Dynamic slit width-based temporary plugging agent evaluation method and application thereof and shale gas development method

Abstract

This invention provides a method for evaluating temporary plugging agents based on dynamic fracture width, its application, and a shale gas extraction method: S1 Take a core sample and set the initial fracture width, plugging pressure, and experimental displacement; S2 Plug with the first temporary plugging agent; S3 Increase the fracture width until the pressure inside the fracture rises above the plugging pressure and stabilizes, then proceed to S4; otherwise, proceed to S5; S4: Repeat S3 until the fracture width reaches its upper limit and the pressure rises above the plugging pressure and stabilizes; S5 Plug with the second temporary plugging agent until the pressure rises above the plugging pressure and stabilizes, then continue increasing the fracture width until it reaches its upper limit and the pressure rises above the plugging pressure and stabilizes, then the combination of the first and second temporary plugging agents is usable; otherwise, proceed to S6: Plug with the nth temporary plugging agent until the fracture width reaches its upper limit and the pressure rises above the plugging pressure and stabilizes, then the combination of the first to nth temporary plugging agents is usable. This invention is applicable to evaluating temporary plugging agents with dynamic fracture widths, especially in shale gas development, simulating real-time changes in plugging capacity and pressure response characteristics within dynamic fracture widths.

Description

Technical Field

[0001] This invention relates to the field of temporary plugging agent evaluation, and in particular to a method for evaluating temporary plugging agents based on dynamic fracture width, its application, and a method for shale gas development. Background Technology

[0002] Shale gas is a crucial component of my country's reserve and production growth, and multi-cluster fracturing in horizontal wells is an effective method for shale gas development. However, due to strong formation heterogeneity and uneven perforation flow distribution, perforation clusters are not fully opened, and some clusters experience excessive fracture extension, ultimately affecting the stimulation effect. Temporary plugging and diversion fracturing technology can effectively control the extension of existing fractures, increasing the fracturing volume and improving the shale gas development effect by opening and expanding new fractures.

[0003] The performance of temporary plugging agents determines the success of temporary plugging fracturing technology. Currently, fixed-width pressure testing devices are mainly used to evaluate the performance of temporary plugging agents and optimize parameters. However, in actual field temporary plugging processes, as the proppant-carrying fluid is continuously pumped in, the fracture width gradually increases, leading to the failure of the temporary plugging layer and severely affecting the effectiveness of the temporary plugging process. Moreover, current experimental evaluation devices and methods for temporary plugging agents in shale gas development do not consider the impact of dynamic fracture width expansion, resulting in certain errors in the experimental results. Summary of the Invention

[0004] To address at least one technical problem in the existing technology, this invention provides a method for evaluating temporary plugging agents based on dynamic fracture width, its application, and a method for shale gas development. Using this method, the temporary plugging performance of plugging agents under dynamically varying fracture widths can be evaluated in real time with high accuracy and efficiency, providing reliable experimental basis for selecting the best plugging agent. This method is particularly suitable for evaluating temporary plugging agents in shale gas development.

[0005] This invention provides a method for evaluating temporary plugging agents based on dynamic gap width, the evaluation method comprising the following steps.

[0006] Step S1: Select the core of the target block and cut it into two rock plates; put the rock plates into the dynamic fracture width simulation device, and set the initial fracture width between the two rock plates and the required sealing pressure of the target reservoir, and set the experimental discharge rate of the sand-carrying fluid carrying the temporary plugging agent.

[0007] Step S2: Select the first temporary plugging agent and use the first sand-carrying liquid to displace the first temporary plugging agent into the crack between the rock plates for temporary plugging, and record the pressure value change in the crack; if the pressure in the crack rises to above the set target reservoir required for plugging and stabilizes, proceed to step S3; otherwise, select a temporary plugging agent with a larger average diameter as the first temporary plugging agent, perform temporary plugging again and record the pressure value change in the crack.

[0008] Step S3: Increase the fracture width using a dynamic fracture width simulation device, reset the experimental discharge rate of the sand-carrying fluid containing the temporary plugging agent, and continue to use the first sand-carrying fluid to displace the first temporary plugging agent into the fracture between the rock plates for temporary plugging, or increase the viscosity of the sand-carrying fluid to obtain a second sand-carrying fluid and use the second sand-carrying fluid to displace the first temporary plugging agent into the fracture between the rock plates for temporary plugging, and record the change in the pressure value inside the fracture; if the pressure value inside the fracture rises above the set target reservoir sealing pressure and stabilizes, proceed to step S4, otherwise proceed to step S5.

[0009] Step S4: Repeat step S3 until the fracture width increases to the upper limit of the fracture width; wherein, if when the fracture width increases to the upper limit of the fracture width, the pressure value inside the fracture rises to above the set target reservoir required for plugging pressure and stabilizes, then the first temporary plugging agent is evaluated as usable.

