Screening method and system of polymer gel for plugging cracks

Abstract

The invention discloses a method and a system for screening polymer gel for plugging cracks. The method comprises the following steps: acquiring multiple test data obtained by performing frequency scanning test, small-amplitude scanning test, creep test and large-amplitude scanning test on to-be-screened polymer gel; evaluating the multiple test data based on test evaluation conditions of the blocked crack, determining to-be-screened polymer gel meeting the test evaluation conditions as the polymer gel for blocking the crack, and further evaluating the nonlinear rheological property of the polymer gel on the basis of linear rheological property evaluation of the polymer gel, so as to obtain the polymer gel for blocking the crack. The problem that existing polymer gel linear rheological parameter evaluation and the plugging effect of the polymer gel in the crack are contradictory is solved, complex and tedious physical simulation experiments are avoided, operation is easy, the polymer gel suitable for crack plugging is rapidly screened out from numerous polymer gel systems, and the method is suitable for large-scale popularization and application. And the screened polymer gel has good plugging performance in cracks.

Description

Technical Field

[0001] The invention relates to the field of oilfield chemistry, and in particular to a screening method and system for polymer gel for plugging cracks. Background Art

[0002] Profile control and plugging of fractures is the key to the sustainable development of fractured reservoirs. Different from conventional high permeability porous matrix profile control and plugging, fracture plugging has higher requirements on the performance of polymer gels. It is necessary to evaluate the long-term plugging ability of different polymer gels in fractures and select the most suitable polymer gel for plugging fractures.

[0003] The existing technology usually draws on the evaluation method of porous reservoir plugging agents, links the plugging ability of the gel with the rheological properties of the polymer gel, characterizes the plugging ability of the polymer gel by the elastic modulus and yield stress of the polymer gel, and evaluates the polymer gel for plugging fractures in combination with fracture core displacement experiments.

[0004] However, there are many polymer gel systems, fracture core displacement is cumbersome, and it is difficult to evaluate the long-term plugging ability of polymer gels in fractures, and it is difficult to screen out polymer gels suitable for fracture plugging scenarios. Summary of the invention

[0005] The present invention provides a method for screening polymer jellies for plugging cracks. In the screening process of polymer jellies for plugging cracks, various types of tests are performed to achieve comprehensive testing of polymer jellies, and polymer jellies suitable for plugging cracks are screened through various types of test results, thereby improving the accuracy of screening polymer jellies for plugging cracks.

[0006] According to one aspect of the present invention, a method for screening a polymer gel for plugging cracks is provided, comprising:

[0007] Obtain multiple test data of the polymer gel to be screened obtained through frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test;

[0008] Based on the test evaluation conditions for plugging cracks, multiple test data are evaluated and processed to determine the polymer jelly to be screened that meets the test evaluation conditions as the polymer jelly for plugging cracks.

[0009] According to another aspect of the present invention, a screening system for polymer jelly for plugging cracks is provided, comprising:

[0010] A frequency scanning test module, used for performing a frequency scanning test on the polymer gel to be screened;

[0011] Small amplitude scanning test module, used for performing small amplitude scanning test on the polymer gel to be screened;

[0012] Creep test module, used to perform creep test on the polymer gel to be screened;

[0013] Large amplitude scanning test module, used for large amplitude scanning test of polymer gel to be screened;

[0014] The processor is used to obtain multiple test data obtained by frequency scanning test, small amplitude scanning test, creep test and large amplitude scanning test of the polymer jelly to be screened; based on the test evaluation conditions for plugging cracks, the multiple test data are evaluated and processed to determine the polymer jelly to be screened that meets the test evaluation conditions as the polymer jelly for plugging cracks.

[0015] The technical solution of the embodiment of the present invention obtains multiple test data obtained by frequency scanning test, small amplitude scanning test, creep test and large amplitude scanning test of the polymer jelly to be screened; evaluates and processes the multiple test data based on the test evaluation conditions for plugging cracks, determines the polymer jelly to be screened that meets the test evaluation conditions, and uses it as the polymer jelly for plugging cracks. On the basis of the evaluation of the linear rheological properties of the polymer jelly, its nonlinear rheological properties are further evaluated, which solves the problem that the existing linear rheological parameter evaluation of polymer jelly is inconsistent with the plugging effect of the polymer jelly in cracks, avoids complicated and tedious physical simulation experiments, is simple to operate, and realizes rapid screening of polymer jelly suitable for crack plugging in numerous polymer jelly systems, and the screened polymer jelly has good plugging performance in cracks.

[0016] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 This is a flow chart of a method for screening a polymer gel for plugging cracks provided in Example 1 of the present invention;

[0019] Figure 2 This is a flow chart of a method for screening a polymer gel for plugging cracks provided in Example 2 of the present invention;

[0020] Figure 3A graph showing the relationship between the first elastic modulus and the viscous modulus of the polymer gels G-1 and G-2 to be screened and the preset first frequency;

[0021] Figure 4 is a graph showing the relationship between the second elastic modulus and the preset first shear strain of the polymer gels G-1 and G-2 to be screened;

[0022] Figure 5 is a graph showing the relationship between the rupture time of the polymer gel G-1 to be screened and the preset shear stress;

[0023] Figure 6 is a graph showing the relationship between the rupture time of the polymer gel G-2 to be screened and the preset shear stress;

[0024] Figure 7 is the elastic Lissajous curve of the polymer gel G-1 to be screened;

[0025] Figure 8 is the elastic Lissajous curve of the polymer gel G-2 to be screened;

[0026] Fig. 9 is the maximum decomposition stress curve of the polymer gel G-1 to be screened;

[0027] Fig.10 is the maximum decomposition stress curve of the polymer gel G-2 to be screened;

[0028] Fig.11 It is a structural schematic diagram of a screening system for polymer jelly for plugging cracks provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0031] Embodiment 1

[0032] Figure 1 This is a flow chart of a method for screening polymer gel for plugging fractures provided in the first embodiment of the present invention. This embodiment is applicable to the water injection development of fractured oil reservoirs. The method can be performed by a screening system for polymer gel for plugging fractures. The screening system for polymer gel for plugging fractures can be implemented in the form of hardware and / or software. The screening system for polymer gel for plugging fractures can be configured in electronic devices such as computers or servers. Figure 1 As shown, the method includes:

[0033] S110, obtaining a plurality of test data obtained by frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test of the polymer gel to be screened.

