Experimental method and device for evaluating fault stability under injection-production alternating stress of gas storage

Abstract

The invention belongs to the technical field of gas storages, and particularly relates to an experimental method and device for evaluating fault stability under injection-production alternating stress of a gas storage. The method comprises the following steps: acquiring reservoir information of a to-be-detected gas storage; making a three-dimensional model according to the reservoir information, and configuring model parameters according to formation water and natural gas initially injected into the three-dimensional model; an injection-production pipe is inserted into the three-dimensional model, the multi-cycle gas injection-production process is simulated, and fault changes in the three-dimensional model are monitored; and optimizing model parameters of the three-dimensional model according to the fault change condition, and determining optimal model parameters. A fault with any dip angle can be simulated, the experimental model comprises a whole geologic body simulating a gas storage, surrounding rocks including a cover layer and a bottom supporting layer and wrapping the periphery of a reservoir body, the reservoir is disconnected by the fault, the contact relation of the two reservoirs can be designed according to the actual condition of the stratum, and an injection-production well is designed in the model. The injection-production well simulates high-speed injection-production of the gas storage.

Description

Technical Field

[0001] The invention belongs to the technical field of gas storage, and in particular relates to an experimental method and device for evaluating fault stability under injection-production alternating stress of a gas storage. Background Art

[0002] Driven by the dual carbon goals of "carbon peak" and "carbon neutrality", natural gas, as an efficient green energy, plays a key role in energy transformation. In recent years, my country's natural gas consumption has grown rapidly at a double-digit rate, with more obvious seasonal and regional differences. As a natural gas "granary" and giant energy battery, underground gas storage has played a major strategic and practical role in responding to emergencies such as changes in the international situation and extreme cold weather, ensuring national economic development and social stability. However, there is a big difference between the construction of gas storage and the development of gas reservoirs. Gas storage has the characteristics of high-speed injection and production, and the reservoir will frequently be under the action of alternating stress. In this case, the stability of the geological body is related to the safe operation of the gas storage, among which the stability evaluation of the fault is crucial. However, there is currently no more reliable experimental device to simulate and evaluate the stability of faults under the alternating stress of injection and production of gas storage. Therefore, technicians in this field are still conducting continuous research to provide stronger theoretical support for the design of gas storage schemes.

[0003] The existing technology takes into account the characteristics that fault sealing is affected by factors such as mudstone smear, formation rock physical properties and associated fracture development. Based on the calculation of parameters such as fault mudstone smear, fault zone breakthrough pressure, and fracture development density in the fault zone, a comprehensive evaluation index of fault sealing is constructed to comprehensively and quantitatively evaluate the fault sealing. However, this method only analyzes the faults in the reservoir, and does not take into account the influence of the cap rock and bottom support layer of the reservoir on its reservoir, resulting in the problem that the degree of matching between the investigated information and the actual information is not high enough. Summary of the invention

[0004] In view of the above problems, the present invention provides an experimental method for evaluating fault stability under injection-production alternating stress in a gas storage reservoir, the method comprising:

[0005] Obtaining reservoir information of the gas storage to be tested;

[0006] Producing a three-dimensional model based on the reservoir information, and configuring model parameters based on the formation water and natural gas initially injected into the three-dimensional model;

[0007] Inserting injection and production pipes into the three-dimensional model, simulating a multi-cycle gas injection and production process, and monitoring fault changes in the three-dimensional model;

[0008] The model parameters of the three-dimensional model are optimized according to the changes in the faults to determine the optimal model parameters.

[0009] Preferably, the reservoir information includes the fault dip angle of the gas storage reservoir to be tested, the physical properties of the reservoir, cap rock and bottom support layer, and the contact relationship of the reservoir;

[0010] The physical properties include porosity, permeability and reservoir thickness of the formation;

[0011] The contact relationship of the reservoir includes whether the faults are offset, the disconnection sites of the faults, the connection positions of the faults, and the connection rates of the faults.

[0012] Preferably, the obtaining of information of the gas storage to be tested includes:

[0013] Determine the fault dip angle of the reservoir to be tested based on the seismic interpretation of the location of the gas storage to be tested;

[0014] The fault dip of the reservoir to be tested is combined with the local logging interpretation and core data to obtain the physical properties of the reservoir, cap rock and bottom support layer as well as the contact relationship of the reservoir.

[0015] Preferably, the three-dimensional model is a cubic structure;

[0016] The three-dimensional model includes a reservoir simulation layer, a cap rock simulation layer and a bottom support simulation layer connected together;

[0017] The physical properties of the reservoir simulation layer, the cap rock simulation layer and the bottom support simulation layer and the contact relationship of the reservoir simulation layer are consistent with the reservoir information.

