Methods and systems for well stimulation using multiple angled fracturing

[0001] The present invention generally relates to methods, systems and devices for inducing cracks in a geological formation, and more particularly relates to methods and devices for placing a first crack with a certain first orientation in a formation, followed by a second crack with a certain second angular orientation in this formation.

[0002] Oil and gas wells often produce hydrocarbons from geological formations. Sometimes it is desirable to make additional cracks in an already cracked geological formation. For example, additional cracks may be desirable for a previously producing well that has been damaged by factors such as the migration of fine grain material. Although an existing crack may still exist, it is no longer effective or it is less effective. In such a situation, the stress caused by the first cracks still exists but does not contribute significantly to production. In another example, making a number of slots may be desirable to increase production from a reservoir bed (see, for example, document WO 0181719, which is considered the closest prior art document that discloses a certain type of system). This scenario can also be used to improve the efficiency of extraction for mining shafts, such as the injection of scrubbing steam, etc. In yet another example, additional cracks may be made to rinse the cuttings.

[0003] Conventional methods for creating additional cracks typically involve making additional cracks with an almost identical angular orientation to the previous cracks. Although such methods increase the number of locations for well drainage, they may not introduce new directions for hydrocarbons to enter the well. The conventional method may also not take into account, or even take more advantage of, stress changes within existing fractures when making new cracks.

[0004] Therefore, there is a need for an improved method of initiating multiple cracks in a wellbore, which method includes tangential forces around the wellbore.

Summary [0005] The present invention generally relates to methods, systems and devices for placing a first fracture with a first orientation in a given formation, followed by a second fracture with a second angular orientation in the same formation.

[0006] An exemplary method of the present invention is intended for fracturing a geological formation. This geological formation includes a borehole having a certain axis. The first crack is made in this geological formation. This first crack is initiated approximately at the fracturing location. The initiation of this first crack is characterized by a certain first orientation line. This first crack temporarily changes the stress field in the geological formation. A second crack is made in the geological formation. This second crack is initiated approximately at the fracturing location. The initiation of this second crack is characterized by a certain second orientation line. The first orientation line and the second orientation line are angled apart.

EP 2 069 607 Przykład1 [0007] An example of a fracturing tool according to the present invention includes a fluid receiving tool body, the tool body comprising a number of fracturing sections, and each fracturing section having at least one opening for supplying fluid to the formation geological, in some angular orientation; and a sleeve disposed in the tool body for diverting fluid to at least one of the fracturing sections, while blocking the escape of fluid from another at least one fracturing section.

[0008] An example of a geological formation fracturing system according to the present invention includes a drilling well transport system selected from the group consisting of a drill string and helical tubing, said drilling well transport system being partially located in a well; a drive mechanism configured to move the transport system in the wellbore; a pump coupled to the oil well transport system to allow fluid to flow through the oil well transport system; and a computer configured to control the operation of the drive mechanism and pump.

[0009] This fracturing tool comprises a tool body intended for receiving fluid, said tool body comprising a number of fracturing sections, each such fracturing section comprising at least one opening for supplying fluid to the geological formation in a certain angular orientation and a sleeve located in the tool body, intended to divert fluid to at least one of the fracturing sections, while the escape of fluid from another at least one of the fracturing sections is blocked.

[0010] The features and advantages of the present invention will be understood by those skilled in the art. Although those skilled in the art can make numerous changes, such changes fall within the scope of the invention.

Brief Description of the Drawings [0011] These drawings illustrate certain aspects of some embodiments of the present invention and should not be used to limit or define this invention.

[0012] Figure 1 is a block diagram of a wellbore and fracturing system;

[0013] Figure 2A is a graphic illustration of a wellbore in a geological formation and the principal stresses acting on this formation;

Figure 2B is a graphic illustration of a well in a geological formation that has undergone fracturing, as well as the main stresses acting on this formation;

[0014] Figure 3 is a flowchart illustrating a method of fracturing a formation in accordance with the present invention;

[0015] Figure 4 is a graphic illustration of a wellbore and multiple cracks at various angles, as well as the location of the fracturing in that wellbore;

[0016] Figure 5 is a graphic illustration of a formation with a high permeability area with two slits;

[0017] Figure 6 is a graphic illustration of drainage to a horizontal well that is fractured at different angular orientations;

[0018] Figures 7A, 7B, and 7C illustrate a cross-sectional view of the fracturing tool, showing some optional features according to one embodiment;

EP 2 069 607 Β1 [0019] Figure 8 is a graphic illustration of a vertical drainage of a wellbore, fractured at different angular orientations;

[0020] Figure 9 is a graphic illustration of a fracturing tool rotating in a horizontal wellbore as well as cracks caused by this fracturing tool.

