A method for enhancing the efficiency of hydraulic fracturing based on the principle of temporary ball pressure holding

Abstract

The present invention belongs to the technical field of coal mine safety and disaster prevention, and specifically relates to a hydraulic fracturing efficiency enhancement method based on the principle of temporary resistance ball pressure holding. The method uses a hydraulic fracturing component and a high-pressure ball pitching pump component. The water tank in the high-pressure ball pitching pump component contains fracturing liquid, and the temporary resistance ball is installed in the ball pitcher. The hydraulic fracturing component and the high-pressure ball pitching pump component are connected through a high-pressure hose and a water injection pipe column. The present invention adds temporary resistance balls during the top coal fracturing process, so that the temporary resistance balls block the original pores and cracks of the coal body along the moving direction of the water body, reduce the filtration of the water body, and then continue to block the new cracks after fracturing, so that the force of hydraulic fracturing continues to act in other directions to form more tiny cracks, thereby expanding the influence range of hydraulic fracturing, controlling the development direction of the cracks generated by hydraulic fracturing, and realizing the controllability of hydraulic fracturing, so that the coal seam is broken more thoroughly, and the coal release process is effectively realized.

Description

Technical Field

[0001] The invention belongs to the technical field of coal mine safety and disaster prevention and control, and in particular relates to a hydraulic fracturing efficiency enhancement method based on the principle of temporary resistance ball pressure holding. Background Art

[0002] There is hard top coal above the coal seam, which cannot collapse under the original mine pressure. Therefore, hydraulic fracturing or explosive blasting is used to pre-crush the hard top coal. However, there are many hazards in using explosive blasting underground in coal mines, the effect of hydraulic fracturing is not obvious, and the coal blocks are too large to be released normally after fracturing. Therefore, for the safe and efficient mining of coal mines, the principle of temporary ball pressure holding is proposed to improve the effect of hydraulic fracturing, so that the hard top coal after fracturing is more broken, which can provide important technical method guarantees for the safe and efficient recovery of existing coal resources. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a hydraulic fracturing efficiency enhancement method based on the principle of temporary ball pressure holding, which is especially suitable for the construction of top coal that is difficult to mine. The method is simple, easy to operate, and highly accurate, which reduces the factors that may cause danger in construction in the coal seam, greatly reduces the construction cost, and minimizes the impact on normal production underground. The technical solution adopted is:

[0004] A hydraulic fracturing efficiency enhancement method based on the temporary ball pressure holding principle, the method using a hydraulic fracturing assembly and a high-pressure ball pump assembly;

[0005] The hydraulic fracturing assembly includes a deflector, a one-way valve, two packers, a choke and a water injection string, which are connected in sequence according to the deflector, the one-way valve, the packer, the choke, the packer and the water injection string;

[0006] The high-pressure ball pitching pump assembly includes a ball pitcher, a fracturing pump, a high-pressure hose, a paperless recorder, and a water tank. The water tank contains fracturing liquid, and a temporary resistance ball is installed in the ball pitcher. The water tank, the fracturing pump, the ball pitcher, and the high-pressure hose are connected in sequence. The paperless recorder is connected to the fracturing pump to record the flow rate and pressure.

[0007] The hydraulic fracturing assembly and the high-pressure ball pump assembly are connected to the water injection pipe column through a high-pressure hose.

[0008] Preferably, a ball pitching cock is provided on the top of the ball pitcher, and a chamber for placing a temporary blocking ball is provided inside, and the chamber is connected to a pipeline of fracturing liquid; the connections between the water tank, fracturing pump, ball pitcher, high-pressure hose, water injection string, packer, throttle, packer, one-way valve and guide are all sealed.

[0009] Preferably, the structure of the temporary blocking ball is a core-shell coated spherical structure, the core material is a composite metal material of Mg, Al, Zn, Cu, and Ni, and the material structure is increased by adding fibers and ceramic phases, and the diameter Φ is 60μm; the shell material is a metal Mg, Al alloy material, and the thickness is less than 10μm; the intermediate filling material selects a rigid temporary blocking agent as the main material, and polyacrylamide and polyvinyl alcohol as auxiliary materials, so that the temporary blocking ball can dissolve by itself; the size of the temporary blocking ball is compatible with the high-pressure ball pitching pump assembly, and the rigid temporary blocking agent is a known material, a material commonly used in the prior art.

[0010] Preferably, the temporary resistance ball has a dissolution time of 120 hours in a potassium chloride solution at 25° C., and a maximum compressive strength of more than 100 MPa.

