Pressure-bearing boundary determination method and device for gas storage cover layer and medium

Abstract

The invention provides a pressure-bearing boundary determination method and device for a gas storage overburden, and a medium, and relates to the technical field of petroleum and natural gas development, and the method comprises the following steps: preparing an overburden sample corresponding to a target gas storage; simulating to obtain a target relation curve chart based on a plurality of influence factors by aiming at the cover layer sample; and determining the pressure-bearing limit of the cover layer sample according to the target relation curve chart. Therefore, on one hand, the pressure-bearing limit, namely the upper limit operation pressure of the gas storage, of the cap layer sample can be quantitatively and accurately determined so as to improve the safety of the gas storage, and on the other hand, the influence of a plurality of influence factors of the gas storage cap layer on the cap layer sample can be accurately and intuitively evaluated so as to fill the blank of comprehensive evaluation of the cap layer under multiple factors; the method provides a new analysis means and technical method for gas storage operation pressure optimization, oil and gas reservoir type storage site selection evaluation, storage construction scheme design, improvement of peak regulation gas quantity, oil and gas, new energy, environmental safety evaluation in the carbon burying field and the like.

Description

Technical Field

[0001] This invention relates to the field of oil and gas development technology, and more specifically, to a method, apparatus, and medium for determining the pressure limit of a gas storage tank cover. Background Technology

[0002] The pressure bearing capacity of the caprock is an important foundation for the construction of gas storage facilities. The construction conditions for gas storage facilities are harsh. At the same time, gas storage facilities are characterized by high-flow-rate, high-intensity, and long-term service, thus requiring the caprock of the gas storage facility to have good sealing performance.

[0003] Currently, the pressure bearing capacity of the caprock mainly provides experimental or evaluation methods for single influencing factors. Since there are few influencing factors, it is not possible to directly obtain an evaluation index for the ultimate pressure bearing capacity of the gas storage caprock that takes into account multiple factors.

[0004] To address the problems of existing technologies, this invention provides a method, apparatus, and medium for determining the pressure limit of a gas storage tank cover. Summary of the Invention

[0005] To address the problems of existing technologies, this invention provides a method, apparatus, and medium for determining the pressure limit of a gas storage tank cover layer. The method includes:

[0006] Prepare caprock samples corresponding to the target gas storage facility;

[0007] For the capping sample, a target relationship curve was simulated based on several influencing factors.

[0008] Based on the target relationship curve chart, the pressure bearing limit of the capping sample is determined.

[0009] According to one embodiment of the present invention, the plurality of influencing factors include: capillary dynamic sealing capability, and the target relationship curve chart includes a first target relationship curve;

[0010] The first target relationship curve is obtained through the following steps:

[0011] The experiment simulating the caprock sample under in-situ effective stress was conducted to obtain a first target relationship curve of the ratio of the first real-time breakthrough pressure to the initial breakthrough pressure as a function of the ratio of the real-time formation pressure to the initial formation pressure; wherein, the first real-time breakthrough pressure is used to characterize the capillary dynamic sealing capability of the caprock sample.

[0012] According to one embodiment of the present invention, the plurality of influencing factors further includes: fatigue effect, and the target relationship curve further includes a plurality of second target relationship curves;

[0013] The second target relationship curve is obtained through the following steps:

[0014] For the caprock sample, multi-cycle injection and production were performed based on the fatigue effect, and a second target relationship curve was obtained by simulating the ratio of the second real-time breakthrough pressure to the initial breakthrough pressure as a function of the ratio of the real-time formation pressure to the initial formation pressure.

[0015] According to one embodiment of the present invention, the plurality of influencing factors further includes: mechanical integrity; the target relationship curve chart includes a first threshold;

[0016] The first threshold is obtained through the following steps:

[0017] The first threshold for characterizing mechanical integrity failure was obtained through rock mechanics strength experiments, geostress tests, and numerical simulation.