[0018] Preferably, a three-dimensional model is produced according to the reservoir information, and model parameters are configured according to the formation water and natural gas initially injected into the three-dimensional model, including:

[0019] Make three-dimensional models;

[0020] Inject formation water and natural gas into the 3D model;

[0021] The model parameters of the three-dimensional model are set according to the amount of injected formation water and natural gas.

[0022] Preferably, before injecting formation water and natural gas into the three-dimensional model, the following steps are included:

[0023] Check the tightness of the 3D model and experimental device;

[0024] The 3D model is pressurized so that the confining pressure of the reservoir simulation layer in the 3D model reaches the real formation pressure.

[0025] Preferably, monitoring the fault changes in the three-dimensional model includes:

[0026] Real-time monitoring of fault movement through CT scanning, laser scanning or microseismic monitoring technology;

[0027] The movement conditions include deformation, displacement and sliding phenomena.

[0028] Preferably, the model parameters of the three-dimensional model are optimized according to the change of the fault, and the optimal model parameters are determined, including:

[0029] According to the changes in the fault, the amount of formation water and natural gas injected into the three-dimensional model is adjusted to change the model parameters until the fault stops sliding, and the model parameters at this moment are used as the optimal model parameters.

[0030] The present invention also provides a fault stability evaluation experimental device under injection-production alternating stress of a gas storage reservoir, the device comprising a three-dimensional model, the three-dimensional model comprising a reservoir simulation layer, a cap rock simulation layer and a bottom support simulation layer;

[0031] An injection and production pipe is arranged around the three-dimensional model, the other end of the injection and production pipe is connected to the gas and water main pipe, and the other end of the injection and production pipe is inserted into the reservoir simulation layer;

[0032] The three-dimensional model is provided with a first monitoring well pipe and a second monitoring well pipe. The first monitoring well pipe passes through the fault, and a third pressure sensor is installed on the upper end of the first monitoring well pipe; the second monitoring well pipe is arranged in the caprock simulation layer, and a fourth pressure sensor is installed on the upper end of the second monitoring well pipe.

[0033] Preferably, the three-dimensional model is connected to the natural gas input pipeline and the formation water input pipeline through a gas-water main pipeline, and the three-dimensional model is connected to the fluid collector through a recovery pipeline. The gas-water main pipeline is provided with a second flow meter and a first pressure sensor, and the recovery pipeline is provided with a first flow meter and a valve.

[0034] Preferably, the three-dimensional model is connected to the confining pressure pump via a second pressure sensor and a valve.

[0035] Preferably, a third pressure sensor is provided on the three-dimensional model.

[0036] Preferably, the reservoir simulation layer includes a complete fault, a partial fault and a complete layer.

[0037] The present invention has the following beneficial effects:

[0038] (1) The present invention can simulate faults with any inclination angle. The experimental model includes the entire geological body of the simulated gas storage reservoir, including the surrounding rocks of the cap rock and the bottom support layer, which are wrapped around the reservoir body. The fault disconnects the reservoir, and the reservoir contact relationship between the two plates can be designed according to the actual situation of the formation. The model designs injection and production wells, which simulate the high-speed injection and production of the gas storage reservoir. During the high-speed injection and production process, the stability of the fault is monitored by microseismic monitoring, CT scanning, laser scanning and other means, thereby providing support for the design of the gas storage reservoir;

[0039] (2) After the pressure of the three-dimensional model in the present invention is stabilized, the injection and production process of multiple cycles is simulated through the injection and production pipe, and the changes of the fault are monitored. Through this experimental device, the injection and production volume and injection and production pressure of the gas storage reservoir can be optimized, and the optimal injection and production volume and pressure can be obtained when the fault does not slide, providing a theoretical basis for the design of the storage capacity parameters of the gas storage reservoir. It can also be used to study the sliding pressure of the fault under different confining pressures;

[0040] (3) The present invention can control the injection rate and production rate of natural gas and formation water into the three-dimensional model through the flow meter, so as to simulate the injection and production process of the gas storage reservoir and optimize the optimal injection rate or production rate without affecting the sealing property of the fault;

[0041] (4) The present invention can record the injection volume and production volume in the model, and can optimize the storage capacity utilization degree of the gas storage model under different injection and production pressures and injection and production speeds, that is, the production degree, the ratio of the production volume to the injection volume, by limiting a variety of conditions, the most important of which is that the fault cannot be active. On this basis, the production speed is optimized to obtain the optimal solution for efficiently utilizing the natural gas in the model;

[0042] (5) The present invention can be made into models of different specifications. When the experimental site is limited and the experimental time is tight, a smaller experimental model can be made, such as a model within 50 cm in length. In this case, the model fault is monitored using laser scanning or CT scanning. However, if the model is too large, it cannot be placed in the scanning device. If there are no more restrictions, a large physical model can be set up, with a model of tens of meters or even hundreds of meters, which is closer to the actual reservoir. In this case, microseismic monitoring can be used to monitor fault slip.

