CN114961715B - Near-well blockage experiment simulation device and method for gas storage - Google Patents
Near-well blockage experiment simulation device and method for gas storage Download PDFInfo
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Abstract
本申请实施例提供一种用于储气库的近井堵塞实验模拟装置及方法。装置包括：岩心夹持器，用于放置实验岩样，岩心夹持器与实验岩样之间形成围压腔；围压注入单元，与围压腔相连，用于向围压腔注入液体；内压注入单元，与实验岩样的入口端相连，用于选择性的向实验岩样的内部注入凝析气或天然气；回压阀，与实验岩样的出口端相连；第一压力监测单元，设置在岩心夹持器上，用于监测围压腔的压力；第二压力监测单元，设置在实验岩样的出口端，用于监测实验岩样的出口压力。通过上述技术方案，能够真实模拟凝析气藏改建储气库的过程以及储气库运行时的多周期注采过程，从而为分析储气库的近井堵塞提供技术支撑，保证储气库的高效稳定运行。
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 and used to inject liquid into the confining pressure cavity; an internal pressure injection unit connected to the inlet end of the experimental rock sample and 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, arranged on the core holder, for monitoring the pressure of the confining pressure cavity; a second pressure monitoring unit, arranged 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
The application relates to the technical field of oil gas development, in particular to a near well blockage experimental simulation device and method for a gas storage.
Background
Depleted oil and gas reservoir gas reservoirs are gas reservoirs built using depleted and abandoned gas reservoirs that have been exploited or retired gas reservoirs exploited to some extent. In addition, various liquid hydrocarbons inevitably exist in the gas storage in the multi-period injection and production process during operation, for example, a ground compressor is usually used for pressurizing injection during gas injection, lubricating oil of the ground compressor is easily injected into the reservoir along with the gas in the movement process of blades or cavities, and the lubricating oil is often subjected to catalytic transformation in a high-temperature and high-pressure environment to cause blockage of near wells and influence the stable operation of the gas storage.
At present, the construction of gas storages in China is still in the early investigation stage, particularly, the gas storages reconstructed from condensate gas reservoirs are rarely studied, and a large number of physical simulation experiments are needed to be carried out for analysis and evaluation on near well blockage caused by multi-period injection and production during the reconstruction of the condensate gas reservoirs and the operation of the gas storages. At present, a near well blockage experimental simulation device and method for an effective gas storage are lacked, and technical support is provided for guaranteeing efficient and stable operation of the gas storage.
Disclosure of Invention
In order to at least partially solve the above problems in the prior art, an object of an embodiment of the present application is to provide a near well blockage experimental simulation apparatus and method for a gas storage.
In order to achieve the above object, a first aspect of the present application provides a near well blockage experimental simulation apparatus for a gas storage, comprising:
the rock core holder is used for placing an experimental rock sample, and a confining pressure cavity is formed between the rock core holder and the experimental rock sample;
The confining pressure injection unit is connected with the confining pressure cavity and used for injecting liquid into the confining pressure cavity;
The internal pressure injection unit is connected with the inlet end of the experimental rock sample and is used for selectively injecting condensate gas or natural gas into the experimental rock sample;
The back pressure valve is connected with the outlet end of the experimental rock sample;
the first pressure monitoring unit is arranged on the core holder and is used for monitoring the pressure of the confining pressure cavity;
And the second pressure monitoring unit is arranged at the outlet end of the experimental rock sample and is used for monitoring the outlet pressure of the experimental rock sample.
In an embodiment of the application, the confining pressure injection unit comprises a confining pressure pump.
In the embodiment of the application, the internal pressure injection unit comprises a displacement pump, a first gas storage element and a second gas storage element, wherein the displacement pump is respectively connected with the inlet end of the first gas storage element and the inlet end of the second gas storage element, the outlet end of the first gas storage element and the outlet end of the second gas storage element are both connected with the inlet end of the experimental rock sample, the first gas storage element is used for storing condensate gas, and the second gas storage element is used for storing natural gas.
In the embodiment of the 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 inlet end of the second gas storage element and the inlet end of the experimental rock sample.