[0034] In this embodiment, the polymer jelly to be screened is a jelly composed of a high molecular polymer, a cross-linking agent, a catalyst, and nanoparticles. The frequency sweep test is a test for screening out polymer jelly with solid-like properties from the polymer jelly to be screened. The small amplitude sweep test is a test for screening out high-strength polymer jelly from the polymer jelly to be screened. The creep test is a test for screening out polymer jelly with smaller microstructural defects from the polymer jelly to be screened. The large amplitude sweep test is a test for screening out polymer jelly that is not easily damaged under large deformation from the polymer jelly to be screened.

[0035] Specifically, multiple polymer jellies to be screened are determined, and according to the types of polymer jellies to be screened, the test conditions of frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test are determined, including strain amplitude and frequency of frequency sweep test, frequency and shear strain of small amplitude sweep test, shear stress of creep test, and frequency and shear strain of large amplitude sweep test. Samples of the same size are taken from multiple polymer jellies to be screened, and frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test are respectively carried out at the same test temperature and using the same test conditions to obtain the corresponding test data of frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test. The above four tests can be carried out simultaneously or sequentially, and this embodiment does not limit this.

[0036] Exemplarily, two types of polymer jellies to be screened are listed, and basic information of the two polymer jellies to be screened is shown in Table 1. It can be understood that the polymer jellies in Table 1 are only examples, and the polymer jellies to be screened can be selected according to user needs.

[0037] Table 1

[0038]

[0039] According to the types of polymer gels G-1 and G-2 to be screened, the strain amplitude and frequency of the frequency sweep test, the frequency and shear strain of the small amplitude sweep test, the shear stress of the creep test, and the frequency and shear strain of the large amplitude sweep test are determined. The samples of polymer gels G-1 and G-2 to be screened are cut into slices with a thickness of about 1 mm, and frequency sweep tests, small amplitude sweep tests, creep tests, and large amplitude sweep tests are performed at a test temperature of 25 degrees Celsius to obtain test data of frequency sweep tests, small amplitude sweep tests, creep tests, and large amplitude sweep tests of polymer gels G-1 and G-2 to be screened.

[0040] S120, evaluating and processing a plurality of test data based on the test evaluation conditions for plugging cracks, and determining a polymer jelly to be screened that meets the test evaluation conditions as the polymer jelly for plugging cracks.

[0041] In this embodiment, the evaluation conditions based on the test of plugging cracks are artificially set evaluation conditions for the test data of the frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test of the polymer gel to be screened. The evaluation conditions can be the threshold range of the test data, or the trend of the test data changing with the test conditions.

[0042] Specifically, according to the test data of the frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test of the polymer jelly to be screened, a relationship diagram between the test data and the test conditions is drawn. According to the relationship diagram between the test data of the frequency sweep test and the test conditions, the morphology of different polymer jelly to be screened is evaluated; according to the threshold range of the value of the test data of the small amplitude sweep test within a certain test condition change range, the strength of different polymer jelly to be screened is evaluated; according to the threshold range of the value of the test data of the creep test under certain test conditions, the microstructural defects of different polymer jelly to be screened are evaluated; according to the relationship diagram between the test data of the large amplitude sweep test and the test conditions, the nonlinear rheological properties of different polymer jelly to be screened are evaluated. The polymer jelly to be screened that meets the test evaluation conditions of the frequency sweep test, the small amplitude sweep test, the creep test and the large amplitude sweep test is determined as the polymer jelly for plugging cracks.

[0043] Exemplarily, based on the test data of the frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test of the polymer gels G-1 and G-2 to be screened, a relationship diagram of the test data and the test conditions is drawn, and the polymer gels G-1 and G-2 to be screened are evaluated from four perspectives: morphology, strength, microstructure defects and nonlinear rheological properties. The results show that the performance of the polymer gel G-1 to be screened is better than that of the polymer gel G-2 to be screened. Because the polymer gel G-1 to be screened meets the test evaluation conditions of having solid-like properties, high strength, relatively small microstructure defects, and not easy to be destroyed under large deformation, the plugging ability of the polymer gel G-1 to be screened is better than the plugging ability of the polymer gel G-2 to be screened. Therefore, the polymer gel G-1 to be screened can be used as a polymer gel for plugging cracks.

[0044] Optionally, when any test data of the polymer jelly to be screened is obtained, the obtained test data is evaluated and processed based on the test evaluation conditions for plugging cracks. When the above evaluation data does not meet the test evaluation conditions for plugging cracks, the next test of the polymer jelly to be screened is stopped.