Detailed description [0021] The present invention generally relates to methods, systems and devices for causing cracks in a geological formation, and more particularly relates to methods and devices for making a first crack having a certain first orientation in a formation, followed by a second crack having a certain second orientation. angular in this formation. Furthermore, the present invention can be used in wells and openings.

[0022] These methods and devices of the present invention may allow for increased performance of the well to be produced by causing multiple cracks caused at different angles with respect to each other in the wellbore.

[0023] Figure 1 is a schematic illustration of an underground wellbore through which fluid can be injected into the geological formation area surrounding this wellbore 100. The fluid can be any composition suitable for the specific injection operation to be made. For example, when the methods of the present invention are used in accordance with a fracturing stimulation treatment, the fracturing fluid may be injected into the geological formation in such a way that a fracture is made or enlarged in the area of ​​the formation surrounding the well 12 and signals are generated stress. Fluid may be injected through an injection device 105 (e.g., a pump). At drilling head 115, drilling well transport device 120 is used to feed and position fracturing tool 125 at a certain point in wellbore 100. In some embodiments, the drilling well transport device 120 may include spiral tubing. In another embodiment, the drilling well transport device 120 may include a drill string that is suitable for both moving the fracturing tool 125 along the well bore 100 and for rotating the fracturing tool 125. The drilling well transport device 120 may be driven by a drive mechanism 130. One or more sensors can be attached to the drilling well transport device 120 and configured to send signals to the control unit 135. This control unit 135 is coupled to the drive unit 130 to control the operation of the drive unit. The control unit 135 is coupled to the injection device 105 to control the injection of fluid into the wellbore 100. The control unit 135 includes one or more processors and an appropriate data carrier.

[0024] Figure 2 is an illustration of the wellbore 205 passing through some formation 210 and the stresses acting on this formation. Basically, the rock of this formation is subjected to the load of everything above it, i.e. the overburden σ_ζ. According to Poisson law, these stresses and the formation pressure effect translate into horizontal stresses σ_χ and Fr._s. Basically, however, the Poisson's ratio is not constant due to the random nature of the rock. Also geological properties, such as formation slope retention and tectonic stresses, may cause other stresses. Therefore, in most cases σ_χ and Fr._s are different.

EP 2 069 607 Β1 [0025] Figure 2B illustrates the wellbore 205 passing through the formation 210 after the crack 215 in the formation 210 is induced. Assuming for the purposes of this example that σ_χ is smaller than o_s, the crack 215 will follow in the y direction. The orientation of this crack, however, is in the x direction. As the term is used herein, the crack orientation is determined by a vector perpendicular to the crack plane.

[0026] When the crack 215 is opened, the crack is pushed in the x direction. Because the boundaries of the formation cannot move, the rock is increasingly compressed, which causes an increase in σ_χ and Fr._s, however, to varying degrees. Over time, the crack will tend to close as the rock returns to its original shape due to increased σ_χ. Changing the two horizontal stresses will cause a change in peripheral stress (shear stress around the well). However, while the crack closes, the stresses in the formation will cause the next crack to proceed in the new direction indicated by the further 220 crack. The method, arrangement and device of the present invention are associated with the initiation of cracks, such as a further crack 220, while the stress field in formation 210 is temporarily changed by a previous crack, such as crack 215.

[0027] If more fluid cannot be absorbed by the existing crack (by chemical or mechanical means), the new peripheral stress will promote the initiation of the crack at an angle relative to the first crack. The minimum tangential stress will be set at an angle between 0 and 90 degrees. This value will depend on the minimum and maximum horizontal stresses, crack width as well as the stress achieved in the crack plane during the formation of the first burn. The tangential stress will not be at 90 degrees, even if the initial horizontal stress is equal.