[0043] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 A diagram showing an experimental method for evaluating fault stability under injection-production alternating stress in a gas storage reservoir according to an embodiment of the present invention;

[0046] Figure 2 A schematic diagram showing the structural connection of an experimental device in an embodiment of the present invention is shown;

[0047] Figure 3 A schematic diagram showing a structure of an implementation method in an embodiment of the present invention is shown;

[0048] Figure 4 A schematic structural diagram showing another implementation method in an embodiment of the present invention;

[0049] Figure 5 The comprehensive column chart of the Triassic Jia-2 to Jia-1 of the H-1 gas field in the embodiment of the present invention is shown;

[0050] Figure 6 A schematic diagram of the initial structure of the three-dimensional model establishment in an embodiment of the present invention is shown;

[0051] Figure 7 A schematic diagram showing the structural connection of an experimental device in an embodiment of the present invention is shown;

[0052] Figure 8 A relationship diagram between different minimum wellhead production pressures and produced gas volumes in an embodiment of the present invention is shown;

[0053] Fig. 9 A schematic structural diagram showing another implementation of a three-dimensional model in an embodiment of the present invention;

[0054] In the figure: 1. three-dimensional model; 101. reservoir simulation layer; 102. caprock simulation layer; 103. bottom support simulation layer; 104. injection and production pipe; 105. first monitoring well pipe; 106. second monitoring well pipe; 2. natural gas input pipeline; 3. formation water input pipeline; 4. recovery pipeline; 5. fluid collector; 6. confining pressure pump; 7. first flow meter; 8. second flow meter; 9. first pressure sensor; 10. second pressure sensor; 11. third pressure sensor; 12. fourth pressure sensor; 13. vacuum pump; 14. first pipeline; 15. gas-water main pipeline; 16. second pipeline; 17. detector. DETAILED DESCRIPTION

[0055] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as being limited to the examples set forth herein; on the contrary, these embodiments are provided so that the present disclosure will be more comprehensive and complete, and the concepts of the example embodiments are fully conveyed to those skilled in the art. The described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced while omitting one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, known technical solutions are not shown or described in detail to avoid obscuring various aspects of the present disclosure.

[0056] In addition, the accompanying drawings are only schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware units or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0057] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the steps. For example, some steps may be decomposed, while some steps may be combined or partially combined, so the actual execution order may change according to the actual situation.

[0058] The terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example.

[0059] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or sub-modules is not necessarily limited to those steps or sub-modules explicitly listed, but may include other steps or sub-modules not explicitly listed or inherent to these processes, methods, products, or apparatuses.

[0060] like Figure 1 As shown, the present invention proposes an experimental method for evaluating fault stability under alternating injection-production stress of a gas storage reservoir, the method comprising:

[0061] S1 obtains reservoir information of the gas storage to be tested;

[0062] The reservoir information includes the fault dip angle of the gas storage reservoir to be tested, the physical properties of the reservoir, cap rock and bottom support layer, and the contact relationship of the reservoir;

[0063] The physical properties include porosity, permeability and reservoir thickness of the formation;

[0064] The contact relationship of the reservoir includes whether the faults are offset, the disconnection sites of the faults, the connection positions of the faults, and the connection rates of the faults.

[0065] S2: making a three-dimensional model according to the reservoir information, and configuring model parameters according to the formation water and natural gas initially injected into the three-dimensional model;

[0066] The three-dimensional model is a cubic structure;

[0067] The three-dimensional model includes a reservoir simulation layer, a cap rock simulation layer and a bottom support simulation layer connected together;

[0068] The physical properties of the reservoir simulation layer, the cap rock simulation layer and the bottom support simulation layer and the contact relationship of the reservoir simulation layer are consistent with the reservoir information.

[0069] S3 inserts an injection and production pipe into the three-dimensional model, simulates a multi-cycle gas injection and production process, and monitors fault changes in the three-dimensional model;

[0070] S4 optimizes the model parameters of the three-dimensional model according to the change of the fault and determines the optimal model parameters.

[0071] Specifically, S1 obtains reservoir information of the gas storage to be tested, including:

[0072] S11 determines the fault dip angle of the reservoir to be tested based on the seismic interpretation of the location of the gas storage to be tested;

[0073] S12 combines the fault dip of the reservoir to be tested with the local logging interpretation and core data to obtain the physical properties of the reservoir, cap rock and bottom support layer as well as the contact relationship of the reservoir.