[0045] Specifically, the polymer jelly to be screened is subjected to frequency scanning test, small amplitude scanning test, creep test and large amplitude scanning test in sequence, and data analysis is performed each time the test data obtained under the corresponding test conditions. The polymer jelly to be screened is evaluated and processed, and the polymer jelly to be screened that meets the test evaluation conditions is screened out according to the evaluation results for subsequent testing, until there is only one polymer jelly to be screened that meets all the test evaluation conditions, that is, a polymer jelly suitable for sealing cracks is obtained, and the screening is terminated.

[0046] Exemplarily, the polymer jellies G-1 and G-2 to be screened are subjected to frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test in sequence; both polymer jellies G-1 and G-2 to be screened have solid-like properties and meet the test evaluation conditions of the frequency sweep test, so a small amplitude sweep test is performed; both polymer jellies G-1 and G-2 to be screened are high-strength polymer jellies and meet the test evaluation conditions of the small amplitude sweep test, so a creep test is performed; both polymer jellies G-1 and G-2 to be screened are high-strength polymer jellies and meet the test evaluation conditions of the small amplitude sweep test, so a creep test is performed; the microstructural defects of polymer jellies G-1 to be screened are relatively small and meet the test evaluation conditions of the creep test, so a large amplitude sweep test is performed, while the microstructural defects of polymer jellies G-2 to be screened are relatively large and do not meet the test evaluation conditions of the creep test, so a large amplitude sweep test is not performed; polymer jellies G-1 to be screened are not easily damaged under large deformation and meet the test evaluation conditions of the large amplitude sweep test, so the screening is terminated. Therefore, the polymer jelly G-1 to be screened can be used as a polymer jelly for sealing cracks.

[0047] The technical solution of this embodiment is to stop subsequent testing on the polymer jellies to be screened that do not meet the evaluation conditions by sequentially performing frequency scanning tests, small amplitude scanning tests, creep tests and large amplitude scanning tests and evaluations on the polymer jellies to be screened, thereby reducing unnecessary subsequent testing processes.

[0048] The technical solution of this embodiment is to obtain multiple test data obtained by frequency scanning test, small amplitude scanning test, creep test and large amplitude scanning test of the polymer jelly to be screened; evaluate and process the multiple test data based on the test evaluation conditions for plugging cracks, determine the polymer jelly to be screened that meets the test evaluation conditions, and use it as the polymer jelly for plugging cracks. On the basis of the evaluation of the linear rheological properties of the polymer jelly, its nonlinear rheological properties are further evaluated, which solves the problem of the contradiction between the existing linear rheological parameter evaluation of polymer jelly and the plugging effect of the polymer jelly in cracks, avoids complicated and tedious physical simulation experiments, is simple to operate, and realizes the rapid screening of polymer jelly suitable for crack plugging in numerous polymer jelly systems, and the screened polymer jelly has good plugging performance in cracks.

[0049] Embodiment 2

[0050] Figure 2 1 is a flow chart of a method for screening a polymer gel for plugging cracks provided in the second embodiment of the present invention. The technical solution of the embodiment of the present invention is further optimized on the basis of any of the above embodiments. Figure 2 As shown, the method includes:

[0051] S210, under the condition of preset strain amplitude and preset first frequency, the first elastic modulus G of the polymer gel to be screened is obtained by frequency scanning test 1 ’ and viscous modulus G″.

[0052] In this embodiment, the preset strain amplitude is the amplitude of strain generated by the polymer gel to be screened under the influence of stress during the frequency sweep test, and the preset strain amplitude is a fixed value. The preset first frequency ω is a plurality of scanning frequencies set for testing the response of the polymer gel to be screened with frequency under a constant strain amplitude during the frequency sweep test of the polymer gel to be screened. The first elastic modulus G 1 ' is the modulus representing the elastic properties of the polymer jelly to be screened in the frequency sweep test, and the viscous modulus G" is the modulus representing the viscous properties of the polymer jelly to be screened in the frequency sweep test.

[0053] Specifically, at the same preset first frequency, different shear stresses are applied to the plurality of polymer gels to be screened, so that the strain amplitudes of the plurality of polymer gels to be screened maintain the preset strain amplitude, and the first elastic modulus G of the plurality of polymer gels to be screened at the preset first frequency is obtained. 1 ' and viscosity modulus G". By changing the preset first frequency, the first elastic modulus G of the plurality of polymer gels to be screened within the range of the preset first frequency is obtained. 1 ′ and the viscosity modulus G″ change with the preset first frequency.

[0054] Exemplarily, a frequency scanning test is performed using a sawtooth parallel plate measurement system (the diameter of the flat plate rotor is 25 mm), and the polymer jelly G-1 and G-2 samples to be screened are cut into thin slices with a thickness of about 1 mm and placed between the parallel plate rotor and the test table with a gap of 1 mm. A layer of low-viscosity mineral oil is applied to the edges of the polymer jelly G-1 and G-2 samples to be screened to prevent evaporation of the jelly. The test temperature is 25 degrees Celsius, and the first elastic modulus and viscous modulus of the polymer jelly G-1 and G-2 to be screened are obtained within the range of a preset strain amplitude and a preset first frequency, as they change with a preset first frequency.

[0055] Optionally, during the frequency sweep test, the strain amplitude is preset to be 1%-5%, and the range of the first frequency is preset to be 0.1 rad·s -1 To 100rad·s -1 .

[0056] Specifically, during the frequency sweep test, the strain amplitude is preset to a fixed value of 1%-5%, and the first frequency is preset to 0.1 rad·s -1 To 100rad·s -1 Multiple values ​​in the range.

