An evaluation method for crack plugging effect of polymer gel plugging agent based on storage modulus

Abstract

The present invention provides an evaluation method for the crack plugging effect of a polymer gel plugging agent based on the storage modulus, and belongs to the technical field of drilling fluid plugging. The evaluation method of the present invention combines the storage modulus of the polymer gel plugging agent with the crack plugging effects such as the maximum pumping pressure, the crack filling degree, and the plugging pressure for evaluation, which can fully understand the performance of the polymer gel plugging agent, including mechanical properties and plugging ability, and can systematically evaluate the plugging effect of a polymer gel plugging agent for a specific formation structure. Moreover, the method of the present invention determines the matching relationship between the storage modulus of the polymer gel plugging agent and its crack plugging effect. By performing a simple storage modulus test on a specific polymer gel plugging agent solution, its specific crack plugging effect can be efficiently predicted, which simplifies the performance evaluation process, provides guidance for the design of the plugging agent, and can better select a polymer gel plugging agent suitable for specific crack plugging needs.

Description

Technical Field

[0001] The invention relates to an evaluation method for crack plugging effect of a polymer gel plugging agent based on storage modulus, and belongs to the technical field of drilling fluid plugging. Background Art

[0002] Well leakage is one of the most common underground complex problems in the current drilling process, and is one of the main technical bottlenecks that restrict the exploration and development speed of oil and gas, natural gas hydrate, geothermal and other reservoirs. Well leakage may occur in different types of formations, among which the leakage in fractured and cave-developed formations is the most serious and the most difficult to solve. Well leakage not only loses a large amount of drilling fluid, making drilling unsustainable, but also greatly prolongs the drilling time, and may cause other underground complex situations and major accidents such as well collapse, stuck drill, blowout, etc., causing significant losses to the drilling project.

[0003] Polymer gel plugging agent is one of the most commonly used plugging materials in oil and gas drilling and production projects. It can generate high-strength block gel in in-situ pores and cracks to achieve high-strength plugging areas. Polymer gel plugging agent can solve the problem of severe leakage or large total leakage, meet the plugging and pumping requirements of different well depths, and can adapt to different depth formations. Under different reaction conditions, it can form polymer gel systems with different mechanical properties, thereby plugging fractures to different degrees.

[0004] Whether a certain polymer gel plugging agent can effectively plug a specific structure of the formation often requires a lot of experiments to verify, which is time-consuming and labor-intensive; and the specific plugging effect of a specific polymer gel plugging agent solution also often requires complex plugging experiments to determine. Therefore, it is of great significance to study a simple and efficient evaluation method for the crack plugging effect of polymer gel plugging agents. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides an evaluation method for the crack plugging effect of a polymer gel plugging agent based on the storage modulus. The method of the present invention is simple and effective; it can not only systematically evaluate the plugging effect of a polymer gel plugging agent on a specific formation structure, but also determine the matching relationship between the storage modulus of the polymer gel plugging agent and its crack plugging effect. By performing a simple storage modulus test on a specific polymer gel plugging agent solution, its specific crack plugging effect can be efficiently predicted, which simplifies the performance evaluation process, provides guidance for the design of plugging agents, and can better select polymer gel plugging agents suitable for specific crack plugging needs, which has important practical application significance.

[0006] The technical solution of the present invention is as follows:

[0007] A method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus, comprising the steps of:

[0008] (1) Determine the simulated fracture core model according to the formation conditions;

[0009] (2) Test the storage modulus of polymer gel plugging agent solutions of different concentrations; inject polymer gel plugging agent solutions of different concentrations into a visualized simulated fracture core model to test the filling degree of the polymer gel plugging agent solution in the fracture; inject polymer gel plugging agent solutions of different concentrations into a simulated fracture core model to test the maximum pumping pressure; plot a double y-axis relationship curve with the storage modulus of polymer gel plugging agent solutions of different concentrations as the horizontal coordinate and the corresponding maximum pumping pressure and filling degree as the vertical coordinate, and obtain the relationship between the storage modulus of polymer gel plugging agent solutions of different concentrations and the filling degree and maximum pumping pressure by fitting;