In the embodiment of the application, the near well blockage experimental simulation device further comprises:
The third pressure monitoring unit is arranged at the inlet end of the experimental rock sample and is used for monitoring the inlet pressure of the experimental rock sample;
And the flow monitoring unit is arranged at the outlet end of the experimental rock sample and is used for monitoring the flow of natural gas flowing out of the outlet end of the experimental rock sample.
In the embodiment of the application, the near well blockage experimental simulation device further comprises:
the insulation box is arranged outside the core holder;
The heater is arranged in the heat preservation box and used for heating the heat preservation box;
the temperature monitoring unit is arranged in the heat preservation box and used for monitoring the temperature in the heat preservation box.
The second aspect of the present application provides a near-well blockage test simulation method for a gas storage, which is applied to the near-well blockage test simulation device for a gas storage, and the near-well blockage test simulation method for a gas storage comprises the following steps:
s1, placing an experimental rock sample into a core holder;
S2, injecting liquid into the confining pressure cavity through the confining pressure injection device, and stopping injecting the liquid when the pressure of the confining pressure cavity monitored by the first pressure monitoring unit reaches the pressure value of the overlying strata of the gas storage;
s3, injecting condensate gas into the experimental rock sample through the internal pressure injection device, and stopping injecting the condensate gas when the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches an original stratum pressure value of the gas storage before the gas storage is established;
S4, adjusting the back pressure valve to enable the outlet pressure of the experimental rock sample to be reduced step by step until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches an initial stratum pressure value of the gas storage in a warehouse establishment process;
S5, natural gas is injected into the experimental rock sample through the internal pressure injection device, and 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 in operation, the natural gas injection is stopped;
s6, regulating the back pressure valve to gradually reduce the outlet pressure of the experimental rock sample 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 in operation;
s7, repeating the step S5 and the step S6 until the preset cycle times are reached.
In the embodiment of the application, before step S1, the near well blockage experimental simulation method further includes:
cleaning and drying the experimental rock sample;
And carrying out vacuumizing treatment on the cleaned and dried experimental rock sample.
In the embodiment of the application, the near well blockage experimental simulation method further comprises the following steps:
acquiring the inlet pressure of an experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of a confining pressure cavity and the flow rate of natural gas flowing out of the outlet end of the experimental rock sample;
And determining the permeability, the porosity and the compression coefficient 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 cavity and the flow rate of the natural gas.
In an embodiment of the present application, determining the permeability, the porosity and the compression coefficient 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 cavity and the flow rate of the natural gas includes:
Determining the permeability of the experimental rock sample according to formula (1):
determining the porosity of the experimental rock sample according to formula (2):
phi=a (P 3-P2)3+b(P3-P2)2+c(P3-P2) +d formula (2)
Determining the compression coefficient of the experimental rock sample according to formula (3):
wherein K represents the permeability of the experimental rock sample, Representing the porosity of the experimental rock sample, C f representing the compression coefficient of the experimental rock sample, P 1 representing the inlet pressure of the experimental rock sample, P 2 representing the outlet pressure of the experimental rock sample, P 3 representing the pressure of the confining pressure chamber, Q representing the flow rate of natural gas, P representing the standard atmospheric pressure, μ representing the viscosity value of natural gas, L representing the length of the experimental rock sample, a representing the cross-sectional area of the experimental rock sample, a, b, C, d representing the regression coefficient.
Through the technical proposal, namely, the confining pressure injection unit is used for injecting liquid into the confining pressure cavity between the core holder and the experimental rock sample to establish confining pressure, the overlying strata pressure suffered by the experimental rock sample can be simulated, the condensate gas or the natural gas is injected into the experimental rock sample through the internal pressure injection unit, the stratum pressure suffered by the experimental rock sample can be simulated, the outlet pressure of the experimental rock sample is changed through adjusting the back pressure valve, the change of the net stress suffered by the experimental rock sample can be simulated, wherein when the condensate gas is injected into the experimental rock sample through the internal pressure injection unit to lead the outlet pressure to reach the original stratum pressure value before the gas storage is built, the outlet pressure of the experimental rock sample is gradually reduced through adjusting the back pressure valve to lead the outlet pressure of the experimental rock sample to reach the original stratum pressure value when the gas storage is built, the method can simulate the initial state of the condensate gas reservoir before the gas reservoir is built, the process of rebuilding the gas reservoir by the condensate gas reservoir and other experiments, after the internal pressure injection unit is used for injecting natural gas into the experimental rock sample to enable the outlet pressure of the natural gas to reach the upper limit pressure value of the gas reservoir during operation, the back pressure valve is regulated to gradually reduce the outlet pressure of the experimental rock sample to enable the outlet pressure of the experimental rock sample to reach the lower limit pressure value of the gas reservoir during operation, and the steps are repeated for a plurality of times, so that the method can simulate the experiments of multi-period injection and production process and the like during operation of the gas reservoir, and can truly simulate the process of rebuilding the gas reservoir by the condensate gas reservoir and the multi-period injection and production process during operation of the gas reservoir, thereby providing technical support for analyzing the near well blockage of the gas reservoir and ensuring the efficient and stable operation of the gas reservoir.