[0010] Step S5: Select the second temporary plugging agent, and use the first sand-carrying fluid to displace the second temporary plugging agent into the cracks between the rock plates for temporary plugging. Record the change in pressure value within the crack. If the pressure value rises above the set target reservoir sealing pressure and stabilizes, use a dynamic crack width simulation device to increase the crack width. Use the first sand-carrying fluid to displace the second temporary plugging agent into the cracks between the rock plates for temporary plugging and record the change in pressure value within the crack until the crack width increases to the upper limit of the crack width and the pressure value within the crack rises above the set target reservoir sealing pressure and stabilizes. If the combination of the first and second temporary plugging agents is used for temporary plugging, it is evaluated as usable, completing the evaluation of temporary plugging failure law and re-plugging; otherwise, proceed to step S6.

[0011] Step S6: Select the nth temporary plugging agent to replace the second temporary plugging agent and implement step S5 until the fracture width increases to the upper limit of the fracture width and the pressure value inside the fracture rises above the set target reservoir required for sealing and stabilizes when the nth temporary plugging agent is used. Then the combination of the first temporary plugging agent, the second temporary plugging agent to the nth temporary plugging agent is evaluated as usable; n is an integer greater than 2.

[0012] In steps S2-S6, the size decreases sequentially from the first temporary plugging agent to the nth temporary plugging agent.

[0013] Preferably, the calculation formulas for the initial crack width between rock slabs and the width of cracks at the construction site are shown in Equation (I). w f V represents the width of the crack at the construction site, in mm; v represents the discharge volume at the construction site, in cm. 3 / min; p is the formation pressure, MPa; H f The crack height at the construction site is in meters (m); E is the Young's modulus of the formation, in gigabytes of water (GPa).

[0014] Preferably, the experimental displacement calculation formula is shown in equation (II), v e =v f w e h e (II), v e For the experimental displacement (cm) 3 / min; v f The fluid velocity at the construction site is expressed in m / s and h. e The experimental crack height is in meters (m); w e The experimental crack width is in meters (m).

[0015] Preferably, the Reynolds number of the experimental displacement is equal to the Reynolds number of the displacement at the construction site.

[0016] Preferably, the Reynolds number for the experimental displacement is calculated using the formula shown in equation (III).

[0017] (III), w e Experimental crack width, m; v e The fluid velocity inside the slit, m / s; ρ e Experimental fluid density, kg / m³ 3 μ e The experimental fluid viscosity, Pa·s; the Reynolds number calculation formula for the discharge at the construction site is: w f V represents the width of the formation fracture, in meters (m); f The fluid velocity at the construction site is expressed in m / s; ρ f The density of the fluid at the site is kg / m³. 3 μ f ρ represents the viscosity of the formation fluid, Pa·s.

[0018] Preferably, step S1 also sets the crack length and crack height between the rock slabs.

[0019] The crack height is verified using formula (V). R is the hydraulic radius, in mm; h e The experimental crack height is in mm; w f The width of the crack at the construction site is in mm.

[0020] Preferably, the content of the temporary plugging agent in the sand-carrying fluid is 0.25wt%-1.25wt%, more preferably 0.75wt%-1wt%.

[0021] Preferably, in steps S2-S6, the size of the temporary plugging agent decreases by 10-30% from the first temporary plugging agent to the nth temporary plugging agent, and more preferably by 15-25%.

[0022] Preferably, the evaluation method further includes: in steps S2-S6, after each time the pressure inside the fracture rises to or exceeds the set target reservoir required for plugging and stabilizes, the temporary plugging agent that is not retained in the rock slab fracture is collected and weighed to calculate the retention rate of the temporary plugging agent, thus completing the evaluation of the retention rate of the temporary plugging agent.

[0023] Preferably, in steps S3-S6, the crack width is increased by 3%-7% of the initial crack width each time, preferably 4%-6%.

[0024] Preferably, the temporary plugging agent evaluation method is implemented through a dynamic crack width temporary plugging system, which includes a pumping device, a dynamic crack width crack simulation device, and a pressure detection device.

[0025] The outlet of the pumping device is connected to the inlet of the dynamic crack width simulation device, and is used to deliver the temporary plugging agent into the rock slab crack of the dynamic crack width simulation device.

[0026] The pressure detection device is connected to the dynamic crack width simulation device and is used to receive the pressure signal in the rock slab crack in the dynamic crack width simulation device and record the pressure value in the crack.

[0027] Preferably, the dynamic crack width simulation device includes a worm gear box, a top plate, a lead screw, an upper movable plate, a bottom plate, a guide rail, an inlet, and an outlet.