[0010] (3) Testing the storage modulus of polymer gel plugging agent solutions of different concentrations during the gelling process; using a simulated crack plugging experiment to test the plugging pressure of polymer gel plugging agent solutions of different concentrations on cracks at different gelling times; using the storage modulus of the polymer gel plugging agent solution during the gelling process as the horizontal coordinate and the corresponding plugging pressure as the vertical coordinate, a relationship curve is drawn, and the relationship between the storage modulus and the crack plugging pressure of polymer gel plugging agent solutions of different concentrations during the gelling process is fitted;

[0011] (4) Testing the storage modulus of polymer gel plugging agent solutions of different concentrations after complete gelation; using a simulated crack plugging experiment to test the plugging pressure of polymer gel plugging agent solutions of different concentrations on cracks after complete gelation; using the storage modulus of polymer gel plugging agent solutions of different concentrations after complete gelation as the abscissa and the corresponding plugging pressure as the ordinate to draw a relationship curve, and fitting to obtain the relationship between the storage modulus and the plugging pressure of polymer gel plugging agent solutions of different concentrations after complete gelation;

[0012] (5) The crack plugging effect of the polymer gel plugging agent is evaluated based on the relationship curve and relationship formula obtained in steps (2) to (4).

[0013] According to the present invention, the simulated fracture core model in step (1) can be purchased commercially or prepared according to the prior art; based on the actual core of the formation and the fracture simulation of the commonly used technology, the underground fracture scale is derived according to the prior art, thereby determining the simulated fracture core model.

[0014] Preferably, the polymer gel plugging agent solution in steps (2), (3) and (4) is an aqueous solution of a polymer gel plugging agent; wherein the mass concentration of the polymer gel plugging agent solution is 12-20%, and the concentration of the polymer gel plugging agent solution is uniformly taken within the above range. The mass concentration of the polymer gel plugging agent solution refers to the solid content thereof, that is, the mass content of the remaining substance after removing water.

[0015] Preferably, in steps (2), (3) and (4) of the present invention, the storage modulus is tested as follows: a high temperature and high pressure rotational rheometer is used to perform a strain sweep test on the sample to obtain the storage modulus.

[0016] Preferably, according to the present invention, in step (2), during the test of the filling degree of the polymer gel plugging agent solution in the crack, the polymer gel plugging agent solution used is a dyed polymer gel plugging agent solution; the preparation method of the dyed polymer gel plugging agent solution is as follows: Sudan III is added to the polymer gel plugging agent solution and fully dispersed; wherein the mass concentration of the dyeing agent is 0.05-0.1%.

[0017] Preferably, according to the present invention, in step (2), during the test of the filling degree of the polymer gel plugging agent solution in the crack, the injection rate of the polymer gel plugging agent solution is 5-15 mL / min.

[0018] According to the preferred embodiment of the present invention, in step (2), the method for testing the filling degree of the polymer gel plugging agent solution in the fracture is as follows: inject the polymer gel plugging agent solution into a vertically placed visualized simulated fracture core model, and when the total injection amount is half of the fracture space volume, observe the distribution state of the polymer gel plugging agent solution in the vertical fracture space; divide the fracture space into upper and lower parts according to the height, and test the ratio of the distribution volume of the polymer gel plugging agent solution in the upper and lower parts of the fracture space, that is, the filling degree of the polymer gel plugging agent solution in the fracture. The closer the above ratio is to 1, the more uniform the distribution of the gel solution in the vertical fracture and the better the filling effect.

[0019] Preferably, according to the present invention, in step (2), during the maximum pumping pressure test, the injection rate of the polymer gel plugging agent solution is 1-3 mL / min.

[0020] Preferably, in step (2) of the present invention, the maximum pumping pressure is tested as follows: a polymer gel plugging agent solution is pumped into a simulated fracture core model, and the maximum pumping pressure is obtained by a pressure sensor.

[0021] According to the present invention, in step (3), the gelling temperature is determined by the properties of the polymer gel plugging agent.

[0022] Preferably, according to the present invention, in step (3), the time selection range of the gelling process is 2h~14h, and the time of the gelling process is uniformly taken within the above range.

