Low-permeability reservoir multi-cycle hydraulic crack expansion method and device and storage medium

Abstract

The invention relates to the technical field of oil and gas field development, in particular to a low-permeability reservoir multi-cycle hydraulic fracture expansion method and device and a storage medium. The low-permeability reservoir multi-cycle hydraulic fracture expansion method comprises the steps that the minimum horizontal principal stress and the rock fracture pressure of rock of a target interval are solved; the bottom hole pressure of the target well is obtained; enabling the reservoir to form a shear fracture expansion area; enabling the reservoir to form a tensional fracture expansion area; establishing a high flow guide channel; closing the well, measuring the pressure drop of the well mouth, and waiting for closing of the tensional crack; and the operation from the third step to the sixth step is repeated, multi-cycle liquid injection is conducted, the seam length is increased, and the expansion area of the seam network is expanded. According to the method, a displacement pressure control method is adopted, the reservoir generates shear fractures and tensile fracture zones, the tensile fractures are supported, high flow guide channels are established, the reservoir transformation volume is further increased, the recovery efficiency is improved, the effective period of measures is prolonged by two times compared with conventional fracturing, the construction cost is reduced by 10%, the oil increase of a single well is improved by 15% or above, and low-permeability reservoir benefit development can be achieved.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, specifically a method, apparatus, and storage medium for multi-circulation hydraulic fracture widening in low-permeability reservoirs. Background Technology

[0002] Low-permeability oil reservoirs have relatively low permeability, reserve abundance, and single-well productivity. Nearly two-thirds of my country's major oilfields are low-permeability reservoirs, making their development crucial. Low-permeability reservoirs are highly heterogeneous; water easily flows through thin, high-permeability layers, and the rocks are highly sensitive and easily damaged, leading to pore blockage. With continuous oilfield development, the reservoir injection-production relationship becomes increasingly complex, and phenomena such as injection failures and well failures to produce oil gradually emerge. Water drive effects are poor, gradually transitioning to depletion-type production. Formation energy declines year by year, making well selection for intervention difficult and resulting in poor development outcomes.

[0003] The main methods for improving the recovery rate of low-permeability reservoirs are hydraulically driven water injection and repeated fracturing of oil wells. Hydraulically driven water injection can effectively solve the problem of water wells not being able to inject water, but it is difficult to control the waterline direction and water channeling is prone to occur. Repeated fracturing can effectively increase oil well production, but production declines rapidly, the effective period is short, costs are high, and the input-output ratio is not up to standard. To improve the development effect of low-permeability reservoirs, it is urgent to change the development method and explore new methods to improve the recovery rate. Summary of the Invention

[0004] This invention provides a method, apparatus, and storage medium for multi-circulation hydraulic fracture widening in low-permeability reservoirs, which overcomes the shortcomings of the prior art. It can effectively solve the problems of low recovery rate, rapid decline in oil well production, short effective period, and high cost in existing low-permeability reservoirs, resulting in substandard input-output ratio.

[0005] One of the technical solutions of this invention is achieved through the following measures: a multi-cycle hydraulic fracture widening method for low-permeability reservoirs, comprising the following steps: The first step is to collect logging data from the target well and determine the minimum horizontal principal stress and rock fracture pressure of the target formation. The second step is to obtain friction data based on the small pressure test analysis and obtain the bottom hole pressure of the target well. The bottom hole pressure of the target well is controlled between the minimum horizontal principal stress and the rock fracture pressure. The third step is to inject fluid into the target well at a low flow rate to create a shear fracture expansion zone in the reservoir. The fourth step is to gradually increase the discharge rate to increase the net pressure of the fractures, thereby creating a tensile fracture expansion zone in the reservoir. The fifth step involves injecting a small amount of proppant to support the tensile fracture zone and establish a high-conductivity channel. Step 6: Close the well, monitor the pressure drop at the wellhead, and wait for the tension fractures to close. Step 7: Repeat steps 3 to 6, injecting fluid in multiple cycles to increase the crack size and expand the crack network expansion zone.

[0006] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: In the first step mentioned above, the collected data includes well logging data, stratigraphic data, structural fault attributes, reservoir physical property data, and relative permeability characteristics of the target well.