[0028] The above is illustrated by the following example. The principal equation for the shear (circumferential) stress distribution is given below:

(r

COSI (20) [0029] Shear stress creates a certain profile around the wellbore. The minimum value occurs at an angle Θ of zero. The shear stress value occurs at maximum at the well surface. It falls quickly to a value equal to the perpendicular primary stress in the range of several rays from the well. The axial stress on the other hand is zero at the borehole.

[0030] The circumferential stress before and after making the first fracture, given the data for the tank, given in Table 1 below is illustrated in Figure 10.

Table 1 - Input parameters for the example

<td>Parameter</td><td>value</td><td>Parameter</td><td>value</td>

<td>CTmin «PSI</td><td> 6000</td><td>Pore ​​pressure, psi</td><td> 5000</td>

<td>Omax&gt; PSI</td><td> 6500</td><td>Stress in the plane of rupture, psi</td><td> 500</td>

<td>about_r, psi</td><td> 7000</td><td>Bore radius, ft</td><td> 0.25</td>

Based on Figure 10, it is obvious that the following occurred:

• The amount of shear stress around the entire well has increased. The largest increase occurred exactly near the location where the first crack was caused.

EP 2 069 607 Β1 • The location of the minimum tangential stress has changed from a Theta angle of zero to a Theta angle of + 38 ° and -38 °.

• There are two favorable orientations for the second crack. The presence of hydraulic perforation / mining will determine which orientation will become the actual orientation of the fracture.

[0031] Lithological heterogeneity may also play a role in determining crack orientation. It is highly desirable to orient the second crack in a favorable orientation to minimize harmfulness. The technique used to create the first crack will apply when making the second crack.

[0032] After making the second fracture, it would be expected that the changes in shear stress would be even more significant relative to the orientation of the third or subsequent fracture. In addition, system symmetry will be lost. Figure 11 illustrates the shear stress profile in the first quadrant for the condition shown in Figure 10 after making two cracks. Minimal shear stress would occur at an angle of about 52 degrees, at a value slightly higher than 4700 psi.

[0033] The shear stress after the first crack was calculated was calculated by counting the increase in stress due to the presence of the crack. Assuming that the crack width is too small to affect the circular shape of the well, the tangential pressure can be calculated using a simulator operating on the basis of a mathematical model. However, the potential angle change will most likely be too small to have a significant effect under real operating conditions.

[0034] This invention can also be used to make many longitudinal cracks crossing a horizontal well. If the horizontal well is drilled in the direction of maximum stress, longitudinal fracture is usually expected. This longitudinal fracture can be performed in situations related to fracturing of the open hole, closed hole with perforations and the fractured space. The preferred method is to make a perforation or a gap or other elements enabling communication along the top and bottom of the well. One of the ways to make communication elements is to use a hydrodynamic technique known as hydrojetting.

[0035] Figure 3 is an operational diagram illustrating an exemplary method of carrying out the method of the present invention, generally indicated by reference numeral 300. This method includes determining one or more geomechanical stresses at the fracturing location as part of step 305. For some embodiments , step 305 may be skipped. For some embodiments, this step includes determining the current minimum stress direction at the fracturing location. In one embodiment, information from inclinometers or from micro-seismic tests performed in adjacent wells is used to determine geomechanical stresses at the fracturing location. For some embodiments, geomechanical stresses at a number of possible fracturing locations are plotted to find one or more locations for fracturing. Step 305 can be performed by the control unit 305 by a computer with one or more processors and an associated storage medium.

[0036] The method 300 further includes initiating the first fracture at approximately the fracturing location as part of step 310. The initiation of the first fracture is characterized by a certain line

EP 2 069 607 pierwszej1 first orientation. Basically, the crack orientation is defined as a normal vector relative to the crack plane. In this case, the characteristic first orientation line is determined by the initiation of the crack and not by its conduct. For some embodiments, the first fracture is substantially perpendicular to the minimum stress direction at the fracture location in the wellbore.

