Experimental device and method for judging plugging effect of multiple sets of cover layers on natural gas

Abstract

The invention belongs to the field of natural gas extraction, and discloses an experimental device and method for judging the plugging effect of multiple sets of cover layers on natural gas, and the device comprises constant-temperature gas containing boxes and sample holders which are arranged in a staggered manner; two ends of the rock sample holder are communicated with the constant-temperature gas container and are provided with valves; each constant-temperature air container is connected with an air supply unit; a heating system, a temperature monitor and a pressure monitor are arranged on each constant-temperature air container; and the gas supply unit, the heating system, the temperature monitor and the pressure monitor are in signal connection with the control system. According to the application, the plurality of constant-temperature gas containers and the sample holders are arranged in a staggered manner, so that the mutual overlapping characteristics of a plurality of sets of cover layers and a gas reservoir are simulated, and the temperature and pressure states of natural gas under each set of cover layer are respectively simulated through the independent constant-temperature gas containers, so that the evaluation on the plugging effect of the plurality of sets of cover layers is realized; errors of an existing breakthrough pressure value measuring method are avoided, and the plugging effect of the cover layer on the natural gas under the stratum condition can be more truly reflected.

Description

Technical Field

[0001] The present application relates to the field of natural gas extraction, and in particular to an experimental device and method for identifying the sealing effects of multiple cap layers on natural gas. Background Art

[0002] Under burial conditions, the preservation of natural gas reservoirs requires multiple constraints, among which the sealing effect of the overlying caprock is the most critical factor. Evaluation of the caprock in natural gas reservoirs typically involves evaluating its effectiveness in sealing natural gas through the breakthrough pressure of caprock rock samples, indirectly assessing its sealing capacity through microscopic pore throat characteristics, and evaluating its effectiveness through formation water chemistry. These methods can reflect the caprock's sealing capacity and its sealing effect on natural gas from different perspectives.

[0003] At present, the main method for conducting breakthrough pressure testing is the step-by-step pressure method (SY / T 5748-2020), which studies and evaluates the plugging effect of the direct caprock (single caprock) overlying the natural gas reservoir. In actual formations, natural gas is prevented from being lost and preserved to this day due to the combined influence of multiple caprocks from generation to accumulation to preservation. However, there are currently no relevant reports on how to evaluate the impact of multiple caprocks on the plugging effect of natural gas, as well as what methods and devices to use to evaluate the plugging effect of multiple caprocks.

[0004] Therefore, it is necessary to establish a method and device that can identify the sealing effect of multiple cap layers on natural gas, objectively and truly reflect the natural gas preservation status under actual formation conditions, and then evaluate the preservation effect of multiple cap layers, understand the sealing capacity of multiple cap layers, and explore and discover more natural gas reservoirs. Summary of the Invention

[0005] At present, the research on natural gas cap rocks is limited to a single set of direct cap rocks overlying the gas reservoir, which is inconsistent with the multiple sets of cap rocks shown in the actual exploration process. It is impossible to draw objective and true conclusions and effectively guide the exploration and discovery of natural gas. The purpose of this application is to overcome the shortcomings of the step-by-step pressure method and establish an experimental device and method for truly evaluating the effectiveness of multiple sets of natural gas capping under formation conditions.

[0006] To achieve the above objectives, this application provides the following technical solutions:

[0007] On the one hand, the present application provides an experimental device for identifying the blocking effect of multiple cap layers on natural gas, comprising multiple staggered constant temperature gas containers and sample holders;

[0008] Both ends of the rock sample holder are connected to the constant temperature gas container and are provided with valves;

[0009] Each constant temperature gas container is connected to the gas supply unit respectively;

[0010] Each constant temperature gas container is equipped with a heating system, temperature monitor and pressure monitor;

[0011] The air supply unit, heating system, temperature monitor and pressure monitor are connected to the control system signal.

[0012] Furthermore, the gas supply unit includes a gas booster pump, and the gas delivery end of the gas booster pump is sequentially connected to the pressure control valve and the gas inlet of each constant temperature gas container.

[0013] Furthermore, the air inlet of each constant temperature gas container is respectively provided with a one-way valve and a first gas valve.