[0007] In the first step above, the process of obtaining the minimum horizontal principal stress and rock fracture pressure of the target layer includes: inputting the collected well logging data into rock mechanics software, and obtaining the minimum horizontal principal stress and rock fracture pressure of the target layer through calculation and analysis.

[0008] In the second step above, the bottom hole pressure of the target well = wellhead pressure + fluid column pressure - frictional resistance.

[0009] The third step above, the process of injecting the fluid, includes: Fluid was injected into the target well using a low flow rate, with a flow rate range of 0.5m. 3 / min to 1.0m 3 When the pressure is at / min, control the wellhead pressure to ensure that the minimum horizontal principal stress is less than the bottom hole pressure of the target well and less than the rock fracture pressure. Increase the injection rate into the target well, with a rate range of 1.0 m³. 3 / min to 3.5m 3 When the pressure is at a certain rate, control the wellhead pressure to ensure that the bottom hole pressure of the target well is greater than (rock fracture pressure + 1 MPa to 2 MPa).

[0010] In step five above, the proppant is silica sand with a concentration of 20 kg / m³. 3 Up to 50kg / m 3 The injection volume of quartz sand is 0.5m. 3 Up to 1m 3 .

[0011] In step six above, the well sump time is 5 to 24 hours.

[0012] In the seventh step above, the criteria for determining whether to expand the fracture mesh expansion zone include: stopping the pump, measuring the wellhead pressure drop, and when the wellhead pressure stabilizes and the bottom hole pressure of the target well is greater than the minimum horizontal principal stress, the construction is terminated.

[0013] The second technical solution of the present invention is achieved through the following measures: an apparatus for applying a multi-circulation hydraulic fracture widening method in low-permeability reservoirs, comprising: The pressure unit is obtained, logging data of the target well is collected, the minimum horizontal principal stress and rock fracture pressure of the target formation are calculated, and friction data are obtained based on the small pressure test analysis to obtain the bottom hole pressure of the target well. In the injection unit, a low flow rate is used to inject fluid into the target well to create a shear fracture expansion zone in the reservoir. The flow rate is gradually increased to increase the net pressure of the fractures, thereby creating a tensile fracture expansion zone in the reservoir. A small amount of proppant is injected to support the tensile fracture zone and establish a high conductivity channel. The system achieves the following: widening of the fracture unit, well closure, logging of wellhead pressure drop, closure of tensile fractures, and repeated acquisition of pressure and injection unit operations. Multiple injection cycles are used to increase fracture length and expand the fracture network expansion zone.

[0014] The third technical solution of the present invention is achieved through the following measures: a storage medium storing a computer program that can be read by a computer, the computer program being configured to execute a multi-cycle hydraulic fracture widening method for low-permeability reservoirs when running.

[0015] This invention employs a displacement pressure control method to induce shear fractures and tensile fracture zones in the reservoir, supports these tensile fractures, establishes high conductivity channels, further increases reservoir stimulation volume, and improves recovery rate. The effective period of this measure is twice that of conventional fracturing, construction costs are reduced by 10%, and single-well oil production is increased by more than 15%, enabling efficient development of low-permeability reservoirs. Attached Figure Description

[0016] Appendix Figure 1 This is a rock mechanics analysis diagram of the target well reservoir in Embodiment 11 of the present invention.

[0017] Appendix Figure 2 This is the control layout for the displacement and pressure changes of the target well in Embodiment 11 of the present invention.

[0018] Appendix Figure 3 This is a hydraulic expansion construction curve diagram of the target well in Embodiment 11 of the present invention.

[0019] Appendix Figure 4 This is a statistical chart of friction data under different displacements in Embodiment 11 of the present invention. Detailed Implementation

[0020] The present invention is not limited to the following embodiments, and the specific implementation can be determined according to the technical solution of the present invention and the actual situation.

