Quantitative evaluation method for sealing performance of shale cover layer and related device

Abstract

The invention discloses a quantitative evaluation method for the sealing performance of a shale cover layer and a related device. The method comprises the following steps: acquiring the percentage of each mineral component in a rock sample of a target evaluation section of the shale cover layer, the mineral Young modulus of each mineral, the test Young modulus of the rock sample and the theoretical Young modulus, and calculating the mechanical deviation uniformity of the cover layer rock; obtaining ringing test data obtained by performing an acoustic emission test on the rock sample, and calculating an acoustic emission feedback factor; the mechanical deviation uniformity and the acoustic emission feedback factor of the cover rock are corrected; according to the cover layer rock mechanical deviation uniformity correction value and the acoustic emission feedback factor correction value, calculating a shale cover layer sealing coefficient; and quantitatively evaluating the sealing performance of the target evaluation section of the cover layer according to the sealing coefficient of the shale cover layer. Internal causes and external causes influencing the sealing performance of the shale cover layer are considered at the same time, the evaluation result is accurate and easy to realize, a large number of mine field tests are avoided, and the efficiency of evaluating the sealing performance of the shale cover layer is improved.

Description

Technical Field

[0001] The invention relates to the field of petroleum and natural gas engineering, and in particular to a quantitative evaluation method for sealing performance of shale caprocks and a related device. Background Art

[0002] China's shale oil and gas resources are extremely rich and have great development potential. They are the most strategic oil replacement resources and have become the main force in China's "14th Five-Year Plan" crude oil reserve increase. Usually, shale oil and gas reservoirs have strong vertical heterogeneity and high-angle fractures. When the reservoir is transformed, it is easy to cause hydraulic fractures to communicate with high-angle fractures in the reservoir, making the vertical fracture height of the reservoir out of control. If the sealing performance of the cap rock is poor, shale oil and gas will escape upward and cause shale oil and gas production capacity loss. Therefore, the sealing performance of the cap rock greatly affects the transformation volume range of the existing reservoir, and it is necessary to make an accurate evaluation of the sealing performance of the cap rock.

[0003] At present, researchers have done a lot of research on the evaluation of the sealing performance of caprocks, but most of them are evaluated from a single aspect such as calculating the effective thickness of the caprock or the displacement pressure. However, there are many factors that affect the sealing performance of shale caprocks, such as the mineral composition and mechanical parameters of the caprock itself, as well as the external temperature and pressure. The factors affecting the sealing performance of the caprock are complex, and it is obviously impossible to accurately and objectively evaluate the sealing ability of the caprock by relying on only one factor. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a quantitative evaluation method and related device for the sealing performance of shale caprock.

[0005] In a first aspect, an embodiment of the present invention provides a method for quantitatively evaluating the sealing performance of a shale cap rock, comprising the following steps:

[0006] Obtain the percentage of each mineral component in the rock sample of the target evaluation section of the shale cap rock;

[0007] Calculating the theoretical Young's modulus of the rock sample according to the percentage of each mineral component in the rock sample and the Young's modulus of each mineral;

[0008] Calculating the mechanical deviation of the cap rock from uniformity based on the theoretical Young's modulus and the experimental Young's modulus of the rock sample;

[0009] Acquiring ringing test data obtained by performing an acoustic emission test on the rock sample, and calculating an acoustic emission feedback factor based on the ringing test data;

[0010] Using the uniformity of mechanical deviation of the cap rock, the acoustic emission feedback factor is corrected to obtain a corrected value of the acoustic emission feedback factor; using the acoustic emission feedback factor, the uniformity of mechanical deviation of the cap rock is corrected to obtain a corrected value of mechanical deviation of the cap rock;

[0011] Calculating the shale caprock sealing coefficient according to the acoustic emission feedback factor correction value and the caprock rock mechanics deviation uniformity correction value;

[0012] According to the shale cap rock sealing coefficient, the sealing performance of the cap rock target evaluation section where the rock sample is located is evaluated.

[0013] In one embodiment, the rock sample of the target evaluation section of the shale cap rock is obtained in advance by:

[0014] The shale cap rock target evaluation section is divided into a number of units and continuous coring is carried out on the units, and the coring rocks are made into rock samples of preset sizes.

[0015] In one embodiment, the percentage of each mineral component in the rock sample is calculated in the following manner:

[0016] The rock sample is placed in an oven and dried to constant weight. The dried rock sample is tested to obtain the mass of each mineral in the rock sample, and the mass percentage of each mineral is calculated according to the following formula:

[0017]

[0018] Where: M i is the mass percentage of each mineral in the rock sample; m i is the mass of each mineral in the rock sample; n is the number of mineral types contained in the rock sample.

[0019] In one embodiment, calculating the theoretical Young's modulus of the rock sample according to the percentage of each mineral component in the rock sample and the Young's modulus of each mineral comprises:

[0020] The theoretical Young's modulus of the rock sample is calculated according to the following formula:

[0021]

[0022] Where: E l is the theoretical Young's modulus of the rock sample; E ki is the Young's modulus of each mineral.