[0028] The top end of the guide rail is perpendicularly connected to the lower surface of the top plate, and the bottom end of the guide rail is perpendicularly connected to the upper surface of the bottom plate. The top plate and the bottom plate are parallel to each other.

[0029] The worm gear box is in contact with the upper surface of the top plate.

[0030] The lead screw passes through the center of the top plate and is connected to the worm gear box. Adjusting the worm gear box drives the lead screw to move up and down.

[0031] The upper movable plate is installed on the guide rails on both sides and is parallel to the bottom plate, used to clamp and fix the rock slab together with the bottom plate.

[0032] The inlet and outlet are located between the upper movable plate and the bottom plate, respectively for receiving temporary plugging agent from the pumping device and discharging temporary plugging agent from the cracks between the rock plates.

[0033] Preferably, the worm gear box is equipped with a rotating handle, and the upper movable plate moves 0.01-0.05mm when the rotating handle is rotated one revolution.

[0034] Preferably, the pumping device and the dynamic crack width simulation device are connected by a pipeline with a length of 6-14cm, more preferably 8-12cm.

[0035] Preferably, the diameter of the first pipeline is 10-14 mm.

[0036] In this invention, the outlet of the dynamic crack width simulation device is connected to a second pipeline, the diameter of which is 2-4 mm.

[0037] Secondly, the present invention provides the application of the temporary plugging agent evaluation method described in the first aspect in shale gas development.

[0038] Thirdly, the present invention provides a method for shale gas development, the method comprising: selecting a suitable temporary plugging agent by means of the temporary plugging agent evaluation method described in the first aspect, and then displacing the suitable temporary plugging agent into the reservoir fractures at the construction site for temporary plugging fracturing.

[0039] The present invention relates to a method for evaluating temporary plugging agents based on dynamic fracture width, its application, and a method for shale gas development, which has the following advantages.

[0040] 1) Based on the physical process of temporary plugging and diverting fracturing technology, establish a performance evaluation system for temporary plugging agents with dynamic variable fracture width to provide experimental basis for the selection of optimal temporary plugging agents.

[0041] 2) It can accurately evaluate the retention rate of the temporary plugging agent, the plugging pressure law of the temporary plugging agent, the failure of the temporary plugging agent, and the re-plugging effect. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the dynamic slit width temporary plugging system of the present invention;

[0043] Figure 2 This is a side view of the dynamic crack width simulation device 2 of the present invention. Detailed Implementation

[0044] In a first aspect, the present invention provides a method for evaluating temporary plugging agents based on dynamic gap width, the evaluation method comprising the following steps:

[0045] Step S1: Select the core of the target block and cut it into two rock plates; put the rock plates into the dynamic fracture width simulation device 2, and set the initial fracture width between the two rock plates and the required sealing pressure of the target reservoir, and set the experimental discharge rate of the sand-carrying fluid carrying the temporary plugging agent.

[0046] Step S2: Select the first temporary plugging agent and use the first sand-carrying liquid to displace the first temporary plugging agent into the crack between the rock plates for temporary plugging, and record the pressure value change in the crack; if the pressure in the crack rises to above the set target reservoir required for plugging and stabilizes, proceed to step S3; otherwise, select a temporary plugging agent with a larger average diameter as the first temporary plugging agent, perform temporary plugging again and record the pressure value change in the crack.

[0047] Step S3: Use the dynamic fracture width simulation device 2 to increase the fracture width, reset the experimental discharge rate of the sand-carrying fluid carrying the temporary plugging agent, and continue to use the first sand-carrying fluid to displace the first temporary plugging agent into the fracture between the rock plates for temporary plugging, or increase the viscosity of the sand-carrying fluid to obtain a second sand-carrying fluid and use the second sand-carrying fluid to displace the first temporary plugging agent into the fracture between the rock plates for temporary plugging, and record the change in the pressure value inside the fracture; if the pressure value inside the fracture rises above the set target reservoir required sealing pressure and stabilizes, proceed to step S4; otherwise, proceed to step S5.

[0048] Step S4: Repeat step S3 until the fracture width increases to the upper limit of the fracture width; wherein, if when the fracture width increases to the upper limit of the fracture width, the pressure value inside the fracture rises to above the set target reservoir required for plugging and stabilizes, then the first temporary plugging agent is evaluated as usable;

[0049] Step S5: Select the second temporary plugging agent, use the first sand-carrying fluid to displace the second temporary plugging agent into the cracks between the rock plates for temporary plugging, and record the change in the pressure value inside the crack. If the pressure value rises above the set target reservoir sealing pressure and stabilizes, use the dynamic crack width simulation device 2 to increase the crack width, use the first sand-carrying fluid to displace the second temporary plugging agent into the cracks between the rock plates for temporary plugging, and record the change in the pressure value inside the crack until the crack width increases to the upper limit of the crack width and the pressure value inside the crack rises above the set target reservoir sealing pressure and stabilizes. If the combination of the first and second temporary plugging agents is used for temporary plugging, it is evaluated as usable, completing the evaluation of the temporary plugging failure law and re-plugging; otherwise, proceed to step S6.