[0021] The present invention will be further described below with reference to embodiments and accompanying drawings: Example 1: This multi-cycle hydraulic fracture widening method for low-permeability reservoirs includes the following steps: The first step is to collect logging data from the target well and determine the minimum horizontal principal stress and rock fracture pressure of the target formation. The second step is to obtain friction data based on the small pressure test analysis and obtain the bottom hole pressure of the target well. The bottom hole pressure of the target well is controlled between the minimum horizontal principal stress and the rock fracture pressure. The third step is to inject fluid into the target well at a low flow rate to create a shear fracture expansion zone in the reservoir. The fourth step is to gradually increase the discharge rate to increase the net pressure of the fractures, thereby creating a tensile fracture expansion zone in the reservoir. The fifth step involves injecting a small amount of proppant to support the tensile fracture zone and establish a high-conductivity channel. Step 6: Close the well, monitor the pressure drop at the wellhead, and wait for the tension fractures to close. Step 7: Repeat steps 3 to 6, injecting liquid in multiple cycles to increase the suture length and expand the suture mesh expansion area.

[0022] This invention employs a displacement pressure control method to induce shear fractures and tensile fracture zones in the reservoir, supports these tensile fractures, establishes high conductivity channels, further increases reservoir stimulation volume, improves recovery rate, reduces construction costs, and achieves efficient development of low-permeability reservoirs.

[0023] The following are further optimizations and / or improvements to the above-mentioned technical solution: Example 2: As an optimization of the above example, in the first step, the collected data includes well logging data, stratigraphic data, structural fault attributes, reservoir physical property data, and relative permeability characteristics of the target well.

[0024] Example 3: As an optimization of the above example, the process of obtaining the minimum horizontal principal stress and rock fracture pressure of the target layer in the first step includes: inputting the collected well logging data into rock mechanics software, and obtaining the minimum horizontal principal stress and rock fracture pressure of the target layer through calculation and analysis.

[0025] Example 4: As an optimization of the above example, in the second step, the bottom hole pressure of the target well = wellhead pressure + fluid column pressure - frictional resistance.

[0026] Example 5: As an optimization of the above examples, the third step, the process of injecting the liquid includes: Fluid was injected into the target well using a low flow rate, with a flow rate range of 0.5m. 3 / min to 1.0m 3 When the pressure is at / min, control the wellhead pressure to ensure that the minimum horizontal principal stress is less than the bottom hole pressure of the target well and less than the rock fracture pressure. Increase the injection rate into the target well, with a rate range of 1.0 m³. 3 / min to 3.5m 3When the pressure is at a certain rate, control the wellhead pressure to ensure that the bottom hole pressure of the target well is greater than (rock fracture pressure + 1 MPa to 2 MPa).

[0027] Example 6: As an optimization of the above example, in step 5, the proppant is quartz sand with a concentration of 20 kg / m³. 3 Up to 50kg / m 3 The injection volume of quartz sand is 0.5m. 3 Up to 1m 3 .

[0028] Example 7: As an optimization of the above example, in step 6, the well suffocation time is 5h to 24h.

[0029] Example 8: As an optimization of the above example, in the seventh step, the criteria for determining the expansion of the fracture mesh expansion zone include: stopping the pump, measuring the wellhead pressure drop, and when the wellhead pressure stabilizes and the bottom pressure of the target well is greater than the minimum horizontal principal stress, the construction is terminated.

[0030] Example 9: Apparatus for the multi-cycle hydraulic fracture widening method for low-permeability reservoirs described above.

[0031] Example 10: The storage medium stores a computer program that can be read by a computer, and the computer program is configured to execute a multi-cycle hydraulic fracture widening method for low-permeability reservoirs when it is run.

[0032] The aforementioned storage media may include, but are not limited to, USB flash drives, read-only memory, portable hard drives, magnetic disks, optical disks, and other media capable of storing computer programs.

[0033] The aforementioned processor can be a central processing unit (CPU), a general-purpose processor, a digital signal processor (DSP), a SiC (Silicon Integrated Circuit) method for multi-cycle hydraulic expansion in low-permeability reservoirs, an FPG (Floating Processing Generator) method for multi-cycle hydraulic expansion in low-permeability reservoirs, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. It can also be a combination that implements computational functions, such as including one or more microprocessor combinations, a combination of a DSP and a microprocessor, etc. The memory can include, but is not limited to, various media capable of storing computer programs, such as USB flash drives, read-only memory, portable hard drives, magnetic disks, or optical disks.

[0034] Those skilled in the art will understand that the embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The solutions in the embodiments of this application can be implemented using various computer languages, such as the object-oriented programming language J and the interpreted scripting language JScript, etc.