[0023] In one embodiment, the experimental Young's modulus of the rock sample is obtained by conducting experimental tests in advance.

[0024] In one embodiment, calculating the uniformity deviation of caprock mechanics according to the theoretical Young's modulus and the experimental Young's modulus of the rock sample includes:

[0025] The mechanical deviation uniformity of the cap rock is calculated according to the following formula:

[0026]

[0027] Where: C is the mechanical deviation uniformity of the cap rock, E s is the experimental Young's modulus of the rock sample.

[0028] In one embodiment, obtaining ringing test data obtained by performing an acoustic emission test on the rock sample, and calculating the acoustic emission feedback factor according to the ringing test data, comprises:

[0029] The acoustic emission test is performed on the rock sample by using a triaxial loading control system and an acoustic emission monitoring system, and the temperature and confining pressure of the rock sample in the test are controlled according to the actual temperature and confining pressure of the target evaluation section of the shale cap rock;

[0030] During the acoustic emission test, the ringing count rate at the start and end of each preset ringing feedback cycle is recorded to obtain the ringing count rate at each ringing feedback moment;

[0031] Subtract the ring count rate at the start time from the ring count rate at the end time of the ring feedback cycle to obtain a ring feedback value; determine the ring feedback cycle corresponding to the positive ring feedback value as the positive ring feedback cycle; and determine the ring feedback cycle corresponding to the negative ring feedback value as the negative ring feedback cycle;

[0032] The acoustic emission feedback factor is calculated based on the maximum ringing feedback value within the ringing positive feedback cycle, the ringing count rate corresponding to the start and end times of the ringing positive feedback cycle where the maximum ringing feedback value is located, and the total number of the ringing positive feedback cycles and the total number of the ringing negative feedback cycles.

[0033] In one embodiment, the calculating the acoustic emission feedback factor includes:

[0034] The acoustic emission feedback factor of the rock sample is calculated according to the following formula:

[0035]

[0036] Where: G is the acoustic emission feedback factor; T is the start time of the ringing positive feedback cycle with the maximum ringing feedback value; N max is the ringing count rate corresponding to time T; T' is the end time of the positive feedback cycle of the ringing with the maximum ringing feedback value; N' max is the ringing count rate corresponding to time T'; a is a constant used to adjust the calculation result of G so that it falls within the preset reasonable range; D z is the number of positive feedback cycles of ringing; D f is the number of ringing negative feedback cycles.

[0037] In one embodiment, the acoustic emission feedback factor is corrected using the caprock mechanical deviation uniformity to obtain an acoustic emission feedback factor correction value, including:

[0038] The acoustic emission feedback factor correction value is calculated according to the following formula:

[0039] B=G·2 C-1 ;

[0040] Where: B is the correction value of the acoustic emission feedback factor.

[0041] In one embodiment, the acoustic emission feedback factor is used to correct the uniformity deviation of the cap rock mechanics to obtain a correction value of the uniformity deviation of the cap rock mechanics, including:

[0042] The correction value of the uniformity deviation of the cap rock mechanics is calculated according to the following formula:

[0043]

[0044] Where: K is the correction value of the deviation of the uniformity of the cap rock mechanics, G max is the preset maximum value of the acoustic emission feedback factor, which is a constant.

[0045] In one embodiment, the shale caprock sealing coefficient is calculated according to the acoustic emission feedback factor correction value and the caprock rock mechanics deviation uniformity correction value, including:

[0046] The sealing coefficient of the shale cap rock is calculated according to the following formula:

[0047] L = B + K;

[0048] Where: L is the sealing coefficient of shale cap rock.

[0049] In a second aspect, an embodiment of the present invention provides a quantitative evaluation device for the sealing performance of a shale caprock, comprising:

[0050] A rock mechanics deviation uniformity calculation module is used to obtain the percentage of each mineral component in the rock sample of the shale cap rock target evaluation section, calculate the theoretical Young's modulus of the rock sample according to the percentage of each mineral component in the rock sample and the mineral Young's modulus of each mineral, and calculate the rock mechanics deviation uniformity of the cap rock according to the theoretical Young's modulus and experimental Young's modulus of the rock sample;

[0051] an acoustic emission feedback factor calculation module, used to obtain ringing test data obtained by performing an acoustic emission test on the rock sample, and calculate the acoustic emission feedback factor according to the ringing test data;

[0052] A correction module, used to correct the acoustic emission feedback factor using the uniformity of mechanical deviation of the cap rock to obtain a correction value of the acoustic emission feedback factor; and to correct the uniformity of mechanical deviation of the cap rock using the acoustic emission feedback factor to obtain a correction value of mechanical deviation of the cap rock;

[0053] A shale caprock sealing coefficient determination module, used to calculate the shale caprock sealing coefficient according to the acoustic emission feedback factor correction value and the caprock rock mechanics deviation uniformity correction value;

[0054] An evaluation module evaluates the sealing performance of the target evaluation section of the cap rock where the rock sample is located according to the sealing coefficient of the shale cap rock.

