CN108956385B - An experimental system for gas diffusion and transport and its experimental method - Google Patents

Abstract

This specification provides an experimental system and an experimental method for gas diffusion and migration. The system includes: a basic environment simulation device for simulating the basic state in which the corresponding gas is adsorbed in the core under geological conditions, and the basic environment simulation device includes a basic rock The sample chamber, as well as the gas pumping part and the gas injection part, the basic rock sample chamber includes a first core holder, and a first gas concentration detector and a first pressure gauge are arranged on the external pipeline of the first core holder; diffusion migration The simulation device includes at least one diffusion migration rock sample chamber, the diffusion migration rock sample chamber includes a second core holder, and the external pipeline of the second core holder is provided with a second gas concentration detector and a second pressure Table; a first valve for making the basic environment simulation device and the diffusion transport simulation device in a state of communication or non-communication. It is a highly reliable experimental solution for gas diffusion and transport, especially for the study of shale gas diffusion and transport.

Description

An experimental system for gas diffusion and transport and its experimental method

technical field

This specification relates to an experimental system for gas diffusion and transport and its experimental method.

Background technique

Shale gas is a typical natural gas accumulation of self-generation and self-storage. It is different from conventional natural gas in that shale gas is generated in the source rock and accumulated nearby without long-distance migration. It is precisely because shale gas has this typical in-situ accumulation model, the diffusion and migration process of shale gas is usually ignored in the research process. However, in fact, the diffusion and migration of shale gas has an important impact on the accumulation of shale gas. Therefore, it is necessary to deeply and systematically study the process of diffusion and migration of shale gas in order to clarify the accumulation mechanism of shale gas and improve shale gas accumulation. exploration efficiency.

At present, there are methods to study the diffusion and migration of shale gas by using numerical simulation methods based on the theory of fluid mechanics. However, the numerical simulation method has poor accuracy and cannot well reflect the process of shale gas diffusion and migration.

SUMMARY OF THE INVENTION

The purpose of this specification is to provide an experimental system and an experimental method for simulating gas diffusion and transport.

In order to achieve the above purpose, on the one hand, this specification provides an experimental system for gas diffusion and transport, the system comprising:

A basic environment simulation device; the basic environment simulation device is used for simulating the basic state in which the corresponding gas is adsorbed in the core under geological conditions; the basic environment simulation device includes a basic rock sample room, and the basic rock sample room respectively communicated with the basic state a gas pumping part and a gas injection part; the basic rock sample chamber includes a first core holder, and a first inlet pipeline and a first outlet pipeline respectively connected to both ends of the first core holder, the first outlet pipeline A first gas concentration detector and a first pressure gauge are arranged on it;

A diffusion and migration simulation device; the diffusion and migration simulation device includes at least one diffusion and migration rock sample chamber, and the diffusion and migration rock sample chamber includes a second core holder, and two core holders respectively connected to the second core holder. a second inlet pipeline and a second outlet pipeline at the end, the second outlet pipeline is provided with a second gas concentration detector and a second pressure gauge;

A first valve for making the first core holder of the basic environment simulation device and the second core holder of the diffusion and migration simulation device in a state of communication or non-communication.

In the experimental system for gas diffusion and migration provided in this specification, a basic environment simulation device is set to simulate the state of the core when a specific gas is stored in the formation environment, and a diffusion and migration simulation device is set to simulate the core when the specific gas is not stored in the formation environment. state; and then connect the two to simulate the process of diffusion and migration of specific gases between cores. The device can simulate the process of gas diffusion and migration, and can obtain necessary research data. Therefore, it is a highly reliable experimental system for gas diffusion and migration, especially for the study of shale gas diffusion and migration.

In the above experimental system for gas diffusion and migration, preferably, the system further includes a constant temperature device, and the basic rock sample chamber and the diffusion and migration rock sample chamber are set in the constant temperature device.