[0014] Furthermore, a second gas valve and an injection gas tank are sequentially arranged between the gas booster pump and the pressure control valve along the direction of gas movement.

[0015] On the other hand, the present application discloses a method for identifying the blocking effects of multiple cap layers on natural gas, based on the above-mentioned device.

[0016] Furthermore, a method for identifying the sealing effect of multiple caprocks on natural gas includes: adjusting the number of sample holders and constant temperature gas containers based on actual formation conditions;

[0017] Obtain columnar samples of each cap layer and load them onto the sample holder according to the actual formation conditions;

[0018] The test conditions are set based on the formation pressure, temperature and formation water density in the gas reservoir below each caprock in the actual formation and the pressure changes in the constant temperature gas container are observed;

[0019] The sealing effect of multiple caprocks on natural gas is identified based on the pressure changes in a constant temperature gas container.

[0020] Furthermore, the test conditions are set based on the formation pressure, temperature and formation water density in the gas reservoir below each caprock in the actual formation and the pressure changes in the constant temperature gas container are observed, including:

[0021] The heating temperature of the corresponding constant temperature gas container is set based on the temperature in the gas reservoir below each set of cap layers in the actual formation;

[0022] Based on the formation pressure in the gas reservoir below each cap layer in the actual formation, a preset pressure value of the corresponding constant temperature gas container is designed, and gas is injected into each constant temperature gas container to increase the pressure. When each constant temperature gas container reaches its corresponding preset pressure value for the first time, its corresponding first gas valve is closed;

[0023] The control system is used to output a pressure value change diagram of each constant temperature gas container, record the pressure value of each constant temperature gas container after the pressure is stabilized, and calculate the pressure difference between adjacent constant temperature gas containers.

[0024] Furthermore, the natural gas blocking effects of multiple cap layers are identified based on the pressure changes in the constant temperature gas container, including:

[0025] Determine the plugging capacity of a single cap layer and multiple cap layers based on the pressure value change diagram;

[0026] The height of the natural gas column that can be blocked is calculated based on the blocking capacity of a single caprock.

[0027] Furthermore, the height of the natural gas column that can be blocked is calculated based on the blocking capacity of a single caprock, including:

[0028] When the pressure curves of the constant temperature gas containers corresponding to the gas reservoirs on both sides of a single cap layer in the pressure change diagram are close to each other after stabilization, the height H of the natural gas column that can be blocked by the single cap layer is calculated using the following formula:

[0029] △P=(ρ 水 -ρ 气 )·g·H

[0030] Where △P is the pressure difference after the pressure of the constant temperature gas container corresponding to the gas reservoirs on both sides of the single cap layer stabilizes, MPa; ρwater is the density of the formation water of the gas reservoir under the single cap layer, g / cm 3 ρ 气 is the density of natural gas in the gas reservoir under a single cap rock, g / cm 3 ; g is the acceleration due to gravity, 9.8N / kg.

[0031] Furthermore, the calculation of the natural gas column height that can be blocked by a single cap layer based on the blocking capabilities of the multiple cap layers further includes:

[0032] When the pressure curves of the constant temperature gas containers corresponding to the gas reservoirs on both sides of a single cap layer in the pressure change diagram shift in the same direction after the pressure stabilizes, the natural gas column height H that can be blocked by the single cap layer is calculated using the following formula:

[0033] (P 10 -P 20 )-△P=(ρwater-ρgas)·g·H

[0034] Among them, (P 10 -P 20 ) is the formation pressure difference of gas reservoirs on both sides of a single cap rock, MPa.

[0035] The technical effects and advantages of this application are:

[0036] Based on the actual situation of natural gas reservoirs being blocked by multiple caprocks during their burial preservation, this application designs an experimental apparatus and evaluation method for the blocking effect of multiple caprocks on natural gas. By staggering multiple constant-temperature gas chambers and sample holders, the overlapping characteristics of multiple caprocks and gas reservoirs are simulated. The apparatus can then simulate the natural gas temperature and pressure state beneath each caprock using independent constant-temperature gas chambers, or obtain natural gas pressure state data beneath each caprock. Finally, software in the control system analyzes and plots the data, displaying the pressure of each constant-temperature gas chamber under steady-state conditions and the pressure difference between them. The actual blocking capacity of each caprock under formation conditions is then determined, ultimately yielding the comprehensive blocking effect of multiple caprocks. This, for the first time, enables the evaluation of the blocking effect of multiple caprocks. The blocking capacity values ​​obtained for each caprock are consistent with the physical properties reflected by the commonly used caprock breakthrough pressure value. However, the blocking capacity values ​​reflected by this apparatus avoid the errors associated with previously published breakthrough pressure determination methods and more accurately reflect the blocking effect of caprocks on natural gas under formation conditions.