[0074] In this embodiment, the contact relationship information of the reservoir includes whether the faults are offset, the disconnection position of the faults, the connection position of the faults, and the connection rate of the faults.

[0075] Specifically, S2 makes a three-dimensional model according to the reservoir information, and configures model parameters according to the formation water and natural gas initially injected into the three-dimensional model, including:

[0076] S21 makes three-dimensional models;

[0077] S22 injects formation water and natural gas into the 3D model;

[0078] S23 sets the model parameters of the three-dimensional model according to the amount of injected formation water and natural gas.

[0079] Before S22 injects formation water and natural gas into the 3D model, it includes:

[0080] S221 Check the tightness of the three-dimensional model and experimental device;

[0081] S222 pressurizes the three-dimensional model so that the confining pressure of the reservoir simulation layer in the three-dimensional model reaches the real formation pressure.

[0082] Specifically, S3 monitors fault changes in the 3D model, including:

[0083] S31 monitors the movement of faults in real time through CT scanning, laser scanning or microseismic monitoring technology;

[0084] The movement conditions described in S32 include deformation, displacement and sliding phenomena.

[0085] In this embodiment, CT scanning and laser scanning technology are used to monitor the movement of the fault in real time for small and medium-sized three-dimensional models; microseismic monitoring technology is used to monitor the movement of the fault for medium and large three-dimensional models. When microseismic monitoring technology is used to monitor the movement of the fault in real time, seismic detectors are set at the four corners of the three-dimensional model.

[0086] Specifically, S4 optimizes the model parameters of the three-dimensional model according to the change of the fault and determines the optimal model parameters, including:

[0087] S41 adjusts the amount of formation water and natural gas injected into the three-dimensional model according to the change of the fault, thereby changing the model parameters until the fault stops sliding, and the model parameters at this moment are used as the optimal model parameters.

[0088] like Figure 2 As shown, the present invention also proposes an experimental device for evaluating fault stability under alternating stress of injection and production of a gas storage reservoir, the device comprising a three-dimensional model 1, the three-dimensional model 1 is connected to a natural gas input pipeline 2 and a formation water input pipeline 3 through a gas-water main pipe 15, the three-dimensional model 1 is connected to a fluid collector 5 through a recovery pipeline 4, the three-dimensional model 1 is connected to a confining pressure pump 6 through a second pressure sensor 10 and a valve, a second flowmeter 8 and a first pressure sensor 9 are provided on the gas-water main pipe 15, and a first flowmeter 7 is provided on the recovery pipeline 4.

[0089] In this embodiment, the three-dimensional model 1 includes a reservoir simulation layer 101, a cap rock simulation layer 102 above the reservoir simulation layer 101, and a bottom support simulation layer 103 below the simulation layer. Figure 3As shown, the reservoir simulation layer 101 is a structure of a complete fault, a partial fault, or a complete layer. An injection and production pipe 104 inserted into the reservoir simulation layer 101 is provided around the 3D model 1, and the other end of the injection and production pipe 104 is connected to the gas-water main pipe 15.

[0090] In this embodiment, at least two monitoring well pipes are provided on the three-dimensional model 1. The first monitoring well pipe 105 passes through the fault and is installed with a third pressure sensor 11; the second monitoring well pipe 106 is set in the caprock simulation layer 102 and is installed with a fourth pressure sensor 12. Figure 3 As shown, the first monitoring well pipe 105 passes through the fault, and the second monitoring well pipe 106 is in the cap rock simulation layer 102. During the gas injection and production simulation process, the first monitoring well pipe 105 and the second monitoring well pipe 106 can monitor the pressure changes in real time, thereby monitoring the sealing of the fault, determining whether there is fluid leakage, the sealing of the cap rock simulation layer 102, whether the fluid has leaked into the cap rock simulation layer 102, and other information.

[0091] In one of the more preferred implementations, the injection and production pipes 104 include four. According to the prepared three-dimensional model 1 which is generally in the shape of a cube, the four injection and production pipes 104 are preferably distributed at the four corners of the three-dimensional model 1. Valves are provided on the injection and production pipes 104, and the experimental device can be used to simulate various injection and production methods such as one injection and one production, same injection and same production, and one injection and multiple productions.

[0092] Another preferred embodiment is as follows Figure 4 As shown, the three-dimensional model 1 is connected to the vacuum pump 13 through the first pipeline 14; the fluid collector 5 is connected to the gas-water main pipeline 15 through the second pipeline 16, and valves are provided on the first pipeline 14 and the second pipeline 16. The gas-water mixture recovered from the fluid collector 5 can be reused in the device to form a loop, reduce emissions, and make the experimental device safer.