[0011] Preferably, the method comprises the following steps:

[0012] Step 1: Connect the hydraulic fracturing assembly and the high-pressure ball pump assembly, inject an appropriate amount of fracturing liquid into the water tank, and put a suitable number and size of temporary resistance balls into the ball pump;

[0013] Step 2: Turn on the fracturing pump, and inject the fracturing liquid in the water tank into the fracturing area through the fracturing pump. During this process, turn on the ball thrower, and the temporary blocking ball inside the ball thrower enters the high-pressure hose and enters the test area together with the liquid, thereby effectively blocking the original pores of the coal body and the fracturing pores generated by the initial fracturing;

[0014] Step 3: When the water injection pressure displayed on the paperless recorder shows a pressure drop, it proves that hydraulic fracturing has been completed in this area. At this time, continue to place temporary barrier balls, which will block the new pores generated by hydraulic fracturing, thereby performing secondary fracturing on the coal body, thereby strengthening the impact range of hydraulic fracturing and ultimately completing the hydraulic fracturing efficiency enhancement process technology.

[0015] Preferably, the high-pressure ball pump assembly releases a large number of temporary blocking balls to effectively block the original pores of the coal body and the fracturing pores generated by the initial fracturing, thereby expanding the effect of hydraulic fracturing.

[0016] Preferably, during the hydraulic fracturing process, the temporary resistance balls move with the fracturing fluid, enter the fracturing area, and seal the primary pores and fissures of the coal seam to prevent filtration, form a pressure-holding space, and then fracture the coal body.

[0017] Preferably, as the hydraulic fracturing process proceeds, the temporary blocking balls move with the fracturing fluid to block newly generated cracks, thereby generating new pressure-holding spaces, performing secondary fracturing, and expanding the degree of fracture creation in the coal body by hydraulic fracturing.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention discloses a hydraulic fracturing efficiency enhancement method based on the temporary resistance ball pressure holding principle. During the top coal fracturing process, temporary resistance balls are added so that the temporary resistance balls follow the movement direction of the water body to block the original pores and cracks in the coal body, thereby reducing the filtration loss of the water body. Subsequently, the new cracks after fracturing are continuously blocked so that the force of hydraulic fracturing continues to act in other directions to form more tiny cracks, thereby expanding the influence range of hydraulic fracturing, controlling the development direction of cracks generated by hydraulic fracturing, and realizing the controllability of hydraulic fracturing, thereby making the coal seam more thoroughly broken and effectively realizing the coal release process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the hydraulic fracturing assembly of the present invention;

[0021] Figure 2 It is a structural schematic diagram of the high-pressure ball pitching pump assembly of the present invention.

[0022] In the figure, 1-inclination; 2-check valve; 3-packer; 4-throttle; 5-water injection string; 6-high-pressure hose; 7-paperless recorder; 8-ball thrower; 9-fracturing pump; 10-water tank. DETAILED DESCRIPTION

[0023] The drawings are for illustrative purposes only; in order to better illustrate the present embodiment, some parts of the drawings are omitted, enlarged or reduced, and do not represent the size of the actual product; the terms "upper", "lower", "left", "right", "top", "outer", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. For those skilled in the art, some well-known structures, materials and their descriptions in the drawings may be omitted, such as rigid temporary plugging agents and fracturing fluids, and therefore cannot be understood as a limitation on the present invention.

[0024] In order to make the technical means, creative features, purpose and efficacy of the present invention easy to understand, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0025] A hydraulic fracturing efficiency enhancement method based on the temporary ball pressure holding principle, the method using a hydraulic fracturing assembly and a high-pressure ball pump assembly;

[0026] The hydraulic fracturing assembly system includes a deflector 1, a one-way valve 2, two packers 3, a choke 4 and a water injection string 5, which are connected in sequence according to the deflector 1, the one-way valve 2, the packer 3, the choke 4, the packer 3 and the water injection string 5;

[0027] The fracturing pump system includes a fracturing pump 9, a high-pressure hose 6, a paperless recorder 7, a water tank 10, and a ball thrower 8. The water tank 10 contains fracturing liquid, and a temporary resistance ball is installed in the ball thrower 8. The water tank 10, the fracturing pump 9, the ball thrower 8, and the high-pressure hose 6 are connected in sequence. The paperless recorder 7 is connected to the fracturing pump 9 to record the flow rate and pressure.

[0028] The hydraulic fracturing assembly and the high-pressure ball pump assembly are connected to the water injection pipe column 5 through a high-pressure hose 6 .