[0057] For example, in the frequency scanning test of the polymer gels G-1 and G-2 to be screened, the preset strain amplitude is 5%, and the preset first frequency is 0.1 rad·s -1 To 100rad·s -1 21 values ​​were selected in the range of 0.1 rad·s -1 To 1 rad·s -1 , 1rad·s -1 To 10rad·s -1 and 10 rad·s -1 To 100rad·s -1 Select 7 values ​​in each of the three ranges.

[0058] S220. Evaluate and process the test data of the frequency sweep test based on the test evaluation conditions for plugging cracks, and determine the polymer gel to be screened that meets the test evaluation conditions; the test evaluation conditions for the frequency sweep test for plugging cracks include: the first elastic modulus does not change with the change of the preset first frequency, and the first elastic modulus is greater than the viscous modulus.

[0059] Specifically, the first elastic modulus G obtained by the frequency sweep test of the polymer gel to be screened is plotted. 1 ′ and the viscosity modulus G″ and the change relationship between the preset first frequency ω, the horizontal axis is the preset first frequency, and the vertical axis is the first elastic modulus G 1 ' or viscous modulus G". If the first elastic modulus G of the polymer gel to be screened 1 If the relationship curve between ′ and the preset first frequency ω is parallel to the horizontal axis, it is considered that the first elastic modulus G 1 ' does not change with the change of the preset first frequency, and if the first elastic modulus G of the polymer jelly to be screened 1 ′ is greater than the viscous modulus G″, the polymer jelly to be screened is considered to have solid-like properties and meet the test evaluation conditions of the frequency sweep test.

[0060] For example, Figure 3 is the first elastic modulus G of the polymer gels G-1 and G-2 to be screened 1 ′ and the viscosity modulus G″ and the change relationship between the preset first frequency ω, the preset first frequency ω is 0.1rad·s -1 To 10rad·s -1 In the range of the first elastic modulus G of the polymer gels G-1 and G-2 to be screened, 1 The relationship curve between ′ and the preset first frequency ω is parallel to the horizontal axis, and the first elastic modulus G 1 ′ is greater than the viscous modulus G″, then the polymer jelly G-1 and G-2 to be screened are both polymer jelly with solid-like properties and meet the test evaluation conditions of the frequency sweep test.

[0061] S230. Under the condition of a preset second frequency and a preset first shear strain, the second elastic modulus in the linear viscoelastic region of the polymer gel to be screened is obtained by a small amplitude scanning test.

[0062] In this embodiment, the preset second frequency is a fixed scanning frequency of the polymer gel to be screened during the small amplitude scanning test. 1 Multiple shear strains are set at a constant frequency to test the response of the polymer gel to be screened to shear strain during the small amplitude scanning test. The linear viscoelastic region is the region where the elastic modulus does not change with shear strain. The second elastic modulus G 2 ' is the modulus representing the elastic properties of the polymer jelly to be screened in the small amplitude sweep test.

[0063] Specifically, at the same preset second frequency, different shear stresses are applied to the plurality of polymer gels to be screened, so that the shear strains of the plurality of polymer gels to be screened maintain the preset first shear strain γ 1 , and obtain the preset first shear strain γ 1 The second elastic modulus G of the multiple polymer gels to be screened 2 ′. By changing the preset first shear strain γ 1 , and obtain the preset first shear strain γ 1 In the range of 2 ′ with the preset first shear strain γ 1 The value of the change.

[0064] Exemplarily, a small amplitude scanning test is performed using a sawtooth parallel plate measurement system (the diameter of the flat plate rotor is 25 mm), the polymer gel G-1 and G-2 samples to be screened are cut into thin slices with a thickness of about 1 mm, and placed between the parallel plate rotor and the test table with a gap of 1 mm. A layer of low-viscosity mineral oil is applied to the edges of the polymer gel G-1 and G-2 samples to be screened to prevent the gel from evaporating. The test temperature is 25 degrees Celsius, and the polymer gel G-1 and G-2 to be screened are obtained at the preset second frequency and the preset first shear strain γ. 1 In the range of the preset first shear strain γ 1 Variation of the second elastic modulus G 2 ′.

[0065] Optionally, during the small amplitude sweep test, the second frequency is preset to be 1 Hz, and the first shear strain is preset to range from 0.1% to 100%.

[0066] Specifically, during the small amplitude scanning test, the second frequency is preset to 1 Hz, and the first shear strain γ is preset to 1There are multiple values ​​in the range of 0.1% to 100%.

[0067] For example, in the small amplitude scanning test of the polymer gels G-1 and G-2 to be screened, the second frequency is preset to be 1 Hz, and the first shear strain γ is preset to be 1 There are 24 values ​​selected within the range of 0.1% to 100%, and 8 values ​​selected in each of the three ranges of 0.1% to 1%, 1% to 10%, and 10% to 100%.

[0068] S240. Evaluate and process the test data of the small amplitude scanning test based on the test evaluation conditions for plugging cracks, and determine the polymer gel to be screened that meets the test evaluation conditions; the test evaluation conditions for the small amplitude scanning test for plugging cracks include: the second elastic modulus in the linear viscoelastic zone is greater than 10Pa.

[0069] Specifically, the second elastic modulus G obtained by the small amplitude scanning test of the polymer gel to be screened at the preset second frequency is plotted. 2 ′ and the preset first shear strain γ 1 The horizontal axis is the preset first shear strain γ 1 , the ordinate is the second elastic modulus G 2 ′. If the first shear strain γ is preset 1 In the range of the second elastic modulus G of the polymer gel to be screened 2 ′ and the preset first shear strain γ 1 The relationship curve is parallel to the horizontal axis, so it can be considered that the second elastic modulus G 2 ′ does not follow the preset first shear strain γ 1 The preset first shear strain γ 1 The range is the linear viscoelastic region. If the second elastic modulus G in the linear viscoelastic region is 2 ′ is greater than 10Pa, the polymer jelly to be screened is considered to be a high-strength polymer jelly, which meets the test evaluation conditions of the small amplitude scanning test.

