System and method for simultaneously measuring gas production characteristics of cores in different occurrence states

Abstract

The present invention discloses a system and method for simultaneously measuring the gas production characteristics of cores in different occurrence states, wherein the system includes a gas collection section, a gas production section and a data acquisition component that are interconnected; the gas collection section simulates the flow process of the bottom horizontal fracture network to the vertical wellbore, and the gas production section simulates the gas production process under different production systems in the vertical wellbore of the formation. The method includes the steps of system connection, system air tightness detection, system space volume calibration, reservoir gas production process simulation, and gas production characteristics calculation of gases in various occurrence states. The system and method of the present invention realize the quantitative evaluation of the gas production rate of adsorbed gas, pore-bound gas, and free gas, and provide a new tool for studying the contribution of gases in different occurrence states to production capacity during the production process. The system and method simulate the production process under real reservoir conditions, and the knowledge obtained from experimental data analysis can be directly used to guide the on-site production of shale / coalbed methane reservoirs.

Description

Technical Field

[0001] The invention belongs to the technical field of core experimental analysis, and in particular relates to a method and a system for simultaneously measuring gas production characteristics of gases in different occurrence states in reservoir cores. Background Art

[0002] The National Energy Administration's "China Natural Gas Development Report (2021)" shows that tight gas reservoirs have gradually become the main contributors to my country's new natural gas reserves, and shale gas and coalbed methane are the main representatives of tight gas reservoirs. In this type of gas reservoir, adsorbed gas is the main form of gas, with a content of up to 85%. The development of technologies such as horizontal drilling and hydraulic fracturing has promoted the industrial development of tight gas reservoirs, but production gas wells generally show the characteristics of "high initial production and rapid decline in the later period". In order to explore the internal mechanism of the decline in production output of shale / coalbed methane reservoirs and provide basic support for innovative technologies, it is urgent to establish an experimental method that simulates the gas production characteristics of gas wells under real formation conditions, reveal the main sources of production in different production stages and the law of declining production capacity, and provide data support for correcting and improving the development theory of tight gas reservoirs and improving production measures. The occurrence state of gas in tight gas reservoirs includes adsorbed gas, pore-bound gas and free gas. The desorption rate test of adsorbed gas includes on-site desorption method and isothermal adsorption method. The former has the problem of long desorption time and difficult calculation of lost gas volume, and the result has a certain deviation from the actual value. The isothermal adsorption measurement results are often larger than the actual gas content of the reservoir, and are mostly used to evaluate the adsorption capacity of the reservoir, but less used to evaluate the gas content; the gas production characteristics test method of pore-bound gas and free gas has not yet appeared in the literature. In short, a method for simultaneously measuring the gas production characteristics of gases in different occurrence states in reservoir cores has not yet been established. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a convenient and effective measurement method and system for measuring the gas production characteristics of gases in different occurrence states in reservoir cores, in order to solve the problems in the prior art such as long desorption time of adsorbed gas, difficulty in calculating the lost gas volume, and inability to measure the gas production characteristics of pore-bound gas and free gas.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A system for simultaneously measuring the gas production characteristics of different occurrence states in the core.

[0006] It includes a gas collection section, a gas production section and a data acquisition component which are interconnected;

[0007] The gas collection section includes a test gas cylinder, a booster pump, an intermediate container, a core holder A, a constant temperature box, a constant pressure and constant speed pump A, a valve A, a valve B, a valve C and a valve D;

[0008] The test gas cylinder is connected to the inlet of the core holder A through a pipeline, the open end of the intermediate container is connected to the pipeline between the test gas cylinder and the core holder A through a connection point A, the booster pump is arranged on the pipeline between the test gas cylinder and the connection point A, the valve A is arranged on the pipeline between the test gas cylinder and the booster pump, the valve B is arranged on the pipeline between the booster pump and the connection point A, the valve C is arranged on the pipeline between the connection point A and the core holder A, a branch pipe A is arranged on the pipeline between valve B and valve C, the valve D is arranged on the branch pipe A, the constant pressure and constant speed pump A is connected to the cylinder of the core holder A to realize the confining pressure displacement of the gas in the core holder A, and the intermediate container and the core holder A and the pipelines connecting them are arranged in a constant temperature box;

[0009] The gas production section includes a pressure regulating valve, a core holder B, a back pressure valve, a back pressure automatic tracking pump, a constant pressure and constant speed pump B and a valve E;