[0029] As a further preferred design, a ball-throwing cock is provided on the top of the ball-throwing device 8, and a chamber for placing a temporary blocking ball is provided inside, and the chamber is connected to a pipeline of the fracturing liquid; the connections among the water tank 10, the fracturing pump 9, the ball-throwing device 8, the high-pressure hose 6, the water injection string 5, the packer 3, the throttle 4, the packer 3, the one-way valve 2, and the guide bevel 1 are all sealed.

[0030] The length of the water injection string 5 is 3m, which is determined according to the drilling depth. The water injection string 5 is initially used to push the connected hydraulic fracturing assembly to the top of the hole, and then the position of the throttle 4 is adjusted by withdrawing a certain length of the water injection string 5.

[0031] The cracks produced by hydraulic fracturing are located in the interval where the choke 4 is located between the two packers 3. By changing the length of the water injection string 5 and adjusting the position of the choke 4, cracks at different positions are produced by fracturing.

[0032] As a further preference, the packer 3 is in the form of an expandable capsule. When the fracturing fluid and the temporary blocking balls injected by the fracturing pump 9 reach a certain pressure, the packer 3 expands, thereby achieving the purpose of blocking the borehole.

[0033] The throttle 4 is stretched by expanding the packers 3 at both ends, thereby opening the water outlet valve of the throttle 4, and then high-pressure water (fracturing liquid in this embodiment) flows out through the throttle 4, and finally hydraulic fracturing of the coal body is achieved in a specific part.

[0034] The structure of the temporary blocking ball is a core-shell coated spherical structure, the core material is a composite metal material of Mg, Al, Zn, Cu, and Ni, and the material structure is increased by adding fibers and ceramic phases, and the diameter Φ is 60μm; the shell material is a metal Mg, Al alloy material, and the thickness is less than 10μm; the intermediate filling material selects a rigid temporary plugging agent as the main material, and polyacrylamide and polyvinyl alcohol as auxiliary materials, so that the temporary blocking ball can dissolve by itself; the size of the temporary blocking ball is compatible with the high-pressure ball pitching pump assembly, and the dissolution time of the temporary blocking ball in a potassium chloride solution at 25°C is 120h, and the maximum compressive resistance exceeds 100MPa, which meets the needs of construction.

[0035] Specifically, when there is no overburden pressure on the top of the extra-thick top coal and it is difficult to collapse, a drilling rig is used to drill holes in the hard top coal, and multi-stage regional hydraulic fracturing is performed on the hard top coal through the drilling holes, so that multiple sections of cracks in different positions are generated in the hard top coal. However, since the original pores and cracks in the coal body are relatively developed, a large amount of liquid will be lost during the hydraulic fracturing process, making it difficult to achieve the fracturing effect. Therefore, temporary barrier balls are added during the hydraulic fracturing process to block the original pores and cracks in the coal body, forming a pressure-holding space, and effectively fracturing the coal body. When cracks are generated in the coal body, the temporary barrier balls further block the newly generated cracks in the direction of liquid migration, thereby further fracturing the coal body. The following method includes the following steps:

[0036] Step 1: Connect the hydraulic fracturing assembly and the high-pressure ball pitching pump assembly, inject an appropriate amount of fracturing liquid into the water tank 10, generally injecting about two-thirds of the volume of the water tank, and put a suitable number and size of temporary resistance balls into the ball pitcher 8 (the temporary resistance balls can be designed and manufactured according to the needs of the construction and the requirements of the high-pressure ball pitching pump assembly; the number of balls put in meets the requirement of large-scale putting);

[0037] Step 2: Turn on the fracturing pump, and inject the fracturing liquid in the water tank into the fracturing area through the fracturing pump. During this process, turn on the ball thrower, and the temporary blocking ball inside the ball thrower enters the high-pressure hose and enters the test area together with the liquid, thereby effectively blocking the original pores of the coal body and the fracturing pores generated by the initial fracturing; the temporary blocking ball can form a pressure-holding space, thereby fracturing the coal body and expanding the degree of hydraulic fracturing;

[0038] Step 3. When the water injection pressure displayed on the paperless recorder shows a pressure drop, it proves that hydraulic fracturing has been completed in this area. At this time, continue to place temporary barrier balls. The temporary barrier balls will block the new pores generated by hydraulic fracturing, and then create new pressure-holding space, thereby performing secondary fracturing on the coal body, expanding the degree of fracture formation in the coal body by hydraulic fracturing, and strengthening the impact range of hydraulic fracturing, ultimately completing the hydraulic fracturing efficiency enhancement process technology.