[0070] For example, Figure 4 is the second elastic modulus G of the polymer gels G-1 and G-2 to be screened 2 ′ and the preset first shear strain γ 1 The linear viscoelastic region of the polymer gel G-1 to be screened is the preset first shear strain γ 1 The linear viscoelastic region of the polymer gel G-2 to be screened is the preset first shear strain γ 1 is in the range of 0.1% to 10%, and the second elastic modulus G of the polymer gels G-1 and G-2 to be screened is 2′ are both greater than 10Pa, it can be considered that the polymer gels G-1 and G-2 to be screened are both high-strength polymer gels, and both meet the test evaluation conditions of the small amplitude scanning test.

[0071] S250, under a preset shear stress, the rupture time of the polymer jelly to be screened is obtained by creep testing the polymer jelly to be screened.

[0072] In this embodiment, the preset shear stress is a plurality of shear stresses set during the creep test of the polymer jelly to be screened in order to test the relationship between the shear strain of the polymer jelly to be screened and the time. The rupture time is the time from the fixed preset shear stress being applied to the rupture of the polymer jelly to be screened.

[0073] Specifically, the same preset shear stress is applied to multiple polymer gels to be screened, and the relationship between the shear strain and time is tested until the polymer gels to be screened break under the given preset shear stress, and the rupture time of the multiple polymer gels to be screened under the preset shear stress is obtained. The preset shear stress is increased step by step until the polymer gel breaks rapidly under the given applied stress, and the values ​​of the rupture time of the multiple polymer gels to be screened changing with the preset shear stress under the multiple preset shear stresses are obtained.

[0074] Exemplarily, a creep test is performed using an MCR302e rheometer module equipped with a sawtooth parallel plate geometry (40 mm in diameter, 1 mm in measuring gap). The polymer gels G-1 and G-2 samples to be screened are cut into slices with a thickness of approximately 1 mm and placed between the parallel plate rotor and the test table. A layer of low-viscosity mineral oil is applied to the edges of the polymer gels G-1 and G-2 samples to be screened to prevent evaporation of the gel. The test temperature is 25 degrees Celsius, and the rupture time of the polymer gels G-1 and G-2 to be screened is obtained under a preset shear stress that increases in steps, and the time varies with the preset shear stress.

[0075] Optionally, during the creep test, the preset shear stress is increased stepwise with a fixed step length based on the initial value, and the end condition of the creep test is that the rupture time of the polymer gel to be screened under the applied shear stress is less than 10s.

[0076] Specifically, during the creep test, the creep test is started with an initial value of the preset shear stress, and the rupture time of the polymer jelly to be screened under the initial preset shear stress is recorded. The preset shear stress is increased by a fixed step size each time for multiple creep tests, and the rupture time of the polymer jelly to be screened under the current preset shear stress is recorded. When the rupture time is less than 10s, the test is stopped.

[0077] Exemplarily, the preset shear stress takes 10 Pa as the initial value and increases in steps of 10 Pa each time. When a certain preset shear stress is applied and the rupture time of the polymer gel to be screened is less than 10 s, the test is stopped.

[0078] S260. Evaluate and process the test data of the creep test based on the test evaluation conditions for plugging cracks to determine the polymer gel to be screened that meets the test evaluation conditions; the test evaluation conditions for the creep test for plugging cracks include: when the preset shear stress is 80Pa, the rupture time of the polymer gel to be screened is greater than 10s.

[0079] Specifically, a graph showing the relationship between the rupture time t and the preset shear stress σ obtained by the creep test of the polymer jelly to be screened is drawn, with the preset shear stress on the horizontal axis and the rupture time on the vertical axis. Under the same preset shear stress, for the same type of polymer jelly to be screened, the shorter the rupture time, the larger the microstructural defects, and the worse the plugging effect in the cracks. If the rupture time of the polymer jelly to be screened is greater than 10s when the preset shear stress is 80Pa, it is considered that the microstructural defects of the polymer jelly to be screened are small and meet the test evaluation conditions of the creep test; if the rupture time of the polymer jelly to be screened is less than 10s when the preset shear stress is 80Pa, it is considered that the microstructural defects of the polymer jelly to be screened are serious and do not meet the test evaluation conditions of the creep test.

[0080] For example, Figure 5 is a graph showing the relationship between the rupture time of the polymer gel G-1 to be screened and the preset shear stress, Figure 6 This is a graph showing the relationship between the rupture time of the polymer gel G-2 to be screened and the preset shear stress. By comparing the rupture times of the polymer gels G-1 and G-2 to be screened, it is found that under the same preset shear stress, the rupture time of the polymer gel G-2 to be screened is much shorter than the destruction time of the polymer gel G-1 to be screened, and the rupture time of the polymer gel G-1 to be screened is less than 10s when the preset shear stress is 80Pa. It can be considered that the microstructure of the polymer gel G-1 to be screened is better than that of the polymer gel G-2 to be screened, and the polymer gel G-1 to be screened meets the test evaluation conditions of the creep test, while the polymer gel G-2 to be screened does not meet the test evaluation conditions of the creep test.

[0081] S270. Under the condition of a preset third frequency and a preset second shear strain, the nonlinear stress response parameters of the polymer gel to be screened are obtained by a large amplitude scanning test.