[0055] In a third aspect, an embodiment of the present invention provides a computing device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the aforementioned method for determining the shale caprock sealing coefficient when executing the program.

[0056] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the aforementioned method for determining the shale caprock sealing coefficient is implemented.

[0057] The beneficial effects of the above technical solution provided by the embodiment of the present invention include at least:

[0058] The quantitative evaluation method and related device for the sealing performance of shale cap layer provided in the embodiment of the present invention comprehensively consider the mineral composition, mechanical properties and external environmental influence of the shale cap layer itself, select and use the uniformity of the cap layer rock mechanics deviation and the acoustic emission feedback factor, and determine the shale cap layer sealing coefficient that can characterize the sealing performance of the shale cap layer. Based on the shale cap layer sealing coefficient, the sealing performance of the shale cap layer can be evaluated. The larger the shale cap layer sealing coefficient, the better the shale cap layer sealing performance. The embodiment of the present invention proposes a quantitative evaluation method for the sealing performance of shale cap layer, while considering the internal and external factors that affect the sealing of the shale cap layer. The evaluation result is accurate and easy to achieve, avoiding a large number of mine tests, improving the efficiency of shale cap layer sealing performance evaluation, reducing economic costs, and having good application prospects.

[0059] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0061] Figure 1 It is a flow chart of a quantitative evaluation method of shale caprock sealing performance in an embodiment of the present invention;

[0062] Figure 2a This is a graph showing the correlation between the ringing count rate and time of the shale sample A1 in the acoustic emission test in the embodiment of the present invention;

[0063] Figure 2b 1 is a graph showing the correlation between the ringing count rate and time of the shale sample A2 in the acoustic emission test in an embodiment of the present invention.

[0064] Figure 3 It is a schematic diagram of the structure of a device for quantitatively evaluating the sealing performance of a shale cap rock in an embodiment of the present invention. DETAILED DESCRIPTION

[0065] This embodiment provides a quantitative evaluation method for the sealing performance of shale caprock. Although the accompanying drawings show exemplary embodiments of the present disclosure, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. Specifically, the following steps are included:

[0066] The embodiment of the present invention provides a quantitative evaluation method for the sealing performance of shale caprock, referring to Figure 1 As shown, the method comprises the following steps:

[0067] S11, obtaining the percentage of each mineral component in the rock sample of the target evaluation section of the shale cap rock;

[0068] S12. Calculate the theoretical Young's modulus of the rock sample according to the percentage of each mineral component in the rock sample and the Young's modulus of each mineral;

[0069] S13, calculating the mechanical deviation of the cap rock from uniformity based on the theoretical Young's modulus and the experimental Young's modulus of the rock sample;

[0070] S14, obtaining ringing test data obtained by performing an acoustic emission test on the rock sample, and calculating the acoustic emission feedback factor according to the ringing test data;

[0071] S15. Correcting the acoustic emission feedback factor using the uniformity of mechanical deviation of the cap rock to obtain a correction value of the acoustic emission feedback factor; Correcting the uniformity of mechanical deviation of the cap rock using the acoustic emission feedback factor to obtain a correction value of mechanical deviation of the cap rock;

[0072] S16. Calculate the sealing coefficient of the shale cap rock according to the correction value of the acoustic emission feedback factor and the correction value of the uniformity of the cap rock mechanics deviation;

[0073] S17. Evaluate the sealing performance of the target evaluation section of the cap rock where the rock sample is located based on the sealing coefficient of the shale cap rock.

[0074] In step S11, the rock sample of the target evaluation section of the shale cap rock can be obtained in advance, for example, by the following method:

[0075] The target evaluation section of the shale cap rock is divided into several units and continuous coring is carried out on several units, and the extracted rocks are made into rock samples of preset sizes.

[0076] For example, the removed rock is prepared into a rock sample with a diameter of 2.5 cm and a length of 5 cm, but the embodiment of the present invention is not limited to the above dimensions.

[0077] Furthermore, in step S11, the percentage of each mineral component in the rock sample can be obtained by the following method:

[0078] First, the rock sample must be dried. The rock sample can be placed in a 100°C oven to dry until it reaches constant weight. Then the dried rock sample is tested using an instrument to obtain the different mineral components in the rock sample and the mass of different mineral types. The mass percentage of each mineral mass in the total mass of the rock sample is calculated according to the following formula:

[0079]

[0080] Where: M i is the mass percentage of each mineral in the rock sample; m i is the mass of each mineral in the rock sample; n is the number of mineral types contained in the rock sample.

[0081] For example, an X-ray diffractometer is used to test and obtain the mineral components and mineral masses in the rock sample, but the embodiments of the present invention are not limited to the above method.

[0082] In step S12, the theoretical Young's modulus of the rock sample is calculated according to the percentage of each mineral component in the rock sample calculated in step S11 and the Young's modulus of each mineral. The theoretical Young's modulus of the rock sample is calculated according to the following formula:

[0083]

[0084] Where: E l is the theoretical Young's modulus of the rock sample; E ki is the Young's modulus of each mineral.

