Near-well blockage experiment simulation device and method for gas storage

Abstract

The embodiment of the present application provides a device and method for simulating near-wellbore blockage experiments for gas storage. The device includes: a core holder for placing an experimental rock sample, a confining pressure cavity is formed between the core holder and the experimental rock sample; a confining pressure injection unit connected to the confining pressure cavity, used to inject liquid into the confining pressure cavity; an internal pressure injection unit connected to the inlet end of the experimental rock sample, used to selectively inject condensate gas or natural gas into the interior of the experimental rock sample; a back pressure valve connected to the outlet end of the experimental rock sample; a first pressure monitoring unit, provided on the core holder, for monitoring the pressure of the confining pressure cavity; a second pressure monitoring unit, provided at the outlet end of the experimental rock sample, for monitoring the outlet pressure of the experimental rock sample. Through the above technical scheme, the process of converting a condensate gas reservoir into a gas storage and the multi-cycle injection and production process during the operation of the gas storage can be truly simulated, thereby providing technical support for analyzing near-wellbore blockage of a gas storage and ensuring efficient and stable operation of the gas storage.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas development, and in particular to a near-wellbore plugging experiment simulation device and method for a gas storage reservoir. Background Art

[0002] A depleted oil and gas reservoir gas storage is a gas storage built using an already depleted and abandoned gas reservoir or a retired gas reservoir that has been mined to a certain extent. For a gas storage converted from a condensate gas reservoir, since the pressure of the condensate gas reservoir will gradually decrease during the exploitation process, when the pressure drops below the dew point, the natural gas will turn into liquid and precipitate in the form of retrograde condensate oil. Retrograde condensate oil accumulates in the near-well area and will cause blockage of the formation seepage channel; at the same time, during the multi-cycle injection and production process of the gas storage during operation, it is inevitable that various liquid hydrocarbons will enter the reservoir. For example, when injecting gas, ground compressors are usually used for boosting injection. The lubricating oil of the ground compressor is easily injected into the reservoir with the gas during the movement of the blades or cavities. The lubricating oil often undergoes catalytic transformation in a high-temperature and high-pressure environment to form sulfur-containing substances and various heavy hydrocarbon components that are more harmful to the reservoir, thereby causing blockage near the well and affecting the stable operation of the gas storage.

[0003] At present, my country is still in the early stage of exploration and research on the construction of gas storage facilities, especially the research on gas storage facilities converted from condensate gas reservoirs is very limited. The near-well blockage caused by multi-cycle injection and production during the conversion of condensate gas reservoirs to gas storage facilities and the operation of gas storage facilities requires a large number of physical simulation experiments for analysis and evaluation. Nowadays, there is a lack of a systematic and effective near-well blockage experimental simulation device and method for gas storage facilities to provide technical support for ensuring the efficient and stable operation of gas storage facilities. Summary of the invention

[0004] In order to at least partially solve the above-mentioned problems existing in the prior art, the purpose of the embodiments of the present application is to provide a near-wellbore blockage experiment simulation device and method for a gas storage reservoir.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a near-well blockage experiment simulation device for a gas storage reservoir, comprising:

[0006] A core holder is used to place the experimental rock sample, and a confining pressure cavity is formed between the core holder and the experimental rock sample;

[0007] A confining pressure injection unit, connected to the confining pressure cavity, and used for injecting liquid into the confining pressure cavity;

[0008] An internal pressure injection unit, connected to the inlet end of the experimental rock sample, is used to selectively inject condensate gas or natural gas into the interior of the experimental rock sample;

[0009] A back pressure valve connected to the outlet end of the experimental rock sample;

[0010] A first pressure monitoring unit, disposed on the core holder, for monitoring the pressure of the confining pressure chamber;

[0011] The second pressure monitoring unit is arranged at the outlet end of the experimental rock sample and is used to monitor the outlet pressure of the experimental rock sample.

[0012] In an embodiment of the present application, the confining pressure injection unit includes a confining pressure pump.

[0013] In an embodiment of the present application, the internal pressure injection unit includes a displacement pump, a first gas storage element and a second gas storage element. The displacement pump is connected to the inlet end of the first gas storage element and the inlet end of the second gas storage element respectively. The outlet end of the first gas storage element and the outlet end of the second gas storage element are both connected to the inlet end of the experimental rock sample. The first gas storage element is used to store condensate gas, and the second gas storage element is used to store natural gas.

[0014] In an embodiment of the present application, a first valve is arranged between the displacement pump and the inlet end of the first gas storage element, a second valve is arranged between the displacement pump and the inlet end of the second gas storage element, and a third valve is arranged between the outlet end of the first gas storage element and the outlet end of the second gas storage element and the inlet end of the experimental rock sample.

[0015] In the embodiment of the present application, the near-well blockage experiment simulation device also includes:

[0016] A third pressure monitoring unit is provided at the inlet end of the experimental rock sample and is used to monitor the inlet pressure of the experimental rock sample;

[0017] The flow monitoring unit is arranged at the outlet end of the experimental rock sample and is used to monitor the flow of the natural gas flowing out from the outlet end of the experimental rock sample.