[0082] In this embodiment, the third frequency is preset as a fixed scanning frequency during the large amplitude scanning test of the polymer gel to be screened. 2The multiple shear strains set for testing the response of the polymer jelly to be screened with shear strain during the large amplitude sweep test at a constant frequency. The nonlinear stress response parameters are the parameters that represent the rheological properties of the polymer jelly to be screened under large deformation in the large amplitude sweep test, including stress σ, strain γ and strain rate

[0083] Specifically, at the same preset third frequency, different shear stresses are applied to the plurality of polymer gels to be screened, so that the shear strains of the plurality of polymer gels to be screened maintain the preset second shear strain γ 2 , and obtain the preset second shear strain γ 2 The nonlinear stress response parameters of multiple polymer gels to be screened are stress σ, strain γ and strain rate. By changing the preset second shear strain γ 2 , and obtain the preset second shear strain γ 2 In the range of 2 The value of the change.

[0084] Exemplarily, a large amplitude scanning test is performed using an MCR302e rheometer equipped with a sawtooth parallel plate geometry (with a diameter of 40 mm and a measuring gap of 1 mm). The polymer gel G-1 and G-2 samples to be screened are cut into thin slices with a thickness of about 1 mm and placed between the parallel plate rotor and the test table. A layer of low-viscosity mineral oil is applied to the edges of the polymer gel G-1 and G-2 samples to be screened to prevent the gel from evaporating. The test temperature is 25 degrees Celsius. The polymer gel G-1 and G-2 samples to be screened are obtained at the preset third frequency and the preset second shear strain γ. 2 In the range of the preset second shear strain γ 2 Varying stress σ, strain γ, and strain rate

[0085] Optionally, during the large amplitude sweep test, the third frequency is preset to be 1 Hz, and the second shear strain is preset to range from 0.1% to 1000%.

[0086] Specifically, during the large amplitude scanning test, the third frequency is preset to 1 Hz, and the second shear strain γ is preset to 2 There are multiple values ​​in the range of 0.1% to 1000%.

[0087] For example, in the large amplitude scanning test of the polymer gels G-1 and G-2 to be screened, the third frequency is preset to be 1 Hz, and the second shear strain γ is preset to be 2Twenty values ​​are selected within the range of 0.1% to 1000%, and five values ​​are selected in each of the four ranges of 0.1% to 1%, 1% to 10%, 10% to 100%, and 100% to 1000%.

[0088] S280. Evaluate and process the test data of large amplitude scanning based on the test evaluation conditions for plugging cracks, and determine the polymer jelly to be screened that meets the test evaluation conditions; the test evaluation conditions for the large amplitude scanning test for plugging cracks include: the texture of the polymer jelly to be screened is toughness determined based on the nonlinear stress response parameters, and the fracture stress determined based on the polymer jelly to be screened is greater than 100Pa.

[0089] Specifically, the different preset second shear strains γ obtained by large amplitude scanning test of the polymer gel to be screened at the preset third frequency are plotted. 2 The relationship diagram of the change of stress σ and strain γ in the corresponding nonlinear stress response parameter, that is, the elastic Lissajous curve has the strain γ as the horizontal coordinate and the stress σ as the vertical coordinate. If the elastic Lissajous curve of the polymer jelly to be screened changes from an ellipse to a "banana-shaped" curve as the preset second shear strain increases, it can be considered that the texture of the polymer jelly to be screened is tough; if the elastic Lissajous curve of the polymer jelly to be screened changes from an ellipse to a "quadrilateral" curve as the preset second shear strain increases, it can be considered that the texture of the polymer jelly to be screened is plastic. Decompose the shear stress corresponding to the preset second shear strain at the preset third frequency obtained by the large amplitude scanning test of the polymer jelly to be screened into elastic stress σ′ and viscous stress σ″, and draw the relationship diagram of the change of elastic stress σ′ and viscous stress σ″ with the preset second shear strain, that is, the maximum decomposed stress curve. Determine the maximum peak value of the elastic stress σ′ in the maximum decomposed stress curve as the rupture stress of the polymer jelly to be screened. If the texture of the polymer jelly to be screened is tough and the fracture stress is greater than 100 Pa, it is considered that the polymer jelly to be screened is not easily damaged under large deformation and meets the test evaluation conditions of the large amplitude scanning test.

[0090] Exemplarily, a polymer gel with high elastic modulus and solid-like properties is subjected to a large amplitude sweep test using RheoCompass software to obtain nonlinear stress response parameters, and to analyze Lissajous curves and maximum decomposed stress curves. Figure 7 is the elastic Lissajous curve of the polymer gel G-1 to be screened, Figure 8is the elastic Lissajous curve of the polymer jelly G-2 to be screened. The elastic Lissajous curve of the polymer jelly G-1 to be screened changes from an ellipse to a "banana-shaped" curve as the preset second shear strain increases, and it can be considered that the texture of the polymer jelly G-1 to be screened is tough; the elastic Lissajous curve of the polymer jelly G-2 to be screened changes from an ellipse to a "quadrilateral" curve as the preset second shear strain increases, and it can be considered that the texture of the polymer jelly G-2 to be screened is plastic. Fig. 9 is the maximum decomposition stress curve of the polymer gel G-1 to be screened, Fig.10 : is the maximum decomposition stress curve of the polymer gel G-2 to be screened. It can be observed that within the test range, the polymer gel G-1 to be screened does not have a peak value of elastic stress σ′, so it can be considered that the polymer gel G-1 to be screened has not been damaged, that is, the polymer gel G-1 to be screened is not easily damaged under large deformation; while the polymer gel G-2 to be screened has a peak value of elastic stress σ′ under the preset second shear strain of about 200%, and the viscous stress σ″ exceeds the elastic stress σ′, it can be considered that the polymer gel G-2 to be screened is damaged under the preset second shear strain of 200%, and its rupture stress is the peak value of elastic stress σ′, and the rupture stress of the polymer gel G-2 to be screened does not exceed 100Pa, it can be considered that the polymer gel G-2 to be screened is easily damaged under large deformation. Therefore, the polymer gel G-1 to be screened meets the test evaluation conditions of the large amplitude scanning test, and the polymer gel G-2 to be screened does not meet the test evaluation conditions of the large amplitude scanning test.