In the above-mentioned experimental system for gas diffusion and transport, preferably, the system further comprises a gas metering device communicated with the diffusion and transport simulation device; the gas metering device is used to measure the gas discharged from the diffusion and transport simulation device in the experiment. amount of gas.

In the above experimental system for gas diffusion and migration, preferably, the diffusion and migration simulation device includes 2-4 diffusion and migration rock sample chambers, and adjacent diffusion and migration rock sample chambers are connected in series.

In the above-mentioned experimental system for gas diffusion and migration, preferably, the first core holder and the second core holder have accommodating cavities of the same specification for placing cores of the same specification.

In the above-mentioned experimental system for gas diffusion and transport, preferably, the pumping part includes a vacuum pump and a vacuum pressure gauge, and the vacuum pump communicates with the first inlet line; when the vacuum pump communicates with the first inlet line There is a vacuum pressure gauge on the pipeline.

In the above experimental system for gas diffusion and migration, preferably, the gas injection part includes a gas storage device, a pressurizing device and a gas injection pressure gauge, the gas storage device is communicated with the pressurizing device, and the pressurizing device The device is communicated with the first inlet line; a gas injection pressure gauge is arranged on the line connecting the pressurizing device with the first inlet line.

In another aspect, the present specification provides an experimental method for conducting gas diffusion transport, the method comprising:

placing the core in the first core holder in a state in which a specific gas is stored simulating certain formation conditions; the formation conditions include temperature and pressure;

placing the core in the second core holder in a state that simulates certain formation conditions without storing the specified gas; the formation conditions include temperature and pressure;

Connecting the first core holder with the second core holder, at this time, the specific gas stored in the core in the first core holder diffuses and migrates to the core in the second core holder;

The data of the concentration and pressure of the specific gas entering the second core holder and discharged from the second core holder during the diffusion and migration process are acquired, and the diffusion and migration of the specific gas is studied in combination with the basic data.

In the above-mentioned experimental method for gas diffusion migration, preferably, the basic data includes: the amount of specific gas discharged from the second core holder, the formation of the first core holder and the second core holder conditional data.

In the above-mentioned experimental method for gas diffusion migration, preferably, the core in the first core holder and the core in the second core holder are samples of the same specification.

In the above-mentioned experimental method for gas diffusion and migration, preferably, the cores in the first core holder and the cores in the second core holder are both standard samples drilled perpendicular to the shale layer or are both parallel to Standard column samples drilled in shale layers.

In the above-mentioned experimental method for gas diffusion transport, preferably, the specific gas is methane.

Description of drawings

FIG. 1 is an experimental device for gas diffusion and transport provided by an embodiment of the present specification.

Description of reference numbers:

1. Vacuum pump, 2. Vacuum pressure gauge, 3. Air extraction valve, 4. Air storage device (high pressure methane), 5. Pressurization device, 6. Air injection pressure gauge, 7. Air injection valve, 8. First plug head, 9, first rock sample, 10, first core holder, 11, first valve, 12, first pressure gauge, 13, first concentration detector (methane), 14, first incubator, 15 , the second plug, 16, the second rock sample, 17, the second core holder, 18, the second valve, 19, the second pressure gauge, 20, the second concentration detector (methane), 21, the second constant temperature box, 22, third plug, 23, third sample, 24, third core holder, 25, third valve, 26, third pressure gauge, 27, third concentration detector (methane), 28, The third incubator, 29, the fourth valve, 30, the gas metering device.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of this specification, the technical solutions of this specification are now described in detail below, but should not be construed as a limitation on the scope of implementation of this specification.

