Design method of temporary plugging formula of gel and granular materials in deep fractured oil and gas layers

Abstract

The present invention discloses a method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers, and belongs to the technical field of working fluid leakage control and reservoir protection. The present invention is based on the following discovery: in the temporary plugging formula of gel and granular materials for deep fractured oil and gas layers, the relationship between the storage modulus and the pressure bearing capacity of the gel is an S-shaped curve, and a tangent is made through the origin to the upper convex arc segment of the S-shaped curve. The compounding of the gel and particles corresponding to the storage modulus at the tangent point can obtain a temporary plugging formula with better plugging capacity during plugging and better flow conductivity after unblocking. Therefore, when designing the formula, a gel formula with a small absolute value of the difference between the storage modulus and the storage modulus at the tangent point is preferably selected. The design method is simple to operate, and the designed formula has a strong pressure bearing capacity during plugging and a good flow conductivity after unblocking.

Description

Technical Field

[0001] The invention relates to the technical field of working fluid leakage control and reservoir protection in petroleum and natural gas engineering, and in particular to a method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers. Background Art

[0002] As the development of oil and gas resources advances deeper into the formation, drilling technology is also facing unprecedented challenges. Deep-ultra-deep fractured oil and gas layers have geological characteristics such as high temperature, high pressure, high ground stress, and well-developed natural fractures with wide fracture widths. Complex downhole conditions often occur during the drilling process, among which the problem of drilling fluid leakage is particularly serious. Drilling fluid leakage will not only cause huge economic losses and extend the drilling cycle, but may also induce drilling accidents such as overflow, blowout and well wall collapse, seriously endangering drilling safety. Drilling fluid leakage in the reservoir section will also cause irreversible reservoir damage and significantly reduce the production of oil and gas wells. Since the harsh geological conditions of deep-ultra-deep layers have brought great difficulties and challenges to reservoir production enhancement and transformation, controlling well leakage and protecting natural fractures are of great significance to the development of deep-ultra-deep oil and gas layers.

[0003] At present, a gel and granular material coordinated temporary plugging technology has been developed to address large-scale fracture leakage in deep and ultra-deep fractured oil and gas layers. This technology uses acid-soluble gel materials in conjunction with high-strength inert granular materials to temporarily plug the fractures. The good deformation ability of the gel material is used to adaptively block the leakage channels and prevent the loss of drilling fluid. Before completion and production, the gel material is selectively removed by acid injection, and the high-strength inert granular material supports the fractures to increase the fracture conductivity.

[0004] Based on existing research, it has been shown that the gel storage modulus is positively correlated with the plugging performance (pressure bearing capacity of the fracture plugging layer). The traditional gel storage modulus optimization method focuses on continuously increasing the storage modulus to improve the gel's plugging performance. The increase in storage modulus can certainly make the gel have better plugging performance, but as the storage modulus of the gel increases, the gel tends to be more and more elastic. The properties of the solid reduce or even lose its flow deformation ability, resulting in the gel only forming a plugging layer near the entrance of the fracture. If the gel and granular material synergistic temporary plugging formula design is based on the traditional gel storage modulus optimization method, a good plugging effect can be obtained, but the granular material cannot be carried into the deep fracture by the gel. After the acid is injected to dissolve the gel before the completion and production, the granular material can only support the fracture near the entrance of the fracture, and the supporting effect is poor. Therefore, the traditional gel storage modulus optimization method is not suitable for the gel and granular material synergistic temporary plugging technology. Summary of the invention

[0005] In order to solve the above problems, the purpose of the present invention is to provide a method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers. The method is based on the following findings of the inventors: in the temporary plugging formula of gel and granular materials for deep fractured oil and gas layers, the relationship between the gel storage modulus and the pressure bearing capacity is an S-shaped curve, and a tangent is made through the origin to the upward convex arc segment of the S-shaped curve. The compound of gel and particles corresponding to the storage modulus at the tangent point can obtain a temporary plugging formula with better plugging ability during plugging and better conductivity after unblocking.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers, comprising the following steps:

[0008] S1. Screening an acid-soluble gel formula, wherein the screening rule includes: preferentially selecting a gel formula having a small absolute value of the difference between the storage modulus and the optimal storage modulus;

[0009] Wherein, determining the optimal storage modulus comprises the following steps:

[0010] S11, determining gel components, configuring gels with different storage moduli by adjusting the content of each gel component, and determining the pressure bearing capacity of the crack plugging layer of the gels with different storage moduli through a crack plugging experiment;

[0011] S12, with the storage modulus as the horizontal coordinate, draw the storage modulus-pressure bearing capacity relationship curve of the gel, and make a tangent through the origin to the upward convex arc segment of the curve, and the storage modulus corresponding to the tangent point is the optimal storage modulus;

[0012] When screening gel formulas, the screening rules also include the acid solubility of the gel. A low acid solubility is not conducive to the recovery of the later conductivity. In specific implementation, an acid solubility threshold can be preset to eliminate gel formulas below the preset acid solubility threshold. The preset acid solubility threshold can be determined as needed, such as 90wt%, 95wt%, etc.

[0013] S2. The gel formula selected in S1 and the non-acid-soluble granular material are used as compound raw materials to prepare synergistic temporary plugging slurries with different gel contents. Through fracture plugging and unplugging experiments, the effective supporting length of the particles in the fracture after unplugging of each synergistic temporary plugging slurry is determined. The synergistic temporary plugging slurry with a long effective supporting length is preferentially selected as the synergistic temporary plugging formula of gel and granular materials for deep fractured oil and gas layers.

[0014] In this step, the granular material needs to have sufficient compressive resistance to provide support. In specific implementation, the crushing rate can be used as a screening index, for example, the granular material with a crushing rate of less than 5wt% under the closure pressure of the cracks in the target layer can be screened.

[0015] As a specific embodiment of the present invention, the particle size of the granular material is 0.3 to 0.5 times the crack width.

[0016] The crack plugging experiment in step S11 is mainly used to determine the pressure bearing capacity of the plugging layer formed after the gel injection. As a specific embodiment of the present invention, the crack plugging experiment includes the operations of generating a plugging layer and testing the pressure bearing capacity of the plugging layer, wherein the operation of generating the plugging layer includes the following steps: injecting gel into the crack in a constant pressure displacement manner until the gel can no longer be injected, which is regarded as forming a stable plugging layer, and continuing to inject gel will not increase the thickness of the plugging layer; the operation of testing the pressure bearing capacity of the plugging layer includes gradually increasing the pressure of the plugging layer inlet fluid until the fluid flow reaches a certain preset threshold value, which is regarded as the fluid penetrating the plugging layer and the plugging of the plugging layer fails.

[0017] In step S2, the crack plugging and unplugging experiment is used to determine the effective support length after the collaborative temporary plugging slurry is unplugged, which includes two steps of forming a plugging layer and breaking the gel. In a specific embodiment of the present invention, the operation of forming the plugging layer is the same as step S11, that is, injecting the collaborative temporary plugging slurry into the crack in a constant pressure displacement manner until the collaborative temporary plugging slurry can no longer be injected; the operation of breaking the gel is to add acid to the crack.