[0085] For example, the Young's modulus of each mineral in the rock sample can be obtained by referring to a rock physics handbook, but the embodiment of the present invention is not limited to the above method.

[0086] In step S13, according to the theoretical Young's modulus of the rock sample calculated in step S12 and the experimental Young's modulus of the rock sample, the mechanical deviation of the cap rock is calculated according to the following formula:

[0087]

[0088] Where: C is the mechanical deviation uniformity of the cap rock, E s is the experimental Young's modulus of the rock sample.

[0089] Further, in step S13, the experimental Young's modulus of the rock sample can be obtained through experimental testing, for example, can be obtained by testing a triaxial rock mechanics system, but the embodiment of the present invention is not limited to the above method.

[0090] The inventors of the present invention have found that the mechanical deviation of the cap rock from uniformity represents the internal heterogeneity of the cap rock. The greater the mechanical deviation of the cap rock from uniformity, the stronger the internal heterogeneity of the cap rock, that is, the worse the internal connectivity of the cap rock, making it less likely for oil and gas in the reservoir to overflow. Therefore, when the mechanical deviation of the cap rock from uniformity is greater, the sealing ability of the cap rock is better.

[0091] The influence of the deviation of the uniformity of the cap rock mechanics on the sealing ability of the cap rock is called the internal factor.

[0092] In step S14, an acoustic emission test is performed on the rock sample to obtain ringing test data obtained in the acoustic emission test. The acoustic emission feedback factor is calculated based on the test data, which can be achieved in the following manner:

[0093] The triaxial loading control system and acoustic emission monitoring system are used to conduct acoustic emission tests on rock samples. The temperature and confining pressure of the rock samples in the test are controlled according to the actual temperature and confining pressure of the target evaluation section of the shale caprock.

[0094] During the acoustic emission test, the ringing count rate at the start and end of each preset ringing feedback cycle is recorded respectively to obtain the ringing count rate at each ringing feedback moment;

[0095] The ringing count rate at the end of the ringing feedback cycle is subtracted from the ringing count rate at the start time to obtain a ringing feedback value; the ringing feedback cycle corresponding to the positive ringing feedback value is determined as the positive ringing feedback cycle; and the ringing feedback cycle corresponding to the negative ringing feedback value is determined as the negative ringing feedback cycle;

[0096] The acoustic emission feedback factor is calculated based on the maximum ringing feedback value within the ringing positive feedback cycle, the ringing count rates corresponding to the start and end times of the ringing positive feedback cycle where the maximum ringing feedback value is located, and the total number of ringing positive feedback cycles and the total number of ringing negative feedback cycles.

[0097] For example: in an acoustic emission test, the test process starts from 0, and the starting ringing feedback time of the ringing count rate is recorded. It is preset from 90s by experience, and the duration of the ringing feedback cycle is preset from experience to 200s. Then, as the test progresses, the ringing feedback times are 290s, 490s, 690s...

[0098] The starting ringing feedback time starts from 90s because in the period of time after the acoustic emission test starts, in order to avoid calculation errors caused by excessive fluctuations in the ringing count rate value, which affects the accuracy of the final cover layer sealing performance evaluation, the test data within 0 to 90s are discarded. However, the embodiment of the present invention does not limit the value of the starting ringing time.

[0099] Similarly, the duration of the ringing feedback cycle is empirically determined based on changes in test data, and the embodiment of the present invention does not limit the duration of the ringing feedback cycle.

[0100] Furthermore, the test data obtained by the above method can be used to calculate the acoustic emission feedback factor according to the following formula:

[0101]

[0102] Where: G is the acoustic emission feedback factor; T is the start time of the ringing positive feedback cycle with the maximum ringing feedback value; N max is the ringing count rate corresponding to time T; T' is the end time of the positive feedback cycle of the ringing with the maximum ringing feedback value; N' max is the ringing count rate corresponding to time T'; a is a constant used to adjust the calculation result of G so that it falls within the preset reasonable range; D z is the number of positive feedback cycles of ringing; D f is the number of ringing negative feedback cycles.

[0103] The inventors of the present invention have discovered that the external environmental factors that affect the sealing performance of the cap rock can be expressed by two parameters: the temperature of the cap rock and the confining pressure it is subjected to. For the same rock at different temperatures and confining pressures, the ringing feedback value changes continuously as the acoustic emission test proceeds. The difference in the ringing feedback value is closely related to the porosity and permeability of the rock, both of which can be reflected in the different connectivity between the cracks inside the rock. Therefore, the ringing test data of the cap rock at different temperatures and confining pressures can well express the connectivity of the rock. When the overall connectivity of the rock is poor, the stronger the cap rock's inhibition of the internal fluid flow, the less likely it is for oil and gas to overflow, and the better the sealing ability of the surface cap rock. Therefore, the acoustic emission test data of rocks at different temperatures and confining pressures can quantitatively express the sealing ability of the shale cap rock.