[0035] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0036] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0037] Example 11: A multi-circulation hydraulic fracture widening method for a low-permeability reservoir (X1) in Xinjiang, comprising the following steps: The first step involves collecting logging data from the target well, including GR, RT, DEN logging data, and production information (as shown in Table 1). This data is used to determine the minimum horizontal principal stress (SH2) and rock fracture pressure (PF) of the target formation. The collected data includes logging data from the target well, stratigraphic data, structural fault attributes, reservoir properties, and relative permeability characteristics. The process for determining the minimum horizontal principal stress and rock fracture pressure of the target formation involves inputting the collected logging data into rock mechanics software (Rockview). Through calculation and analysis, the minimum horizontal principal stress of the target formation (73.1 MPa) and the rock fracture pressure (79.2 MPa) are obtained. Figure 1 As shown in Table 2 (in Table 2, SH1 is the maximum horizontal injection stress, SH2 is the minimum horizontal principal stress, and PF is the rock fracture pressure); Figure 1 As can be seen from Table 2, the longitudinal minimum principal stress data curve and the fracture pressure data curve (target layer) are consistent with the data in Table 2; The second step involves reducing the displacement in stages and obtaining friction data for different displacements based on low-pressure test analysis (e.g., ...). Figure 4 As shown), displacement 0.8m 3 / min, frictional resistance approximately 9MPa, obtain the bottom hole pressure of the target well (e.g. Figure 2 As shown in the figure, the bottom hole pressure of the target well = wellhead pressure + fluid column pressure - frictional resistance, and the bottom hole pressure of the target well is controlled between the minimum horizontal principal stress and the rock fracture pressure. The third step involves injecting fluid into the target well at a low flow rate to create a shear fracture expansion zone in the reservoir. The low flow rate is 0.8 m³ / min. 3 / min, control 39.5MPa < wellhead pressure < 45.6MPa, ensuring the minimum horizontal principal stress of the target formation rock is < bottomhole pressure < rock fracture pressure, inject for 12 hours (time can be adjusted according to production conditions), inject 432m³ of fluid. 3 Among them, the simulated construction curve (after 3 rounds of operation) is as follows: Figure 3 As shown; The fourth step is to gradually increase the displacement to 2.0m. 3 Increase the net fracture pressure by 1 / min, control the wellhead pressure to >57.6MPa, and ensure the bottom hole pressure is >(rock fracture pressure + 1MPa). Inject fluid for 30m. 3 This causes the reservoir to form a tensile fracture expansion zone, such as Figure 3 As shown; The fifth step involves injecting 40 / 70 mesh quartz sand proppant at a concentration of 20 kg / m³. 3 Up to 50kg / m 3 The amount of sand injected is 0.5m. 3 Pumps are stopped intermittently to support tensile fracture zones and establish high flow channels, such as... Figure 3 As shown; Step 6: Close the well, monitor the pressure drop at the wellhead, and wait for the tension fractures to close. Figure 3 As shown; Step 7: Repeat steps 3 to 6, perform multiple cycles of fluid injection to increase the fracture length, stop the pump and measure the pressure drop. If (wellhead pressure (stable) + fluid column pressure) > the minimum horizontal principal stress SH2 of the rock in the target layer, the construction is completed, and the fracture network expansion zone is achieved.

[0038] In summary, this invention employs a displacement pressure control method to induce shear fractures and tensile fracture zones in the reservoir, supports the tensile fractures, establishes high conductivity channels, further increases the reservoir stimulation volume, and improves the recovery rate. The effective period of this measure is twice that of conventional fracturing, the construction cost is reduced by 10%, and the oil production per well is increased by more than 15%, enabling efficient development of low-permeability reservoirs.

[0039] The above technical features constitute the preferred embodiment of the present invention, which has strong adaptability and optimal implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the requirements of different situations.