[0050] Step S6: Select the nth temporary plugging agent to replace the second temporary plugging agent and implement step S5 until the fracture width increases to the upper limit of the fracture width and the pressure value inside the fracture rises above the set target reservoir required for sealing and stabilizes when the nth temporary plugging agent is used. Then the combination of the first temporary plugging agent, the second temporary plugging agent to the nth temporary plugging agent is evaluated as usable; n is an integer greater than 2.

[0051] In steps S2-S6, the size decreases sequentially from the first temporary plugging agent to the nth temporary plugging agent.

[0052] In this invention, the required sealing pressure data for the target reservoir can be obtained from construction data at the construction site, or from relevant numerical simulations initiated based on reservoir data and construction parameters; the above methods for obtaining the required sealing pressure for the target reservoir are all conventional methods used in the field.

[0053] In step S3 of this invention, the viscosity of the second sand-carrying liquid is 25-30% higher than that of the first sand-carrying liquid. This can be understood as each increase in the viscosity of the sand-carrying liquid being 25-30% of the previous viscosity; for example, increasing the viscosity of the first sand-carrying liquid by 25-30% yields the second sand-carrying liquid, increasing the viscosity of the second sand-carrying liquid by 25-30% yields the third sand-carrying liquid, and so on.

[0054] In this invention, the calculation formulas for the initial crack width between the rock slabs and the crack width at the construction site are shown in Equation (I). w f 'v' represents the width of the crack at the construction site, in mm; 'v' represents the discharge volume at the construction site, in cm. 3 / min; p is the formation pressure, MPa; H f Let be the crack height at the construction site, in meters (m); and E be the Young's modulus of the formation, in gigabytes of pressure (GPa). Both the Young's modulus and formation pressure can be measured at the construction site using conventional methods in this field. The crack height at the construction site can be obtained using microseismic monitoring technology. In step S1 of this invention, the initial crack width can be calculated and determined using equation (I).

[0055] In this invention, the experimental displacement calculation formula is shown in equation (II), v e =v f w e h e (II), v e For the experimental displacement (cm) 3 / min; v f The fluid velocity at the construction site is expressed in m / s and h. e The experimental crack height is in meters (m); w e The experimental crack width is in meters (m). The fluid velocity at the construction site is the same as the discharge rate at the construction site, which is known.

[0056] In this invention, to ensure that the discharge volume during on-site construction corresponds to the discharge volume during indoor experiments and to further improve the accuracy of the temporary plugging agent evaluation method, preferably, the Reynolds number of the experimental discharge volume is equal to that of the discharge volume during construction.

[0057] In this invention, the Reynolds number for the experimental displacement is calculated using formula (III). (III), w e Experimental crack width, m; v e Experimental fluid velocity (experimental displacement), m / s; ρ e Experimental fluid density, kg / m³ 3 μ e , the viscosity of the experimental fluid, Pa·s.

[0058] In this invention, the Reynolds number calculation formula for the displacement at the construction site is as follows: In the formula: w f V represents the width of the crack in the strata (construction site), in meters. f The fluid velocity at the construction site is expressed in m / s; ρ f The density of the fluid at the construction site is kg / m³. 3 μ f ρ represents the viscosity of the formation fluid, Pa·s.

[0059] In this invention, step S1 also sets the crack length and crack height between the rock plates; the crack length can be set according to the API standard, i.e., the American Petroleum Institute standard, which is a commonly used setting method in the field.

[0060] The crack height is determined by formula (V). R is the hydraulic radius, in mm; h e The experimental crack height is in mm; w f The width of the crack at the construction site is in mm. The hydraulic radius can be obtained from data at the construction site, a method well-known in the art.

[0061] In this invention, the content of the temporary plugging agent in the sand-carrying fluid is 0.25wt%-1.25wt%, preferably 0.75wt%-1wt%.

[0062] In a preferred embodiment of the present invention, in steps S2-S6, the size of the temporary plugging agent decreases by 10-30% sequentially from the first temporary plugging agent to the nth temporary plugging agent, preferably by 15-25% sequentially; adopting this preferred size ratio can further improve the accuracy of the evaluation method.