[0093] The steps of using this experimental device to evaluate the fault stability under the alternating stress of injection and production in gas storage are as follows:

[0094] a. Connect the first pipeline 14, use the vacuum pump 13 to evacuate the three-dimensional model 1, and check the sealing of the three-dimensional model 1 and the entire device;

[0095] b. Using the confining pressure pump 6 to pressurize the three-dimensional model 1, so that the confining pressure of the reservoir simulation layer 101 in the three-dimensional model 1 reaches the real formation pressure;

[0096] c. Inject natural gas and formation water into the three-dimensional model 1 through the natural gas input pipeline 2 and the formation water input pipeline 3 connected to the injection and production pipe 104, so as to reach the state before the construction of the reservoir in the late stage of gas reservoir development;

[0097] d. After the reservoir pressure is stabilized, a multi-cycle gas injection and production process is started through the injection and production wells. During this period, the pressure changes in the reservoir simulation layer 101 are monitored in real time, and the changes in the faults are monitored to see if there are deformation, displacement, or sliding phenomena. Through this experiment, the parameters of the injection and production gas volume and injection and production pressure of the gas storage can be optimized, and the optimal injection and production gas volume and pressure can be obtained without the fault sliding.

[0098] Example

[0099] This embodiment takes a gas storage in Sichuan as an example before the construction of a gas reservoir in the late stage of development to further illustrate this solution. The gas storage has a reservoir fault, and it is necessary to investigate the fault stability under the alternating stress of injection and production, determine the optimal injection and production volume and pressure of the gas storage when the fault does not slide, and provide a theoretical basis for the design of the storage capacity parameters of the gas storage.

[0100] first step:

[0101] The fault dip angle of the reservoir to be tested is determined based on the seismic interpretation of the location of the gas storage reservoir to be tested, and the physical properties of the reservoir, cap rock and bottom support layer as well as the contact relationship of the reservoir are obtained in combination with the local well logging interpretation and core data.

[0102] Specifically, the core data of the area to be studied are used to obtain the physical properties of the reservoir, cap rock and bottom support layer, and the physical properties include the porosity, permeability and reservoir thickness of the formation; the fault dip angle of the reservoir and the contact relationship information of the reservoir are obtained by interpreting the logging data or seismic data of the area to be studied; the contact relationship information of the reservoir includes whether the fault is offset, the disconnection point of the fault, the connection position of the fault, and the connection rate of the fault.

[0103] For example, the geological profile of H-1 gas storage is as follows: the direct cap rock is Jiaer 3 , is 90m of limestone + gypsum, the reservoir construction includes Jiaer 2 Kazuyoshi 1 ~ Jia 1 and 2. Jia 2 2 The stratum is 40m of limestone + dolomite + gypsum, Jiaer 1 The strata are 20m of gypsum + dolomite + limestone, the strata of Jia 1 are 300m of limestone, and the bottom supporting layer is 90m of purple-red mudstone at the top of Fei 4.

[0104] The physical parameters of each layer are shown in Table 1, a data table of rock microscopic sealing parameters. In real reservoirs, there are interlayers, that is, the physical properties of the reservoir are very good, but there may be interlayers with poor physical properties in the middle. Therefore, a three-dimensional model can be made in proportion according to the actual situation. The physical parameters of reservoirs of different thicknesses are slightly different, and the average physical parameters are obtained based on core sampling tests.

[0105] Table 1

[0106]

[0107]

[0108] The comprehensive column chart of Triassic Jia-2 to Jia-1 of H-1 gas field is attached. Figure 5 .

[0109] Step 2:

[0110] According to the information obtained in the previous step, a 50cm*50cm*50cm small regular three-dimensional model 1 is made. The three-dimensional model 1 is used to simulate the geological body of the gas storage reservoir. The three-dimensional model 1 includes a reservoir simulation layer 101, a cap layer simulation layer 102 and a bottom support simulation layer 103 connected together. The physical properties of the reservoir simulation layer 101, the cap layer simulation layer 102 and the bottom support simulation layer 103 and the contact relationship of the reservoir simulation layer 101 are consistent with the information of the gas storage to be tested obtained in the previous step. That is, the upper layer and the lower layer of the reservoir simulation layer 101 are made according to the properties of the cap layer and the bottom support layer of the geological body of the gas storage reservoir (the components include gypsum and other materials commonly used to make models). The physical properties of the cap layer simulation layer 102 and the bottom support simulation layer 103 are very poor, and there is basically no storage space and no fluid. The middle layer wraps the reservoir body, that is, the reservoir simulation layer 101 structure that simulates the reservoir. The model is made according to the actual physical property parameters of the gas reservoir. Although the model is divided into several layers, in order to restore the reservoir environment to a higher degree, the layers of the model have different physical properties, but they are not separate individuals, but a whole that is interconnected.