[0104] In the embodiment of the present invention, the influence of the acoustic emission feedback factor on the sealing ability of the cover layer is referred to as an external factor.

[0105] Here, the process of calculating the mechanical deviation uniformity of the cap rock in steps S11-S13 and the process of calculating the acoustic emission feedback factor in step S14 are two independent calculation steps, and the embodiment of the present invention does not limit the order in which the two are executed.

[0106] In step S15, since the mechanical deviation uniformity of the caprock and the acoustic emission feedback factor affect each other and present different influence trends, it is necessary to correct these two influencing factors.

[0107] The acoustic emission feedback factor is corrected using the mechanical deviation uniformity of the cap rock, and the corrected value of the acoustic emission feedback factor is calculated by the following formula:

[0108] B=G·2 C-1 ;

[0109] Where: B is the correction value of the acoustic emission feedback factor.

[0110] Furthermore, the acoustic emission feedback factor is used to correct the uniformity deviation of the cap rock mechanics, and the correction value of the uniformity deviation of the cap rock mechanics is calculated by the following formula:

[0111]

[0112] Where: K is the correction value of the deviation of the uniformity of the cap rock mechanics, G max is the preset maximum value of the acoustic emission feedback factor, which is a constant.

[0113] In step S15, there is no limitation on the order of calculating the correction value of the acoustic emission feedback factor and the correction value of the uniformity of the cap rock mechanics deviation.

[0114] When calculating the correction value of the uniformity deviation of the cap rock mechanics, G in the formula max In specific implementation, empirical values ​​can be used.

[0115] In step S16, after obtaining the correction value of the uniformity of the cap rock mechanics deviation and the correction value of the acoustic emission feedback factor according to step S15, the two are summed to obtain the shale cap rock sealing coefficient:

[0116] L = B + K;

[0117] Where: L is the sealing coefficient of shale cap rock.

[0118] In step S17, by comparing the numerical values ​​of the shale caprock sealing coefficients of different rock samples, the sealing performance of the target evaluation sections of the shale caprocks where the different rock samples are located can be quantitatively compared.

[0119] The present invention proposes a quantitative evaluation method for the sealing performance of shale caprock, which divides the factors affecting the sealing capacity of shale caprock into internal factors and external factors. According to the mineral composition and mechanical properties of the caprock itself, the mechanical deviation uniformity of the caprock is calculated to express the heterogeneity of the rock, and the influence of the internal factors on the sealing capacity of the caprock is obtained. Through the acoustic emission test, the destruction process of the caprock under different temperatures and confining pressures is tracked, the acoustic emission feedback factor is calculated, and the influence of the external factors on the sealing capacity of the shale caprock is obtained. The internal and external factors are corrected respectively, and the sealing coefficient of the shale caprock is defined by comprehensively considering the internal and external factors, so as to quantitatively evaluate the sealing performance of the shale caprock.

[0120] A specific example is used to illustrate the quantitative evaluation method of the sealing performance of the shale cap rock.

[0121] The first step is rock sample preparation: the shale caprock target evaluation section is divided into several units, and continuous coring is carried out for each evaluation unit. The rock coring depth is 2500-2540m, and two rock samples with a diameter of 2.5cm and a length of 5cm are prepared from the extracted rocks, which are numbered A1 and A2.

[0122] The second step is the analysis of the mineral composition of the rock samples: the two prepared rock samples are placed in a 100°C oven and dried to constant weight. The dried rock samples are tested using an X-ray diffractometer to obtain the mineral types and mineral contents in rock samples A1 and A2. The mineral types include dolomite, quartz, calcite, feldspar, pyrite and clay. The percentage of each mineral component in the standard rock sample can be obtained according to the following formula:

[0123]

[0124] Where: M i is the calculated percentage of each mineral component, %; m i is the weight of each mineral in the rock sample, g; n is the number of mineral types contained in the rock sample, dimensionless.

[0125] The percentage of each mineral in the obtained rock samples A1 and A2 is listed in the following Table 1.

[0126] Table 1

[0127]

[0128] The third step is to calculate the theoretical Young's modulus of the rock sample: According to the percentage of each mineral component in the rock sample obtained in the second step, and the mineral Young's modulus of each mineral in the rock sample obtained by consulting the rock physics handbook, the theoretical Young's modulus of the rock sample is calculated using the following formula:

[0129]

[0130] Where: E l is the theoretical Young's modulus of the rock sample; E ki is the Young's modulus of each mineral.

[0131] The fourth step is to calculate the mechanical deviation uniformity of the cap rock: Based on the theoretical Young's modulus of the rock sample obtained in the second step and the experimental Young's modulus of the rock sample obtained through the triaxial rock mechanics system test, the mechanical deviation uniformity of the cap rock is calculated by the following formula:

[0132]

[0133] Where: C is the mechanical deviation uniformity of the cap rock, E s is the experimental Young's modulus of the rock sample.

[0134] Through the third and fourth steps, the Young's modulus of each mineral in rock samples A1 and A2 can be obtained, as shown in Table 2 below, and the theoretical Young's modulus, experimental Young's modulus and mechanical deviation uniformity of the cap rock of rock samples A1 and A2 can be obtained, as shown in Table 3 below.