[0018] Compared with the existing technology, it has the following advantages:

[0019] The method for designing a temporary plugging formula of gel and granular materials proposed in the present invention is simple to operate. The formula designed by this method can effectively plug large-scale cracks during drilling and carry high-strength inert particles into the deep part of the cracks. Before completion and production, the gel material is dissolved by acid injection to leave a supporting crack with a large effective length, thereby increasing the fracture conductivity and improving oil and gas production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the relationship curve between the storage modulus of SMG gel and the pressure bearing capacity of the crack plugging layer;

[0021] Figure 2 This is a curve diagram showing the relationship between the storage modulus of the shear thixotropic gel and the pressure bearing capacity of the crack sealing layer. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0023] Example 1

[0024] The plugging formula of this embodiment is aimed at deep fractured oil and gas layers in a certain area. After studying the geological data and well logging data of the area, it is predicted that the reservoir fracture width is 10.0 mm and the fracture closure pressure is 30.0 MPa. The basic raw materials designed for the formula of this embodiment are SMG gel and LCC100 particles with a particle size of 4 mm, among which the SMG gel component comes from Xinjiang Gredis Petroleum Technology Co., Ltd.; LCC100 particles come from Chengdu Dedao Industrial Co., Ltd., which is a high-strength inert granular material that does not react with acid and has a mass crushing rate of 4.1% under a pressure of 30.0 MPa.

[0025] The method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers of this embodiment includes the following steps:

[0026] S1. Screening acid-soluble gel formulas, the screening rules include:

[0027] Gel formulas with a small absolute value of the difference between the storage modulus and the optimal storage modulus are preferably selected;

[0028] Wherein, determining the optimal storage modulus includes the following steps:

[0029] S11 and SMG gel components were used as raw materials, and SMG gels with different storage moduli were prepared by changing the amount of cross-linking agent polyethylene glycol (PEG-200). After testing, their acid solubility was greater than 92wt%. Then, the pressure bearing capacity of the crack sealing layer of gels with different storage moduli was determined through crack sealing experiments.

[0030] This fracture plugging experiment was tested using a high-temperature and high-pressure plugging instrument made by Southwest Petroleum University. In the fracture core model used, the width of the fracture was 10.0 mm and the length was 1000.0 mm. The specific steps of the experiment were as follows: the fracture core model was loaded into the holder of the high-temperature and high-pressure plugging instrument, and the confining pressure was set to 30 MPa; the heating switch of the high-temperature and high-pressure plugging instrument was turned on, and the temperature was set to 120 ° C (simulating the formation temperature); gel was loaded into the kettle of the high-temperature and high-pressure plugging instrument, and the downstream valve of the holder was closed; the initial displacement pressure was controlled to be no higher than 0.5 MPa, and the downstream valve of the holder was opened after the plugging layer was formed; the displacement pressure was gradually increased until the plugging layer was broken, and the pressure bearing capacity of the fracture plugging layer was recorded. The test results are shown in Table 1.

[0031] Table 1 Data table of pressure bearing capacity of crack sealing layer of SMG gel with different storage modulus

[0032]

[0033] S12. With the storage modulus as the horizontal coordinate, draw a storage modulus-pressure bearing capacity relationship curve of the gel, and draw a tangent through the origin to the upward convex arc segment of the curve. The storage modulus corresponding to the tangent point is the optimal storage modulus.

[0034] like Figure 1 As shown in the figure, the plane rectangular coordinate system scatter diagram of the storage modulus of SMG gel and the pressure bearing capacity of the crack plugging layer is first drawn, and then the relationship curve between the storage modulus of SMG gel and the pressure bearing capacity of the crack plugging layer is obtained by the polynomial fitting method, R 2 =0.99646. Finally, a tangent line is drawn above the curve through the origin of the coordinate system. The storage modulus corresponding to the tangent point is 7.2 kPa.

[0035] Therefore, SMG gel with a storage modulus of 6.8 kPa was selected as the preferred gel formulation.