Additional features and advantages of embodiments of the application will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of embodiments of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain, without limitation, the embodiments of the application. In the drawings:
FIG. 1 is a schematic diagram of a near well plugging experimental simulation apparatus for a gas storage provided in an embodiment of the present application;
FIG. 2 is a graph of the variation in permeability of an experimental rock sample at the time of multi-cycle injection and production for example one of the near well plugging experimental simulation methods for gas reservoirs provided in the examples of the present application;
Fig. 3 is a graph showing the variation of the porosity of an experimental rock sample at the time of multi-cycle injection and production in an embodiment one of the near well plugging experimental simulation method for gas reservoirs provided in the embodiment of the present application.
Description of the reference numerals
1.2, Experimental rock samples;
3. a confining pressure injection unit, a back pressure valve;
5. 6, a second pressure monitoring unit;
7. a displacement pump 8, a first gas storage element;
9. the first valve is arranged on the first gas storage element;
11. a second valve, a third valve;
13. 14, a flow monitoring unit;
15. A heat preservation box, a heater and a heating device;
17. And a temperature monitoring unit.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it should be understood that the detailed description described herein is merely for illustrating and explaining the embodiments of the present application, and is not intended to limit the embodiments of the present application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
Fig. 1 is a schematic structural diagram of a near well blockage experimental simulation device for a gas storage according to an embodiment of the present application. In one embodiment of the present application, as shown in fig. 1, there is provided a near well plugging experimental simulation apparatus for a gas storage, comprising a core holder 1 for holding an experimental rock sample 2, a confining pressure injection unit 3 connected to the confining pressure cavity for injecting a liquid into the confining pressure cavity, an internal pressure injection unit connected to an inlet end of the experimental rock sample 2 for selectively injecting condensate gas or natural gas into an interior of the experimental rock sample 2, a back pressure valve 4 connected to an outlet end of the experimental rock sample 2, a first pressure monitoring unit 5 provided on the core holder 1 for monitoring a pressure of the confining pressure cavity, and a second pressure monitoring unit 6 provided at an outlet end of the experimental rock sample 2 for monitoring an outlet pressure of the experimental rock sample 2.
Specifically, the core holder 1 may be a hollow structure, and is used for placing an experimental rock sample 2, where the experimental rock sample 2 may be a natural core that is drilled, and is prepared after cleaning, drying, vacuumizing, and other treatments, and the shape of the experimental rock sample 2 may be a plunger shape, and is suitable for clamping. A confining pressure cavity is formed between the core holder 1 and the experimental rock sample 2, and liquid is injected into the confining pressure cavity through the confining pressure injection unit 3 to establish confining pressure, so that the overburden pressure applied by the experimental rock sample 2 can be simulated, wherein the overburden pressure refers to the pressure of an upper overburden layer in a reservoir layer on a lower rock unit. In general, there are relatively narrow passages, i.e. pore throats, interconnecting pores in a rock mass or body, so that fluids can circulate through the rock mass. By injecting condensate gas or natural gas into the inside of the experimental rock sample 2 through the internal pressure injection unit, it is possible to simulate the formation pressure to which the experimental rock sample 2 is subjected, wherein the formation pressure refers to the fluid pressure to which the rock in the reservoir is subjected. By varying the outlet pressure of the experimental rock sample 2 by adjusting the back pressure valve 4, the change in net stress experienced by the experimental rock sample 2, where net stress is the difference between the overburden pressure and the formation pressure, also known as the effective overburden pressure, can be simulated.