Referring to FIG. 1 , an embodiment of the present specification provides an experimental system for gas diffusion and transport, which includes:

A basic environment simulation device; the basic environment simulation device is used to simulate the basic state in which the corresponding gas is adsorbed in the core under geological conditions; the basic environment simulation device includes a basic rock sample room, and a gas extraction part and a gas extraction part respectively connected with the basic rock sample room. Gas injection part; the basic rock sample chamber includes a first core holder 10, and a first inlet pipeline and a first outlet pipeline respectively connected to both ends of the first core holder 10, and the first outlet pipeline is provided with a first gas concentration detector 13 and first pressure gauge 12;

The diffusion and migration simulation device; the diffusion and migration simulation device includes at least one diffusion and migration rock sample chamber, and the diffusion and migration rock sample chamber includes a second core holder 17, and a second core holder 17 connected to both ends of the second core holder 17 respectively. Two inlet pipelines and a second outlet pipeline, and a second gas concentration detector 20 and a second pressure gauge 19 are arranged on the second outlet pipeline;

The first valve 11 is used to make the first core holder 10 of the basic environment simulation device and the second core holder 17 of the diffusion and migration simulation device in a communication or non-communication state.

In some embodiments, the diffusion and migration simulation device includes 2-4 diffusion and migration rock sample chambers, and adjacent diffusion and migration rock sample chambers are connected in series. Different diffusion rock sample chambers can place cores of the same lithology, or cores of different lithologies. Therefore, the device can simulate the diffusion and transport of gas under different lithologic combinations. In the embodiment shown in FIG. 1 , the diffusion and migration simulation device has two diffusion and migration rock sample chambers, which are connected in series. The first diffusion and migration rock sample chamber is provided with a second core holder 17, two ends of the second core holder 17 are connected with a second inlet pipeline and a second outlet pipeline, and the second outlet pipeline is provided with a second core holder 17. The second gas concentration detector 20 and the second pressure gauge 19 . Similarly, a third core holder 24 is arranged in the second diffusion and migration rock sample chamber, and both ends of the third core holder 24 are connected with a third inlet pipeline and a third outlet pipeline, and the third outlet pipeline is provided with There is a third gas concentration detector 27 and a third pressure gauge 26 .

Continuing to refer to FIG. 1 , in this embodiment, the core holders in the two diffusion migration rock sample chambers are connected in series, that is, the second outlet line of the second core holder 17 and the third core holder 24 The third inlet line is connected.

In some embodiments, necessary valves may be provided on the inlet line or the outlet line of the core holder of the diffusion migration chamber to facilitate the control of communication or blocking between adjacent core holders. In the embodiment shown in FIG. 1 , a second valve 18 is provided on the second outlet line of the second core holder 17 ; a third valve 25 is provided on the second outlet line of the third core holder 24 .

In some embodiments, each core holder is a core holder capable of providing confining pressure for simulating the pressure state of the core in the formation environment. The core holder can bear a certain pressure. In the embodiment shown in FIG. 1 , the maximum pressure that the first core holder 10 , the second core holder 17 and the third core holder 24 can bear is 80MPa . In addition, when in use, the sides of the core column samples (the first rock sample 9, the second rock sample 16, and the third rock sample 23) can be wrapped with rubber sleeves, leaving only the top and bottom surfaces; The sample is placed in the inner cavity of the core holder, and the two end faces are closed with plugs. Corresponding outlet line or inlet line can be connected to the plug as appropriate. In the embodiment shown in FIG. 1 , both ends of the first core holder 10 have first plugs 8 ; both ends of the second core holder 17 have second plugs 15 ; and the third core holder 24 There are third plugs 22 at both ends.

In some embodiments, in order to better simulate the formation temperature, the system further includes a constant temperature device, wherein the basic rock sample chamber and the diffusion and migration rock sample chamber can be set in one constant temperature device, or can be separately set at their respective constant temperatures in the device. In the embodiment shown in FIG. 1 , the basic rock sample chamber is set in the constant temperature box 14 , and the two diffusion and migration rock sample chambers are set in the constant temperature box 21 and the constant temperature box 28 respectively. This separate setting method is beneficial to control the temperature separately. Of course, they can also be set to a uniform temperature during testing (for example, to simulate the temperature of the same formation). Therefore, the device can simulate the diffusion and transport of gases under various temperature and pressure field conditions. Specifically, the temperature adjustment range of the incubator can be 18-120°C.

