95 kg / m³) and tested with added viscosifiers, each in an amount of 1,425 kg / m³, as shown in table 16 below.

TABLE 16

<td>Viscosifi- sweaty</td><td>PLASTIC VISCOSITY (CP)</td><td>Point elóastico (kg / 100 m²)</td>

<td>None</td><td></td><td></td>

<td>(witness)</td><td> 4.0</td><td> 34.16</td>

<td>NaH2PO4</td><td> 6.5</td><td> 75.64</td>

<td>NaHCO3</td><td> 4.0</td><td> 34.16</td>

<td>Al2SO4.9H2O</td><td> 4.5</td><td> 34.10</td>

Miscellaneous properties

Due to the chemical composition, it is essentially impossible to oxidize MgAl (OH) 4.7Cl0.3. This is of great interest to the oil industry, since it is not possible to completely eliminate oxygen and heat in drilling operations.

MgAl (OH) 4.7Cl0.3 was also unaffected by topical bacteria. Samples of fluids formulated with periodic exposure to air have been stored for approximately 6 months and no bacterial colonies have been observed.

MgAl (OH) 4.7Cl0.3 is also totally soluble in mineral acids. This is of great importance, since it is often desirable to acidify formations after a well has been drilled.

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