After the condensate gas is injected into the experimental rock sample 2 through the internal pressure injection unit to enable the outlet pressure of the condensate gas to reach the original stratum pressure value before the gas storage is built, the outlet pressure of the experimental rock sample 2 is gradually reduced through adjusting the back pressure valve 4 to enable the outlet pressure of the experimental rock sample to reach the original stratum pressure value when the gas storage is built, and experiments such as the initial state of the condensate gas storage before the gas storage is built and the process of rebuilding the gas storage by the condensate gas storage can be simulated. After natural gas is injected into the experimental rock sample 2 through the internal pressure injection unit to enable the outlet pressure of the natural gas to reach the upper limit pressure value of the gas storage in operation, the outlet pressure of the experimental rock sample is reduced step by step through adjusting the back pressure valve 4 to enable the natural gas to reach the lower limit pressure value of the gas storage in operation, the steps are repeated for a plurality of times, and experiments such as multi-period injection and production processes of the gas storage in operation can be simulated. By the method, the process of rebuilding the gas storage by the condensate gas reservoir and the multi-period injection and production process during the operation of the gas storage can be truly simulated, so that technical support is provided for analyzing the near well blockage of the gas storage, and the high-efficiency and stable operation of the gas storage is ensured.
In one embodiment, the confining pressure injection unit 3 comprises a confining pressure pump.
In particular, the overburden pressure to which the rock in the reservoir is subjected may be considered to be generally constant, so that the confining pressure pump may be a constant pressure pump connected to the confining pressure chamber by a pipeline, wherein the liquid injected into the confining pressure chamber may be clean water for simulating the groundwater environment.
In one embodiment, the internal pressure injection unit comprises a displacement pump 7, a first gas storage element 8 and a second gas storage element 9, wherein the displacement pump 7 is respectively connected with the inlet end of the first gas storage element 8 and the inlet end of the second gas storage element 9, the outlet end of the first gas storage element 8 and the outlet end of the second gas storage element 9 are both connected with the inlet end of the experimental rock sample 2, the first gas storage element 8 is used for storing condensate gas, and the second gas storage element 9 is used for storing natural gas.
Specifically, by pumping liquid into the first gas storage element 8 or the second gas storage element 9 by 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 inside of the experimental rock sample 2. The condensate gas and the natural gas can be compounded through ground sampling, ground condensate oil and ground natural gas are compounded according to a direct phase recovery method, the condensate oil is produced and sampled from a gas storage, and the ground natural gas is prepared according to the composition.
Further, 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.
Specifically, when it is necessary to inject condensate gas into the inside of the experimental rock sample 2, the back pressure valve 4 and the second valve 11 may be closed, and the first valve 10 and the third valve 12 may be opened. When it is desired to inject natural gas into the interior of the laboratory rock sample 2, the back pressure valve 4 and the first valve 10 may be closed and the second valve 11 and the third valve 12 may be opened.
In one embodiment, the near-well plugging experimental simulation device further comprises a third pressure monitoring unit 13 arranged at the inlet end of the experimental rock sample 2 for monitoring the inlet pressure of the experimental rock sample 2, and a flow monitoring unit 14 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.
Specifically, the first pressure monitoring unit 5, the second pressure monitoring unit 6, and the third pressure monitoring unit 13 may each employ a high-precision pressure gauge, and the flow monitoring unit 14 may employ a high-precision flow meter.
In one embodiment, the near-well blockage experimental simulation device further comprises an insulation box 15 arranged outside the core holder 1, a heater 16 arranged in the insulation box 15 and used for heating the insulation box 15, and a temperature monitoring unit 17 arranged in the insulation box 15 and used for monitoring the temperature in the insulation box 15.
Specifically, the incubator 15 is heated by the heater 16, so that a high-temperature environment can be provided for the experimental rock sample 2, and the stratum environment can be simulated more truly.