[0037] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures indicated in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of an experimental device for identifying the blocking effect of multiple cap layers on natural gas in this application;

[0039] Figure 2 This is a diagram of the pressure value changes measured in an embodiment of the present application.

[0040] Figure numerals: 1. Pressure monitor; 2. First gas valve; 3. One-way valve; 4. Valve; 5. Temperature monitor; 6. Sample holder; 7. Constant temperature gas container; 8. Pressure control valve; 9. Injection gas tank; 10. Gas booster pump; 11. Second gas valve; 12. Control system. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0042] On the one hand, if Figure 1As shown, the present application provides an experimental device for identifying the sealing effect of multiple cap layers on natural gas, comprising staggered constant temperature gas containers 7 and sample holders 6, for simulating the overlapping characteristics of multiple cap layers and gas reservoirs;

[0043] Both ends of the rock sample holder 6 are connected to the constant temperature gas container 7 and are provided with valves 4;

[0044] Each constant temperature gas container 7 is connected to the gas supply unit to simulate the pressure state of the natural gas under each cover layer;

[0045] Each constant temperature gas container 7 is provided with a heating system, a temperature monitor 5 and a pressure monitor 1, which are used to simulate the temperature state of the natural gas under each cover layer;

[0046] The air supply unit, the heating system, the temperature monitor 5 and the pressure monitor 1 are connected to the control system 12 via signal connections.

[0047] In some embodiments of the present application, the gas supply unit includes a gas booster pump 10, the gas delivery end of the gas booster pump 10 is connected in sequence to a pressure control valve 8 and the air inlet of each constant temperature gas container 7, and the pressure control valve 8 is used to accurately control the pressure injected into the constant temperature gas container 7.

[0048] In some embodiments of the present application, the air inlet of each constant temperature gas container 7 is respectively provided with a one-way valve 3 and a first gas valve 2, which are respectively used to prevent gas backflow and start and stop of air intake.

[0049] In some embodiments of the present application, a second gas valve 11 and an injection gas tank 9 are arranged in sequence between the gas booster pump 10 and the pressure control valve 8 along the direction of gas movement, wherein the injection gas tank 9 is used for pressure buffering to prevent damage to various instruments and the constant temperature gas container 7 caused by excessive pressure changes.

[0050] The device is used as follows:

[0051] Step 1: Obtain the formation pressure, temperature, and formation water density of each gas reservoir beneath the caprock under formation conditions. Based on the actual geological conditions, select the required number of sample holders 6 and constant temperature gas containers 7. Prepare cylindrical samples from the caprock. Evacuate the samples and saturate the formation water corresponding to each sample at 30 MPa. Caprock samples must be drilled perpendicular to the caprock.

[0052] Step 2. Before the experiment begins, first check whether the valve 4 of each constant temperature gas container 7 is open, then check the pressure state of the gas injected into the gas tank 9, and finally turn on the gas booster pump 10. Adjust the pressure control valve 8 to increase the pressure step by step according to different pressure segments and durations to the maximum pressure value that meets the experimental requirements. Check the status of each instrument through the control system 12 to check the sealing.

[0053] Step 3: During the experiment, each constant temperature gas container 7 (the number of constant temperature gas containers 7 is selected based on the experimental requirements) is selectively injected with gas at a corresponding pressure or maintained without gas. Based on the experimental requirements, each constant temperature gas container 7 is selectively heated to the required temperature, and then the pressure and temperature are maintained constant. By observing the data displayed on the control system 10, when the pressure in each constant temperature gas container 7 remains stable, the pressure value of each constant temperature gas container 7 and the pressure difference between the constant temperature gas containers 7 are recorded.