[0063] And / or, the evaluation method further includes: in steps S2-S6, after each time the pressure inside the fracture rises above the set target reservoir required for plugging and stabilizes, the temporary plugging agent that is not retained in the fracture between the rock plates is collected and weighed to calculate the retention rate of the temporary plugging agent, thus completing the evaluation of the retention rate of the temporary plugging agent.

[0064] In this invention, in steps S3-S6, the crack width is increased by 3%-7% of the initial crack width each time, preferably 4%-6%. This preferred crack width variation allows for more accurate evaluation of the temporary plugging agent.

[0065] In this invention, the upper limit of the crack width is calculated using the PKN model, and the PKN model formula is shown in equation (VI). v e For experimental displacement, cm 3 / min; p is the formation pressure, MPa; H fThe crack height at the construction site is in meters (m); E is the Young's modulus of the formation, in gigabytes of water (GPa).

[0066] In this invention, after step S2 is completed, the temporary plugging pressure law of the temporary plugging agent can be evaluated. The temporary plugging pressure law is the trend of the pressure value in the crack from 0 to above the set target reservoir sealing pressure and then stabilizing, starting from the use of the first sand-carrying fluid to drive the first temporary plugging agent into the crack between the rock plates for temporary plugging.

[0067] In this invention, the temporary plugging agent evaluation method is implemented through a temporary plugging system with dynamic gap width, such as... Figure 1 As shown, the dynamic crack width temporary plugging system includes a pumping device 1, a dynamic crack width crack simulation device 2, and a pressure detection device 3;

[0068] The outlet of the pumping device 1 is connected to the inlet of the dynamic crack width simulation device 2, and is used to deliver the temporary plugging agent into the rock slab crack of the dynamic crack width simulation device 2.

[0069] The pressure detection device 3 is connected to the dynamic crack width simulation device 2 and is used to receive the pressure signal in the rock slab crack in the dynamic crack width simulation device 2 and record the pressure value in the crack.

[0070] In this invention, such as Figure 2 As shown, the dynamic crack width simulation device 2 includes a worm gear box 21, a top plate 22, a lead screw 23, an upper movable plate 24, a bottom plate 25, a guide rail 26, an inlet 27, and an outlet 28.

[0071] The top end of the guide rail 26 is perpendicularly connected to the lower surface of the top plate 22, and the bottom end of the guide rail 26 is perpendicularly connected to the upper surface of the bottom plate 25. The top plate 22 and the bottom plate 25 are parallel to each other.

[0072] The worm gear box 21 is in contact with the upper surface of the top plate 22;

[0073] The lead screw 23 passes through the center of the top plate 22 and is connected to the worm gear box 21. The lead screw 23 can be moved up and down by adjusting the worm gear box 21.

[0074] The upper movable plate 24 is mounted on the guide rails 26 on both sides and is parallel to the bottom plate 25, and is used to clamp and fix the rock slab with the bottom plate 25;

[0075] The inlet 27 and outlet 28 are located between the upper movable plate 24 and the bottom plate 25, respectively for receiving the temporary plugging agent from the pumping device 1 and discharging the temporary plugging agent from the crack between the rock plates.

[0076] In this invention, the lower surface of the movable plate 24 contacts one of the two rock slabs and is fixed by a lead screw 30. Since the movable plate 24 is fixed on the guide rails 26 on both sides, when the pressure inside the rock slab joint increases, the movable plate 24 and the rock slab in contact with it will not tilt or deflect in the horizontal direction, but will only move vertically along the guide rail direction.

[0077] In this invention, the upper surface of the base plate 25 is in contact with the other of the two rock slabs. Since the base plate 25 is immovable, the rock slab in contact with the base plate 25 does not move when the movable plate 24 moves vertically.

[0078] In this invention, the worm gear box 21 is equipped with a rotating handle 29. When the rotating handle 29 rotates one revolution, the upper movable plate 24 moves by 0.01-0.05mm.

[0079] In this invention, the pumping device 1 and the dynamic crack width simulation device 2 are connected by a pipeline 4. The length of the first pipeline 4 is 6-14 cm, preferably 8-12 cm. Excessive length can cause the temporary plugging agent to settle prematurely in the pipeline, affecting the accuracy of the experiment; using this preferred pipeline length can further improve the accuracy of the evaluation method.

[0080] In this invention, if the diameter of the pipeline is too small, the temporary plugging agent will prematurely clog the pipeline and fail to enter the crack to form an effective seal. To avoid pipeline blockage and ensure effective sealing, and to further improve the accuracy of the evaluation method, preferably, the diameter of the first pipeline 4 is 10-14 mm. The outlet of the dynamic crack width simulation device 2 is connected to a second pipeline 5, the diameter of which is 2-4 mm.