[0018] In the embodiment of the present application, the near-well blockage experiment simulation device also includes:

[0019] An insulation box is arranged outside the core holder;

[0020] A heater is arranged in the incubator and is used to heat the incubator;

[0021] The temperature monitoring unit is arranged in the incubator and is used to monitor the temperature in the incubator.

[0022] The second aspect of the present application provides a near-wellbore blockage experiment simulation method for a gas storage, which is applied to the near-wellbore blockage experiment simulation device for a gas storage, and the near-wellbore blockage experiment simulation method for a gas storage comprises the following steps:

[0023] S1. Place the experimental rock sample into the core holder;

[0024] S2, injecting liquid into the confining pressure cavity through the confining pressure injection device, and stopping the injection of liquid when the pressure of the confining pressure cavity monitored by the first pressure monitoring unit reaches the pressure value of the overlying rock formation of the gas storage reservoir;

[0025] S3, injecting condensate gas into the interior of the experimental rock sample through the internal pressure injection device, and stopping the injection of condensate gas when the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the original formation pressure value of the gas storage before the storage is built;

[0026] S4, adjusting the back pressure valve so that the outlet pressure of the experimental rock sample is gradually reduced until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the initial formation pressure value when the gas storage reservoir is built;

[0027] S5, injecting natural gas into the interior of the experimental rock sample through the internal pressure injection device, and stopping the injection of natural gas when the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the upper limit pressure value of the gas storage reservoir during operation;

[0028] S6. Regulate the back pressure valve so that the outlet pressure of the experimental rock sample is gradually reduced until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the lower limit pressure value of the gas storage reservoir during operation;

[0029] S7, repeat step S5 and step S6 until the preset number of cycles is reached.

[0030] In the embodiment of the present application, before step S1, the near-well blockage experiment simulation method further includes:

[0031] Clean and dry the experimental rock samples;

[0032] The cleaned and dried experimental rock samples were vacuum treated.

[0033] In the embodiment of the present application, the near-wellbore plugging experiment simulation method further includes:

[0034] Obtaining the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber, and the flow rate of the natural gas flowing out of the outlet end of the experimental rock sample;

[0035] The permeability, porosity and compressibility of the experimental rock sample are determined according to the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber and the flow rate of natural gas.

[0036] In the embodiment of the present application, the permeability, porosity and compressibility of the experimental rock sample are determined according to the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber and the flow rate of natural gas, including:

[0037] The permeability of the experimental rock sample is determined according to formula (1):

[0038]

[0039] The porosity of the experimental rock sample is determined according to formula (2):

[0040] φ=a(P3-P2) 3 +b(P3-P2) 2 +c(P3-P2)+d formula (2)

[0041] The compression coefficient of the experimental rock sample is determined according to formula (3):

[0042]

[0043] Where K represents the permeability of the experimental rock sample, represents the porosity of the experimental rock sample, C f represents the compression coefficient of the experimental rock sample, P1 represents the inlet pressure of the experimental rock sample, P2 represents the outlet pressure of the experimental rock sample, P3 represents the pressure of the confining pressure chamber, Q represents the flow rate of natural gas, P represents the standard atmospheric pressure, μ represents the viscosity value of natural gas, L represents the length of the experimental rock sample, A represents the cross-sectional area of ​​the experimental rock sample, and a, b, c, and d represent regression coefficients.

[0044] Through the above technical scheme, that is, by injecting liquid into the confining pressure cavity between the core holder and the experimental rock sample through the confining pressure injection unit to establish confining pressure, the overburden pressure on the experimental rock sample can be simulated, and by injecting condensate gas or natural gas into the interior of the experimental rock sample through the internal pressure injection unit, the formation pressure on the experimental rock sample can be simulated, and by adjusting the back pressure valve to change the outlet pressure of the experimental rock sample, the change of the net stress on the experimental rock sample can be simulated, wherein, after the condensate gas is injected into the interior of the experimental rock sample through the internal pressure injection unit to make its outlet pressure reach the original formation pressure value before the gas storage reservoir is built, the outlet pressure of the experimental rock sample is gradually reduced by adjusting the back pressure valve to make it reach the initial formation pressure when the gas storage reservoir is built. The value can simulate the initial state of the condensate gas reservoir before the construction of the gas storage and the process of converting the condensate gas reservoir into a gas storage. When natural gas is injected into the experimental rock sample through the internal pressure injection unit to make its outlet pressure reach the upper limit pressure value of the gas storage during operation, the outlet pressure of the experimental rock sample is gradually reduced by adjusting the back pressure valve to make it reach the lower limit pressure value of the gas storage during operation. Repeating the above steps many times can simulate the multi-cycle injection and production process of the gas storage during operation. In this way, the process of converting the condensate gas reservoir into a gas storage and the multi-cycle injection and production process of the gas storage during operation can be truly simulated, thereby providing technical support for analyzing the near-well blockage of the gas storage and ensuring the efficient and stable operation of the gas storage.

[0045] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0047] Figure 1 It is a structural schematic diagram of a near-well blockage experiment simulation device for a gas storage provided in an embodiment of the present application;

[0048] Figure 2 It is a curve diagram of the change of the permeability of the experimental rock sample during multi-cycle injection and production in Example 1 of the near-well blockage experimental simulation method for a gas storage provided in the embodiments of the present application;

[0049] Figure 3 It is a curve chart of the porosity change of the experimental rock sample during multi-cycle injection and production in Example 1 of the near-wellbore blockage experimental simulation method for a gas storage provided in the embodiments of the present application.