[0054] Step 4: Based on the data from control system 10, the sealing capacity of each cap layer under formation conditions is determined. Based on the pressure change distribution diagram output by control system 10, the natural gas sealing capacity of each cap layer, or the combined sealing effect of multiple cap layers, is determined. Simultaneously, combined with parameters obtained from the actual formation, the height to which each cap layer can seal the gas reservoir is calculated.

[0055] On the other hand, the present application provides a method for identifying the blocking effects of multiple cap layers on natural gas, based on the above-mentioned device.

[0056] In some embodiments of the present application, a method for identifying the sealing effect of multiple cap layers on natural gas includes: adjusting the number of sample holders 6 and constant temperature gas containers 7 based on actual formation conditions;

[0057] Obtain columnar samples of each cover layer and load them onto the sample holder 6 according to the actual formation conditions;

[0058] Setting test conditions based on the formation pressure, temperature and formation water density in the gas reservoir below each cap layer in the actual formation and observing the pressure changes in the constant temperature gas container 7;

[0059] The natural gas blocking effects of multiple cap layers are identified based on the pressure changes in the constant temperature gas container 7.

[0060] In some embodiments of the present application, setting test conditions based on the formation pressure, temperature, and formation water density in the gas reservoir below each cap layer in the actual formation and observing the pressure change of the constant temperature gas container 7 includes:

[0061] The heating temperature of the corresponding constant temperature gas container 7 is set based on the temperature in the gas reservoir below each set of cap layers under the actual formation;

[0062] Based on the formation pressure in the gas reservoir below each cap layer in the actual formation, a preset pressure value of the corresponding constant temperature gas container 7 is designed, and gas is injected into each constant temperature gas container 7 to increase the pressure. When each constant temperature gas container 7 reaches its corresponding preset pressure value for the first time, its corresponding first gas valve 2 is closed;

[0063] The control system 12 is used to output a pressure value variation diagram of each constant temperature gas container 7 , record the pressure value of each constant temperature gas container 7 after the pressure is stabilized, and calculate the pressure difference between adjacent constant temperature gas containers 7 .

[0064] In some embodiments of the present application, the natural gas blocking effects of multiple cap layers are identified based on the pressure changes in the constant temperature gas container 7, including:

[0065] Determine the plugging capacity of a single cap layer and multiple cap layers based on the pressure value change diagram;

[0066] The height of the natural gas column that can be blocked is calculated based on the blocking capacity of a single caprock.

[0067] In some embodiments of the present application, the height of the natural gas column that can be blocked by a single caprock is calculated based on its blocking capability, including:

[0068] When the pressure curves of the constant temperature gas containers 7 corresponding to the gas reservoirs on both sides of the single cap layer in the pressure value variation diagram are close to each other after stabilization, the natural gas column height H that can be blocked by the single cap layer is calculated using the following formula:

[0069] △P=(ρ 水 -ρ 气 )·g·H

[0070] Wherein, ΔP is the pressure difference after the pressure of the constant temperature gas container 7 corresponding to the gas reservoirs on both sides of the single cap layer is stabilized, MPa; ρ 水 is the density of the formation water in the gas reservoir under the single cap rock, g / cm 3 ρ 气 is the density of the natural gas in the gas reservoir under the single cap rock, g / cm 3 ; g is the acceleration due to gravity, 9.8N / kg.

[0071] In some embodiments of the present application, the calculation of the natural gas column height that can be blocked based on the blocking capability of a single cap layer further includes:

[0072] When the pressure curves of the constant temperature gas container 7 corresponding to the gas reservoirs on both sides of the single cap layer in the pressure value change diagram shift in the same direction after the pressure stabilizes, the natural gas column height H that can be blocked by the single cap layer is calculated using the following formula:

[0073] (P 10 -P 20 )-△P=(ρ 水 -ρ 气 )·g·H

[0074] Among them, (P 10 -P 20 ) is the formation pressure difference of the gas reservoirs on both sides of the single cap rock, MPa.

[0075] In order to better illustrate this solution, the following examples are provided.