[0018] According to one embodiment of the present invention, the pressure limit is obtained through the following steps:

[0019] Based on the target relationship curve chart, a second threshold is determined to characterize the failure of the capillary dynamic sealing capability;

[0020] The smaller of the first threshold and the second threshold is determined as the pressure limit.

[0021] According to an embodiment of the present invention, the second threshold is determined by the following steps:

[0022] A third target relationship curve is determined as a function of the real-time formation pressure difference between the caprock and the reservoir below the caprock and the ratio of the real-time formation pressure to the initial formation pressure.

[0023] Determine the first intersection point of the first target relationship curve and the third target relationship curve, and the second intersection point of the second target relationship curve and the third target relationship curve;

[0024] The smaller value of the x-coordinate between the first intersection point and the second intersection point is determined as the second threshold.

[0025] According to one embodiment of the present invention, the target gas storage facility includes a first gas storage facility and a second gas storage facility;

[0026] The method further includes:

[0027] The first set in the first target relationship curve chart corresponding to the first gas storage facility and the second set in the second target relationship curve chart corresponding to the second gas storage facility are determined respectively, wherein the first set and the second set both include a first threshold, a second threshold and a pressure limit;

[0028] Plot the first target relationship curve chart and the second target relationship curve chart on a single graph, and compare the size relationship between the first set and the second set.

[0029] According to another aspect of the invention, a device for determining the pressure limit of a gas storage tank cover is also provided, performing the method as described in any of the preceding claims, the device comprising:

[0030] The preparation module is used to prepare the caprock sample corresponding to the target gas storage facility;

[0031] The simulation module is used to simulate and obtain a target relationship curve chart for the capping sample based on several influencing factors.

[0032] The determination module is used to determine the pressure limit of the capping sample based on the target relationship curve chart.

[0033] According to one embodiment of the present invention, the plurality of influencing factors include: capillary dynamic sealing capability, and the target relationship curve chart includes a first target relationship curve;

[0034] The simulation module is also used to simulate the experiment of the caprock sample under in-situ effective stress, and obtain a first target relationship curve of the ratio of the first real-time breakthrough pressure to the initial breakthrough pressure as a function of the ratio of the real-time formation pressure to the initial formation pressure; wherein, the first real-time breakthrough pressure is used to characterize the capillary dynamic sealing capability of the caprock sample.

[0035] This invention provides a method, apparatus, and medium for determining the pressure limit of a gas storage tank cover layer, which has the following advantages compared with the prior art:

[0036] This invention evaluates caprock samples based on several influencing factors to obtain a target relationship curve, which is then used to determine the pressure limit of the caprock samples. This allows for the quantitative and accurate determination of the pressure limit of the caprock samples, i.e., the upper limit operating pressure of the gas storage facility, thus improving the safety of the gas storage facility. Furthermore, it enables an accurate and intuitive assessment of the impact of several influencing factors on the caprock samples, filling the gap in comprehensive evaluation of caprocks under multiple factors. This provides new analytical tools and technical methods for optimizing gas storage operating pressure, evaluating oil and gas reservoir site selection, designing storage construction schemes, increasing peak-shaving gas volume, and environmental safety assessments in the fields of oil and gas, new energy, and carbon sequestration.

[0037] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0038] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0039] Figure 1 A flowchart of a method for determining the pressure limit of a gas storage tank cover layer according to an embodiment of the present invention is shown;

[0040] Figure 2 A schematic diagram of a target relationship curve chart according to an embodiment of the present invention is shown;

[0041] Figure 3 A schematic diagram of a target relationship curve diagram according to yet another embodiment of the present invention is shown;

[0042] Figure 4 A block diagram of a pressure limit determination device for a gas storage tank cover layer according to an embodiment of the present invention is shown.

[0043] Figure 5 A schematic diagram of a target relationship curve diagram according to yet another embodiment of the present invention is shown;

[0044] Figure 6 A schematic diagram of a target relationship curve diagram according to yet another embodiment of the present invention is shown.