In some embodiments, the core holders in the base rock chamber and the diffusion migration rock chamber may be of the same size or different sizes. The same size means that the sample chamber of the core holder has the same size of floor area and column height. In this case, cores of the same size can be placed. Therefore, it is possible to simulate the diffusion and transport of gas in a fixed channel of equal cross-section, which is convenient for analyzing the law of diffusion and transport. As for the core, it can be the same-phase core or the core of different lithofacies, which can be determined according to the needs of the experiment. The "same phase" of the geological species refers to the rock whose mineral composition, structural composition, etc. are the same.

In some embodiments, the system further includes a gas metering device in communication with the diffusion transport simulation device; the gas metering device is used to meter the amount of gas expelled from the diffusion transport simulation device in the experiment. In the embodiment shown in FIG. 1 , the gas metering device 30 is arranged outside the diffusion and migration simulation device, and the two are communicated through pipelines. A fourth valve 29 is provided on the communication line.

In some embodiments, the specific arrangement of the air extraction part is not limited, and it can be used to extract the air in the first core holder 10 . In order to reflect the pumping situation, a vacuum pressure gauge can be set on the pumping line. The monitoring range of the vacuum pressure gauge can be -0.1 to 0MPa. In the embodiment shown in FIG. 1 , the pumping part includes a vacuum pump 1 and a vacuum pressure gauge 2, and the vacuum pump 1 is communicated with the first inlet line of the first core holder 10; the line connecting the vacuum pump 1 with the first inlet line There is a vacuum pressure gauge 2 on it. In addition, a suction valve 3 may also be provided on the pipeline connecting the vacuum pump 1 with the first inlet pipeline.

In some embodiments, the specific setting of the gas injection part is not limited, and it can be used to inject a specific gas of a certain pressure into the first core holder 10 . The monitoring range of the gas injection pressure gauge can be 0 to 60MPa. In the embodiment shown in FIG. 1 , the gas injection part includes a gas storage device (high pressure methane) 4, a pressurizing device 5 and a gas injection pressure gauge 6; the gas storage device 4 is communicated with the pressurizing device 5, and the pressurizing device 5 is connected to The first inlet pipeline of the first core holder is in communication; a gas injection pressure gauge 6 is arranged on the pipeline connecting the pressurizing device 5 with the first inlet pipeline. In addition, a gas injection valve 7 may also be provided on the pipeline connecting the pressurizing device 5 with the first inlet pipeline.

Embodiments of this specification also provide an experimental method for gas diffusion and transport, the method comprising:

(1) make the core placed in the first core holder be in a state in which a specific gas is stored under simulated certain formation conditions; the formation conditions include temperature and pressure;

(2) the core placed in the second core holder is in a state where no specific gas is stored under simulated certain formation conditions; the formation conditions include temperature and pressure;

(3) making the first core holder communicate with the second core holder, at this time, the specific gas stored in the core in the first core holder diffuses and migrates to the core in the second core holder;

(4) Obtain the data of the concentration and pressure of the specific gas entering the second core holder and discharged from the second core holder with time during the diffusion and migration process, and study the diffusion and migration of the specific gas in combination with the basic data.

In some embodiments, several second core holders may be provided, and the second core holders may be connected in series.

In some embodiments, the base data may include: the amount of specific gas expelled from the second core holder, formation condition data for the first core holder and the second core holder.

In some embodiments, the core in the first core holder and the core in the second core holder are samples of the same size. In addition, the two cores can be selected with the same or different lithology samples as required.

In some embodiments, the cores in the first core holder and the cores in the second core holder are both standard samples drilled perpendicular to the shale layer or standard columns drilled parallel to the shale layer Sample.

In some embodiments, the specific gas is methane.

In some embodiments, corresponding simulation experiments are performed using the experimental device for gas diffusion and transport provided in this specification.