[0081] In this invention, such as Figure 1 As shown, the pumping device 1 includes a preparation container 11, a pump 12, and a temperature and stirring controller 13; the preparation container 11 is used to prepare a sand-carrying liquid containing a temporary plugging agent; the pump 12 is connected to the top inlet of the preparation container 11 through a pipeline, and is used to pump the sand-carrying liquid containing the temporary plugging agent into the dynamic crack width simulation device 2; the temperature and stirring controller 13 is connected to the top of the preparation container 11 through a pipeline, and is used to control the temperature and stirring device in the preparation container 11.

[0082] Secondly, the present invention provides the application of the temporary plugging agent evaluation method described in the first aspect in shale gas development.

[0083] Thirdly, the present invention provides a method for shale gas development, the method comprising: selecting a suitable temporary plugging agent by means of the temporary plugging agent evaluation method described in the first aspect, and then displacing the suitable temporary plugging agent into the reservoir fractures at the construction site for temporary plugging fracturing.

[0084] The adapted temporary plugging agent displaces the target reservoir fractures and seals them, causing the fractures to deflect and increasing the complexity of the fracture network, thus enabling further efficient development of the target reservoir.

[0085] The following detailed description of preferred embodiments of the present invention illustrates the principles of the invention and is not intended to limit the scope of the invention.

[0086] Example 1

[0087] Based on formulas (I)-(VI) and API standards, the initial fracture width between the two rock plates was calculated to be 4 mm, the length to be 17.8 cm, and the height to be 3.8 cm. The experimental discharge rate of the sand-carrying fluid carrying the temporary plugging agent was 25 ml / min. The upper limit of the fracture width was determined to be 4.8 mm by the PKN model. The required sealing pressure for the target reservoir was obtained from the construction site data to be 3 MPa.

[0088] Step S1: Select a core sample from the target block and cut it into two rock slabs with a width of 3cm, a length of 17.8cm, a height of 1.3cm, and a chamfer of 35°. Place the rock slabs into the dynamic fracture width simulation device 2, and set the initial fracture width between the two rock slabs to 4mm. The required sealing pressure for the target reservoir is 3MPa, and the experimental discharge rate of the sand-carrying fluid carrying the temporary plugging agent is 25ml / min. The diameter of the first pipeline 4 is 12mm, the length is 6-14cm, and the diameter of the second pipeline 5 is 3mm.

[0089] Step S2: Using a first sand-carrying liquid with a viscosity of 30 mp.s, 15 g of the first temporary plugging agent with an average diameter of 2.32 mm was displaced into the crack between the rock slabs for temporary plugging. The pressure value change in the crack was recorded, and the pressure in the crack finally stabilized at 3.2 MPa. At the same time, the amount of temporary plugging agent that did not remain in the crack of the rock slab was recorded as 1.3 g, so the retention rate was 91.3%.

[0090] Step S3: Rotate the rotating handle 29 on the worm gear box 21 to increase the width of the crack between the rock plates by 0.2 mm. Set the experimental flow rate to 25 ml / min and continue to displace 15 g of the first temporary plugging agent into the crack between the rock plates. It is observed that the pressure value inside the crack recorded by the pressure detection device 3 is still higher than 3 MPa. At the same time, the amount of temporary plugging agent that is not retained in the crack of the rock plate is recorded as 2.1 g, so the retention rate is 86%.

[0091] Continue rotating handle 29 to increase the width of the crack between the rock slabs by another 0.2 mm. Set the experimental flow rate to 25 ml / min and continue to displace 15 g of the first temporary plugging agent into the crack between the rock slabs. It is observed that the pressure value inside the crack recorded by pressure detection device 3 is still higher than 3 MPa. At the same time, the amount of temporary plugging agent that is not retained in the crack of the rock slab is recorded as 2.8 g, so the retention rate is 81.3%.

[0092] Continue rotating handle 29 to increase the width of the crack between the rock slabs by another 0.2 mm. Set the experimental flow rate to 25 ml / min and continue to displace 15 g of the first temporary plugging agent into the crack between the rock slabs. Observe that the pressure value inside the crack recorded by pressure detection device 3 is less than 3 MPa, and proceed to step S5.

[0093] Step S5: 5g of the second temporary plugging agent with an average diameter of 1.77mm was continued to be driven into the crack between the rock slabs. It was observed that the pressure value inside the crack recorded by the pressure detection device 3 was higher than 3MPa. At the same time, the amount of temporary plugging agent that was not retained in the crack of the rock slab was recorded as 0.4g, so the retention rate was 92.0%.