[0050] Description of Reference Numerals

[0051] 1. Core holder; 2. Experimental rock sample;

[0052] 3. Confining pressure injection unit; 4. Back pressure valve;

[0053] 5. First pressure monitoring unit; 6. Second pressure monitoring unit;

[0054] 7. displacement pump; 8. first gas storage element;

[0055] 9. Second gas storage element; 10. First valve;

[0056] 11. Second valve; 12. Third valve;

[0057] 13. A third pressure monitoring unit; 14. A flow monitoring unit;

[0058] 15. Incubator; 16. Heater;

[0059] 17. Temperature monitoring unit. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present application, and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0061] Figure 1 Schematic diagram of the structure of the near-well blockage experiment simulation device for gas storage provided in the embodiment of the present application. Figure 1 As shown, in one embodiment of the present application, a near-wellbore blockage experiment simulation device for a gas storage reservoir is provided, including: a core holder 1, used to place an experimental rock sample 2, and a confining pressure cavity is formed between the core holder 1 and the experimental rock sample 2; a confining pressure injection unit 3, connected to the confining pressure cavity, used to inject liquid into the confining pressure cavity; an internal pressure injection unit, connected to the inlet end of the experimental rock sample 2, used to selectively inject condensate gas or natural gas into the interior of the experimental rock sample 2; a back pressure valve 4, connected to the outlet end of the experimental rock sample 2; a first pressure monitoring unit 5, arranged on the core holder 1, used to monitor the pressure of the confining pressure cavity; a second pressure monitoring unit 6, arranged at the outlet end of the experimental rock sample 2, used to monitor the outlet pressure of the experimental rock sample 2.

[0062] Specifically, the core holder 1 can be a hollow structure for placing the experimental rock sample 2. The experimental rock sample 2 can be a natural core drilled and prepared after cleaning, drying, vacuuming and other treatments. The shape of the experimental rock sample 2 can be a plunger, which is suitable for clamping. A confining pressure cavity is formed between the core holder 1 and the experimental rock sample 2. Liquid is injected into the confining pressure cavity through the confining pressure injection unit 3 to establish confining pressure, which can simulate the overburden pressure on the experimental rock sample 2, wherein the overburden pressure refers to the pressure exerted on the lower rock unit by the upper covering rock layer in the reservoir. Generally speaking, there are relatively narrow channels connecting pores in the rock mass or soil mass, namely pore throats, so that fluids can flow in the rock mass. Condensate gas or natural gas is injected into the interior of the experimental rock sample 2 through the internal pressure injection unit, which can simulate the formation pressure on the experimental rock sample 2, wherein the formation pressure refers to the fluid pressure borne by the rock in the reservoir. By adjusting the back pressure valve 4 to change the outlet pressure of the experimental rock sample 2, the change of the net stress on the experimental rock sample 2 can be simulated, wherein the net stress refers to the difference between the overburden pressure and the formation pressure, also known as the effective overburden pressure.

[0063] After the condensate gas is injected into the experimental rock sample 2 by the internal pressure injection unit so that its outlet pressure reaches the original formation pressure value before the gas storage is built, the outlet pressure of the experimental rock sample 2 is gradually reduced by adjusting the back pressure valve 4 so that it reaches the initial formation pressure value when the gas storage is built, so that the initial state of the condensate gas reservoir before the gas storage is built and the process of converting the condensate gas reservoir into a gas storage can be simulated. When natural gas is injected into the experimental rock sample 2 by the internal pressure injection unit so that its outlet pressure reaches the upper limit pressure value when the gas storage is in operation, the outlet pressure of the experimental rock sample is gradually reduced by adjusting the back pressure valve 4 so that it reaches the lower limit pressure value when the gas storage is in operation, and the above steps are repeated many times, so that the multi-cycle injection and production process when the gas storage is in operation can be simulated. Through this type of method, the process of converting the condensate gas reservoir into a gas storage and the multi-cycle injection and production process when the gas storage is in operation can be truly simulated, thereby providing technical support for analyzing the near-well blockage of the gas storage and ensuring the efficient and stable operation of the gas storage.

[0064] In one embodiment, the confining pressure injection unit 3 includes a confining pressure pump.

[0065] Specifically, the overlying strata pressure on the rocks in the reservoir can usually be considered constant, so the confining pressure pump can be a constant pressure pump connected to the confining pressure chamber through a pipeline, wherein the liquid injected into the confining pressure chamber can be clean water to simulate the groundwater environment.

[0066] In one embodiment, the internal pressure injection unit includes a displacement pump 7, a first gas storage element 8 and a second gas storage element 9. The displacement pump 7 is connected to the inlet end of the first gas storage element 8 and the inlet end of the second gas storage element 9 respectively. The outlet end of the first gas storage element 8 and the outlet end of the second gas storage element 9 are both connected to the inlet end of the experimental rock sample 2. The first gas storage element 8 is used to store condensate gas, and the second gas storage element 9 is used to store natural gas.