[0091] Optionally, the polymer gel to be screened is aged at a preset ambient temperature before being tested.

[0092] Specifically, the polymer gel to be screened is placed at a preset ambient temperature for a period of time for aging treatment before being tested.

[0093] Exemplarily, the polymer gel to be screened is placed at 70 degrees Celsius for 10 days for aging treatment before being subjected to frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test.

[0094] S290. Determine the polymer jelly to be screened that meets the test evaluation conditions as the polymer jelly for sealing cracks.

[0095] The technical scheme of this embodiment obtains the first elastic modulus and viscous modulus of the polymer jelly to be screened obtained by frequency scanning test, the second elastic modulus in the linear viscoelastic zone obtained by small amplitude scanning test, the rupture time obtained by creep test, and the nonlinear stress response parameter obtained by large amplitude scanning test, and evaluates and processes multiple test data based on the test evaluation conditions for plugging cracks, and determines the polymer jelly to be screened that meets the test evaluation conditions as the polymer jelly for plugging cracks. On the basis of the evaluation of the linear rheological properties of the polymer jelly, its nonlinear rheological properties are further evaluated, which solves the problem of the contradiction between the existing evaluation of the linear rheological parameters of polymer jelly and the plugging effect of the polymer jelly in cracks, avoids complicated and tedious physical simulation experiments, is simple to operate, and realizes the rapid screening of polymer jelly suitable for crack plugging in numerous polymer jelly systems, and the screened polymer jelly has good plugging performance in cracks.

[0096] Embodiment 3

[0097] Fig.11 Schematic diagram of the structure of a screening system for polymer gel for plugging cracks provided in the third embodiment of the present invention. Fig.11 As shown, the system includes:

[0098] A frequency scanning test module 1, used for performing a frequency scanning test on the polymer gel to be screened;

[0099] A small amplitude scanning test module 2, used for performing a small amplitude scanning test on the polymer gel to be screened;

[0100] Creep test module 3, used for performing creep test on the polymer gel to be screened;

[0101] A large amplitude scanning test module 4, used for performing a large amplitude scanning test on the polymer gel to be screened;

[0102] Processor 5 is used to obtain multiple test data obtained by frequency scanning test, small amplitude scanning test, creep test and large amplitude scanning test of the polymer jelly to be screened; evaluate and process the multiple test data based on the test evaluation conditions for plugging cracks, and determine the polymer jelly to be screened that meets the test evaluation conditions as the polymer jelly for plugging cracks.

[0103] Specifically, the frequency scanning test module 1 can be connected to the processor 5 by means of communication connection and / or line connection, and transmit the test data to the processor 5; the small amplitude scanning test module 2 can be connected to the processor 5 by means of communication connection and / or line connection, and transmit the test data to the processor 5; the creep test module 3 can be connected to the processor 5 by means of communication connection and / or line connection, and transmit the test data to the processor 5; the large amplitude scanning test module 4 can be connected to the processor 5 by means of communication connection and / or line connection, and transmit the test data to the processor 5.

[0104] The technical solution of this embodiment is to obtain multiple test data obtained by frequency scanning test, small amplitude scanning test, creep test and large amplitude scanning test of the polymer jelly to be screened; evaluate and process the multiple test data based on the test evaluation conditions for plugging cracks, determine the polymer jelly to be screened that meets the test evaluation conditions, and use it as the polymer jelly for plugging cracks. On the basis of the evaluation of the linear rheological properties of the polymer jelly, its nonlinear rheological properties are further evaluated, which solves the problem of the contradiction between the existing linear rheological parameter evaluation of polymer jelly and the plugging effect of the polymer jelly in cracks, avoids complicated and tedious physical simulation experiments, is simple to operate, and realizes the rapid screening of polymer jelly suitable for crack plugging in numerous polymer jelly systems, and the screened polymer jelly has good plugging performance in cracks.

[0105] On the basis of the above embodiment, optionally, the frequency scanning test module 1 is specifically used for: obtaining the first elastic modulus and viscous modulus of the polymer jelly to be screened through a frequency scanning test under a preset strain amplitude and a preset first frequency.

[0106] Based on the above embodiment, optionally, the preset strain amplitude of the frequency sweep test module 1 is 1%-5%, and the preset first frequency range is 0.1 rad·s -1 To 100rad·s -1 .

[0107] On the basis of the above embodiment, optionally, the small amplitude scanning test module 2 is specifically used for: obtaining the second elastic modulus in the linear viscoelastic region of the polymer jelly to be screened by a small amplitude scanning test under a preset second frequency and a preset first shear strain.

[0108] On the basis of the above embodiment, optionally, the preset second frequency of the small amplitude scanning test module 2 is 1 Hz, and the preset first shear strain ranges from 0.1% to 100%.

[0109] On the basis of the above embodiment, optionally, the creep test module 3 is specifically used for: obtaining the rupture time of the polymer jelly to be screened by creep testing the polymer jelly to be screened under a preset shear stress.