[0039] Compared with the original hydraulic fracturing technology, under the same pressure, flow and other parameter conditions, this method can effectively expand the fracturing range of hydraulic fracturing and enhance the hydraulic fracturing effect, thereby making the rock formation more comprehensive and ultimately achieving efficient and safe top coal release.

[0040] In the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] Other places not mentioned adopt the common practices in the prior art and will not be described in detail here.

[0042] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A hydraulic fracturing efficiency enhancement method based on the principle of temporary ball pressure holding, characterized in that: The method uses a hydraulic fracturing assembly, a high pressure ball pitching pump assembly; The hydraulic fracturing assembly includes a deflector, a one-way valve, two packers, a choke and a water injection string, which are connected in sequence according to the deflector, the one-way valve, the packer, the choke, the packer and the water injection string; The high-pressure ball pitching pump assembly includes a ball pitcher, a fracturing pump, a high-pressure hose, a paperless recorder, and a water tank. The water tank contains fracturing liquid, and a temporary resistance ball is installed in the ball pitcher. The water tank, the fracturing pump, the ball pitcher, and the high-pressure hose are connected in sequence. The paperless recorder is connected to the fracturing pump to record the flow rate and pressure. The hydraulic fracturing assembly and the high-pressure ball pump assembly are connected to the water injection string through a high-pressure hose; The structure of the temporary blocking ball is a core-shell coated spherical structure, the core material is a composite metal material of Mg, Al, Zn, Cu, Ni, and the material structure is increased by adding fiber and ceramic phase, and the diameter Φ is 60μm; the shell material is a metal Mg, Al alloy material, and the thickness is less than 10μm; the intermediate material selects a rigid temporary plugging agent as the main material, and polyacrylamide and polyvinyl alcohol as auxiliary materials; the size of the temporary blocking ball is compatible with the high-pressure ball pump assembly; the dissolution time of the temporary blocking ball at 25°C is 120h, and the maximum compressive resistance exceeds 100Mpa; The method comprises the following steps: Step 1: Connect the hydraulic fracturing assembly and the high-pressure ball pump assembly, inject an appropriate amount of fracturing liquid into the water tank, and put a suitable number and size of temporary resistance balls into the ball pump; Step 2: Turn on the fracturing pump, and inject the fracturing liquid in the water tank into the fracturing area through the fracturing pump. During this process, turn on the ball thrower, and the temporary blocking ball inside the ball thrower enters the high-pressure hose and enters the test area together with the liquid, thereby effectively blocking the original pores of the coal body and the fracturing pores generated by the initial fracturing; Step 3: When the water injection pressure displayed on the paperless recorder shows a pressure drop, it proves that hydraulic fracturing has been completed in this area. At this time, continue to place temporary barrier balls, which will block the new pores generated by hydraulic fracturing, thereby performing secondary fracturing on the coal body, thereby strengthening the impact range of hydraulic fracturing and ultimately completing the hydraulic fracturing efficiency enhancement process technology.

2. A hydraulic fracturing efficiency enhancement method based on the temporary ball pressure holding principle according to claim 1, characterized in that: A ball pitching cock is arranged on the top of the ball pitcher, and a chamber for placing a temporary blocking ball is arranged inside the chamber, and the chamber is connected to a pipeline of fracturing liquid; the connections between the water tank, fracturing pump, ball pitcher, high-pressure hose, water injection string, packer, throttle, packer, one-way valve and guide are all sealed.

3. The method for enhancing the efficiency of hydraulic fracturing based on the temporary ball pressure holding principle according to claim 1, characterized in that: The high-pressure ball-throwing pump assembly releases a large number of temporary blocking balls to effectively block the original pores of the coal body and the fracturing pores generated by the initial fracturing, thereby expanding the effect of hydraulic fracturing.

4. The method for enhancing the efficiency of hydraulic fracturing based on the temporary ball pressure holding principle according to claim 1, characterized in that: During the hydraulic fracturing process, the temporary resistance balls move with the fracturing fluid and enter the fracturing area, blocking the original pores and cracks in the coal seam to prevent filtration, form a pressure-holding space, and then fracture the coal body.

5. A hydraulic fracturing efficiency enhancement method based on the temporary ball pressure holding principle according to claim 4, characterized in that: As the hydraulic fracturing process proceeds, the temporary resistance balls move with the fracturing fluid to block the newly generated cracks, thereby creating new pressure-holding space, performing secondary fracturing, and expanding the degree of fracture creation in the coal body by hydraulic fracturing.

Images