[0036] S2, using the gel formula screened in S1 and the non-acid-soluble granular material (LCC100) as compound raw materials, prepare gel and granular synergistic temporary plugging slurries with granular mass contents of 10%, 15%, 20%, and 25%, respectively, and determine the effective support length of the granules in the fracture after the gel and granular synergistic temporary plugging slurry is unblocked through fracture plugging and unblocking experiments. The specific steps of the experiment are as follows: 1) Load the fracture core model into the holder of the high-temperature and high-pressure plugging instrument and set the confining pressure to 30MPa; 2) Turn on the heating switch of the high-temperature and high-pressure plugging instrument and set the temperature to 120℃ (simulating the formation temperature); 3) Add water to the high-temperature and high-pressure plugging instrument. Gel and particle coordinated temporary plugging slurry were loaded into the axe body, and the downstream valve of the clamp was closed; 4) The initial displacement pressure was controlled to be no higher than 0.5MPa, and the downstream valve of the clamp was opened after the plugging layer was formed; 5) The displacement pressure was gradually increased until the plugging layer was broken, and the pressure bearing capacity of the fracture plugging layer was recorded; 6) Steps 1) to 4) were repeated, and the displacement pressure was gradually increased to the pressure bearing capacity, and the pressure was relieved and the downstream valve of the clamp was closed; 7) 10% hydrochloric acid plugging solution was loaded into the kettle of the high temperature and high pressure plugging instrument, and the displacement pressure was controlled to 0.5MPa; 8) After waiting for 1 hour, the fracture core model was taken out and disassembled to measure the effective support length of particle B in the fracture. The results are shown in Table 2.

[0037] Table 2 Data of effective support length of fractures of synergistic temporary plugging slurry prepared with SMG gel with storage modulus of 6.8 kPa

[0038] LCC100 mass concentration / % 10 15 20 25 Effective support length / mm 422.6 698.9 870.2 626.0

[0039] According to the test results in Table 2, the gel and particle synergistic temporary plugging slurry with the longest effective support length was selected as the gel and particle material synergistic temporary plugging formula for deep fractured oil and gas layers, that is, the final formula was determined to be: 80wt% SMG gel with a storage modulus of 6.8kPa + 20wt% 4.0mm LCC100 particles, and this formula was recorded as formula #1.

[0040] Comparative Example 1

[0041] SMG gel with a storage modulus of 9.8 kPa and the particle material of Example 1 were used as compound materials, and gel and particle synergistic temporary plugging slurries with particle mass contents of 10%, 15%, 20%, and 25% were configured, and crack plugging and unplugging experiments were performed to determine the effective support length of the particles in the crack after unplugging of each gel and particle synergistic temporary plugging slurry. The test results are shown in Table 3.

[0042] Table 3 Data of effective support length of fractures of synergistic temporary plugging slurry prepared with SMG gel with storage modulus of 9.8 kPa

[0043] LCC100 mass concentration / % 10 15 20 25 Effective support length / mm 189.4 211.9 289.7 233.7

[0044] According to the data in Table 3, the final preferred formula is determined to be: 80wt% SMG gel with a storage modulus of 9.8kPa+20wt% 4.0mm LCC100 particles. This formula is recorded as Formula #2.

[0045] Comparative Example 2

[0046] The SMG gel with a storage modulus of 3.8 kPa and the granular material of Example 1 were used as compound materials, and the gel and particle synergistic temporary plugging slurries with particle mass contents of 10%, 15%, 20%, and 25% were configured. Through crack plugging and unplugging experiments, the effective support length of the particles in the crack after unplugging of each gel and particle synergistic temporary plugging slurry was determined. The test results are shown in Table 4.

[0047] Table 4 Data of effective support length of fractures of synergistic temporary plugging slurry prepared with SMG gel with storage modulus of 3.8 kPa

[0048] LCC100 mass concentration / % 10 15 20 25 Effective support length / mm 756.3 873.2 989.2 1000.0

[0049] According to the data in the above table, the final preferred formula is determined to be: 75wt% SMG gel with a storage modulus of 3.8kPa+25wt% 4.0mm LCC100 particles. This formula is recorded as Formula #3.