[0111] The three-dimensional model 1 obtained by this method can simulate the fault structure with any inclination angle, or the reservoir structure where the reservoir has been completely disconnected, and the shape of the fault and the disconnection of the reservoir cap layer and the bottom support layer can be designed according to the actual situation, such as Figure 6 The fault shown is a schematic diagram of a fault that disconnects the reservoir cap rock.

[0112] In the prior art, core physical experiments are generally used for testing, that is, the core obtained from the underground is directly placed in the core holder for experiment, and experiments are carried out under different injection and production pressures and confining pressures respectively to test whether the core physical properties have changed significantly after pressurization and decompression. The experimental results are used to evaluate the physical property change characteristics of the bottom support layer of the cap layer reservoir under the influence of the alternating injection and production stress of the gas storage reservoir, whether the physical property of the bottom support layer of the cap layer changes greatly, resulting in failure or reduction of the sealing property. The above is a method for detecting the sealing property of the bottom support layer of the cap layer. There are fewer experimental methods for fault sealing, most of which use geomechanical modeling for numerical simulation or mathematical methods for calculation. When the existing experiments are carried out on the fault sealing property, the influence of the bottom support layer of the cap layer around the reservoir is not considered, nor is the process of high-speed gas injection and production, and various injection and production parameters and the degree of storage capacity utilization cannot be optimized at the same time. In the present invention, the cap layer on the upper part of the reservoir and the bottom support layer on the lower part are still taken into consideration, and the obtained three-dimensional model 1 is used to simulate the stability of the fault under the alternating injection and production stress of the gas storage reservoir, and the result is closer to the state of the actual gas storage reservoir.

[0113] Step 3:

[0114] Insert injection and production pipes 104 simulating the injection and production wells at the four corners of the obtained three-dimensional model 1. The injection and production pipes 104 can be made of high temperature and high pressure resistant materials (such as steel) into cylindrical pipelines to pass through the surrounding rock, even if the injection and production pipes 104 pass through the cap rock simulation layer 102 to reach the reservoir simulation layer 101. The other end of the injection and production pipe 104 is connected to the natural gas input pipeline 2 and the formation water input pipeline 3 (or the gas-water mixing main pipe), that is, the injection and production pipe 104 can simulate multiple injection and production modes such as one injection and one production, simultaneous injection and simultaneous production, and one injection and multiple production.

[0115] In the three-dimensional model 1, at least two monitoring well pipes are provided, and pressure gauges are installed in the monitoring well pipes. The first monitoring well pipe 105 passes through the fault, and the second monitoring well pipe 106 is in the cap rock simulation layer 102. During the injection and production simulation process, the monitoring well pipes at the two locations can monitor the pressure changes in real time, thereby monitoring the sealing of the fault, whether there is fluid leakage, and the sealing of the cap rock simulation layer 102, whether the fluid has leaked into the cap rock simulation layer 102, etc. Figure 3 shown.

[0116] The pressure change of the reservoir body (ie, the reservoir simulation layer 101) can also be monitored in real time during the injection and production process of the gas storage.

[0117] At the same time, the confining pressure method is adopted. The outermost part of the cube model is pressurized from six sides at the same time. A steel plate as large as the model surface can be connected through a pump to pressurize the inside and monitor the pressure changes of the reservoir in real time.

[0118] Step 4:

[0119] First, refer to Figure 7, connect the three-dimensional model 1 obtained in the third step to the experimental device, and inject formation water and natural gas into the three-dimensional model 1 through the natural gas input pipeline 2 and the formation water input pipeline 3 to achieve the state before the construction of the gas reservoir in the late stage of development; after the pressure of the three-dimensional model 1 is stabilized, the multi-cycle gas injection and production process is simulated through the injection and production pipe 104, and the changes in the fault are monitored. Through this experimental device, the parameters of the gas injection and production volume and injection and production pressure of the gas storage can be optimized, and the optimal gas injection and production volume and pressure can be obtained without the fault sliding.

[0120] In the experimental device, in addition to the three-dimensional model 1, the three-dimensional model 1 is also connected to the natural gas input pipeline 2 and the formation water input pipeline 3 through the gas-water main pipe 15, that is, the natural gas input pipeline 2 and the formation water input pipeline 3 transport the natural gas and formation water to the three-dimensional model 1 through the delivery pump, the three-dimensional model 1 is connected to the fluid collector 5 through the recovery pipeline 4, the three-dimensional model 1 is also connected to the confining pressure pump 6, and the gas-water main pipe 15 and the recovery pipeline 4 are both provided with flow meters.