[0023] Preferably, in step (3) of the present invention, the testing method of the plugging pressure is as follows: adding a polymer gel plugging agent solution to a high temperature and high pressure dynamic and static leakage tester to allow the polymer gel plugging agent solution to fill the fracture model; then raising the temperature to the gelling temperature, and after gelling for different times, slowly increasing the displacement pressure of the plugging tester until a large amount of leakage suddenly occurs. The pressure corresponding to this is the plugging pressure.

[0024] According to the present invention, in step (4), the gelling temperature and gelling time are determined by the properties of the polymer gel plugging agent.

[0025] Preferably, in step (4) of the present invention, the testing method of the plugging pressure is as follows: adding polymer gel plugging agent solutions of different concentrations into a high-temperature and high-pressure dynamic and static leakage tester to allow the polymer gel plugging agent solution to fill the fracture model; then raising the temperature to the gelling temperature, and after complete gelling, slowly increasing the displacement pressure of the plugging tester until a large amount of leakage suddenly occurs. The corresponding pressure is the plugging pressure.

[0026] Preferably, in step (5), the crack plugging effect of the polymer gel plugging agent on a specific formation structure is evaluated based on the relationship curve and relationship equation obtained in steps (2) to (4); or, the crack plugging effect is evaluated based on the relationship curve and relationship equation obtained in steps (2) to (4) by testing the storage modulus of the polymer gel plugging agent solution, the storage modulus of the polymer gel plugging agent solution during or after gelation.

[0027] The technical features and beneficial effects of the present invention are as follows:

[0028] 1. The present invention will consider polymer gel plugging agents of different concentrations and structures to obtain samples with different storage moduli. It also introduces the simulation of crack plugging experiments, and by preparing cracks of a certain size, it is closer to the actual application scenario. This helps to more accurately evaluate the performance of polymer gel plugging agents in the crack plugging process.

[0029] 2. The present invention selects storage modulus as a parameter to characterize the performance of polymer gel plugging agent because it can reflect the key elastic properties of the material, can be used to predict plugging effects, simplifies the performance evaluation process, provides guidance for material design, and is reliable.

[0030] 3. The present invention proposes a comprehensive evaluation method, which is simple and effective, and can systematically evaluate the plugging effect of a polymer gel plugging agent on a specific formation structure, so as to better select a polymer gel plugging agent suitable for specific fracture plugging needs. By combining the storage modulus of the polymer gel plugging agent with the fracture plugging effect such as the maximum pumping pressure, fracture filling degree, and plugging pressure for evaluation, the performance of the polymer gel plugging agent, including mechanical properties and plugging ability, can be fully understood. The present invention establishes a matching relationship between the storage modulus and the crack plugging effect, and establishes a suitable fitting formula. By simply testing the storage modulus of the polymer gel plugging agent solution and the storage modulus of the polymer gel plugging agent solution during or after complete gelling, the crack plugging effect thereof can be efficiently predicted; and for a polymer gel plugging agent solution of unknown concentration, the crack plugging effect thereof can also be efficiently predicted by testing its storage modulus and the storage modulus after complete gelling; for a polymer gel plugging agent solution of known concentration, the crack plugging effect at different gelling times can be evaluated by testing the storage modulus, and whether complete gelling can be predicted.

[0031] 4. The evaluation method of the present invention can more accurately evaluate the performance of polymer gel plugging agents, especially the performance related to crack plugging. By establishing a matching relationship between the storage modulus and the crack plugging effect, it can provide guidance to designers on how to select appropriate material parameters and optimize application conditions, and more quickly and accurately screen and optimize polymer gel plugging agents, improve the plugging efficiency, and thus better meet actual needs, which has important practical application significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a fitting diagram of the relationship between the storage modulus of the polymer gel plugging agent solution of different concentrations in Example 1 and its maximum pumping pressure and filling degree in the crack;

[0033] Figure 2 is a fitting diagram of the relationship between the storage modulus of the polymer gel plugging agent solution at different gelling times in Example 1 and its plugging pressure on cracks;

[0034] Figure 3 It is a fitting diagram of the relationship between the storage modulus of the polymer gel plugging agent solutions of different concentrations in Example 1 after complete gelation and the plugging pressure on the cracks. DETAILED DESCRIPTION

[0035] The present invention is further described below with reference to specific examples, but is not limited thereto. The raw materials used in the examples are all conventional raw materials and can be obtained commercially; the methods described are all conventional methods and prior art unless otherwise specified.