Claims

1. A method of multi-cycle hydraulic fracture spreading in low permeability reservoirs, characterized in that, The method comprises the following steps: In the first step, the logging data of the target well is collected, and the minimum horizontal principal stress and rock breakdown pressure of the target layer are calculated. In the second step, the friction data is calculated according to the small pressure test analysis, and the bottom hole pressure of the target well is obtained, wherein the bottom hole pressure of the target well is controlled between the minimum horizontal principal stress and the rock breakdown pressure. In the third step, liquid injection is performed on the target well at a low displacement, so that a shear fracture expansion zone is formed in the reservoir. In the fourth step, the displacement is gradually increased to increase the net pressure of the fracture, so that a tensile fracture expansion zone is formed in the reservoir. In the fifth step, a small amount of proppant is injected to support the tensile fracture zone and establish a high conductivity channel. In the sixth step, the well is shut in, the wellhead pressure drop is measured, and the tensile fracture is closed. In the seventh step, the third to sixth steps are repeated to perform multiple cycle liquid injection, increase the fracture size, and realize the expansion of the fracture network expansion zone.

2. The low permeability reservoir multi-cycle hydraulic fracture spreading method of claim 1, wherein, In the first step, the collected data includes logging data, stratification data, structural fault attributes, reservoir physical property data, and relative permeability characteristics of the target well.

3. The low permeability reservoir multi-cycle hydraulic fracture opening method of claim 1 or 2, wherein, In the first step, the calculation process of the minimum horizontal principal stress and the rock breakdown pressure of the target layer includes: inputting the collected logging data into a rock mechanics software, and calculating and analyzing to obtain the minimum horizontal principal stress and the rock breakdown pressure of the target layer.

4. The low permeability reservoir multi-cycle hydraulic fracture opening method of claim 1 or 2 or 3, wherein, In the second step, the bottom hole pressure of the target well = wellhead pressure + liquid column pressure - friction.

5. The low permeability reservoir multi-cycle hydraulic fracture spreading method according to any one of claims 1 to 4, wherein, In the third step, the liquid injection process includes: The liquid is injected into the target well at a low flow rate, and the low flow rate ranges from 0.5 m 3 / min to 1.0 m 3 / min, the wellhead pressure is controlled, and the minimum horizontal principal stress is less than the bottom hole pressure of the target well and less than the rock fracture pressure. The injection liquid is injected into the target well at a flow rate ranging from 1.0 m 3 / min to 3.5 m 3 / min, and the wellhead pressure is controlled so that the bottom hole pressure of the target well is > (rock fracture pressure + 1 MPa to 2 MPa).

6. The low permeability reservoir multi-cycle hydraulic fracture spreading method of any of claims 1-5, wherein, In the fifth step, the proppant is quartz sand, and the concentration of the quartz sand is 20 kg / m 3 to 50 kg / m 3 . The injection amount of the quartz sand is 0.5 m 3 to 1 m 3 .

7. The low permeability reservoir multi-cycle hydraulic fracture spreading method of any of claims 1-6, wherein, In the sixth step, the shut-in time is 5 to 24 hours.

8. The low permeability reservoir multi-cycle hydraulic fracture spreading method of any of claims 1-7, wherein, In the seventh step, the judgment standard for realizing the expansion of the fracture network expansion zone includes: stopping the pump, measuring the wellhead pressure drop, and when the wellhead pressure is stable, the bottom hole pressure of the target well > the minimum horizontal principal stress, the construction is ended.

9. An apparatus for applying a low permeability reservoir multi-cycle hydraulic fracture extension method according to any one of claims 1 to 8, characterized in that, The method comprises: In the pressure acquisition unit, the logging data of the target well is collected, the minimum horizontal principal stress and rock breakdown pressure of the target layer are calculated, and the friction data is calculated according to the small pressure test analysis to obtain the bottom hole pressure of the target well. In the liquid injection unit, liquid injection is performed on the target well at a low displacement to form a shear fracture expansion zone in the reservoir, the displacement is gradually increased to increase the net pressure of the fracture, so that a tensile fracture expansion zone is formed in the reservoir, and a small amount of proppant is injected to support the tensile fracture zone and establish a high conductivity channel. In the fracture expansion unit, the well is shut in, the wellhead pressure drop is measured, and the tensile fracture is closed, and the operations of the pressure acquisition unit and the liquid injection unit are repeated to perform multiple cycle liquid injection, increase the fracture length, and realize the expansion of the fracture network expansion zone.

10. A storage medium, characterized by The storage medium has a computer program readable by a computer stored thereon, and the computer program is configured to execute the low-permeability reservoir multi-cycle hydraulic fracture expansion method according to any one of claims 1 to 8 when running.

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