[0045] In the accompanying drawings, the same parts use the same reference numerals. Also, the drawings are not drawn to scale. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0047] In the field of oil and gas exploration and development, caprock sealing performance evaluation primarily focuses on static sealing. Static sealing performance is mainly assessed through geological evaluation and static experimental studies. This is because the geological environment is relatively stable during the oil and gas accumulation process and the development of conventional oil and gas reservoirs, and caprock sealing performance changes very slowly during this process, especially considering it to be constant in past oil and gas development and utilization. Therefore, current mainstream caprock assessment techniques are mostly conducted under the assumption of constant caprock sealing performance. The analytical content includes evaluating the caprock's lithology, minerals, thickness, stratigraphic distribution characteristics, rock permeability and porosity, as well as the static breakthrough pressure and displacement pressure of the caprock rocks.

[0048] In the field of gas storage (including natural gas peak-shaving storage and carbon dioxide buried storage), the initial assessment methods all followed the previous static sealing evaluation system, mostly using the static geological research results obtained during the oil and gas exploration and development stage as a reference for the design of storage construction and operation plans. However, through continuous exploration and extensive practice, it has been found that, taking peak-shaving oil and gas reservoirs as an example, the multi-cycle strong injection and production during the operation of gas storage facilities leads to changes in the sealing performance of the caprock in a short period of time (i.e., dynamic sealing performance). This change in objective geological conditions directly affects the determination of the pressure limit of the gas storage caprock and the scientific design of subsequent operation plans.

[0049] In recent years, the assessment of the sealing capacity of gas storage caprocks considering dynamic changes has gradually attracted the attention of scholars both domestically and internationally. Currently published technologies and concepts mainly provide experimental or evaluation methods for single influencing factors of caprock dynamic sealing performance, but none support the comprehensive analysis of the dynamic pressure-bearing capacity of the caprock under multiple factors, nor do they directly integrate operational indicators such as the upper and lower operating pressure limits of the gas storage facility. Especially when oil companies increase gas storage capacity and working gas volume by raising the upper operating pressure, the assessment of the multi-factor dynamic sealing limits of the caprock in the scheme design still lacks an intuitive, simple, and reliable evaluation method.

[0050] The existing technology (CN114464324A) mentions a method, apparatus, storage medium, and equipment for determining dynamic capillary force, including: obtaining pore throat distribution, pore throat radius, and capillary force data of low-permeability cores through experimental testing, and determining the dynamic capillary force based on displacement pressure and equilibrium pressure. This invention establishes a method for describing the dynamic capillary force effect on a macroscopic scale, which can reflect the dynamic change characteristics of capillary force during high-speed injection and production, providing corresponding technical support for single-well injection and production capacity analysis, dynamic storage capacity evaluation of oil and gas reservoirs, and understanding the distribution law of gas-water / oil-water. The steps differ from those of this invention.

[0051] Existing technology (CN113790853A) mentions a comprehensive testing platform for the dynamic sealing performance of caprock in a gas storage facility. This platform comprises a triaxial alternating mechanical control system, a temperature loading system, a gas pressurization system, a core saturation loading system, a seepage outlet monitoring system, an acoustic detection system, and a data acquisition and display system, all connected via high-pressure pipelines, valves, and an electrical system. This platform features temperature and confining pressure loading systems, as well as vacuum and saturation systems, enabling simulation of temperature, confining pressure, and formation water conditions under formation conditions, and facilitating experimental testing of caprock sealing performance. This differs from the steps described in this invention.

[0052] To address the aforementioned deficiencies in the prior art, this invention provides a method, apparatus, and medium for determining the pressure limit of a gas storage tank cover layer. Figure 1A flowchart of a method for determining the pressure limit of a gas storage tank cover layer according to an embodiment of the present invention is shown, the method comprising:

[0053] S101, Prepare the caprock sample corresponding to the target gas storage facility;

[0054] S102, for the caprock sample, based on several influencing factors, the target relationship curve was simulated and obtained;

[0055] S103. Determine the pressure limit of the cap layer sample based on the target relationship curve chart.