[0036] Example 1

[0037] Polymer E solution (polymer gel plugging agent solution):

[0038] The polymer E solution includes the following raw materials in percentage by mass: 15% acrylamide monomer, 0.6% organic polymer crosslinking agent N-hydroxymethyl acrylamide, 1.5% fiber toughening agent, 0.5% resin toughening agent, 2.5% flow pattern regulator lithium bentonite, 0.01% initiator tert-butyl hydroperoxide, and the balance is water.

[0039] The preparation method of polymer E solution comprises the following steps: adding acrylamide monomer and organic polymer crosslinking agent to water in sequence, stirring at 300 rpm until completely dissolved, to obtain mixed solution A; adding fiber toughening agent to the mixed solution A, stirring at 300 rpm until uniformly dispersed, to obtain mixed solution B; adding resin toughening agent to the mixed solution B, stirring at 300 rpm until uniformly dispersed, to obtain mixed solution C; adding flow type regulator to the mixed solution C, stirring at 550 rpm until uniformly dispersed, to obtain mixed solution D; adding initiator to the mixed solution D, stirring at 550 rpm until viscous, to obtain polymer gel plugging agent solution for standby use.

[0040] A method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus, comprising the steps of:

[0041] (1) Determine the simulated fracture core model

[0042] According to the formation conditions and the fracture simulation of common technologies, the scale of underground fractures was derived according to the existing technology, and the average width of the formation fractures was judged to be 3mm. Therefore, a visual simulation fracture core model with a fracture length of 50cm, a fracture height of 30cm, and a fracture width of 3mm and a steel column pressure-resistant fracture core model with an inlet and outlet size of 20×3mm were made by self-made.

[0043] (2) Prepare polymer E solutions with mass concentrations of 12%, 14%, 16%, 18%, and 20% respectively; the mass concentration of polymer E solution refers to the solid content, that is, the mass content of the remaining substance after removing water. The storage modulus of the above polymer E solution was tested using a high temperature and high pressure rotational rheometer, and the steps are as follows: The polymer E solutions with different concentrations were subjected to a 0.1%-1000% strain sweep test to test the corresponding storage modulus. The storage moduli of polymer E solutions with different concentrations are shown in Table 1.

[0044] The preparation method of dyeing polymer E solution is as follows: Sudan III is added to the polymer gel plugging agent solution and fully dispersed; wherein the mass concentration of the dyeing reagent is 0.05%.

[0045] The filling performance of the prepared polymer E solution of different concentrations on the vertical fracture space was tested using a visual simulated fracture core model. The steps are as follows: 1000 mL of dyed polymer E solution was placed in the middle container, and water was injected into the middle container at a rate of 10 mL / min using a large displacement horizontal flow pump. The polymer E solution was injected into the vertically placed visual simulated fracture core model by pushing the piston; when the total injection amount was half of the fracture space volume, the distribution state of the dyed polymer E solution in the vertical fracture space was observed; the fracture space was divided into upper and lower parts according to the height, and the ratio of the distribution volume of the dyed polymer E solution in the upper and lower parts of the fracture space was tested, that is, the filling degree of the polymer E solution in the fracture. The above test was repeated with the concentration of the dyed polymer E solution changed. The data of the filling degree of polymer E solution of different concentrations in the fracture are shown in Table 1 below.

[0046] Table 1 Data on the storage modulus of polymer E solutions of different concentrations and their filling degree for vertical crack space

[0047]

[0048] The maximum pumping pressure of the prepared polymer E solution of different concentrations was tested by using a simulated crack plugging experimental device, and the steps are as follows: using a high temperature and high pressure dynamic and static plugging experimental device, polymer E solutions of different concentrations were injected into the steel column pressure-resistant crack core model at an injection rate of 2 mL / min, and the maximum pumping pressure was obtained by a pressure sensor. The data of the maximum pumping pressure are shown in Table 2 below.