[0121] The three-dimensional model 1 includes a reservoir simulation layer 101, a cap rock simulation layer 102 above the reservoir simulation layer 101, and a bottom support simulation layer 103 below the simulation layer. The reservoir simulation layer 101 is a structure of a complete fault, a partial fault, or a complete layer.

[0122] The three-dimensional model 1 is provided with an injection and production pipe 104 inserted into the reservoir simulation layer 101 on the periphery, and the other end of the injection and production pipe 104 is connected to the gas and water main pipe 15; at least two monitoring well pipes are provided on the three-dimensional model 1, one monitoring well pipe passes through the fault and is installed with a third pressure sensor 11; the other monitoring well pipe is set in the caprock simulation layer 102 and is installed with a fourth pressure sensor 12. The injection and production pipes 104 include four, and the four injection and production pipes 104 are distributed at the four corners of the three-dimensional model 1, and valves are provided on the injection and production pipes 104.

[0123] In this embodiment, the three-dimensional model 1 is connected to the vacuum pump 13 through the first pipeline 14; the fluid collector 5 is connected to the air-water main pipeline 15 through the second pipeline 16, and a valve is provided on the pipeline.

[0124] The specific experimental steps are as follows:

[0125] a. Use the vacuum pump 13 in the experimental device to evacuate the three-dimensional model 1 and check the sealing of the three-dimensional model 1 and the entire device;

[0126] b. Then the confining pressure pump 6 is used to pressurize the three-dimensional model 1 so that the confining pressure of the reservoir simulation layer 101 in the three-dimensional model 1 reaches the real formation pressure, which is 20 MPa in this embodiment;

[0127] c. Inject natural gas and formation water into the three-dimensional model 1 through the natural gas input pipeline 2 and the formation water input pipeline 3 connected to the injection and production pipe 104, so as to reach the state before the construction of the reservoir in the late stage of gas reservoir development;

[0128] d. After the reservoir pressure stabilizes, a multi-cycle gas injection and production process is started through the injection and production wells. During this period, CT scanning and laser scanning technology are used to monitor the changes in reservoir pressure in real time, monitor the changes in faults, including whether the faults are deformed, displaced, or slipped. Through this experiment, the parameters of the gas injection and production volume and injection and production pressure of the gas storage can be optimized, and the optimal gas injection and production volume and pressure can be obtained without the fault slipping.

[0129] Figure 8 is a graph showing the relationship between different minimum wellhead production pressures and produced gas volumes. In this embodiment, the gas volume and outlet pressure of the gas storage reservoir to be tested are 8.7×10 3 m 3 The working gas volume increases with the decrease of the lower limit wellhead pressure. When the wellhead pressure drops to 6MPa, it is the lowest wellhead pressure under the existing pipeline network conditions, and the produced gas volume can reach 8.7×10 3 m 3 .

[0130] In this scheme, theoretically speaking, the larger the model, the higher the degree of restoration, and the closer the experimental results are to the optimal gas injection and production volume and pressure of the actual gas storage, that is, the more reliable the evaluation of fault stability under the alternating stress of gas storage injection and production. For small and medium-sized three-dimensional models 1, CT scanning and laser scanning technology are used to monitor the movement of faults in real time; for medium and large three-dimensional models 1, microseismic monitoring technology is used to monitor the movement of faults in real time.

[0131] The experimental device that uses microseismic monitoring technology to monitor the movement of the fault in real time needs to set detectors 17 at the four corners of the three-dimensional model 1, such as Fig. 9 shown.

[0132] Those skilled in the art should understand that although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An experimental method for evaluating fault stability under alternating injection-production stress in a gas storage facility, characterized in that: The method comprises: Obtaining reservoir information of the gas storage to be tested; Producing a three-dimensional model based on the reservoir information, and configuring model parameters based on the formation water and natural gas initially injected into the three-dimensional model; Inserting injection and production pipes into the three-dimensional model, simulating a multi-cycle gas injection and production process, and monitoring fault changes in the three-dimensional model; The model parameters of the three-dimensional model are optimized according to the changes in the faults to determine the optimal model parameters.

2. The experimental method for evaluating fault stability under alternating injection-production stress of a gas storage reservoir according to claim 1 is characterized in that: The reservoir information includes the fault dip angle of the gas storage reservoir to be tested, the physical properties of the reservoir, cap rock and bottom support layer, and the contact relationship of the reservoir; The physical properties include porosity, permeability and reservoir thickness of the formation; The contact relationship of the reservoir includes whether the faults are offset, the disconnection sites of the faults, the connection positions of the faults, and the connection rates of the faults.