The following is an application example of using the experimental device shown in Figure 1 to study the diffusion and migration of shale gas. The specific steps are as follows:

1. Study the vertical diffusion and migration of shale gas

Three samples with different lithologies were selected, and a column sample (standard column sample with a diameter of 2.54 cm and a length of 3 cm) was drilled perpendicular to the shale layer to obtain the first rock sample 9, the second rock sample 16 and the third rock sample 23 , wrap the side of the column sample with a rubber sleeve, leaving only the top and bottom surfaces, and put the wrapped samples into the first core holder 10, the second core holder 17, and the third core respectively in vertical order. Gripper 24.

Adjust the three core holders so that the samples are subjected to the same confining pressure (i.e., the formation pressure of the simulated formation), and adjust the incubators of the three sample chambers to the same temperature (i.e., the in-situ temperature of the simulated formation); open the pumping valve 3 , make sure that other valves are closed, and turn on the vacuum pump 1 to evacuate the inside of the first rock sample 9 to a vacuum. Turn off the vacuum pump 1 and the pumping valve 3 to ensure that the basic rock sample chamber is not connected to the diffusion and migration rock sample chamber.

Open the gas injection valve 7, the pressurizing device 5 and the gas storage device 4 (internal storage of high-pressure methane), start to charge the first rock sample 9 in the first core holder 10 with methane, and use the pressurizing device 5 to ensure the methane energy It is charged into the pores of the first rock sample 9. When the methane gas content in the first rock sample 9 reaches the in-situ gas content of the simulated formation, the gas injection valve 7 , the pressurizing device 5 and the gas storage device 4 are closed.

Open the first valve 11 , the second valve 18 , the third valve 25 and the fourth valve 29 , so that the shale gas spontaneously diffuses and migrates from the first rock sample 9 to the second rock sample 16 and the third rock sample 23 , through the first pressure gauge 12, the second pressure gauge 19 and the third pressure gauge 26 to record the pressure change with time during the shale gas diffusion process, through the first concentration detector (methane) 13, the second concentration detector (methane ) 20 and a third concentration detector (methane) 27 to monitor the time-dependent change of methane concentration during the diffusion of shale gas.

2. Study on the lateral diffusion and migration of shale gas

Three samples with the same lithology were selected, and a column sample (standard column sample with a diameter of 2.54 cm and a length of 3 cm) was drilled parallel to the shale layer to obtain the fourth, fifth and sixth rock samples. The side of the sample is wrapped with a rubber sleeve, leaving only the top and bottom surfaces, and the samples wrapped with the rubber sleeve are placed in the first core holder 10, the second core holder 17, and the third core holder respectively in vertical order. twenty four.

Adjust the three core holders according to the variation of the lateral formation pressure of the simulated formation, so that the confining pressure of the three rock samples is the same as the formation pressure of different structural parts, and the temperature of the three incubators is adjusted so that the three rock samples are subject to The temperature is the same as the formation temperature in different structural parts;

Open the pumping valve 3, ensure that other valves are closed, and turn on the vacuum pump 1 to evacuate the fourth rock sample to a vacuum. Turn off the vacuum pump 1 and the pumping valve 3 to ensure that the basic rock sample chamber is not connected to the diffusion and migration rock sample chamber.

Open the gas injection valve 7, the pressurizing device 5 and the gas storage device 4 (internal storage of high-pressure methane), start to charge the first rock sample 9 in the first core holder 10 with methane, and use the pressurizing device 5 to ensure the methane energy Filled into the pores of the fourth rock sample. When the methane gas content in the fourth rock sample reaches the in-situ gas content of the simulated formation, the gas injection valve 7 , the pressurizing device 5 and the gas storage device 4 are closed.

Open the first valve 11, the second valve 18, the third valve 25 and the fourth valve 29, so that the shale gas spontaneously diffuses and migrates from the fourth rock sample to the fifth rock sample and the sixth rock sample. A pressure gauge 12, a second pressure gauge 19 and a third pressure gauge 26 record the pressure changes with time during the diffusion of shale gas, through the first concentration detector (methane) 13, the second concentration detector (methane) 20 and The third concentration detector (methane) 27 monitors the time-dependent change of the methane concentration during the diffusion of the shale gas.