[0135] Table 2

[0136]

[0137]

[0138] Table 3

[0139]

[0140] The fifth step is acoustic emission test: an acoustic emission test is conducted on the rock samples. A triaxial loading control system and an acoustic emission monitoring system are used to control the temperature and confining pressure of the rock samples in the test according to the actual temperature and confining pressure of the target evaluation section of the shale cap rock.

[0141] During the acoustic emission test, the ringing count rate at the start and end of each preset ringing feedback cycle is recorded respectively to obtain the ringing count rate at each ringing feedback moment;

[0142] The ringing count rate at the end of the ringing feedback cycle is subtracted from the ringing count rate at the start time to obtain the ringing feedback value; the ringing feedback cycle corresponding to the positive ringing feedback value is determined as the positive ringing feedback cycle; and the ringing feedback cycle corresponding to the negative ringing feedback value is determined as the negative ringing feedback cycle.

[0143] In the fifth step, the ringing feedback time starts from 90s. This is because the data between 0 and 90s fluctuates greatly and cannot reflect the real results. Therefore, the test data between 0 and 90s are discarded according to the law of data change. Preferably, the acoustic emission test ringing feedback cycle is divided into sections with a time change of every 200s. The selection of the ringing feedback cycle is obtained based on the empirical value of the data change during the test.

[0144] The correlation diagram between the ringing count rate and time of the acoustic emission test of rock samples A1 and A2 is shown in the figure Figure 2a and Figure 2b In Figure 2, the horizontal axis represents the time process of the acoustic emission test, and the coordinate axis represents the ringing count rate recorded at different ringing feedback moments.

[0145] Step 6: Calculate the acoustic emission feedback factor: Based on the maximum ringing feedback value obtained within the positive feedback cycle, the ringing count rate corresponding to the start and end times of the positive feedback cycle where the maximum ringing feedback value is located, and the total number of positive feedback cycles and the total number of negative feedback cycles, the acoustic emission feedback factor can be calculated according to the following formula:

[0146]

[0147] Where: G is the acoustic emission feedback factor; T is the start time of the ringing positive feedback cycle with the maximum ringing feedback value; N max is the ringing count rate corresponding to time T; T' is the end time of the positive feedback cycle of the ringing with the maximum ringing feedback value; N' max is the ringing count rate corresponding to time T'; a is a constant used to adjust the calculation result of G so that it falls within the preset reasonable range; D z is the number of positive feedback cycles of ringing; D f is the number of ringing negative feedback cycles.

[0148] In order to make the calculation result of the acoustic emission feedback factor within a reasonable range, the constant a in the acoustic emission feedback factor formula is taken as 100.

[0149] The acoustic emission feedback factors of rock samples A1 and A2 were calculated by the above method, as shown in Table 4 below.

[0150] Table 4

[0151]

[0152]

[0153] It can be seen from Table 4 above that for the A1 rock sample, the ringing positive feedback period with the maximum ringing feedback value is 3290-3490s, and for the A2 rock sample, the ringing positive feedback period with the maximum ringing feedback value is 3090-3290s.

[0154] Here, whether to calculate the mechanical deviation of the cap rock from uniformity or the acoustic emission feedback factor first has no effect on the final evaluation of the sealing performance of the cap rock. Therefore, the order of implementation of the process from the first step to the fourth step and the process from the fifth step to the sixth step can be selected according to actual conditions.

[0155] Step 7: Correction of the uniformity of the mechanical deviation of the cap rock and the acoustic emission feedback factor: Since the uniformity of the mechanical deviation of the cap rock and the acoustic emission feedback factor influence each other and show different influence trends, it is necessary to correct these two influencing factors.

[0156] The acoustic emission feedback factor is corrected by using the mechanical deviation uniformity of the cap rock to obtain the corrected value of the acoustic emission feedback factor. The corrected value of the acoustic emission feedback factor can be calculated according to the following formula:

[0157] B=G·2 C-1 ;

[0158] Where: B is the correction value of the acoustic emission feedback factor.

[0159] The acoustic emission feedback factor is used to correct the uniformity deviation of the cap rock mechanics to obtain the uniformity deviation correction value of the cap rock mechanics. The uniformity deviation correction value of the cap rock mechanics can be calculated according to the following formula:

[0160]

[0161] Where: K is the correction value of the deviation of the uniformity of the cap rock mechanics, G max is the preset maximum value of the acoustic emission feedback factor, which is a constant.

[0162] In the seventh step, the order of correcting the acoustic emission feedback factor and correcting the uniformity of the mechanical deviation of the cap rock can be arbitrarily selected.

[0163] According to experience, the default G max Take it as 4.50.

[0164] The corrected values ​​of acoustic emission feedback factors and uniformity deviation of caprock mechanics of rock samples A1 and A2 are shown in Table 5 below.