[0056] Among them, several influencing factors used to evaluate the dynamic sealing performance of capillary samples can include capillary dynamic sealing capacity, mechanical integrity, and fatigue effect. Capillary dynamic sealing capacity is mainly measured by direct measurement method; mechanical integrity is mainly analyzed by rock mechanical strength test, geostress test and numerical simulation method of natural samples in gas storage; fatigue effect is mainly analyzed by alternating stress method and multi-cycle injection and production.

[0057] This invention evaluates caprock samples based on several influencing factors to obtain a target relationship curve, which is then used to determine the pressure limit of the caprock samples. This allows for the quantitative and accurate determination of the pressure limit of the caprock samples, i.e., the upper limit operating pressure of the gas storage facility, thus improving the safety of the gas storage facility. Furthermore, it enables an accurate and intuitive assessment of the impact of several influencing factors on the caprock samples, filling the gap in comprehensive evaluation of caprocks under multiple factors. This provides new analytical tools and technical methods for optimizing gas storage operating pressure, evaluating oil and gas reservoir site selection, designing storage construction schemes, increasing peak-shaving gas volume, and environmental safety assessments in the fields of oil and gas, new energy, and carbon sequestration.

[0058] In one possible embodiment, several influencing factors include: capillary dynamic sealing capability, and the target relationship curve chart includes a first target relationship curve;

[0059] The first target relationship curve is obtained through the following steps:

[0060] Experiments simulating caprock samples under in-situ effective stress were conducted to obtain a first target relationship curve between the ratio of the first real-time breakthrough pressure to the initial breakthrough pressure and the ratio of the real-time formation pressure to the initial formation pressure.

[0061] The first real-time breakthrough pressure can be used to characterize the capillary dynamic sealing capability of the capillary sample.

[0062] like Figure 2As shown, the first real-time breakthrough pressure of the caprock sample decreases as the real-time formation pressure increases. It should be noted that the first real-time breakthrough pressure of some gas storage caprock samples may increase with rising real-time formation pressure, depending on the actual geological conditions and the gas storage facility's operating conditions.

[0063] In one possible embodiment, several influencing factors further include: fatigue effect, and the target relationship curve further includes several second target relationship curves;

[0064] The second target relationship curve is obtained through the following steps:

[0065] For caprock samples, multi-cycle injection and production were performed based on fatigue effects, and the second target relationship curve of the ratio of the second real-time breakthrough pressure to the initial breakthrough pressure as a function of the ratio of the real-time formation pressure to the initial formation pressure was obtained through simulation.

[0066] Depend on Figure 2 It can be seen that during the multi-cycle injection and production operation of the gas storage facility, as the injection and production cycle increases, the second real-time breakthrough pressure fluctuates and rises slightly.

[0067] In one possible embodiment, several influencing factors also include: mechanical integrity; the target relationship curve chart includes a first threshold;

[0068] The first threshold is obtained through the following steps:

[0069] A first threshold for characterizing mechanical integrity failure was obtained through rock mechanics strength experiments, geostress tests, and numerical simulation.

[0070] like Figure 2 As shown, the first threshold is 1.8, which means that when the formation rock undergoes tensile failure, the first threshold is 1.8. In other words, when the ratio of real-time formation pressure to initial formation pressure is greater than 1.8, the mechanical integrity of the caprock fails.

[0071] In this way, the first threshold was determined, providing a basis for determining the pressure limit.

[0072] In one possible embodiment, the pressure limit is obtained through the following steps:

[0073] Based on the target relationship curve chart, determine the second threshold used to characterize the failure of the capillary dynamic sealing capability;

[0074] The smaller of the first threshold and the second threshold is determined as the pressure limit.

[0075] This allows for the accurate determination of the pressure limit, ensuring the safety of the caprock sample.