It can be seen that the experimental system and experimental method for gas diffusion and migration provided by the embodiments of this specification can intuitively and conveniently observe and study the diffusion and migration process of shale gas in different lithologies and under different temperature and pressure field conditions.

Claims (8)

1. An experimental method for gas diffusion migration is characterized by specifically comprising the following steps:

enabling a rock core arranged in the first rock core holder to be in a state of simulating that specific gas is stored under certain stratum conditions; the formation conditions include temperature and pressure;

enabling the core arranged in the second core holder to be in a state of simulating that specific gas is not stored under certain stratum conditions; the formation conditions include temperature and pressure;

communicating the first core holder with the second core holder, wherein specific gas stored in the core in the first core holder diffuses and migrates to the core in the second core holder;

acquiring data of the change of the concentration and the pressure of specific gas entering and exhausted from the second core holder along with time in the diffusion migration process, and researching the diffusion migration of the specific gas by combining basic data;

the method is completed by an experimental system for gas diffusion migration, which comprises the following steps:

a base environment simulation device; the basic environment simulation device is used for simulating a basic state of corresponding gas adsorbed in a rock core under a geological condition; the basic environment simulation device comprises a basic rock sample chamber, and an air exhaust part and an air injection part which are respectively communicated with the basic rock sample chamber; the basic rock sample chamber comprises a first rock core holder, a first inlet pipeline and a first outlet pipeline which are respectively connected to two ends of the first rock core holder, and a first gas concentration detector and a first pressure gauge are arranged on the first outlet pipeline;

the air exhaust part comprises a vacuum pump and a vacuum pressure gauge, and the vacuum pump is communicated with the first inlet pipeline; a vacuum pressure gauge is arranged on a pipeline of the vacuum pump communicated with the first inlet pipeline;

the gas injection part comprises a gas storage device, a pressurizing device and a gas injection pressure gauge, the gas storage device is communicated with the pressurizing device, and the pressurizing device is communicated with the first inlet pipeline; a gas injection pressure gauge is arranged on a pipeline of the pressurizing device communicated with the first inlet pipeline;

a diffusion migration simulation device; the diffusion migration simulation device comprises 2-4 diffusion migration rock sample chambers, adjacent diffusion migration rock sample chambers are communicated in series, and diffusion migration of gas under different lithologic combination conditions is simulated; the diffusion migration rock sample chamber comprises a second rock core holder, a second inlet pipeline and a second outlet pipeline which are respectively connected to two ends of the second rock core holder, and a second gas concentration detector and a second pressure gauge are arranged on the second outlet pipeline;

and the first valve is used for enabling the first core holder of the basic environment simulation device and the second core holder of the diffusion migration simulation device to be in a communication or non-communication state.

2. The experimental method for gas diffusion migration according to claim 1, wherein the system further comprises a constant temperature device, and the base rock sample chamber and the diffusion migration rock sample chamber are arranged in the constant temperature device.

3. The experimental method of gas diffusion migration according to claim 1, characterized in that the system further comprises a gas metering device communicated with said diffusion migration simulating device; the gas metering device is used for metering the amount of gas discharged from the diffusion transport simulation device in an experiment.

4. The experimental method for gas diffusion migration according to claim 1, wherein the first core holder and the second core holder have accommodating cavities with the same specification and are used for accommodating cores with the same specification.

5. The experimental method for carrying out gas diffusion migration according to claim 1, characterized in that said basic data comprise: the amount of the specific gas exhausted from the second core holder, and formation condition data of the first core holder and the second core holder.

6. The experimental method for gas diffusion migration according to claim 1, wherein the core in the first core holder and the core in the second core holder are samples of the same specification.

7. The experimental method for gas diffusion migration according to claim 6, wherein the core in the first core holder and the core in the second core holder are both standard samples drilled perpendicular to the shale layer or are both standard samples drilled parallel to the shale layer.

8. The experimental method for carrying out gas diffusion transport according to claim 1, characterized in that said specific gas is methane.

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