[0037] The initiation of the first fracture causes a temporary change in the stress field in the geological formation, as discussed above with reference to Figures 2A and 2B. The duration of this change in the stress field may depend on such factors as the size of the first crack, rock mechanics in the formation, fracturing fluid, as well as later injected crimping agents (proppant), if used. Due to the temporary nature of changes in the stress field in the formation, the system has limited time to initiate a second fracture at approximately the fracturing location before such temporary stress changes dissipate to a state below the level at which another fracture at the fracturing site is obtained, which is preferably reoriented. Therefore, as part of step 315, a second fracture is initiated approximately at the fracturing location, before these temporarily occurring stresses resulting from the first fracture are dispersed. For some embodiments, the first and second fractures are initiated within 24 hours of each other. In other embodiments, the first and second fractures are initiated within four hours of each other. In yet other embodiments, the first and second fractures are initiated within an hour of each other.

[0038] The initiation of the second crack is characterized by a certain second orientation line. The first orientation line and the second orientation line are at an angle to each other. The plane in which this relative position is measured may vary, depending on the fracturing tool and fracturing technique. For some embodiments, the relative angular alignment is measured on a plane substantially normal to the well axis at the fracturing location. For some embodiments, this relative angular alignment is measured on a plane substantially parallel to the well axis at the fracturing location.

[0039] In some embodiments, step 315 is performed using a fracturing tool 125, which tool is suitable for fracturing in various orientations, without having to be rotated by the drive unit 130. Such a tool can be used when the transport elements The 120 wellbore is a spiral tubing. In other embodiments, the relative angular alignment between the initiation of the cracks is obtained by rotating the drill string 130 by the drive unit 130 or otherwise reorienting the fracturing tool 125. In general, any relative angular position between orientation lines can be used. For some embodiments, the angular orientation is between 45 ° and 135 °. More specifically, for some embodiments, the angular orientation is about 90 °. In yet other embodiments, the angular orientation is oblique.

[0040] As part of step 320, the method includes initiating one or more additional cracks approximately at the fracturing location. Each of these additionally initiated cracks has a certain orientation line that has a certain relative angular orientation with respect to existing orientation lines for cracks already caused at approximately the fracturing location. In case of

EP 2 069 607 -1 of some embodiments, step 320 is omitted. Step 320 may be particularly useful for fracturing thin coal seams or diatomite formations.

[0041] The fracturing tool may be moved in the wellbore so as to initiate one or more other fractures at one or more other fracturing locations, as part of step 325. For example, steps 310, 315, and optionally 320, may be performed for one or more additional fracturing locations in the wellbore. An embodiment is shown in Figure 4. Cracks 410 and 415 are initiated at approximately one first fracturing location in borehole 405. Cracks 420 and 425 are initiated at approximately one second fracturing location in wellbore 405. For some embodiments, as illustrated in Figure 4, the cracks at two or more fracturing locations, such as cracks 410 - 425, each of which has a certain orientation and is different in angle. In other embodiments, cracks at two or more fracturing locations have crack initiation orientations that are substantially identical in angular. For some embodiments, angular orientation can be determined based on geomechanical stresses around the fracturing location.

[0042] Figure 5 is an illustration of formation 505 that includes an area 510 with increased permeability compared to other parts of formation 505 shown in this figure. For fracturing to increase hydrocarbon production, it is generally desirable to perform fracturing in an area with higher permeability, such as area 510. This high permeable area 510, however, reduces stress toward the area 510, whereby the crack will tend to increase parallel to area 510. In the embodiment of the fracturing depicted in Figure 5, the first crack 515 is caused substantially perpendicular to the direction minimum stress. This first crack 515 causes a change in the stress field in formation 505, whereby the second crack 520 can be initiated towards area 510. When crack 520 reaches area 510, it may tend to proceed in area 510 due to the stress field within area 510 . In this embodiment, the first fracture 515 may be referred to as sacrificial fracture, because its primary purpose was simply to cause a temporary change in the stress field in the formation 505, which allows the second fracture 520 to move inward within area 510.

[0043] Figure 6 illustrates fluid drainage leading from the formation to a horizontal wellbore 605 that has been fractured in accordance with method 100. In this situation, the effective surface area for drainage to the wellbore 605 is increased, compared to a fracturing case with only one angular orientation. In the example shown in Figure 6, fluid flowing along planes 610 and 615 may enter well 605. In addition, the flow flowing in fracture 615 need not enter the wellbore radially, which limits fluid flow. FIG.

also shows the flow of the stream into the fracture 615 in a parallel manner; and it then flows through fracture 615 in a manner parallel to fracture 610. This scenario results in a very efficient flow flow to the well.