[0050] Fracture plugging experiments were conducted on the variable width fracture core model using formula #1, formula #2, and formula #3 to test the pressure bearing capacity of the fracture plugging layer of each group of formulas; and then unplugging experiments were conducted to test the permeability recovery rate and stress sensitivity coefficient of the supporting fractures of each group of formulas after acid injection unplugging. The experimental data are shown in Table 5.

[0051] Permeability recovery rate test steps: 1) Place the variable width fracture core model into the holder and test its permeability K at different confining pressure points 0i; 2) Set the confining pressure to 30MPa, turn on the heating switch of the high-temperature and high-pressure plugging instrument, and set the temperature to 120℃; 3) Load the gel and particle coordinated temporary plugging slurry into the axe of the high-temperature and high-pressure plugging instrument, and close the downstream valve of the clamp; 4) Control the initial displacement pressure not higher than 0.5MPa, and open the downstream valve of the clamp after the plugging layer is formed; 5) Gradually increase the displacement pressure until the plugging layer is broken, and record the pressure bearing capacity of the crack plugging layer; 6) Repeat steps 1) to 4), gradually increase the displacement pressure to the pressure bearing capacity, relieve the pressure and close the downstream valve of the clamp; 7) Load 10% hydrochloric acid plugging solution into the axe of the high-temperature and high-pressure plugging instrument, and control the displacement pressure to 0.5MPa; 8) After waiting for 1h, test the permeability K of the variable width fracture core model at different confining pressure points 1i , the calculation formula is as follows:

[0052]

[0053] In the formula, R A is the permeability recovery rate of the supporting fracture; k 0i is the permeability of the variable width fracture core model without proppant particles in the i-th test; k 1i is the permeability of the core model with variable width fractures containing supporting particles in the i-th test.

[0054] Table 5 Experimental data of sealing effect and crack support effect of each group of formulas

[0055]

[0056] According to the above test results, by comparing formula #1 with formula #2, the formula designed by the gel storage modulus optimization method of this patent has only reduced the pressure bearing capacity by 10.2%, and the support crack permeability recovery rate has increased by 59.2%, and the stress sensitivity coefficient has decreased by 19.4%. It is enough to see that the gel storage modulus optimization method proposed by this patent is more suitable for the gel and granular material coordinated temporary plugging technology than the traditional gel storage modulus optimization method. By comparing formula #1 with formula #3, if a smaller gel storage modulus than the one optimized by this patent is selected, the support effect is indeed slightly better than the formula designed by this patent, but the pressure bearing capacity of this formula has seriously declined to only 3.9MPa. Therefore, comprehensively speaking, formula #1 should be selected, which has better plugging performance and drainage performance after unblocking.