[0165] Table 5

[0166]

[0167] Step 8: Calculate the closure coefficient of the shale cap rock: According to the correction value of the acoustic emission feedback factor and the correction value of the uniformity of the cap rock mechanics deviation, the closure coefficient of the shale cap rock is calculated according to the following formula:

[0168] L=B+K

[0169] Where: L is the sealing coefficient of shale cap rock, dimensionless.

[0170] Through calculation, the shale caprock sealing coefficients of rock samples A1 and A2 are L A1 =1.44,L A2 =2.72, obviously, L A1 <L A2 , indicating that the sealing performance of the cap rock in the A2 rock sample area is better than that in the A1 rock sample area.

[0171] Based on the same inventive concept, an embodiment of the present invention also provides a quantitative evaluation device for the sealing performance of shale cap layers. Since the principle of the problem solved by the device is similar to the aforementioned quantitative evaluation method for the sealing performance of shale cap layers, the implementation of the device can refer to the implementation of the aforementioned method, and the repeated parts will not be repeated.

[0172] The embodiment of the present invention provides a quantitative evaluation device for the sealing performance of shale caprock, referring to Figure 3 As shown, including:

[0173] The rock mechanics deviation uniformity calculation module 31 is used to obtain the percentage of each mineral component in the rock sample of the target evaluation section of the shale cap rock, calculate the theoretical Young's modulus of the rock sample according to the percentage of each mineral component in the rock sample and the mineral Young's modulus of each mineral, and calculate the rock mechanics deviation uniformity of the cap rock according to the theoretical Young's modulus and the experimental Young's modulus of the rock sample;

[0174] The acoustic emission feedback factor calculation module 32 is used to obtain the ringing test data obtained by performing an acoustic emission test on the rock sample, and calculate the acoustic emission feedback factor according to the ringing test data;

[0175] The correction module 33 is used to correct the acoustic emission feedback factor using the mechanical deviation uniformity of the cap rock to obtain a correction value of the acoustic emission feedback factor; and to correct the mechanical deviation uniformity of the cap rock using the acoustic emission feedback factor to obtain a correction value of the mechanical deviation uniformity of the cap rock;

[0176] A shale caprock sealing coefficient determination module 34 is used to calculate the shale caprock sealing coefficient according to the acoustic emission feedback factor correction value and the caprock rock mechanics deviation uniformity correction value;

[0177] The evaluation module 35 evaluates the sealing performance of the target evaluation section of the cap rock where the rock sample is located according to the sealing coefficient of the shale cap rock.

[0178] An embodiment of the present invention provides a computing device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the method for determining the sealing coefficient of the shale cap layer as described above is implemented.

[0179] An embodiment of the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, the method for determining the sealing coefficient of a shale cap layer as described above is implemented.

[0180] Obviously, those skilled in the art can make various changes to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these changes.

Claims

1. A quantitative evaluation method for the sealing performance of shale caprock, characterized in that: include: Obtain the percentage of each mineral component in the rock sample of the target evaluation section of the shale cap rock; Calculating the theoretical Young's modulus of the rock sample according to the percentage of each mineral component in the rock sample and the Young's modulus of each mineral; Calculating the mechanical deviation of the cap rock from uniformity based on the theoretical Young's modulus and the experimental Young's modulus of the rock sample; Acquiring ringing test data obtained by performing an acoustic emission test on the rock sample, and calculating an acoustic emission feedback factor based on the ringing test data; Using the mechanical deviation uniformity of the cap rock, the acoustic emission feedback factor is corrected to obtain a corrected value of the acoustic emission feedback factor; Using the acoustic emission feedback factor, the mechanical deviation uniformity of the cap rock is corrected to obtain a correction value of the mechanical deviation uniformity of the cap rock; Calculating the shale caprock sealing coefficient according to the acoustic emission feedback factor correction value and the caprock rock mechanics deviation uniformity correction value; According to the shale cap rock sealing coefficient, the sealing performance of the cap rock target evaluation section where the rock sample is located is evaluated.

2. The method according to claim 1, characterized in that The rock sample of the target evaluation section of the shale cap rock is obtained in advance by the following method: The shale cap rock target evaluation section is divided into a number of units and continuous coring is carried out on the units, and the coring rocks are made into rock samples of preset sizes.

3. The method according to claim 1, characterized in that The percentage of each mineral component in the rock sample is calculated in the following way: The rock sample is placed in an oven and dried to constant weight. The dried rock sample is tested to obtain the mass of each mineral in the rock sample, and the mass percentage of each mineral is calculated according to the following formula: Where: M i is the mass percentage of each mineral in the rock sample; m i is the mass of each mineral in the rock sample; n is the number of mineral types contained in the rock sample.

4. The method according to claim 1, characterized in that Calculating the theoretical Young's modulus of the rock sample according to the percentage of each mineral component in the rock sample and the Young's modulus of each mineral, including: The theoretical Young's modulus of the rock sample is calculated according to the following formula: Where: E l is the theoretical Young's modulus of the rock sample; E ki is the Young's modulus of each mineral.