[0076] In one possible embodiment, the second threshold is determined by the following steps:

[0077] A third objective relationship curve is determined for the real-time formation pressure difference between the caprock and the reservoir below the caprock as a function of the ratio of real-time formation pressure to initial formation pressure.

[0078] Determine the first intersection point of the first target relationship curve and the third target relationship curve, and the second intersection point of the second target relationship curve and the third target relationship curve;

[0079] The smaller value of the x-coordinate between the first intersection point and the second intersection point is determined as the second threshold.

[0080] Generally, the real-time formation pressure difference increases with the increase of real-time formation pressure. Of course, due to differences in burial depth and formation pressure gradient, the slope of the third objective relationship curve will vary for different gas storage facilities.

[0081] Depend on Figure 2 It can be seen that the first intersection point of the first target relationship curve and the third target relationship curve is point A; the second intersection point of the third target relationship curve and the second target relationship curve is point B. The x-coordinate of point A is 1.4, which is less than the x-coordinate of point B (1.44). Therefore, the x-coordinate of point A can be determined as the second threshold.

[0082] In this way, the second threshold can be obtained based on the first target relationship curve, the second target relationship curve, and the third target relationship curve, thus improving the accuracy of the second threshold.

[0083] like Figure 3 As shown, the target gas storage facility includes a first gas storage facility and a second gas storage facility;

[0084] The method also includes:

[0085] The first set in the first target relationship curve chart corresponding to the first gas storage facility and the second set in the second target relationship curve chart corresponding to the second gas storage facility are determined respectively. The first set and the second set both include a first threshold, a second threshold and a pressure limit.

[0086] Plot the first target relationship curve and the second target relationship curve on the same graph, and compare the size relationship between the first set and the second set.

[0087] like Figure 3 As shown, the target gas storage facilities include a first gas storage facility A and a second gas storage facility B. The first target relationship curve chart for gas storage A includes the fourth and fifth target relationship curves; the second target relationship curve chart for gas storage B includes the sixth and seventh target relationship curves. Figure 3It can be seen that the first threshold value of the caprock sample in gas storage A is 1.67, the second threshold value is 1.4, and the first pressure limit value is 1.4. In gas storage B, the first threshold value is 1.89, the second threshold value is 1.52, and the second pressure limit value is 1.52. Therefore, it can be concluded that capillary sealing failure, mechanical integrity failure, and pressure limit failure occur preferentially in the caprock sample of gas storage A compared to gas storage B.

[0088] This allows for comparison of the performance of different gas storage facilities, which plays an important role in site selection evaluation, construction scheme design, and operational pressure optimization for oil and gas reservoirs, as well as in environmental safety assessments in the fields of oil and gas, new energy, and carbon storage.

[0089] The method for determining the pressure limit of a gas storage tank cover layer provided by this invention can also be used in conjunction with a computer-readable storage medium. The storage medium stores a computer program, which is executed to run the method for determining the pressure limit of a gas storage tank cover layer. The computer program is capable of executing computer instructions, which include computer program code. The computer program code can be in the form of source code, object code, executable file, or some intermediate form.

[0090] Computer-readable storage media can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0091] It should be noted that the contents of computer-readable storage media may be appropriately added to or subtracted from the contents according to the requirements of legislation and patent practice in a jurisdiction. For example, in some jurisdictions, according to legislation and patent practice, computer-readable storage media may not include electrical carrier signals and telecommunication signals.

[0092] According to another aspect of the present invention, an apparatus for determining the pressure limit of a gas storage tank cover layer is also provided, which performs a method for determining the pressure limit of a gas storage tank cover layer. Figure 4 A block diagram of a device for determining the pressure limit of a gas storage tank cover layer according to an embodiment of the present invention is shown, as follows: Figure 4 As shown, the device includes:

[0093] Preparation module 510 is used to prepare caprock samples corresponding to the target gas storage facility;

[0094] Simulation module 520 is used to simulate the target relationship curve chart for caprock samples based on several influencing factors;

[0095] The determination module 530 is used to determine the pressure limit of the cap layer sample based on the target relationship curve chart.