3. The experimental method for evaluating fault stability under alternating injection-production stress of a gas storage reservoir according to claim 2 is characterized in that: The obtaining of information of the gas storage to be tested includes: Determine the fault dip angle of the reservoir to be tested based on the seismic interpretation of the location of the gas storage to be tested; The fault dip of the reservoir to be tested is combined with the local logging interpretation and core data to obtain the physical properties of the reservoir, cap rock and bottom support layer as well as the contact relationship of the reservoir.

4. The experimental method for evaluating fault stability under alternating injection-production stress of a gas storage reservoir according to claim 1, characterized in that: The three-dimensional model is a cubic structure; The three-dimensional model includes a reservoir simulation layer, a cap rock simulation layer and a bottom support simulation layer connected together; The physical properties of the reservoir simulation layer, the cap rock simulation layer and the bottom support simulation layer and the contact relationship of the reservoir simulation layer are consistent with the reservoir information.

5. The experimental method for evaluating fault stability under injection-production alternating stress of a gas storage reservoir according to claim 1, characterized in that: A three-dimensional model is produced according to the reservoir information, and model parameters are configured according to the formation water and natural gas initially injected into the three-dimensional model, including: Make three-dimensional models; Inject formation water and natural gas into the 3D model; The model parameters of the three-dimensional model are set according to the amount of injected formation water and natural gas.

6. The experimental method for evaluating fault stability under alternating injection-production stress of a gas storage reservoir according to claim 1, characterized in that: Before injecting formation water and gas into the 3D model, include: Check the tightness of the 3D model and experimental device; The 3D model is pressurized so that the confining pressure of the reservoir simulation layer in the 3D model reaches the real formation pressure.

7. The experimental method for evaluating fault stability under alternating injection-production stress of a gas storage reservoir according to claim 1, characterized in that: The monitoring of fault changes in the three-dimensional model includes: Real-time monitoring of fault movement through CT scanning, laser scanning or microseismic monitoring technology; The movement conditions include deformation, displacement and sliding phenomena.

8. The experimental method for evaluating fault stability under injection-production alternating stress of a gas storage reservoir according to claim 1, characterized in that: Optimize the model parameters of the 3D model according to the changes in the fault and determine the optimal model parameters, including: According to the changes in the fault, the amount of formation water and natural gas injected into the three-dimensional model is adjusted to change the model parameters until the fault stops sliding, and the model parameters at this moment are used as the optimal model parameters.

9. Experimental device for evaluating fault stability under alternating injection and production stress of gas storage, characterized in that: The device comprises a three-dimensional model (1), wherein the three-dimensional model (1) comprises a reservoir simulation layer (101), a cap rock simulation layer (102) and a bottom support simulation layer (103); An injection and production pipe (104) is arranged around the three-dimensional model (1), the other end of the injection and production pipe (104) is connected to the gas and water main pipe (15), and the other end of the injection and production pipe (104) is inserted into the reservoir simulation layer (101); The three-dimensional model (1) is provided with a first monitoring well pipe (105) and a second monitoring well pipe (106); the first monitoring well pipe (105) passes through the fault, and a third pressure sensor (11) is installed at the upper end of the first monitoring well pipe (105); the second monitoring well pipe (106) is arranged in the caprock simulation layer (102), and a fourth pressure sensor (12) is installed at the upper end of the second monitoring well pipe (106).

10. The fault stability evaluation experimental device under injection-production alternating stress of a gas storage reservoir according to claim 9, characterized in that: The three-dimensional model (1) is connected to a natural gas input pipeline (2) and a formation water input pipeline (3) via a gas-water main pipeline (15); the three-dimensional model (1) is connected to a fluid collector (5) via a recovery pipeline (4); a second flow meter (8) and a first pressure sensor (9) are provided on the gas-water main pipeline (15); and a first flow meter (7) and a valve are provided on the recovery pipeline (4).

11. The fault stability evaluation experimental device under injection-production alternating stress of a gas storage reservoir according to claim 10, characterized in that: The three-dimensional model (1) is connected to the confining pressure pump (6) via a second pressure sensor (10) and a valve.

12. The fault stability evaluation experimental device under injection-production alternating stress of a gas storage reservoir according to claim 11, characterized in that: The three-dimensional model (1) is provided with a third pressure sensor (11).

13. The fault stability evaluation experimental device under injection-production alternating stress of a gas storage reservoir according to claim 9, characterized in that: The reservoir simulation layer (101) includes a complete fault, a partial fault and a complete layer.

Images