[0044J In general, additional cracks, regardless of their orientation, provide better drainage to the well. Each crack will drain a portion of the formation. However, many cracks with different angular orientations will ensure the use of larger volumes of the formation, as was the case before7

EP 2 069 607 ione1 represented by the exemplary drainage areas illustrated in Figure 8. The increased volume of drained formation with a number of cracks of different orientation may cause the well to produce more fluid per unit of time.

[0045] A fragmentary view of an example fracturing tool 125, generally indicated by reference numeral 700, suitable for use with method 300, is shown in Figures 7A-7C. This fracturing tool 700 includes at least two fracturing sections, such as fracturing sections 705 and 710. Each of sections 705 and 710 is configured to perform fracturing at a certain angular orientation according to the section design. In one embodiment, the fluid flowing out of section 710 can be oriented obliquely, such as at an angle between 45 ° to 90 °, relative to the fluid flowing out of section 705. In another embodiment, the fluid flow from section 705 and the fluid flow from section 710 are substantially perpendicular. [0046] This fracturing tool includes a selection member 715, such as a sleeve, for starting or stopping fluid flow from one or more sections 705 and 710. In the embodiment illustrated here, the selection member 715 is a slide sleeve that is retained on its own. by a hook, for example. While the selection member 715 is in the position shown in Fig. 7A, fluid entering the tool body 700 exits through section 705.

[0047] A valve, such as a ball valve 725, is at least partially located in the tool body 700. This ball valve 725 includes an operating arm, enabling this ball valve 725 to slide slidably along the interior of the tool body 700, but not to leave the tool body 700. In this way, the ball valve 725 prevents fluid from escaping from the end of the fracturing tool 125. The end of the ball valve 725 with the operating arm can be prevented from falling out of the tool body 700 by, for example, using a ball seat (not shown).

[0048] The fracturing tool further includes a releasable member, such as an anchor 720, attached behind the sliding sleeve. In one embodiment, this anchor is fixed in place with, for example, a J-type socket.

[0049] In one embodiment, when the crack is induced by sections 705, this anchor 720 is released. In one embodiment, the treble is released by quickly and briefly flooding the well until the J-shaped hook attached to the treble 725 is free from the gap. In other embodiments, the release of the anchor 720 can be controlled by a control unit 135 that actuates the actuator to release the anchor 720. As illustrated in Figure 7B, the anchor 720 causes the selection member 715 to move forward, causing fluid escapes through section 710.

[0050] As illustrated in Figure 7C, the ball valve 725 with the operating arm can change the position of the tool by pushing the anchor 720 back to the locked state in the tool body 700. The ball valve 725 may also push the selection member 715 back to its original position before a crack has started. The ball valve 725 can be pushed back into the tool body 700 by, for example, flooding the well.

[0051] Another example of the fracturing tool 125 is shown in Figure 9. The tool body 910 receives the fracturing fluid through drill string 905. The tool body has an inner portion and an outer portion. Fracturing corridors pass from part 5 of the outer part at an angle, causing fluid to come out of the tool body 910 at a certain angle

EP 2 069 607 kątem1 angle to the well axis. Due to the angular orientation of the fracturing corridors, many cracks with different angular orientations can be introduced into the formation by reorienting the tool body 810. In one embodiment, the tool body is rotated to reorient the tool body to 810, the direction of fracturing returns in different orientations, and to crack 915 and 920. For example, the tool body can rotate 180 °. In the embodiment shown in Figure 9, where the cracks 915 and 920 are induced in a horizontal or deflected portion by the rake direction, the drill hole 805 can rotate more than the desired rotation of the tool body 910 to account for friction.

[0052] Therefore, the present invention is well adapted to be able to achieve the objectives and advantages mentioned herein, as well as those that result from it. The specific embodiments disclosed above are illustrative only because the present invention may be modified and performed in various but equivalent ways obvious to those skilled in the art using the disclosure provided herein. Moreover, no restrictions are foreseen as to the structural or design details presented herein other than as described in the claims below. It is therefore obvious that the specific illustrative embodiments disclosed above may be altered or modified, and any such variations are considered to be within the scope and spirit of the present invention. Also, the terms given in the claims have their simple, usually meaning, unless otherwise explicitly and clearly defined by the patent holder.