[0110] On the basis of the above embodiment, optionally, the preset shear stress of the creep test module 3 is increased in a fixed step size based on the initial value, and the end condition of the creep test is that the rupture time of the polymer gel to be screened under the applied shear stress is less than 10s.

[0111] On the basis of the above embodiment, optionally, the large amplitude scanning test module 4 is specifically used to obtain the nonlinear stress response parameters of the polymer gel to be screened through a large amplitude scanning test under a preset third frequency and a preset second shear strain.

[0112] On the basis of the above embodiment, optionally, the preset third frequency of the large-amplitude scanning test module 4 is 1 Hz, and the preset second shear strain ranges from 0.1% to 1000%.

[0113] Based on the above embodiment, optionally, the polymer jelly to be screened is subjected to aging treatment at a preset ambient temperature before being tested.

[0114] On the basis of the above embodiment, optionally, the test evaluation conditions of the frequency scanning test for plugging cracks of the processor 5 include: the first elastic modulus does not change with the change of the preset first frequency, and the first elastic modulus is greater than the viscous modulus.

[0115] On the basis of the above embodiment, optionally, the test evaluation conditions of the small amplitude scanning test for plugging cracks of the processor 5 include: the second elastic modulus in the linear viscoelastic zone is greater than 10Pa.

[0116] On the basis of the above embodiment, optionally, the test evaluation conditions of the creep test for plugging cracks of the processor 5 include: when the preset shear stress is 80Pa, the rupture time of the polymer jelly to be screened is greater than 10s.

[0117] On the basis of the above embodiment, optionally, the test evaluation conditions of the large-amplitude scanning test for sealing cracks of the processor 5 include: the texture of the polymer jelly to be screened is toughness determined based on the nonlinear stress response parameters, and the fracture stress determined based on the polymer jelly to be screened is greater than 100Pa.

[0118] The screening system for polymer jelly for plugging cracks provided in the embodiment of the present invention can execute the screening method for polymer jelly for plugging cracks provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

Claims

1. A method for screening polymer jelly for plugging cracks, characterized in that: include: Obtain multiple test data of the polymer gel to be screened obtained through frequency sweep test, small amplitude sweep test, creep test and large amplitude sweep test; The plurality of test data are evaluated and processed based on the test evaluation conditions for plugging cracks, and the polymer jelly to be screened that meets the test evaluation conditions is determined as the polymer jelly for plugging cracks.

2. The method according to claim 1, characterized in that The test data includes: Under the condition of a preset strain amplitude and a preset first frequency, the first elastic modulus and the viscous modulus of the polymer jelly to be screened are obtained by the frequency scanning test; Under the condition of a preset second frequency and a preset first shear strain, a second elastic modulus in the linear viscoelastic region of the polymer jelly to be screened obtained by the small amplitude scanning test; Under a preset shear stress, the rupture time of the polymer jelly to be screened obtained by the creep test; Under the condition of a preset third frequency and a preset second shear strain, the nonlinear stress response parameters of the polymer jelly to be screened are obtained by the large amplitude scanning test.

3. The method according to claim 2, characterized in that The test evaluation conditions for sealing cracks include: The first elastic modulus does not change with a change in a preset first frequency, and the first elastic modulus is greater than the viscous modulus; The second elastic modulus in the linear viscoelastic region is greater than 10 Pa; When the preset shear stress is 80 Pa, the rupture time of the polymer gel to be screened is greater than 10 s; The texture of the polymer jelly to be screened determined based on the nonlinear stress response parameter is tough, and the fracture stress determined based on the polymer jelly to be screened is greater than 100 Pa.

4. The method according to claim 1, characterized in that: When any test data of the polymer jelly to be screened is obtained, an evaluation is performed on the obtained test data based on the test evaluation conditions for plugging cracks. When the above evaluation data does not meet the test evaluation conditions for plugging cracks, the next test of the polymer jelly to be screened is stopped.

5. The method according to any one of claims 1 to 4, characterized in that The polymer gel to be screened is subjected to an aging treatment at a preset ambient temperature before being tested.

6. The method according to claim 2, characterized in that During the frequency sweep test, the preset strain amplitude is 1%-5%, and the preset first frequency range is 0.1 rad·s -1 To 100rad·s -1 .

7. The method according to claim 2, characterized in that During the small amplitude sweep test, the preset second frequency is 1 Hz, and the preset first shear strain ranges from 0.1% to 100%.

8. The method according to claim 2, characterized in that: During the creep test, the preset shear stress is increased in a fixed step size based on the initial value, and the end condition of the creep test is that the rupture time of the polymer gel to be screened under the applied shear stress is less than 10s.

9. The method according to claim 2, characterized in that: During the large amplitude sweep test, the preset third frequency is 1 Hz, and the preset second shear strain ranges from 0.1% to 1000%.

10. A screening system for polymer gel for plugging cracks, characterized in that: include, A frequency scanning test module (1), used for performing the frequency scanning test on the polymer gel to be screened; A small amplitude scanning test module (2), used for performing the small amplitude scanning test on the polymer gel to be screened; A creep test module (3), used for performing the creep test on the polymer jelly to be screened; A large amplitude scanning test module (4), used for performing the large amplitude scanning test on the polymer gel to be screened; A processor (5) is used to obtain a plurality of test data obtained by frequency scanning test, small amplitude scanning test, creep test and large amplitude scanning test of the polymer jelly to be screened; based on the test evaluation conditions for plugging cracks, the plurality of test data are evaluated and processed, and the polymer jelly to be screened that meets the test evaluation conditions is determined as the polymer jelly for plugging cracks.

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