[0067] Specifically, by pumping liquid into the first gas storage element 8 or the second gas storage element 9 through the displacement pump 7, the condensate gas in the first gas storage element 8 or the natural gas in the second gas storage element 9 can be injected into the interior of the experimental rock sample 2. Among them, the condensate gas and the natural gas can be compounded by ground sampling, using ground condensate oil and ground natural gas according to the direct phase recovery method, the condensate oil comes from the production sampling of the gas storage reservoir, and the ground natural gas is prepared according to the composition.

[0068] Furthermore, in one embodiment, a first valve 10 is arranged between the displacement pump 7 and the inlet end of the first gas storage element 8, a second valve 11 is arranged between the displacement pump 7 and the inlet end of the second gas storage element 9, and a third valve 12 is arranged between the outlet end of the first gas storage element 8 and the outlet end of the second gas storage element 9 and the inlet end of the experimental rock sample 2.

[0069] Specifically, when it is necessary to inject condensate gas into the experimental rock sample 2, the back pressure valve 4 and the second valve 11 can be closed, and the first valve 10 and the third valve 12 can be opened. When it is necessary to inject natural gas into the experimental rock sample 2, the back pressure valve 4 and the first valve 10 can be closed, and the second valve 11 and the third valve 12 can be opened.

[0070] In one embodiment, the near-wellbore blockage experimental simulation device also includes: a third pressure monitoring unit 13, which is arranged at the inlet end of the experimental rock sample 2, for monitoring the inlet pressure of the experimental rock sample 2; a flow monitoring unit 14, which is arranged at the outlet end of the experimental rock sample 2, for monitoring the flow of natural gas flowing out from the outlet end of the experimental rock sample 2.

[0071] Specifically, the first pressure monitoring unit 5 , the second pressure monitoring unit 6 and the third pressure monitoring unit 13 may all adopt high-precision pressure gauges, and the flow monitoring unit 14 may adopt a high-precision flow meter.

[0072] In one embodiment, the near-wellbore plugging experiment simulation device also includes: an insulation box 15, which is arranged outside the core clamp 1; a heater 16, which is arranged in the insulation box 15 and is used to heat the insulation box 15; and a temperature monitoring unit 17, which is arranged in the insulation box 15 and is used to monitor the temperature in the insulation box 15.

[0073] Specifically, by heating the heat preservation box 15 through the heater 16, a high temperature environment can be provided for the experimental rock sample 2, thereby simulating the formation environment more realistically.

[0074] Through the above technical scheme, that is, by injecting liquid into the confining pressure cavity between the core holder and the experimental rock sample through the confining pressure injection unit to establish confining pressure, the overburden pressure on the experimental rock sample can be simulated, and by injecting condensate gas or natural gas into the interior of the experimental rock sample through the internal pressure injection unit, the formation pressure on the experimental rock sample can be simulated, and by adjusting the back pressure valve to change the outlet pressure of the experimental rock sample, the change of the net stress on the experimental rock sample can be simulated, wherein, after the condensate gas is injected into the interior of the experimental rock sample through the internal pressure injection unit to make its outlet pressure reach the original formation pressure value before the gas storage reservoir is built, the outlet pressure of the experimental rock sample is gradually reduced by adjusting the back pressure valve to make it reach the initial formation pressure when the gas storage reservoir is built. The value can simulate the initial state of the condensate gas reservoir before the construction of the gas storage and the process of converting the condensate gas reservoir into a gas storage. When natural gas is injected into the experimental rock sample through the internal pressure injection unit to make its outlet pressure reach the upper limit pressure value of the gas storage during operation, the outlet pressure of the experimental rock sample is gradually reduced by adjusting the back pressure valve to make it reach the lower limit pressure value of the gas storage during operation. Repeating the above steps many times can simulate the multi-cycle injection and production process of the gas storage during operation. In this way, the process of converting the condensate gas reservoir into a gas storage and the multi-cycle injection and production process of the gas storage during operation can be truly simulated, thereby providing technical support for analyzing the near-well blockage of the gas storage and ensuring the efficient and stable operation of the gas storage.

[0075] The embodiment of the present application further provides a near-wellbore blockage experiment simulation method for a gas storage, which is applied to the above-mentioned near-wellbore blockage experiment simulation device for a gas storage. The near-wellbore blockage experiment simulation method for a gas storage includes:

[0076] Step S1: placing the experimental rock sample into the core holder;

[0077] Step S2: injecting liquid into the confining pressure chamber through the confining pressure injection device, and stopping the injection of liquid when the pressure of the confining pressure chamber monitored by the first pressure monitoring unit reaches the pressure value of the overlying rock formation of the gas storage reservoir;

[0078] Step S3: injecting condensate gas into the interior of the experimental rock sample through the internal pressure injection device, and stopping the injection of condensate gas when the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the original formation pressure value of the gas storage before the storage is built;

[0079] Step S4: adjusting the back pressure valve so that the outlet pressure of the experimental rock sample is gradually reduced until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the initial formation pressure value when the gas storage reservoir is built;

[0080] Step S5: injecting natural gas into the interior of the experimental rock sample through the internal pressure injection device, and stopping the injection of natural gas when the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the upper limit pressure value of the gas storage reservoir during operation;

[0081] Step S6: adjusting the back pressure valve so that the outlet pressure of the experimental rock sample is gradually reduced until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the lower limit pressure value of the gas storage reservoir during operation;

[0082] Step S7: Repeat steps S5 and S6 until a preset number of cycles is reached.