[0096] According to one embodiment of the present invention, several influencing factors include: capillary dynamic sealing capability, and the target relationship curve chart includes a first target relationship curve;

[0097] The simulation module 520 is also used to simulate the experiment of the caprock sample under in-situ effective stress to obtain the first target relationship curve of the ratio of the first real-time breakthrough pressure to the initial breakthrough pressure as a function of the ratio of the real-time formation pressure to the initial formation pressure; wherein, the first real-time breakthrough pressure is used to characterize the capillary dynamic sealing ability of the caprock sample.

[0098] In summary, this invention provides a method, apparatus, and medium for determining the pressure limit of a gas storage tank cover layer, which has the following advantages compared with the prior art:

[0099] This invention evaluates caprock samples based on several influencing factors to obtain a target relationship curve, which is then used to determine the pressure limit of the caprock samples. This allows for the quantitative and accurate determination of the pressure limit of the caprock samples, i.e., the upper limit operating pressure of the gas storage facility, thus improving the safety of the gas storage facility. Furthermore, it enables an accurate and intuitive assessment of the impact of several influencing factors on the caprock samples, filling the gap in comprehensive evaluation of caprocks under multiple factors. This provides new analytical tools and technical methods for optimizing gas storage operating pressure, evaluating oil and gas reservoir site selection, designing storage construction schemes, increasing peak-shaving gas volume, and environmental safety assessments in the fields of oil and gas, new energy, and carbon sequestration.

[0100] Example 1: Gas storage facility A is located in a basin in eastern China, with a caprock of silty mudstone. Core samples were taken from the caprock of a typical area of ​​gas storage facility A and processed into experimental standard samples. Simulating different operating pressures of the gas storage facility, dynamic breakthrough pressure measurements were conducted on the experimental standard samples to determine the caprock breakthrough pressure under different formation pressure conditions. The ratio of this breakthrough pressure to the initial breakthrough pressure of the formation at gas storage facility A was calculated. A fourth target relationship curve was plotted, showing the ratio of the first real-time breakthrough pressure to the initial breakthrough pressure for gas storage facility A versus the ratio of real-time formation pressure to the initial formation pressure. (See figure). Figure 5 As shown.

[0101] Depend on Figure 5 It can be seen that as the formation pressure increases, the breakthrough pressure basically exhibits a slow linear decrease. Subsequently, a fifth target relationship curve was plotted for the ratio of the reservoir-caprock pressure difference to the initial formation pressure corresponding to gas storage A, versus the ratio of the real-time formation pressure to the initial formation pressure. Figure 5It can be seen that as reservoir pressure increases, the pressure difference between the reservoir and caprock increases, and the fifth target relationship curve shows a linear upward relationship. When the pressure difference between the reservoir and caprock equals the first real-time breakthrough pressure, it indicates that natural gas leakage is about to occur in the caprock, and the corresponding formation pressure ratio is the critical pore pressure. At this time, γ m The formation pressure ratio corresponding to point (A) is 1.4, which is the third threshold. Furthermore, based on field stress and mechanical testing data, the formation pressure ratio corresponding to the tensile failure strength of gas storage A is 1.67, which is the fourth threshold. Therefore, the pressure limit of the caprock of gas storage A is 1.4. Natural gas leakage will occur if the upper operating pressure of the gas storage exceeds 1.4 times the initial formation pressure.