[0076] Example

[0077] The sealing effect of multiple caprocks on natural gas in the central Sichuan Basin is used as an embodiment of the device and method of the present application. In the central Sichuan Basin, four gas reservoirs are developed from bottom to top, namely the Dengying Formation, Longwangmiao Formation, Xixiangchi Formation and Qixia-Maokou Formation. Above each gas reservoir are the Qiongzhusi Formation, Gaotai Formation, Liangshan Formation and Jialingjiang Formation caprocks. Regionally, the development of gas reservoirs is not complete. When the Gaotai Formation caprock above the Longwangmiao Formation has a strong sealing ability, the Xixiangchi Formation gas reservoir may not be formed in the upper part because the natural gas is blocked under the Gaotai Formation. At the same time, when the Liangshan Formation caprock above the Xixiangchi Formation is missing, the Xixiangchi Formation may not form a gas reservoir because the natural gas is lost. Therefore, the overpressured natural gas in the Longwangmiao Formation could be completely blocked by the overlying direct caprock, the Gaotai Formation, preventing it from escaping. Alternatively, if the Gaotai Formation caprock fails to completely block the natural gas in the Longwangmiao Formation, the natural gas could break through the Gaotai Formation caprock and enter the Xixiangchi Formation, whereupon the Liangshan Formation caprock on top of the Xixiangchi Formation continues to block the natural gas. There is also the possibility that natural gas could break through the Liangshan Formation caprock again. To determine whether the multiple caprocks in this area are capable of blocking the underlying natural gas, experiments and analysis using the apparatus and methods of this application are needed.

[0078] S1. Clarify the distribution of natural gas and caprocks in the central Sichuan region and obtain information on pressure, temperature, and formation water in the corresponding formations. The vertical superposition relationship between natural gas reservoirs and caprocks in the central Sichuan region and the characteristics of formation parameters are shown in Table 1. Rock samples drilled vertically from the caprocks were loaded into sample holder 6 according to standard specifications, and the top and bottom of the samples were identified. Different samples were installed in the order shown in Table 1.

[0079] Table 1 Vertical superposition relationship between natural gas reservoirs and caprocks and stratigraphic parameter characteristics in the central Sichuan region

[0080]

[0081] S2. This device can carry out various types of plugging experiments. Taking the plugging effect experiments of two sets of caprocks as an example, two rock sample holders and three constant temperature gas containers are selected. The constant temperature gas containers 7 and sample holders 6 corresponding to each natural gas reservoir and caprock are set according to the corresponding relationship shown in Table 1.

[0082] S21: Close the gas valves 4 of the third and fourth constant temperature gas containers, and then slowly start injecting gas into the first, second, and third constant temperature gas containers. During the gas injection process, the temperatures of the first, second, and third constant temperature gas containers are set according to the formation temperature in Table 1. When each constant temperature gas container 7 reaches its corresponding preset pressure value for the first time, its corresponding first gas valve 2 is closed. In this embodiment, the first gas valve 2 of the third constant temperature gas container is closed first, and gas is no longer supplied to it. Similarly, after the second and first constant temperature gas containers reach the corresponding gas injection pressures for the first time, their first gas valves 2 are closed. Then, the corresponding temperatures of each constant temperature gas container 7 are maintained, and the gas booster pump 10 is turned off.

[0083] S22: Observe the control system 12. When the gas pressures in the three constant temperature gas containers 7 are stable and the data of the corresponding pressure monitors 1 no longer change, record the pressure values ​​and pressure differences of the three constant temperature gas containers 7 and output a pressure value change graph of the constant temperature gas containers 7 through the control system 12. The pressure value change graph is shown in FIG. Figure 2 The experimental results are shown in Table 2.

[0084] Table 2 Experimental results 1

[0085]