[0083] Specifically, in step S1, the prepared experimental rock sample is placed in the core holder, and at the same time, the overburden stratum pressure value of the gas storage, the original formation pressure value of the gas storage before the construction of the gas storage, the initial formation pressure value of the gas storage when the gas storage is constructed, the upper limit pressure value of the gas storage when it is in operation, and the lower limit pressure value of the gas storage when it is in operation can be determined according to the operation data of the gas storage, wherein the original formation pressure value of the gas storage before the construction of the gas storage refers to the original formation pressure value of the condensate gas reservoir before it is converted into a gas storage, that is, the formation pressure value of the condensate gas reservoir before exploitation, and the initial formation pressure value of the gas storage when the gas storage is constructed refers to the initial formation pressure value of the condensate gas reservoir when it is converted into a gas storage, that is, the formation pressure value when the condensate gas reservoir has been exploited and abandoned or exploited to a certain extent and retired. It can be understood that, since the pressure of the condensate gas reservoir will gradually decrease during the exploitation process, the original formation pressure value of the gas storage before the construction of the gas storage is greater than the initial formation pressure value of the gas storage when it is constructed.

[0084] In step S2, liquid is injected into the confining pressure chamber through the confining pressure injection device to establish confining pressure, so that it reaches the overburden pressure value, and the confining pressure is kept constant during the entire simulation experiment. At the same time, the core holder can be heated and the temperature can be adjusted to the reservoir temperature of the gas storage reservoir, so as to simulate the formation environment more realistically. In order to establish pressure at the outlet of the experimental rock sample in subsequent steps, back pressure can be added to the outlet of the experimental rock sample in advance or the back pressure valve can be closed, wherein the initial back pressure can be the same as the initial formation pressure value when the gas storage reservoir is built.

[0085] In step S3, the compounded condensate gas is injected into the interior of the experimental rock sample by the internal pressure injection device until the outlet pressure of the experimental rock sample increases to the original formation pressure value before the gas storage reservoir was built, so as to realize the experimental simulation of the initial state of the condensate gas reservoir. At the same time, it is also possible to. It is understandable that the initial state of the condensate gas reservoir will be maintained for a period of time. Therefore, the outlet pressure of the experimental rock sample can be maintained at the original formation pressure value before the gas storage reservoir was built, and maintained for several hours, for example, it can be maintained for 12 hours. Among them, when injecting condensate gas, the inlet pressure of the experimental rock sample needs to be less than the pressure of the confining pressure chamber, otherwise leakage may occur.

[0086] In step S4, the back pressure valve is adjusted to reduce the outlet pressure of the experimental rock sample step by step, for example, by 3 to 5 MPa each time, until the outlet pressure of the experimental rock sample is reduced to the initial formation pressure value when the gas storage is built, so as to realize the experimental simulation of the condensate gas reservoir exploitation process. At the same time, condensate gas can also be injected into the interior of the experimental rock sample step by step to simulate the process of cushioning gas. After the simulation of cushioning gas is completed, condensate gas is injected again to increase the outlet pressure of the experimental rock sample to the upper limit pressure value of the gas storage when it is in operation, so as to realize the experimental simulation of the process of converting the condensate gas reservoir into a gas storage.

[0087] In step S5, the compounded natural gas is injected into the interior of the experimental rock sample by the internal pressure injection device until the outlet pressure of the experimental rock sample increases to the upper limit pressure value of the gas storage reservoir during operation, so as to realize the experimental simulation of the gas injection process of the gas storage reservoir. It is understandable that due to the relatively large displacement pressure, it takes a certain amount of time for the natural gas to form pressure inside the experimental rock sample. Therefore, the outlet pressure of the experimental rock sample can be maintained at the upper limit pressure value of the gas storage reservoir during operation and maintained for several hours, for example, it can also be maintained for 12 hours. Among them, when injecting natural gas, the inlet pressure of the experimental rock sample also needs to be less than the pressure of the confining pressure chamber to avoid leakage.

[0088] In step S6, the back pressure valve is adjusted so that the outlet pressure of the experimental rock sample is gradually reduced, for example, it can also be reduced by 3 to 5 MPa each time, until the outlet pressure of the experimental rock sample is reduced to the lower limit pressure value of the gas storage reservoir during operation, so as to realize the experimental simulation of the gas production process of the gas storage reservoir. After the experimental simulation of the gas production process is completed, the pressure can be kept stable for a period of time, for example, for 4 hours, and then the next stage of simulation experiment can be started.

[0089] In step S7, after completing the simulated gas production of step S6, the simulated gas injection of step S5 and the simulated gas production of step S6 are repeated until a preset number of cycles is reached. The preset number of cycles can be set according to the number of cycles of the multi-cycle gas injection and production cycle of the gas storage, for example, it can be set to 5 times.