[0102] Example 2: Gas storage facility B is located in western China, with a caprock primarily composed of mudstone. Core samples were taken from the caprock of a typical area of ​​gas storage facility B and processed into experimental standard samples. Simulating the complex injection and production conditions of the gas storage facility (i.e., different formation pressure conditions), dynamic breakthrough pressure measurements were conducted on the natural caprock core samples to determine the caprock breakthrough pressure under different formation pressure conditions. The ratio of this breakthrough pressure to the initial breakthrough pressure under the formation conditions of gas storage facility B was calculated. A sixth target relationship curve was plotted for the ratio of the first real-time breakthrough pressure to the initial breakthrough pressure corresponding to gas storage facility B, as a function of the ratio of real-time formation pressure to the initial formation pressure. (See figure). Figure 6 As shown.

[0103] Depend on Figure 6 It can be seen that as the formation pressure increases, the breakthrough pressure of gas storage cell B exhibits a non-linear decreasing trend, and decreases significantly when it exceeds the formation pressure coefficient of 1.2. Subsequently, the seventh target relationship curve was plotted, showing the ratio of the reservoir-caprock pressure difference to the initial formation pressure versus the ratio of the real-time formation pressure to the initial formation pressure. As the reservoir pressure increases, the reservoir-caprock pressure difference of gas storage cell B increases, and the seventh target relationship curve shows a linear increasing relationship. When the reservoir-caprock pressure difference equals the breakthrough pressure, it indicates that natural gas leakage is imminent in the caprock of gas storage cell B, and the corresponding formation pressure is the critical pore pressure. At this point, γ... m The formation pressure ratio corresponding to point (B) is 1.52, which is the fifth threshold. Meanwhile, based on in-situ stress and mechanical testing data, the formation pressure ratio corresponding to the tensile failure strength of gas storage cell B is 1.89, which is the sixth threshold. Therefore, from... Figure 6 It is known that the pressure limit of the cover layer of gas storage B is 1.52. Natural gas leakage will occur if the upper limit pressure of the gas storage exceeds 1.52 times the initial formation pressure. The formation pressure ratio when the formation undergoes tensile failure is 1.89.

[0104] Example 3: The diagram shown in this invention is a normalized diagram, which can support comprehensive comparative analysis of the pressure bearing limits of different gas storage cap layers, so as to clarify the design of gas storage operation schemes and the understanding of results. The breakthrough pressure data and mechanical strength data of Examples 1 and 2 are integrated into... Figure 3 It can be seen that as the formation pressure increases after gas injection, the sealing performance of the caprock of gas storage B decreases significantly. However, the formation pressure ratio at which capillary closure fails in gas storage B is higher than that in gas storage A, indicating significant differences in caprock sealing performance across different regions. Furthermore, the formation pressure ratios corresponding to tensile failure strength for gas storage A and B are 1.67 and 1.89, respectively, while the ratios corresponding to the critical point of capillary closure failure are 1.4 and 1.52, respectively. This suggests that capillary closure failure and mechanical integrity occur preferentially over mechanical failure in both gas storage A and B. Based on this invention, the caprock pressure bearing capacity of gas storage A is determined to be 1.4, and the caprock pressure bearing capacity of gas storage B is determined to be 1.52.

[0105] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0106] In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0107] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0108] Certain terms are used throughout this application to refer to specific system components. As those skilled in the art will recognize, the same components may often be referred to by different names, and therefore this application is not intended to distinguish those components that differ only in name and not in function. In this application, the terms “comprise,” “include,” and “have” are used in an open-ended manner and should therefore be interpreted as meaning “including, but not limited to…”. Furthermore, the terms “substantially,” “materially,” or “approximately” as used herein refer to industry-accepted tolerances for the corresponding terms. The term “coupling,” as may be used herein, includes direct coupling and indirect coupling via additional components, elements, circuits, or modules, wherein, for indirect coupling, the intermediate component, element, circuit, or module does not alter the information of the signal but may adjust its current level, voltage level, and / or power level. Inferred coupling (e.g., one element is inferredly coupled to another element) includes direct and indirect coupling between two elements in the same manner as “coupling.”