[0057] Example 2

[0058] The plugging formula of this embodiment is aimed at deep fractured oil and gas layers in a certain area. After studying the geological data and well logging data of the area, it is predicted that the reservoir fracture width is 8.0 mm and the fracture closure pressure is 35.0 MPa. The basic raw materials of the formula design of this embodiment are shear thixotropic gel and ceramsite with a particle size of 3 mm. Among them, the shear thixotropic gel is a gel material that can be broken by acid injection. The preparation method thereof is as follows: firstly, a certain mass of acrylamide is weighed and dissolved in deionized water in a three-necked flask, and a certain proportion of high temperature crosslinking agent BWL (high temperature crosslinking agent BW L is a high molecular weight polyacrylamide microgel crosslinker synthesized by reverse microemulsion polymerization using acrylamide AM as a polymerization monomer, and has a large number of -C=C- active reactive groups. The specific preparation method is as follows: (1) acrylamide (AM) and ammonium persulfate (APS) in a mass ratio of 1:1 are stirred and fully dissolved in deionized water to obtain an AM aqueous solution and an initiator aqueous solution; (2) Span 80 and Tween 60 are mixed in a mass ratio of 5:12, and cyclohexane 4 times the mass of the mixture is added and stirred to obtain an active oil phase solution; (3) using a dropwise addition method to add the AM aqueous solution to the active oil phase solution, stirring evenly and clarifying to obtain an AM reverse microemulsion, and using a dropwise addition method to add the APS aqueous solution to the AM reverse microemulsion, stirring and reacting for 4 hours under a 60°C water bath condition to obtain a stable and translucent BWL microemulsion; (4) using an excess of anhydrous ethanol to precipitate the modified BWL microemulsion, and washing the product for more than three times, drying and crushing at 60°C to obtain a BWL crosslinker powder), stirring for a period of time to obtain a solution A; weighing a certain amount of lithium magnesium silicate and placing it in a calcined Use a low-speed stirrer to stir the mixture for 20-30 minutes in a cup until the solution is free of lumps, uniform and precipitated, and obtain solution B; weigh a certain amount of ammonium persulfate and sodium bisulfite (mass ratio 1:1) and dissolve them in deionized water to prepare a 30% concentration initiator solution; mix the prepared solutions A and B in a three-necked flask, add the initiator solution dropwise, continue stirring for 30 minutes, and connect the nitrogen bottle to the three-necked flask, introduce nitrogen for deoxygenation, and after completion, transfer the blend to a 60°C water bath for polymerization for 6 hours to obtain a shear thixotropic gel. Among them, the amount of acrylamide added is 7.5%, the amount of high temperature crosslinking agent BWL added ranges from 0.4% to 1.5%, the amount of lithium magnesium silicate added is 4%, and the amount of initiator system added is 0.4%. Ceramsite is a high-strength inert granular material that can be purchased commercially.

[0059] The method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers of this embodiment includes the following steps:

[0060] S1. Screening acid-soluble gel formulas, the screening rules include:

[0061] Gel formulas with a small absolute value of the difference between the storage modulus and the optimal storage modulus are preferably selected;

[0062] Wherein, determining the optimal storage modulus includes the following steps:

[0063] S11. Shear thixotropic gels with different storage moduli were prepared by changing the amount of high temperature crosslinking agent BWL. The pressure bearing capacity of the fracture plugging layer of gels with different storage moduli was determined by fracture plugging experiments. This test was conducted using a high temperature and high pressure plugging instrument made by Southwest Petroleum University. In the fracture core model used, the width of the fracture was 8.0 mm and the length was 1000.0 mm. The specific steps are as follows: load the fracture core model into the holder of the high temperature and high pressure plugging instrument and set the confining pressure to 35 MPa; turn on the heating switch of the high temperature and high pressure plugging instrument and set the temperature to 140 °C (simulating formation temperature); load gel A into the axe body of the high temperature and high pressure plugging instrument and close the downstream valve of the holder; control the initial displacement pressure to be no higher than 0.5 MPa, and open the downstream valve of the holder after the plugging layer is formed; gradually increase the displacement pressure until the plugging layer is broken, and record the pressure bearing capacity of the fracture plugging layer. The test results are shown in Table 6.

[0064] Table 6 Storage modulus of shear thixotropic gel and pressure bearing capacity of crack sealing layer

[0065]

[0066] S12. With the storage modulus as the horizontal coordinate, draw a storage modulus-pressure bearing capacity relationship curve of the gel, and draw a tangent through the origin to the upward convex arc segment of the curve. The storage modulus corresponding to the tangent point is the optimal storage modulus.

[0067] like Figure 2 As shown in the figure, the plane rectangular coordinate system scatter diagram of the storage modulus of the shear thixotropic gel and the pressure bearing capacity of the crack plugging layer is first drawn, and then the relationship curve between the storage modulus of the SMG gel and the pressure bearing capacity of the crack plugging layer is obtained by the polynomial fitting method, R 2 =0.9961. Finally, a tangent line is drawn above the curve through the origin of the coordinate system. The storage modulus corresponding to the tangent point is 6.0 kPa.

[0068] Therefore, the shear thixotropic gel with a storage modulus of 6.1 kPa was selected as the preferred gel formula.