[0090] Furthermore, in one embodiment, before step S1, the near-wellbore plugging experiment simulation method further includes:

[0091] Clean and dry the experimental rock samples;

[0092] The cleaned and dried experimental rock samples were vacuum treated.

[0093] Specifically, first, all the fluids originally existing in the experimental rock samples need to be cleaned. Considering that the solvent and cleaning method of the crude oil in the pores of the experimental rock samples will affect the structure of the clay minerals, the experimental rock samples can be washed to hydrophilic according to the provisions of SY / T 5336 based on the composition of the experimental rock samples. Among them, if the composition of the experimental rock samples is unknown before washing, the crude oil in the experimental rock samples can be washed with a mixture of alcohol and rice. If the mineralization of the formation water is higher than 2000 mg / L or the formation water data is unknown, it is also necessary to use methanol and other reagents to desalinate the experimental rock samples.

[0094] Secondly, when drying the experimental rock samples, in order to ensure that the properties of clay and gypsum in the experimental rock samples do not change, the drying temperature needs to be controlled at no more than 60°C, and the relative humidity should be controlled at 40% to 50%. Each experimental rock sample should be dried to constant weight for no less than 48 hours, and weighed every 8 hours after 48 hours. The difference between the two weighings is less than 10 mg, which is considered to be up to standard.

[0095] Finally, since the near-well blockage of the gas storage reservoir will have various degrees of influence on the porosity, permeability, rock compression coefficient, etc. of the reservoir, and ultimately affect the efficient and stable operation of the gas storage reservoir, saturated air is required to measure the initial permeability and porosity of the experimental rock sample before conducting the simulation experiment. Specifically, the dried experimental rock sample is vacuumed, the initial permeability of the experimental rock sample is measured by saturated air, the saturated pressure is maintained for at least 12 hours, and the mass difference of the experimental rock sample before and after saturation is measured, and the effective pore volume and porosity of the experimental rock sample are calculated according to the formula. Among them, the initial permeability of the experimental rock sample measured by saturated air and the effective pore volume and porosity of the experimental rock sample calculated can refer to the prior art, and the embodiments of this application will not be repeated.

[0096] In one embodiment, the near-wellbore plugging experimental simulation method further includes:

[0097] Obtaining the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber, and the flow rate of the natural gas flowing out of the outlet end of the experimental rock sample;

[0098] The permeability, porosity and compressibility of the experimental rock sample are determined according to the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber and the flow rate of natural gas.

[0099] Further, in one embodiment, the above steps of determining the permeability, porosity and compressibility of the experimental rock sample according to the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber and the flow rate of natural gas may include the following steps:

[0100] The permeability of the experimental rock sample is determined according to formula (1):

[0101]

[0102] The porosity of the experimental rock sample is determined according to formula (2):

[0103] φ=a(P3-P2) 3 +b(P3-P2) 2 +c(P3-P2)+d Formula (2)

[0104] The compression coefficient of the experimental rock sample is determined according to formula (3):

[0105]

[0106] Where K represents the permeability of the experimental rock sample, represents the porosity of the experimental rock sample, C f represents the compression coefficient of the experimental rock sample, P1 represents the inlet pressure of the experimental rock sample, P2 represents the outlet pressure of the experimental rock sample, P3 represents the pressure of the confining pressure chamber, Q represents the flow rate of natural gas, P represents the standard atmospheric pressure, μ represents the viscosity value of natural gas, L represents the length of the experimental rock sample, A represents the cross-sectional area of ​​the experimental rock sample, and a, b, c, and d represent regression coefficients.

[0107] Specifically, during the simulated gas injection process, the outlet pressure of the experimental rock sample gradually increases, and during the simulated gas production process, the outlet pressure of the experimental rock sample gradually decreases. Experimental data can be obtained at multiple pressure points, and the permeability, porosity and compression coefficient of the experimental rock sample corresponding to the pressure point can be calculated. At the same time, in the process of simulating the reconstruction of a gas storage facility from a condensate gas reservoir, experimental data can also be obtained at multiple pressure points, and the permeability, porosity and compression coefficient of the experimental rock sample corresponding to the pressure point can be calculated. In this way, combined with the initial permeability, initial porosity and initial compression coefficient of the experimental rock sample measured before the simulation experiment, the change rate of the permeability, porosity and compression coefficient of the experimental rock sample during the simulation experiment can be calculated. Therefore, through the near-well plugging experiment simulation of the gas storage facility, the key parameters of the reservoir such as permeability, porosity and compression coefficient can be identified as the gas storage facility is built and the injection and production cycle during operation changes, providing an important reference for the efficient and stable operation of the gas storage facility, storage capacity calculation and multi-cycle time-varying numerical simulation.

[0108] Specifically, the change rate of the permeability of the experimental rock sample can be determined by the following formula:

[0109]

[0110] The porosity change rate of the experimental rock sample can be determined by the following formula:

[0111]

[0112] The rate of change of the compression coefficient of the experimental rock sample can be determined by the following formula:

[0113]

[0114] Among them, D stk represents the rate of change of the permeability of the experimental rock sample, represents the porosity change rate of the experimental rock sample, D stc Represents the rate of change of the compression coefficient of the experimental rock sample, K i represents the initial permeability of the experimental rock sample, K n represents the permeability of the experimental rock sample calculated at the nth outlet pressure, represents the initial porosity of the experimental rock sample, represents the porosity of the experimental rock sample calculated at the nth outlet pressure, C i represents the initial compression coefficient of the experimental rock sample, C n Represents the compression coefficient of the experimental rock sample calculated at the nth outlet pressure.