Through the technical proposal, namely, the confining pressure injection unit is used for injecting liquid into the confining pressure cavity between the core holder and the experimental rock sample to establish confining pressure, the overlying strata pressure suffered by the experimental rock sample can be simulated, the condensate gas or the natural gas is injected into the experimental rock sample through the internal pressure injection unit, the stratum pressure suffered by the experimental rock sample can be simulated, the outlet pressure of the experimental rock sample is changed through adjusting the back pressure valve, the change of the net stress suffered by the experimental rock sample can be simulated, wherein when the condensate gas is injected into the experimental rock sample through the internal pressure injection unit to lead the outlet pressure to reach the original stratum pressure value before the gas storage is built, the outlet pressure of the experimental rock sample is gradually reduced through adjusting the back pressure valve to lead the outlet pressure of the experimental rock sample to reach the original stratum pressure value when the gas storage is built, the method can simulate the initial state of the condensate gas reservoir before the gas reservoir is built, the process of rebuilding the gas reservoir by the condensate gas reservoir and other experiments, after the internal pressure injection unit is used for injecting natural gas into the experimental rock sample to enable the outlet pressure of the natural gas to reach the upper limit pressure value of the gas reservoir during operation, the back pressure valve is regulated to gradually reduce the outlet pressure of the experimental rock sample to enable the outlet pressure of the experimental rock sample to reach the lower limit pressure value of the gas reservoir during operation, and the steps are repeated for a plurality of times, so that the method can simulate the experiments of multi-period injection and production process and the like during operation of the gas reservoir, and can truly simulate the process of rebuilding the gas reservoir by the condensate gas reservoir and the multi-period injection and production process during operation of the gas reservoir, thereby providing technical support for analyzing the near well blockage of the gas reservoir and ensuring the efficient and stable operation of the gas reservoir.
The embodiment of the application also provides a near well blockage experimental simulation method for the gas storage, which is applied to the near well blockage experimental simulation device for the gas storage, and comprises the following steps:
step S1, placing an experimental rock sample into a core holder;
s2, injecting liquid into the confining pressure cavity through the confining pressure injection device, and stopping injecting the liquid when the pressure of the confining pressure cavity monitored by the first pressure monitoring unit reaches the pressure value of the overlying strata of the gas storage;
S3, injecting condensate gas into the experimental rock sample through the internal pressure injection device, and stopping injecting the condensate gas when the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches an original stratum pressure value of the gas storage before the gas storage is built;
S4, adjusting a back pressure valve to gradually reduce the outlet pressure of the experimental rock sample until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches an initial stratum pressure value of the gas storage in a warehouse establishment process;
S5, injecting natural gas into the experimental rock sample through the internal pressure injection device, and stopping injecting 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 in operation;
Step S6, adjusting a back pressure valve to gradually reduce the outlet pressure of the experimental rock sample until the outlet pressure of the experimental rock sample monitored by the second pressure monitoring unit reaches a lower limit pressure value of the gas storage in operation;
and S7, repeating the step S5 and the step S6 until the preset cycle times are reached.
Specifically, in step S1, the prepared experimental rock sample is placed in the core holder, and meanwhile, an overburden pressure value of the gas storage, an original formation pressure value before the gas storage is built, an initial formation pressure value when the gas storage is built, an upper limit pressure value when the gas storage is operated, and a lower limit pressure value when the gas storage is operated can be determined according to operation data of the gas storage, wherein the original formation pressure value before the gas storage is built refers to an original formation pressure value before the gas storage is rebuilt into the gas storage, namely, a formation pressure value before the gas storage is mined, and the initial formation pressure value when the gas storage is built refers to an initial formation pressure value when the gas storage is rebuilt into the gas storage, namely, a formation pressure value when the gas storage is mined out or is mined to a certain extent out. It will be appreciated that the original formation pressure value of the gas reservoir prior to reservoir establishment is greater than the original formation pressure value of the gas reservoir at reservoir establishment, as the pressure of the condensate gas reservoir gradually decreases during production.
In step S2, liquid is injected into the confining pressure cavity through the confining pressure injection device to establish confining pressure so as to enable the confining pressure to reach the overlying strata pressure value, and the confining pressure is kept unchanged in the whole simulation experiment process. Meanwhile, the core holder can be heated, and the temperature is regulated to the reservoir temperature of the gas storage, so that the stratum environment is simulated more truly. In order to build up pressure at the outlet of the experimental rock sample in a subsequent step, a back pressure may also be added or a back pressure valve may be closed at the outlet of the experimental rock sample in advance, wherein the initial back pressure may be the same as the initial formation pressure value of the gas reservoir when the reservoir is built up.