[0094] Continue rotating handle 29 to increase the width of the crack between the rock slabs by another 0.2 mm. Set the experimental flow rate to 25 ml / min and continue to displace 5 g of the second temporary plugging agent into the crack between the rock slabs. Observe that the pressure value inside the crack recorded by pressure detection device 3 is still greater than 3 MPa. Stop the experiment and complete the evaluation of the failure law of temporary plugging and re-plugging. The combination of the first and second temporary plugging agents is evaluated as usable for temporary plugging. At the same time, record that the amount of temporary plugging agent not retained in the crack of the rock slab is 0.6 g, so the retention rate is 88.0%.

[0095] As can be seen from the above embodiments, the evaluation method of the present invention is applicable to evaluating the performance of temporary plugging agents with dynamic fracture width, and is particularly suitable for evaluating the performance of temporary plugging agents in the shale gas development process. The present invention can simulate in real time the change in the sealing capacity of a temporary plugging agent after the dynamic expansion of the fracture width in an artificial fracture, and can detect the pressure response characteristics of the temporary plugging agent inside the artificial fracture in real time. Therefore, it provides a systematic experimental method for evaluating the performance of temporary plugging agents.

[0096] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for evaluating a dynamic slit width-based temporary plugging agent, characterized in that, The evaluation method includes the following steps: Step S1: Select the core of the target block and cut it into two rock plates; put the rock plates into the dynamic fracture width simulation device (2), and set the initial fracture width between the two rock plates and the required sealing pressure of the target reservoir, and set the experimental discharge rate of the sand-carrying fluid carrying the temporary plugging agent. Step S2: Select the first temporary plugging agent and use the first sand-carrying liquid to displace the first temporary plugging agent into the crack between the rock plates for temporary plugging, and record the pressure value change in the crack; if the pressure in the crack rises to above the set target reservoir required for plugging and stabilizes, proceed to step S3; otherwise, select a temporary plugging agent with a larger average diameter as the first temporary plugging agent, perform temporary plugging again and record the pressure value change in the crack. Step S3: Use the dynamic fracture width simulation device (2) to increase the fracture width, reset the experimental discharge rate of the sand-carrying fluid carrying the temporary plugging agent, and continue to use the first sand-carrying fluid to displace the first temporary plugging agent into the fracture between the rock plates for temporary plugging, or increase the viscosity of the sand-carrying fluid to obtain a second sand-carrying fluid and use the second sand-carrying fluid to displace the first temporary plugging agent into the fracture between the rock plates for temporary plugging, and record the change in the pressure value inside the fracture; if the pressure value inside the fracture rises above the set target reservoir required sealing pressure and stabilizes, then proceed to step S4, otherwise proceed to step S5; Step S4: Repeat step S3 until the fracture width increases to the upper limit of the fracture width; wherein, if when the fracture width increases to the upper limit of the fracture width, the pressure value inside the fracture rises to above the set target reservoir required for plugging and stabilizes, then the first temporary plugging agent is evaluated as usable; Step S5: Select the second temporary plugging agent, use the first sand-carrying fluid to drive the second temporary plugging agent into the cracks between the rock plates for temporary plugging, and record the change in the pressure value inside the crack. If the pressure value rises above the set target reservoir required for sealing and stabilizes, use the dynamic crack width simulation device (2) to increase the crack width, use the first sand-carrying fluid to drive the second temporary plugging agent into the cracks between the rock plates for temporary plugging and record the change in the pressure value inside the crack until the crack width increases to the upper limit of the crack width and the pressure value inside the crack rises above the set target reservoir required for sealing and stabilizes. If the combination of the first temporary plugging agent and the second temporary plugging agent is used for temporary plugging, it is evaluated as usable, and the evaluation of the temporary plugging failure law and re-plugging is completed; otherwise, proceed to step S6. Step S6: Select the nth temporary plugging agent to replace the second temporary plugging agent and implement step S5 until the fracture width increases to the upper limit of the fracture width and the pressure value inside the fracture rises above the set target reservoir required for sealing and stabilizes when the nth temporary plugging agent is used. Then the combination of the first temporary plugging agent, the second temporary plugging agent to the nth temporary plugging agent is evaluated as usable; n is an integer greater than 2. In steps S2-S6, the size decreases sequentially from the first temporary plugging agent to the nth temporary plugging agent.

2. The method of claim 1, wherein, The calculation formulas for the initial crack width between the rock slabs and the crack width at the construction site are shown in Equation (I). w f 'v' represents the width of the crack at the construction site, in mm; 'v' represents the discharge volume at the construction site, in cm. 3 / min; p is the formation pressure, MPa; H f The crack height at the construction site is in meters (m); E is the Young's modulus of the formation, in gigabytes of water (GPa).