[0115] For more details about the near-wellbore blockage experimental simulation method for a gas storage facility in the embodiment of the present application, please refer to the above description of the near-wellbore blockage experimental simulation device for a gas storage facility, and the same or corresponding technical effects as those of the above-mentioned near-wellbore blockage experimental simulation device for a gas storage facility can be achieved, so they will not be repeated here.

[0116] In summary, through the above method, that is, injecting liquid into the confining pressure cavity between the core holder and the experimental rock sample through the confining pressure injection unit to establish confining pressure, the overburden pressure on the experimental rock sample can be simulated, and the condensate gas or natural gas is injected into the interior of the experimental rock sample through the internal pressure injection unit to simulate the formation pressure on the experimental rock sample, and the outlet pressure of the experimental rock sample is changed by adjusting the back pressure valve to simulate the change of the net stress on the experimental rock sample, wherein, after the condensate gas is injected into the interior of the experimental rock sample through the internal pressure injection unit to make its outlet pressure reach the original formation pressure value before the gas storage reservoir is built, the outlet pressure of the experimental rock sample is gradually reduced by adjusting the back pressure valve to make it reach the initial formation pressure value when the gas storage reservoir is built. The force value can simulate the initial state of the condensate gas reservoir before the construction of the gas storage and the process of converting the condensate gas reservoir into a gas storage. After natural gas is injected into the experimental rock sample through the internal pressure injection unit to make its outlet pressure reach the upper limit pressure value of the gas storage during operation, the outlet pressure of the experimental rock sample is gradually reduced by adjusting the back pressure valve to make it reach the lower limit pressure value of the gas storage during operation. Repeating the above steps many times can simulate the multi-cycle injection and production process of the gas storage during operation. In this way, the process of converting the condensate gas reservoir into a gas storage and the multi-cycle injection and production process of the gas storage during operation can be truly simulated, thereby providing technical support for analyzing the near-well blockage of the gas storage and ensuring the efficient and stable operation of the gas storage.

[0117] In order to illustrate that the near-wellbore plugging experimental simulation method for a gas storage provided in the embodiment of the present application is capable of identifying the changing patterns of key parameters such as reservoir permeability, porosity and compressibility during the construction process of the gas storage and the injection-production cycle during operation, the results of Example 1 are listed below for illustration.

[0118] Embodiment 1

[0119] In the first embodiment, a simulation experiment of near-wellbore blockage of a gas storage reservoir was conducted according to the above-mentioned simulation method for near-wellbore blockage experiment of a gas storage reservoir.

[0120] The initial data of the experimental rock samples before the simulation experiment is shown in Table 1.

[0121] Table 1

[0122] Length (cm) 4.88 Diameter(cm) 2.47 Dry weight (g) 56.78 Initial porosity 0.10 <![CDATA[Initial permeability (10 -3 μm 2 )]]> 0.1458 Water saturation (%) 5.2

[0123] The permeability and porosity data of the experimental rock samples in the first gas injection and production cycle simulation experiment are shown in Table 2.

[0124] Table 2

[0125]

[0126] The permeability and porosity data of the experimental rock samples in the second gas injection and production cycle simulation experiment are shown in Table 3.

[0127] Table 3

[0128]

[0129] The permeability and porosity data of the experimental rock samples in the third gas injection and production cycle simulation experiment are shown in Table 4.

[0130] Table 4

[0131]

[0132] The permeability and porosity data of the experimental rock samples in the fourth gas injection and production cycle simulation experiment are shown in Table 5.

[0133] Table 5

[0134]

[0135] The permeability and porosity data of the experimental rock samples in the fifth gas injection and production cycle simulation experiment are shown in Table 6.

[0136] Table 6

[0137]

[0138] According to the initial permeability and initial porosity of the experimental rock sample measured before the simulation experiment, and the permeability and porosity of the experimental rock sample calculated during the simulation experiment, the following can be drawn: Figure 2 The permeability curve of the experimental rock sample during multi-cycle injection and production is shown in Figure 3 The porosity change curve of the experimental rock sample during multi-cycle injection and production is shown.

[0139] from Figure 2 and Figure 3 It can be seen that the permeability of the experimental rock sample increased during the second injection-production cycle simulation experiment, and then continued to decrease as the injection-production cycle progressed; the porosity of the experimental rock sample decreased by 7.8% relative to multiple cycles.

[0140] By analyzing the experimental results, the near-wellbore blockage experimental simulation method for a gas storage provided in the embodiment of the present application can identify the changing patterns of key parameters such as reservoir permeability, porosity and compressibility during the construction process of the gas storage and the injection-production cycle during operation, thereby providing technical support for analyzing near-wellbore blockage of a gas storage and ensuring efficient and stable operation of the gas storage.