5. The method according to claim 1, characterized in that The experimental Young's modulus of the rock sample is obtained by conducting experimental tests in advance.

6. The method according to claim 1, characterized in that According to the theoretical Young's modulus and the experimental Young's modulus of the rock sample, the mechanical deviation of the cap rock is calculated, including: The mechanical deviation uniformity of the cap rock is calculated according to the following formula: Where: C is the uniformity of the mechanical deviation of the cap rock, E s is the experimental Young's modulus of the rock sample.

7. The method according to claim 1, characterized in that Acquiring ringing test data obtained by performing an acoustic emission test on the rock sample, and calculating an acoustic emission feedback factor according to the ringing test data, including: The acoustic emission test is performed on the rock sample by using a triaxial loading control system and an acoustic emission monitoring system, and the temperature and confining pressure of the rock sample in the test are controlled according to the actual temperature and confining pressure of the target evaluation section of the shale cap rock; During the acoustic emission test, the ringing count rate at the start and end of each preset ringing feedback cycle is recorded to obtain the ringing count rate at each ringing feedback moment; Subtract the ring count rate at the start time from the ring count rate at the end time of the ring feedback cycle to obtain a ring feedback value; determine the ring feedback cycle corresponding to the positive ring feedback value as the positive ring feedback cycle; and determine the ring feedback cycle corresponding to the negative ring feedback value as the negative ring feedback cycle; The acoustic emission feedback factor is calculated based on the maximum ringing feedback value within the ringing positive feedback cycle, the ringing count rate corresponding to the start and end times of the ringing positive feedback cycle where the maximum ringing feedback value is located, and the total number of the ringing positive feedback cycles and the total number of the ringing negative feedback cycles.

8. The method according to claim 7, characterized in that The calculating the acoustic emission feedback factor comprises: The acoustic emission feedback factor of the rock sample is calculated according to the following formula: Where: G is the acoustic emission feedback factor; T is the start time of the ringing positive feedback cycle with the maximum ringing feedback value; N max is the ringing count rate corresponding to time T; T' is the end time of the positive feedback cycle of the ringing with the maximum ringing feedback value; N' max is the ringing count rate corresponding to time T'; a is a constant used to adjust the calculation result of G so that it falls within the preset reasonable range; D z is the number of positive feedback cycles of ringing; D f is the number of ringing negative feedback cycles.

9. The method according to any one of claims 1 to 8, characterized in that: The acoustic emission feedback factor is corrected using the mechanical deviation uniformity of the cap rock to obtain a corrected value of the acoustic emission feedback factor, including: The acoustic emission feedback factor correction value is calculated according to the following formula: B=G·2 C-1 ; Where: B is the correction value of the acoustic emission feedback factor.

10. The method according to any one of claims 1 to 8, characterized in that The acoustic emission feedback factor is used to correct the uniformity deviation of the cap rock mechanics to obtain a correction value of the uniformity deviation of the cap rock mechanics, including: The correction value of the uniformity deviation of the cap rock mechanics is calculated according to the following formula: Where: K is the correction value of the deviation of the uniformity of the cap rock mechanics, G max is the preset maximum value of the acoustic emission feedback factor, which is a constant.

11. The method according to any one of claims 1 to 8, characterized in that: The shale caprock sealing coefficient is calculated according to the acoustic emission feedback factor correction value and the caprock rock mechanics deviation uniformity correction value, including: The sealing coefficient of the shale cap rock is calculated according to the following formula: L = B + K; Where: L is the sealing coefficient of shale cap rock.

12. A quantitative evaluation device for the sealing performance of shale caprock, characterized in that: include: A rock mechanics deviation uniformity calculation module is used to obtain the percentage of each mineral component in the rock sample of the shale cap rock target evaluation section, calculate the theoretical Young's modulus of the rock sample according to the percentage of each mineral component in the rock sample and the mineral Young's modulus of each mineral, and calculate the rock mechanics deviation uniformity of the cap rock according to the theoretical Young's modulus and experimental Young's modulus of the rock sample; an acoustic emission feedback factor calculation module, used to obtain ringing test data obtained by performing an acoustic emission test on the rock sample, and calculate the acoustic emission feedback factor according to the ringing test data; A correction module, used to correct the acoustic emission feedback factor using the mechanical deviation uniformity of the cap rock to obtain a correction value of the acoustic emission feedback factor; Using the acoustic emission feedback factor, the mechanical deviation uniformity of the cap rock is corrected to obtain a correction value of the mechanical deviation uniformity of the cap rock; A shale caprock sealing coefficient determination module, used to calculate the shale caprock sealing coefficient according to the acoustic emission feedback factor correction value and the caprock rock mechanics deviation uniformity correction value; An evaluation module evaluates the sealing performance of the target evaluation section of the cap rock where the rock sample is located according to the sealing coefficient of the shale cap rock.

13. A computing device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for determining the shale caprock sealing coefficient as described in any one of claims 1 to 11 is implemented.

14. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for determining the shale caprock sealing coefficient according to any one of claims 1 to 11 is implemented.

Images