[0049] Table 2 Data of storage modulus of polymer E solutions with different concentrations and their pumping pressure in the cracks

[0050]

[0051] With the storage modulus of polymer E solutions of different concentrations as the horizontal axis, and the filling degree of the vertical crack space and the maximum pumping pressure in the crack as the vertical axis, a double y-axis scatter plot is drawn and fitted, as shown in Figure 1 As shown, the storage modulus of polymer E solutions with different concentrations and their filling degree in the vertical crack space are fitted with formula a; the storage modulus of polymer E solutions with different concentrations and their maximum pumping pressure in the crack are fitted with formula b. The matching relationship between the storage modulus of polymer gel and its crack plugging effect is evaluated using the fitting curve and fitting formula.

[0052] The fitting formula a of the storage modulus of polymer E solutions with different concentrations and their filling degree of vertical crack space:

[0053]

[0054] The fitting formula b of the storage modulus of polymer E solutions with different concentrations and their maximum pumping pressure in the cracks:

[0055]

[0056] From Table 1, Table 2 and Figure 1 It can be seen that as the concentration of polymer E solution increases, the storage modulus increases, and its maximum pumping pressure in the crack also increases accordingly. In addition, as the storage modulus increases, the crack filling effect of polymer E solution becomes better.

[0057] (3) Prepare a polymer E solution with a mass concentration of 14%. After the polymer E solution is gelled at 120°C for 2h, 4h, 6h, 8h, 10h, 12h, and 14h, the storage modulus test is performed as follows: The polymer gels with different gelling times during the gelling process are subjected to a 0.1%-1000% strain sweep test to determine the corresponding storage modulus.

[0058] The simulated crack plugging test device was used to test the plugging pressure of the prepared polymer E solution with a concentration of 14% on the cracks at different gelling times; the steps are as follows: using a high temperature and high pressure dynamic and static plugging test device, a polymer E solution with a concentration of 14% was injected into the steel column pressure crack core model to fill the fracture model with the polymer E solution; at a high temperature of 120°C, after standing for 2h, 4h, 6h, 8h, 10h, 12h, and 14h, clean water was injected, and the pressure change at the outlet during injection was recorded. When a large amount of leakage suddenly occurs at the outlet, the corresponding pressure is the plugging pressure. The storage modulus of the polymer gel with different gelling times during the gelling process and its plugging pressure on the cracks are shown in Table 3 below.

[0059] Table 3 Data on the storage modulus of polymer gels at different gelling times and their sealing pressure on cracks during gelling

[0060]

[0061] With the storage modulus of the polymer gel at different gelation times in the gelation process as the horizontal axis and its plugging pressure on the crack as the vertical axis, a scatter plot is drawn and fitted, such as Figure 2 As shown, the storage modulus of polymer gel at different gelling times and its crack plugging pressure fitting formula c are obtained during the gelling process. The matching relationship between the storage modulus of polymer gel at different gelling times and its crack plugging effect is evaluated using the fitting curve and fitting formula.

[0062] The fitting formula c of the storage modulus of polymer gel at different gelation times and its plugging pressure on cracks is:

[0063] According to the relationship curve and relationship table 3 and Figure 2 It can be seen that in the process of polymer gelation in cracks, the longer the gelation time, the greater the storage modulus, and the greater the plugging pressure on the cracks. That is, as the storage modulus of the polymer gel increases, its crack plugging effect becomes better.

[0064] The above method was repeated with varying concentrations of the polymer E solution to obtain the relationship between the storage modulus and the crack plugging pressure during the gelation process of polymer E solutions with different concentrations.

[0065] By changing the gelling temperature, the relationship between the storage modulus and the crack plugging pressure of the polymer E solution during the gelling process at different temperatures can be obtained.

[0066] (4) Prepare polymer E solutions with mass concentrations of 12%, 14%, 16%, 18%, and 20%, respectively, and form gel at 120°C, i.e., completely gel; then use a high temperature and high pressure rotational rheometer to perform a storage modulus test, the steps are as follows: perform a 0.1%-1000% strain scan on the obtained gel sample to test its corresponding storage modulus.