[0069] S2. Using the gel formula selected in S1 and the non-acid-soluble granular material (ceramsite) as compound raw materials, the gel and granular synergistic temporary plugging slurries with granular mass contents of 10%, 15%, 20% and 25% were prepared, and the effective supporting length of the granules in the fracture after the gel and granular synergistic temporary plugging slurries were determined through fracture plugging and unplugging experiments. The specific steps are as follows: 1) The fracture core model was loaded into the holder of the high-temperature and high-pressure plugging instrument, and the confining pressure was set to 35MPa; 2) The heating switch of the high-temperature and high-pressure plugging instrument was turned on, and the temperature was set to 140℃ (simulating the formation temperature); 3) The axe of the high-temperature and high-pressure plugging instrument was filled with water. Load the gel and particle coordinated temporary plugging slurry, and close the downstream valve of the clamp; 4) Control the initial displacement pressure not higher than 0.5MPa, and open the downstream valve of the clamp after the plugging layer is formed; 5) Gradually increase the displacement pressure until the plugging layer is broken, and record the pressure bearing capacity of the fracture plugging layer; 6) Repeat steps 1) to 4), gradually increase the displacement pressure to the pressure bearing capacity, unload the pressure and close the downstream valve of the clamp; 7) Load 10% hydrochloric acid plugging solution into the axe of the high temperature and high pressure plugging instrument, and control the displacement pressure to 0.5MPa; 8) Wait for 1 hour, take out the fracture core model, disassemble it and measure the effective support length of particle B in the fracture. The results are shown in Table 7.

[0070] Table 7 Data of effective support length of cracks of synergistic temporary plugging slurry prepared with shear thixotropic gel with storage modulus of 6.1 kPa

[0071] Ceramic aggregate mass concentration / % 10 15 20 25 Effective support length / mm 812.1 873.0 734.6 711.7

[0072] According to the test results in the above table, the gel and particle synergistic temporary plugging slurry with the longest effective support length was selected as the synergistic temporary plugging formula of gel and particle materials for deep fractured oil and gas layers. That is, the final formula was determined to be: 85wt% shear thixotropic gel with a storage modulus of 6.1kPa + 15wt% 3.0mm expanded clay. This formula is recorded as Formula #4.

[0073] Comparative Example 3:

[0074] A shear thixotropic gel with a storage modulus of 8.0 kPa and the granular material of Example 2 were used as compound materials, and gel and particle synergistic temporary plugging slurries with particle mass contents of 10%, 15%, 20%, and 25%, respectively, were configured. Through crack plugging and unblocking experiments, the effective support length of the particles in the crack after unblocking of each gel and particle synergistic temporary plugging slurry was determined. The test results are shown in Table 8.

[0075] Table 8 Data of effective support length of cracks of synergistic temporary plugging slurry prepared with shear thixotropic gel with storage modulus of 8.0 kPa

[0076]

[0077] According to the data in the above table, the final preferred formula is determined to be: 85wt% shear thixotropic gel with a storage modulus of 8.0 kPa + 15wt% 3.0 mm ceramsite, and this formula is recorded as formula #5.

[0078] Comparative Example 4:

[0079] A shear thixotropic gel with a storage modulus of 4.0 kPa and the granular material of Example 2 were used as compound materials, and gel and particle synergistic temporary plugging slurries with particle mass contents of 10%, 15%, 20%, and 25%, respectively, were configured. Through crack plugging and unblocking experiments, the effective support length of the particles in the crack after unblocking of each gel and particle synergistic temporary plugging slurry was determined. The test results are shown in Table 9.

[0080] Table 9 Data of effective support length of cracks of synergistic temporary plugging slurry prepared with shear thixotropic gel with storage modulus of 4.0 kPa

[0081] Ceramic aggregate mass concentration / % 10 15 20 25 Effective support length / mm 737.8 863.2 876.3 986.6

[0082] According to the data in the above table, the final preferred formula is determined to be: 75wt% shear thixotropic gel with a storage modulus of 4.0 kPa + 25% 3.0 mm ceramsite, and this formula is recorded as formula #6.