[0109] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0110] The embodiments of the present invention are given for illustrative and descriptive purposes only, and are not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention, and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

[0111] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and variations in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection for this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A method for determining the pressure limit of a gas storage tank cover layer, characterized in that, The method includes: Prepare caprock samples corresponding to the target gas storage facility; For the capping sample, a target relationship curve was simulated based on several influencing factors; Based on the target relationship curve chart, the pressure bearing limit of the capping sample is determined.

2. The method as described in claim 1, characterized in that, The influencing factors include: capillary dynamic sealing capability, and the target relationship curve chart includes a first target relationship curve; The first target relationship curve is obtained through the following steps: The experiment simulating the caprock sample under in-situ effective stress was conducted to obtain a first target relationship curve of the ratio of the first real-time breakthrough pressure to the initial breakthrough pressure as a function of the ratio of the real-time formation pressure to the initial formation pressure; wherein, the first real-time breakthrough pressure is used to characterize the capillary dynamic sealing capability of the caprock sample.

3. The method as described in claim 2, characterized in that, The aforementioned influencing factors also include: fatigue effect; the target relationship curve also includes several second target relationship curves. The second target relationship curve is obtained through the following steps: For the caprock sample, multi-cycle injection and production were performed based on the fatigue effect, and a second target relationship curve was obtained by simulating the ratio of the second real-time breakthrough pressure to the initial breakthrough pressure as a function of the ratio of the real-time formation pressure to the initial formation pressure.

4. The method as described in claim 3, characterized in that, The aforementioned influencing factors also include: mechanical integrity; the target relationship curve chart includes a first threshold; The first threshold is obtained through the following steps: The first threshold for characterizing mechanical integrity failure was obtained through rock mechanics strength experiments, geostress tests, and numerical simulation.

5. The method as described in claim 4, characterized in that, The pressure limit is obtained through the following steps: Based on the target relationship curve chart, a second threshold is determined to characterize the failure of the capillary dynamic sealing capability; The smaller of the first threshold and the second threshold is determined as the pressure limit.

6. The method as described in claim 5, characterized in that, The second threshold is determined by the following steps: A third target relationship curve is determined as a function of the real-time formation pressure difference between the caprock and the reservoir below the caprock and the ratio of the real-time formation pressure to the initial formation pressure. Determine the first intersection point of the first target relationship curve and the third target relationship curve, and the second intersection point of the second target relationship curve and the third target relationship curve; The smaller value of the x-coordinate between the first intersection point and the second intersection point is determined as the second threshold.

7. The method as described in claim 6, characterized in that, The target gas storage facility includes a first gas storage facility and a second gas storage facility; The method further includes: The first set in the first target relationship curve chart corresponding to the first gas storage facility and the second set in the second target relationship curve chart corresponding to the second gas storage facility are determined respectively, wherein the first set and the second set both include a first threshold, a second threshold and a pressure limit; Plot the first target relationship curve chart and the second target relationship curve chart on a single graph, and compare the size relationship between the first set and the second set.

8. A storage medium, characterized in that, It includes a series of instructions for performing the method steps as described in any one of claims 1-7.

9. A device for determining the pressure limit of a gas storage tank cover layer, characterized in that, The apparatus for performing the method as described in any one of claims 1-7 comprises: The preparation module is used to prepare the caprock sample corresponding to the target gas storage facility; The simulation module is used to simulate and obtain a target relationship curve chart for the capping sample based on several influencing factors. The determination module is used to determine the pressure limit of the capping sample based on the target relationship curve chart.

10. The apparatus as claimed in claim 9, characterized in that, The influencing factors include: capillary dynamic sealing capability, and the target relationship curve chart includes a first target relationship curve; The simulation module is also used to simulate the experiment of the caprock sample under in-situ effective stress, and obtain a first target relationship curve of the ratio of the first real-time breakthrough pressure to the initial breakthrough pressure as a function of the ratio of the real-time formation pressure to the initial formation pressure; wherein, the first real-time breakthrough pressure is used to characterize the capillary dynamic sealing capability of the caprock sample.

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