In step S3, the mixed condensate gas is injected into the experimental rock sample through the internal pressure injection device until the outlet pressure of the experimental rock sample is increased to the original stratum pressure value of the gas storage before the reservoir is established, so that experimental simulation of the initial state of the condensate gas reservoir is realized. At the same time, the two can also be paired. It will be appreciated that the initial state of the condensate reservoir will be maintained for a period of time, so that the outlet pressure of the experimental rock sample may be maintained at the original formation pressure value of the reservoir prior to its construction and for a period of hours, for example 12 hours. Wherein, when condensate gas is injected, the inlet pressure of the experimental rock sample needs to be smaller than the pressure of the confining pressure cavity, otherwise leakage can occur.
In step S4, the back pressure valve is adjusted to enable the outlet pressure of the experimental rock sample to be reduced step by step, for example, 3-5 mpa is reduced each time until the outlet pressure of the experimental rock sample is reduced to an initial stratum pressure value when the gas storage is under construction, and experimental simulation of the condensate gas reservoir exploitation process is achieved. Meanwhile, the process of injecting condensate gas step by step to simulate the bottom gas can be further performed, after the bottom gas is simulated, the condensate gas is injected again, so that the outlet pressure of the experimental rock sample is increased to the upper limit pressure value of the gas storage during operation, and experimental simulation of the process of rebuilding the gas storage by the condensate gas reservoir is realized.
In step S5, the compounded natural gas is injected into the experimental rock sample through the internal pressure injection device until the outlet pressure of the experimental rock sample is increased to the upper limit pressure value of the gas storage in operation, so that experimental simulation of the gas injection process of the gas storage is realized. It will be appreciated that, due to the relatively high displacement pressure ratio, it takes a certain time for the natural gas to build up pressure inside the laboratory rock sample, and therefore the outlet pressure of the laboratory rock sample may be maintained at the upper pressure level at which the reservoir is operating for several hours, for example, again for 12 hours. When natural gas is injected, the inlet pressure of the experimental rock sample is required to be smaller than the pressure of the confining pressure cavity, so that leakage is avoided.
In step S6, the back pressure valve is adjusted to enable the outlet pressure of the experimental rock sample to be reduced step by step, for example, 3-5 mpa can be reduced each time until the outlet pressure of the experimental rock sample is reduced to the lower limit pressure value of the gas storage in operation, and experimental simulation of the gas production process of the gas storage is achieved. After the experimental simulation of the gas production process is finished, the pressure can be kept stable for a period of time, for example, for 4 hours, and then the simulation experiment of the next stage is started.
In step S7, after the simulated gas production in step S6 is completed, the simulated gas injection in step S5 and the simulated gas production in step S6 are repeated until the preset cycle number is reached. The preset cycle number can be set according to the cycle number of multi-cycle gas injection and production cycles of the gas storage, for example, can be set to 5 times.
Further, in one embodiment, prior to step S1, the near well blockage experimental simulation method further includes:
cleaning and drying the experimental rock sample;
And carrying out vacuumizing treatment on the cleaned and dried experimental rock sample.
Specifically, firstly, all the fluid originally existing in the experimental rock sample needs to be completely cleaned, and considering that the solvent and the cleaning mode for cleaning crude oil in the pores of the experimental rock sample can influence the structure of clay minerals, the experimental rock sample can be washed to be hydrophilic according to the specification of SY/T5336. If the components of the experimental rock sample are unknown before oil washing, the mixture of alcohol and rice can be used for washing crude oil of the experimental rock sample, and if the mineralization degree of formation water is higher than 2000mg/L or the data of unknown formation water, reagents such as methanol and the like are also needed for desalting the experimental rock sample.
And secondly, when the experimental rock sample is dried, in order to ensure that the properties of clay and gypsum in the experimental rock sample are not changed, the drying temperature is required to be controlled to be not higher than 60 ℃, and the relative humidity is controlled to be 40% -50%. Each experimental rock sample is dried to constant weight, the drying time is not less than 48h, weighing is carried out once every 8h after 48h, and the difference between the two weighing is 10mg smaller, so that the standard is reached.