[0083] Fracture plugging experiments were conducted on the variable width fracture core model using formula #4, formula #5, and formula #6 to test the pressure bearing capacity of the fracture plugging layer of each group of formulas; and then unplugging experiments were conducted to test the permeability recovery rate and stress sensitivity coefficient of the supporting fractures of each group of formulas after acid injection unplugging. The experimental data are shown in Table 10.

[0084] Table 10 Experimental data of sealing effect and crack support effect of each group of formulas

[0085]

[0086] According to the above test results, by comparing formula #4 with formula #5, the formula designed by the gel storage modulus optimization method of this patent compared with the traditional gel storage modulus optimization method has only decreased its pressure bearing capacity by 5.1%, and the permeability recovery rate of the supported cracks has increased by 69.6%, and the stress sensitivity coefficient has decreased by 45.2%. It is enough to see that the gel storage modulus optimization method proposed by this patent is more suitable for the gel and granular material coordinated temporary plugging technology than the traditional gel storage modulus optimization method. By comparing formula #4 with formula #6, if a smaller gel storage modulus than that optimized by this patent is selected, the support effect is indeed slightly better than the formula designed by this patent, but the pressure bearing capacity of this formula is only 4.8MPa. Therefore, comprehensively speaking, formula #4 should be selected, which has better plugging performance and drainage performance after unblocking.

[0087] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed in the embodiments of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers, characterized in that: The steps include: S1. Screening an acid-soluble gel formula, wherein the screening rule includes: preferentially selecting a gel formula having a small absolute value of the difference between the storage modulus and the optimal storage modulus; Wherein, determining the optimal storage modulus comprises the following steps: S11, determining gel components, configuring gels with different storage moduli by adjusting the content of each gel component, and determining the pressure bearing capacity of the crack plugging layer of each gel through a crack plugging experiment; S12, with the storage modulus as the horizontal coordinate, draw the storage modulus-pressure bearing capacity relationship curve of the gel, and make a tangent through the origin to the upward convex arc segment of the curve, and the storage modulus corresponding to the tangent point is the optimal storage modulus; S2, using the gel formula and non-acid-soluble granular material selected in S1 as compound raw materials, preparing synergistic temporary plugging slurries with different gel contents, and determining the effective support length of the particles in the fracture after each synergistic temporary plugging slurry is unblocked through fracture plugging and unblocking experiments, and preferentially selecting the synergistic temporary plugging slurry with a long effective support length as the synergistic temporary plugging formula of gel and granular materials for deep fractured oil and gas layers; The fracture plugging experiment in step S11 includes an operation of generating a plugging layer, and the operation of generating a plugging layer includes the following steps: injecting gel into the fracture in a constant pressure displacement manner until the gel cannot be injected; The crack plugging and unblocking experiment in step S2 includes the following steps: Generate a plugging layer, and inject the coordinated temporary plugging slurry into the fracture in a constant pressure displacement mode until the coordinated temporary plugging slurry can no longer be injected; Add acid to the crack to unblock it.

2. The method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers according to claim 1, characterized in that: The screening rule for screening the gel formula in step S1 also includes that the acid solubility of the gel is greater than a first threshold.

3. The method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers according to claim 2, characterized in that: The first threshold is 90 wt %.

4. The method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers according to claim 1, characterized in that: The crushing rate of the granular material under the target layer fracture closure pressure is less than a second threshold value.

5. The method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers according to claim 4, characterized in that: The second threshold value is 5 wt %.

6. The method for designing a temporary plugging formula of gel and granular materials for deep fractured oil and gas layers according to claim 1, characterized in that: The particle size of the granular material is 0.3 to 0.5 times the width of the crack.

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