[0067] The simulated crack plugging experimental device was used to test the prepared polymer E solutions with concentrations of 12%, 14%, 16%, 18%, and 20% respectively after gelling at 120°C, that is, after complete gelling, the plugging pressure on the cracks. The steps are as follows: using a high temperature and high pressure dynamic and static plugging experimental device, the polymer E solutions with concentrations of 12%, 14%, 16%, 18%, and 20% were injected into the steel column pressure-resistant crack core model, and gelled at a high temperature of 120°C, that is, after complete gelling, clean water was injected, and the pressure change at the outlet during injection was recorded. When a large amount of leakage suddenly occurs at the outlet, the corresponding pressure is the plugging pressure. The storage modulus of the polymer gel after the polymer E solution with different concentrations is completely gelled and the data on its plugging pressure on the cracks are shown in Table 4 below.

[0068] Table 4 Data on the storage modulus of polymer gels and their sealing pressure on cracks after the polymer E solutions with different concentrations are completely gelled

[0069]

[0070] The storage modulus of the polymer gel after the polymer E solution with different concentrations is completely gelled is used as the horizontal axis, and the plugging pressure of the polymer gel on the crack is used as the vertical axis to draw a scatter plot and perform fitting, as shown in the figure below: Figure 3 As shown, the storage modulus of the polymer gel after complete gelation at different concentrations and its crack plugging pressure fitting formula d are obtained. The matching relationship between the storage modulus of the polymer gel after gelation and its crack plugging effect is evaluated using the fitting curve and fitting formula.

[0071] The storage modulus of polymer gels with different concentrations after complete gelation and their sealing pressure on cracks are fitted with the formula d:

[0072]

[0073] According to the relationship curve and relationship table 4 and Figure 3 It can be seen that after polymer gels of different concentrations are completely gelled in the cracks, the greater the concentration, the greater the storage modulus, and the greater the plugging pressure on the cracks. That is, as the storage modulus of the polymer gel increases, its crack plugging effect becomes better.

[0074] (5) Evaluate the crack plugging effect of the polymer gel plugging agent on a specific formation structure based on the relationship curve and relationship formula obtained in steps (2) to (4). By testing the storage modulus of the polymer E solution, the storage modulus of the polymer E solution during or after gelation, and substituting the relationship curve and relationship formula obtained in steps (2) to (4), the crack plugging effect can be predicted.

[0075] It can be seen from the above data that the present invention is a method for evaluating the matching relationship between the storage modulus of a polymer gel and its crack plugging effect, and further accurately describes the relationship between the storage modulus of a polymer gel and its crack plugging effect through the step of fitting the formula. This method can provide guidance for the design and application of polymer gels and improve the prediction and optimization of crack plugging effects.

[0076] The preferred evaluation method of the present invention is described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus, comprising the steps of: (1) Determine the simulated fracture core model according to the formation conditions; (2) Test the storage modulus of polymer gel plugging agent solutions of different concentrations; inject polymer gel plugging agent solutions of different concentrations into a visualized simulated fracture core model to test the filling degree of the polymer gel plugging agent solution in the fracture; inject polymer gel plugging agent solutions of different concentrations into a simulated fracture core model to test the maximum pumping pressure; plot a double y-axis relationship curve with the storage modulus of polymer gel plugging agent solutions of different concentrations as the horizontal coordinate and the corresponding maximum pumping pressure and filling degree as the vertical coordinate, and obtain the relationship between the storage modulus of polymer gel plugging agent solutions of different concentrations and the filling degree and maximum pumping pressure by fitting; (3) Testing the storage modulus of polymer gel plugging agent solutions of different concentrations during the gelling process; using a simulated crack plugging experiment to test the plugging pressure of polymer gel plugging agent solutions of different concentrations on cracks at different gelling times; using the storage modulus of the polymer gel plugging agent solution during the gelling process as the horizontal coordinate and the corresponding plugging pressure as the vertical coordinate, a relationship curve is drawn, and the relationship between the storage modulus and the crack plugging pressure of polymer gel plugging agent solutions of different concentrations during the gelling process is fitted; (4) Testing the storage modulus of polymer gel plugging agent solutions of different concentrations after complete gelation; using a simulated crack plugging experiment to test the plugging pressure of polymer gel plugging agent solutions of different concentrations on cracks after complete gelation; using the storage modulus of polymer gel plugging agent solutions of different concentrations after complete gelation as the abscissa and the corresponding plugging pressure as the ordinate to draw a relationship curve, and fitting to obtain the relationship between the storage modulus and the plugging pressure of polymer gel plugging agent solutions of different concentrations after complete gelation; (5) The crack plugging effect of the polymer gel plugging agent is evaluated based on the relationship curve and relationship formula obtained in steps (2) to (4).