Finally, because the near well blockage of the gas storage can influence the porosity, permeability, rock compression coefficient and the like of the reservoir to various degrees, the high-efficiency stable operation of the gas storage is influenced finally, and therefore, the initial permeability and the porosity of the experimental rock sample are required to be measured by saturated air before a simulation experiment is carried out. Specifically, the dried experimental rock sample is vacuumized, the initial permeability of the experimental rock sample is measured by saturated air, the saturation pressure is maintained for at least 12 hours, the mass difference of the experimental rock sample before and after saturation is measured, and the effective pore volume and the porosity of the experimental rock sample are calculated according to a formula. The initial permeability of the saturated air measurement experimental rock sample and the effective pore volume and the porosity of the calculation experimental rock sample can be referred to the prior art, and the embodiments of the present application are not repeated.
In one embodiment, the near well plugging experimental simulation method further comprises:
acquiring the inlet pressure of an experimental rock sample, the outlet pressure of the experimental rock sample, the pressure of a confining pressure cavity and the flow rate of natural gas flowing out of the outlet end of the experimental rock sample;
And determining the permeability, the porosity and the compression coefficient 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 cavity and the flow rate of the natural gas.
Further, in one embodiment, the determining the permeability, the porosity and the compression coefficient 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 cavity and the flow rate of the natural gas in the above steps may include the steps of:
Determining the permeability of the experimental rock sample according to formula (1):
determining the porosity of the experimental rock sample according to formula (2):
phi=a (P 3-P2)3+b(P3-P2)2+c(P3-P2) +d formula (2)
Determining the compression coefficient of the experimental rock sample according to formula (3):
wherein K represents the permeability of the experimental rock sample, Representing the porosity of the experimental rock sample, C f representing the compression coefficient of the experimental rock sample, P 1 representing the inlet pressure of the experimental rock sample, P 2 representing the outlet pressure of the experimental rock sample, P 3 representing the pressure of the confining pressure chamber, Q representing the flow rate of natural gas, P representing the standard atmospheric pressure, μ representing the viscosity value of natural gas, L representing the length of the experimental rock sample, a representing the cross-sectional area of the experimental rock sample, a, b, C, d representing the regression coefficient.
Specifically, in the process of simulating gas injection, the outlet pressure of the experimental rock sample is gradually increased, in the process of simulating gas production, the outlet pressure of the experimental rock sample is gradually reduced, experimental data can be obtained at a plurality of pressure points, the permeability, the porosity and the compression coefficient of the experimental rock sample corresponding to the pressure points are calculated, meanwhile, in the process of simulating reconstruction of a gas storage from a condensate gas reservoir, the experimental data can be obtained at a plurality of pressure points, the permeability, the porosity and the compression coefficient of the experimental rock sample corresponding to the pressure points are calculated, and thus, the initial permeability, the initial porosity and the initial compression coefficient of the experimental rock sample measured before simulation experiment are combined, the change rate of the permeability, the change rate of the porosity and the change rate of the compression coefficient of the experimental rock sample in the process of simulating experiment can be calculated, so that key parameters such as the permeability, the porosity and the compression coefficient of a reservoir are identified along with the change of the gas storage construction process and the injection period of the gas storage during operation, and important reference rules such as high-efficiency stable operation, storage capacity calculation and multi-period numerical simulation are provided for the time-varying and the like.
Specifically, the rate of change of the permeability of the experimental rock sample can be determined by the following formula:
The rate of change of the porosity of the experimental rock sample can be determined by the following formula:
the rate of change of the compression coefficient of the experimental rock sample can be determined by the following formula:
Wherein D stk represents the rate of change of the permeability of the experimental rock sample, Representing the rate of change of the porosity of the experimental rock sample, D stc representing the rate of change of the compression coefficient of the experimental rock sample, K i representing the initial permeability of the experimental rock sample, K n representing the permeability of the experimental rock sample calculated at the nth outlet pressure,Representing the initial porosity of the experimental rock sample,Representing the porosity of the experimental rock sample at the nth outlet pressure, C i represents the initial compression coefficient of the experimental rock sample, and C n represents the compression coefficient of the experimental rock sample at the nth outlet pressure.
For more details regarding the near-well blockage test simulation method for the gas storage in the embodiment of the present application, reference may be made to the above description regarding the near-well blockage test simulation device for the gas storage, and the same or corresponding technical effects as those of the near-well blockage test simulation device for the gas storage described above may be obtained, so that the description thereof will not be repeated here.