[0086] S3, based on the pressure change of the constant temperature gas container 7, the blocking effect of multiple cap layers on natural gas is judged. Figure 2 As can be seen in Figure a, the pressure of the third constant temperature gas container did not change, while the pressure of the second constant temperature gas container did change, indicating that the cap layer 1 failed to effectively seal the underlying gas reservoir 1. Under the sealing effect of the cap layer 2, the natural gas in the gas reservoir 1 was sealed and no longer lost. Figure 2 The △P1 value in a represents the plugging capacity of the cap layer 1. This value does not represent the actual breakthrough pressure value of the cap layer 1, but represents the plugging capacity under the current temperature and pressure conditions of the gas reservoir. Figure 2 It can be judged that the cap layer 1 fails to seal the natural gas in gas reservoir 1. The pressure curves of the constant temperature gas container 7 corresponding to gas reservoirs 1 and 2 after pressure stabilization are close to each other. Therefore, according to formula (1) and the data in Table 2, the density of natural gas in gas reservoir 1 is selected as 0.0029 g / cm 3 Calculations show that the natural gas column height H that can be blocked by cap rock 1 under current formation conditions is 405 m, indicating that the natural gas column height in reservoir 1 is greater than 405 m. Because cap rock 2 has already effectively blocked the natural gas in reservoirs 1 or 2, there is no need to determine its blocking capacity.

[0087] Furthermore, assuming that the measured pressure value change diagram is as follows Figure 2 b, the experimental results are shown in Table 3. Figure 2b It can be seen that both cap layer 1 and cap layer 2 are unable to block the natural gas. The pressure curves of the constant temperature gas container 7 corresponding to gas reservoir 1 and gas reservoir 2 after stabilization are offset in the same direction. The sealing capacity of cap layer 1 and the height of the natural gas column that can be blocked are calculated by formula (2). Among them, the sealing capacity value of cap layer 1 is: (P 10 -P 20 )-△P1=1MPa. Under the current formation conditions, the natural gas column height that can be blocked by cap layer 1 is 101m, indicating that the natural gas column height in gas reservoir 1 exceeds 101m. Regarding the sealing capacity of cap layer 2, since the pressure value curves of the constant temperature gas container 7 corresponding to gas reservoir 3 and gas reservoir 2 after pressure stabilization are close to each other, formula (1) is used to obtain the sealing capacity value of cap layer 2, which is 2MPa. This pressure value can block a natural gas column height of 202m, indicating that the natural gas column height in gas reservoir 2 exceeds 202m. Neither of these two cap layers can block gas reservoir 1 or gas reservoir 2.

[0088] Table 3 Experimental results 2

[0089]

[0090] Furthermore, assuming that the measured pressure value change diagram is as follows Figure 2 When shown in c, it means that the sealing effect of cap layer 1 is very good, so there is no need to calculate the sealing capacity of cap layer 1 and cap layer 2.

[0091] Furthermore, assuming that the measured pressure value change diagram is as follows Figure 2 d. The experimental results are shown in Table 4, indicating that caprocks 1 and 2 work together to form an effective seal. The pressure value curves of the constant temperature gas container 7 corresponding to gas reservoirs 1 and 2 after stabilization are close to each other. According to formula (1), the sealing capacity of caprock 1 is 4 MPa. Under the formation conditions, caprock 1 can seal a 405 m natural gas column, which also indicates that the height of the natural gas column in gas reservoir 1 exceeds 405 m. The pressure value curves of the constant temperature gas container 7 corresponding to gas reservoirs 3 and 2 after stabilization are offset in the same direction. According to formula (2), caprock 2 seals a 101 m gas column, indicating that the height of the natural gas column in gas reservoir 2 is 101 m, and the sealing capacity of caprock 2 may exceed 101 m. The combined action of caprocks 1 and 2 effectively seals gas reservoirs 1 and 2.

[0092] Table 4 Experimental results 3

[0093]

[0094] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. An experimental device for identifying the blocking effect of multiple cap layers on natural gas, characterized in that: It comprises a plurality of staggeredly arranged constant temperature gas containers (7) and sample holders (6); Both ends of the sample holder (6) are in communication with the constant temperature gas container (7) and are provided with valves (4); Each of the constant temperature gas containers (7) is connected to a gas supply unit respectively; Each of the constant temperature gas containers (7) is provided with a heating system, a temperature monitor (5) and a pressure monitor (1); The gas supply unit, heating system, temperature monitor (5) and pressure monitor (1) are connected to the control system (12) by signals.

2. The experimental device for identifying the blocking effect of multiple cap layers on natural gas according to claim 1, characterized in that: The gas supply unit comprises a gas booster pump (10), and the gas delivery end of the gas booster pump (10) is sequentially connected to a pressure control valve (8) and the gas inlet of each of the constant temperature gas containers (7).