[0141] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0142] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for simulating near-wellbore blockage experiments for gas storage, characterized in that: A near-wellbore blockage experiment simulation device for a gas storage reservoir is applied, and the near-wellbore blockage experiment simulation device for a gas storage reservoir comprises: A core holder, used for placing an experimental rock sample, wherein a confining pressure cavity is formed between the core holder and the experimental rock sample; a confining pressure injection unit, connected to the confining pressure chamber and used for injecting liquid into the confining pressure chamber; An internal pressure injection unit, connected to the inlet end of the experimental rock sample, for selectively injecting condensate gas or natural gas into the interior of the experimental rock sample; a back pressure valve connected to the outlet end of the experimental rock sample; a first pressure monitoring unit, disposed on the core holder, for monitoring the pressure of the confining pressure chamber; A second pressure monitoring unit is provided at the outlet end of the experimental rock sample and is used to monitor the outlet pressure of the experimental rock sample; The near-wellbore plugging experimental simulation method comprises the following steps: S1, placing the experimental rock sample into the core holder; S2, injecting the liquid into the confining pressure chamber through the confining pressure injection unit, and stopping the injection of the liquid when the pressure of the confining pressure chamber monitored by the first pressure monitoring unit reaches the overlying rock formation pressure value of the gas storage reservoir; S3, injecting the condensate gas into the interior of the experimental rock sample through the internal pressure injection unit, and stopping the injection of the condensate gas when the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the original formation pressure value of the gas storage before the gas storage is built; S4, adjusting the back pressure valve so that the outlet pressure of the experimental rock sample is gradually reduced until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the initial formation pressure value of the gas storage when the gas storage is built; S5, injecting the natural gas into the interior of the experimental rock sample through the internal pressure injection unit, and stopping the injection of the natural gas when the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the upper limit pressure value of the gas storage during operation; S6. Regulating the back pressure valve so that the outlet pressure of the experimental rock sample is gradually reduced until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches the lower limit pressure value of the gas storage reservoir during operation; S7, repeating step S5 and step S6 until a preset number of cycles is reached; Obtaining the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber, and the flow rate of the natural gas flowing out of the outlet end of the experimental rock sample; Determining the permeability, porosity and compressibility of the experimental rock sample according to the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber and the flow rate of the natural gas; The step of determining the permeability, porosity and compressibility of the experimental rock sample according to the inlet pressure of the experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of the confining pressure chamber and the flow rate of the natural gas comprises: The permeability of the experimental rock sample is determined according to formula (1): Formula (1) The porosity of the experimental rock sample is determined according to formula (2): Formula (2) The compression coefficient of the experimental rock sample is determined according to formula (3): Formula (3) in, K represents the permeability of the experimental rock sample, φ represents the porosity of the experimental rock sample, C f represents the compressibility factor of the experimental rock sample, P 1 represents the inlet pressure of the experimental rock sample, P 2 represents the outlet pressure of the experimental rock sample, P 3 represents the pressure of the confining pressure chamber, Q represents the flow rate of the natural gas, P represents standard atmospheric pressure, μ represents the viscosity value of the natural gas, L represents the length of the experimental rock sample, A represents the cross-sectional area of ​​the experimental rock sample, and a, b, c, and d represent regression coefficients.

2. The near-wellbore plugging experimental simulation method according to claim 1, characterized in that: Before step S1, the near-wellbore plugging experimental simulation method further includes: Clean and dry the experimental rock samples; The cleaned and dried experimental rock samples were vacuum treated.

3. The method for simulating near-wellbore blockage experiment for a gas storage according to claim 1, characterized in that: The confining pressure injection unit includes a confining pressure pump.

4. The method for simulating near-wellbore blockage experiment for a gas storage according to claim 1, characterized in that: The internal pressure injection unit includes a displacement pump, a first gas storage element and a second gas storage element. The displacement pump is connected to the inlet end of the first gas storage element and the inlet end of the second gas storage element respectively. The outlet end of the first gas storage element and the outlet end of the second gas storage element are both connected to the inlet end of the experimental rock sample. The first gas storage element is used to store the condensate gas, and the second gas storage element is used to store the natural gas.

5. The method for simulating near-wellbore blockage experiment for a gas storage according to claim 4, characterized in that: A first valve is arranged between the displacement pump and the inlet end of the first gas storage element, a second valve is arranged between the displacement pump and the inlet end of the second gas storage element, and a third valve is arranged between the outlet end of the first gas storage element, the outlet end of the second gas storage element and the inlet end of the experimental rock sample.

6. The method for simulating near-wellbore blockage experiment for a gas storage according to claim 1, characterized in that: The near-well blockage experimental simulation device also includes: a third pressure monitoring unit, disposed at the inlet end of the experimental rock sample, for monitoring the inlet pressure of the experimental rock sample; A flow monitoring unit is arranged at the outlet end of the experimental rock sample and is used to monitor the flow of the natural gas flowing out from the outlet end of the experimental rock sample.

7. The method for simulating near-wellbore blockage experiment for a gas storage according to claim 1, characterized in that: The near-well blockage experimental simulation device also includes: A heat preservation box, arranged outside the core holder; A heater, disposed in the heat preservation box, for heating the heat preservation box; The temperature monitoring unit is arranged in the heat preservation box and is used to monitor the temperature in the heat preservation box.

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