In summary, by the above method, namely, 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 suffered by the experimental rock sample can be simulated, the condensate gas or natural gas can be injected into the experimental rock sample through the internal pressure injection unit, the formation pressure suffered by the experimental rock sample can be simulated, and the outlet pressure of the experimental rock sample can be changed by adjusting the back pressure valve, the change of the net stress suffered by the experimental rock sample can be simulated, wherein when the condensate gas is injected into the experimental rock sample through the internal pressure injection unit to enable the outlet pressure to reach the original formation pressure value before the gas storage is built, the outlet pressure of the experimental rock sample is gradually reduced through adjusting the back pressure valve to enable the outlet pressure of the experimental rock sample to reach the original formation pressure value when the gas storage is built, the method can simulate the initial state of the condensate gas reservoir before the gas reservoir is built, the process of rebuilding the gas reservoir by the condensate gas reservoir and other experiments, after the internal pressure injection unit is used for injecting natural gas into the experimental rock sample to enable the outlet pressure of the natural gas to reach the upper limit pressure value of the gas reservoir during operation, the back pressure valve is regulated to gradually reduce the outlet pressure of the experimental rock sample to enable the outlet pressure of the experimental rock sample to reach the lower limit pressure value of the gas reservoir during operation, and the steps are repeated for a plurality of times, so that the method can simulate the experiments of multi-period injection and production process and the like during operation of the gas reservoir, and can truly simulate the process of rebuilding the gas reservoir by the condensate gas reservoir and the multi-period injection and production process during operation of the gas reservoir, thereby providing technical support for analyzing the near well blockage of the gas reservoir and ensuring the efficient and stable operation of the gas reservoir.
In order to illustrate that the near well plugging experimental simulation method for the gas storage provided by the embodiment of the application can identify the change rule of key parameters such as permeability, porosity, compression coefficient and the like of a reservoir along with the gas storage construction process and the gas injection and recovery period during operation, the results of the first embodiment are listed below for illustration.
Example 1
According to the method for simulating the near well blockage experiment of the gas storage, a simulation experiment is performed on the near well blockage of the gas storage.
Initial data of experimental rock samples before the start of the simulation are shown in table 1.
TABLE 1
| Length (cm) | 4.88 | Diameter (cm) | 2.47 |
| Dry weight (g) | 56.78 | Initial porosity | 0.10 |
| Initial permeability (10 -3μm2) | 0.1458 | Saturation with water (%) | 5.2 |
The data of permeability and porosity of the experimental rock samples in the first gas injection and production cycle simulation are shown in table 2.
TABLE 2
The data of permeability and porosity of the experimental rock samples in the second gas injection and production cycle simulation are shown in table 3.
TABLE 3 Table 3
The data of the permeability and porosity of the experimental rock samples in the third gas injection and production cycle simulation experiment are shown in table 4.
TABLE 4 Table 4
The data of the permeability and porosity of the experimental rock samples in the fourth gas injection and production cycle simulation experiment are shown in table 5.
TABLE 5
The data of the permeability and porosity of the experimental rock samples in the fifth gas injection and production cycle simulation experiment are shown in table 6.
TABLE 6
From the initial permeability and the initial porosity of the experimental rock sample measured before the simulation experiment, and the permeability and the porosity of the experimental rock sample calculated during the simulation experiment, a variation graph of the permeability of the experimental rock sample at the time of multi-cycle injection and production as shown in fig. 2 and a variation graph of the porosity of the experimental rock sample at the time of multi-cycle injection and production as shown in fig. 3 can be drawn.
From fig. 2 and 3, it can be seen that the permeability of the experimental rock sample increases during the second injection period simulation experiment, and then decreases continuously as the injection period cycle proceeds, and the porosity of the experimental rock sample decreases by 7.8% over multiple periods.
By analyzing the experimental results, the near well blockage experimental simulation method for the gas storage provided by the embodiment of the application can identify the change rule of key parameters such as the permeability, the porosity, the compression coefficient and the like of a reservoir along with the gas storage construction process and the gas injection and recovery period during the operation period, 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.
It should be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
The foregoing is merely exemplary of the present application and is not intended to limit the present application. Various modifications and variations of the present application will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the application are to be included in the scope of the claims of the present application.
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