3. The method of claim 1 or 2, wherein The experimental discharge calculation formula is shown as formula (II), v e = v f w e h e (II), v e is an experimental discharge, cm 3 / min; v f is a fluid flow rate at a construction site, m / s; h e is an experimental fracture height, m; and w e is an experimental fracture width, m. Preferably, the Reynolds number of the experimental displacement is equal to the Reynolds number of the displacement at the construction site; Preferably, the Reynolds number for the experimental displacement is calculated using the formula shown in equation (III). w e Experimental crack width, m; v e Experimental fluid velocity, m / s; ρ e Experimental fluid density, kg / m³ 3 μ e The experimental fluid viscosity, Pa·s; the Reynolds number calculation formula for the discharge at the construction site is: w f V represents the width of the formation fracture, in meters (m); f The fluid velocity at the construction site is expressed in m / s; ρ f The density of the fluid at the construction site is kg / m³. 3 μ f Formation fluid viscosity, Pa·s.

4. The evaluation method for temporary plugging agents according to any one of claims 1-3, characterized in that, Step S1 also sets the crack length and crack height between the rock slabs; wherein the crack height is verified by formula (V), R is the hydraulic radius, mm; h e is the experimental crack height, mm; w f is the crack width at the construction site, mm.

5. The method of claim 1-4, wherein, In the sand-carrying fluid containing the temporary plugging agent, the content of the temporary plugging agent is 0.25wt%-1.25wt%, preferably 0.75wt%-1wt%. And / or, in steps S2-S6, from the first temporary plugging agent to the nth temporary plugging agent, the size decreases by 10-30% sequentially, preferably by 15-25% sequentially; And / or, the evaluation method further includes: in steps S2-S6, after each time the pressure inside the fracture rises to above the set target reservoir required for plugging and stabilizes, the temporary plugging agent that is not retained in the fracture between the rock plates is collected and weighed to calculate the retention rate of the temporary plugging agent, thus completing the evaluation of the retention rate of the temporary plugging agent. And / or, in steps S3-S6, the crack width is increased by 3%-7% of the initial crack width each time, preferably 4%-6%.

6. The method of claim 1-5, wherein, The temporary plugging agent evaluation method is implemented through a dynamic crack width temporary plugging system, which includes a pumping device (1), a dynamic crack width crack simulation device (2), and a pressure detection device (3). The outlet of the pumping device (1) is connected to the inlet of the dynamic crack width simulation device (2) to deliver the temporary plugging agent into the rock slab crack of the dynamic crack width simulation device (2). The pressure detection device (3) is connected to the dynamic crack width simulation device (2) and is used to receive the pressure signal in the rock slab crack in the dynamic crack width simulation device (2) and record the pressure value in the crack.

7. The method of claim 6, wherein the temporary plugging agent is evaluated by the method of claim 1. The dynamic crack width simulation device (2) includes a worm gear box (21), a top plate (22), a lead screw (23), an upper movable plate (24), a bottom plate (25), a guide rail (26), an inlet (27), and an outlet (28); The top end of the guide rail (26) is perpendicularly connected to the lower surface of the top plate (22), the bottom end of the guide rail (26) is perpendicularly connected to the upper surface of the bottom plate (25), and the top plate (22) and the bottom plate (25) are parallel to each other. The worm gear box (21) is in contact with the upper surface of the top plate (22); The lead screw (23) passes through the center of the top plate (22) and is connected to the worm gear box (21). The lead screw (23) can be moved up and down by adjusting the worm gear box (21). The upper movable plate (24) is mounted on the guide rail (26) and is parallel to the bottom plate (25) for clamping and fixing the rock slab with the bottom plate (25); The inlet (27) and outlet (28) are located between the upper movable plate (24) and the bottom plate (25), respectively for receiving the temporary plugging agent from the pumping device (1) and discharging the temporary plugging agent from the crack between the rock plates.

8. The method of claim 7, wherein the temporary plugging agent is evaluated by the method of claim 1. The worm gear box (21) is equipped with a rotating handle (29). When the rotating handle (29) rotates one revolution, the upper movable plate (24) moves by 0.01-0.05 mm. And / or, the pumping device (1) and the dynamic crack width simulation device (2) are connected by a first pipeline (4), the length of which is preferably 6-14cm, more preferably 8-12cm; And / or, the diameter of the first pipeline (4) is 10-14 mm; And / or, the outlet of the dynamic crack width simulation device (2) is connected to a second pipeline (5), the diameter of which is preferably 2-4 mm.

9. The application of the temporary plugging agent evaluation method according to any one of claims 1-8 in shale gas development.

10. A method of shale gas development, characterized by, The method includes: selecting a suitable temporary plugging agent using the temporary plugging agent evaluation method according to any one of claims 1-8, and then using the suitable temporary plugging agent to displace the reservoir fractures at the construction site for temporary plugging fracturing.

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