2. The evaluation method for crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: The polymer gel plugging agent solution in steps (2), (3) and (4) is an aqueous solution of a polymer gel plugging agent; wherein the mass concentration of the polymer gel plugging agent solution is 12-20%, and the concentration of the polymer gel plugging agent solution is uniformly taken within the above range.

3. The evaluation method for crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: In steps (2), (3) and (4), the storage modulus is tested as follows: a rotational rheometer is used to perform a strain sweep test on the sample to obtain the storage modulus.

4. The method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: In step (2), during the test of the filling degree of the polymer gel plugging agent solution in the crack, the polymer gel plugging agent solution used is a dyed polymer gel plugging agent solution; the preparation method of the dyed polymer gel plugging agent solution is as follows: Sudan III is added to the polymer gel plugging agent solution and fully dispersed; wherein the mass concentration of the dyeing agent is 0.05-0.1%.

5. The method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: In step (2), during the test of the filling degree of the polymer gel plugging agent solution in the crack, the injection rate of the polymer gel plugging agent solution is 5-15 mL / min.

6. The evaluation method for crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: In step (2), the method for testing the filling degree of the polymer gel plugging agent solution in the fracture is as follows: inject the polymer gel plugging agent solution into a vertically placed visualized simulated fracture core model, and when the total injection amount is half of the fracture space volume, observe the distribution state of the polymer gel plugging agent solution in the vertical fracture space; divide the fracture space into upper and lower parts according to the height, and test the ratio of the distribution volume of the polymer gel plugging agent solution in the upper and lower parts of the fracture space, that is, the filling degree of the polymer gel plugging agent solution in the fracture.

7. The method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: In step (2), during the maximum pumping pressure test, the injection rate of the polymer gel plugging agent solution is 1-3 mL / min; In step (2), the maximum pumping pressure is tested as follows: a polymer gel plugging agent solution is pumped into a simulated fracture core model, and the maximum pumping pressure is obtained through a pressure sensor.

8. The method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: In step (3), the time selection range of the gelation process is 2h~14h, and the time of the gelation process is uniformly taken within the above range.

9. The method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: In step (3), the plugging pressure is tested as follows: a polymer gel plugging agent solution is added to a dynamic and static leakage tester to allow the polymer gel plugging agent solution to fill the fracture model; then the temperature is raised to the gelling temperature, and after gelling for different times, the displacement pressure of the plugging tester is slowly increased until a large amount of leakage suddenly occurs. The corresponding pressure is the plugging pressure.

10. The method for evaluating crack plugging effect of polymer gel plugging agent based on storage modulus according to claim 1, characterized in that: In step (4), the plugging pressure is tested as follows: adding polymer gel plugging agent solutions of different concentrations into the dynamic and static leakage tester to fill the fracture model with the polymer gel plugging agent solution; then raising the temperature to the gelling temperature, and after the gelling is complete, slowly increasing the displacement pressure of the plugging tester until a large amount of leakage suddenly occurs. The corresponding pressure is the plugging pressure; In step (5), the crack plugging effect of the polymer gel plugging agent on the specific formation structure is evaluated according to the relationship curve and relationship formula obtained in steps (2) to (4); or, by testing the storage modulus of the polymer gel plugging agent solution, the storage modulus of the polymer gel plugging agent solution during the gelation process or after complete gelation, the crack plugging effect is evaluated according to the relationship curve and relationship formula obtained in steps (2) to (4).

Images