3. The experimental device for identifying the blocking effect of multiple cap layers on natural gas according to claim 2, characterized in that: The air inlet of each of the constant temperature gas containers (7) is respectively provided with a one-way valve (3) and a first gas valve (2).

4. The experimental device for identifying the blocking effect of multiple cap layers on natural gas according to claim 2, characterized in that: A second gas valve (11) and an injection gas tank (9) are sequentially arranged between the gas booster pump (10) and the pressure control valve (8) along the direction of gas movement.

5. A method for identifying the blocking effect of multiple cap layers on natural gas, characterized in that: The method is based on the device described in any one of claims 1 to 4 to identify the sealing effects of multiple cap layers on natural gas.

6. The method for identifying the blocking effect of multiple cap layers on natural gas according to claim 5, characterized in that: include: Adjust the number of sample holders (6) and constant temperature gas containers (7) based on actual formation conditions; Obtaining columnar samples of each set of cap layers and loading them onto the sample holder (6) according to actual formation conditions; Setting test conditions based on the formation pressure, temperature and formation water density in the gas reservoir below each set of cap layers in the actual formation and observing the pressure change of the constant temperature gas container (7); The natural gas blocking effects of multiple cover layers are judged based on the pressure changes of the constant temperature gas container (7).

7. The method for identifying the blocking effect of multiple cap layers on natural gas according to claim 6, characterized in that: The test conditions are set based on the formation pressure, temperature and formation water density in the gas reservoir under each set of cap layers under the actual formation and the pressure change of the constant temperature gas container (7) is observed, including: Setting the heating temperature of the constant temperature gas container (7) based on the temperature of the gas reservoir below each set of cap layers in the actual formation; Based on the formation pressure in the gas reservoir below each set of cap layers under the actual formation, a preset pressure value corresponding to the constant temperature gas container (7) is designed, and gas is injected into each constant temperature gas container (7) to increase the pressure, and when each constant temperature gas container (7) reaches its corresponding preset pressure value for the first time, its corresponding first gas valve (2) is closed; The control system (12) is used to output a pressure value change diagram of each constant temperature gas container (7), record the pressure value of each constant temperature gas container (7) after the pressure is stabilized, and calculate the pressure difference between adjacent constant temperature gas containers (7).

8. The method for identifying the blocking effect of multiple cap layers on natural gas according to claim 7, characterized in that: The method of judging the natural gas blocking effects of multiple cover layers based on the pressure change of the constant temperature gas container (7) includes: Determining the plugging capacity of a single cap layer and multiple cap layers based on the pressure value variation diagram; The height of the natural gas column that can be blocked is calculated based on the blocking capacity of a single caprock.

9. The method for identifying the blocking effect of multiple cap layers on natural gas according to claim 8, characterized in that: The calculation of the natural gas column height that can be blocked based on the blocking capability of a single caprock includes: When the pressure curves of the constant temperature gas containers (7) corresponding to the gas reservoirs on both sides of the single cap layer in the pressure value variation diagram are close to each other after pressure stabilization, the natural gas column height H that can be blocked by the single cap layer is calculated using the following formula: △P=(ρ 水 -r 气 )·g·H Wherein, ΔP is the pressure difference after the pressure of the constant temperature gas container (7) corresponding to the gas reservoirs on both sides of the single cap layer is stabilized, MPa; ρ 水 is the density of the formation water in the gas reservoir under the single cap rock, g / cm 3 ρ 气 is the density of the natural gas in the gas reservoir under the single cap rock, g / cm 3 ; g is the acceleration due to gravity, 9.8N / kg.

10. The method for identifying the blocking effect of multiple cap layers on natural gas according to claim 9, characterized in that: The calculation of the natural gas column height that can be blocked by a single cap layer based on the blocking capabilities of multiple cap layers further includes: When the pressure value curves of the constant temperature gas containers (7) corresponding to the gas reservoirs on both sides of the single cap layer in the pressure value variation diagram shift in the same direction after the pressure is stabilized, the natural gas column height H that can be blocked by the single cap layer is calculated using the following formula: (P 10 -P 20 )-△P=(ρ 水 -r 气 )·g·H Among them, (P 10 -P 20 ) is the formation pressure difference of the gas reservoirs on both sides of the single cap rock, MPa.

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