[0010] The air inlet of the core holder B is connected to the air outlet of the core holder A through a pipeline, and the pressure regulating valve is arranged on the pipeline between the core holder A and the core holder B; the back pressure automatic tracking pump is connected between the core holder B cylinder and the inlet pipeline of the core holder B to form a constant pressure displacement of the core in the core holder B; the air inlet of the back pressure valve is connected to the air outlet of the core holder B through a pipeline, and the constant pressure and constant speed pump B is connected to the air inlet side of the back pressure valve; a branch pipe B is arranged on the pipeline connecting the core holder B and the back pressure valve, and the valve E is arranged on the branch pipe B;

[0011] The data acquisition component includes a data terminal, a pressure sensor A, a pressure sensor B, a pressure sensor C, a pressure sensor D, a pressure sensor E, a pressure sensor F and a gas mass flowmeter; the pressure sensor A is arranged on the pipeline between valve B and valve C, the pressure sensor B is arranged on the cylinder of the core holder A to test the confining pressure in the core holder A, the pressure sensor C is arranged on the pipeline connecting the core holder A and the pressure regulating valve, the pressure sensor D is arranged on the pipeline between the pressure regulating valve and the core holder B, the pressure sensor E is arranged on the cylinder of the core holder B to test the confining pressure in the core holder B, the pressure sensor F is arranged on the pipeline between the core holder B and the back pressure valve, and the air outlet of the back pressure valve is connected to the gas mass flowmeter through a pipeline; the pressure sensor A, the pressure sensor B, the pressure sensor C, the pressure sensor D, the pressure sensor E, the pressure sensor F and the gas mass flowmeter are respectively connected to the data terminal, and the data of each pressure sensor is recorded through the data terminal;

[0012] The intermediate container is filled with samples of the core research block, and the intermediate container simulates the reservoir characteristics under the conditions of bottom temperature and original water saturation under the action of the test gas cylinder and the booster pump; the gas collection section simulates the flow process of the bottom horizontal fracture network to the vertical wellbore, and the gas production section simulates the gas production process under different production systems in the vertical wellbore of the formation.

[0013] The present invention also relates to a method for simultaneously measuring gas production characteristics of cores in different occurrence states, comprising the following steps:

[0014] S1. System connection:

[0015] Connect and assemble the gas collection section, gas production section and data acquisition component components;

[0016] S2. System air tightness test;

[0017] Put a fake core in the core holder A and the core holder B, and use constant pressure and constant speed pump A and constant pressure and constant speed pump B to drive at a constant pressure. The drive pressure is higher than the formation pressure. The back pressure valve is set to the formation pressure, and the pressure regulating valve is adjusted to the maximum. The thermostat maintains the formation temperature. Open valves A, B and C, close valves D and E, and use a booster pump to fill helium with the same pressure value as the formation pressure into the intermediate container and the core holder A and the core holder B. After the pressure stabilizes, close valves A and B. After standing, observe the values ​​of pressure sensors A, C and E. If the pressure value does not change, it means that the system is airtight and the experiment begins. If the pressure changes, use soapy water to detect the gas leakage of the system, perform sealing treatment and then perform airtightness test again.

[0018] S3. System space volume calibration:

[0019] The volume V0 of the space between the pressure regulating valve A and valve B is calibrated. During the whole calibration process, valve D is always in the closed state; the volume between valve B and valve C is V′0, and the volume between valve C and the pressure regulating valve is V″0. The steps for calibrating the system space volume V0 are as follows:

[0020] 1) A through-hole dummy core is placed in the core holder A. The pore volume of the dummy core is known as V′. A constant speed and constant pressure pump connected to the core holder A is used for displacement at a constant pressure.

[0021] 2) Filling the intermediate container with a non-porous column with a volume of V1;

[0022] 3) Close valve A, valve B and valve C, and close the pressure regulating valve;

[0023] 4) Open valve A and valve B to fill the intermediate container with gas at a certain pressure, then close valve A and valve B. After the reading of pressure sensor A stabilizes, record its value as P1;

[0024] 5) Open valve C, and wait for the readings of pressure sensor A and pressure sensor C to stabilize and record their values ​​as P2;

[0025] 6) After adjusting the pressure regulating valve to empty the system, repeat steps 2), 3), 4), and 5), changing the volume of the column filled in the intermediate container each time, and complete at least 3 sets of data tests;

[0026] 7) According to Boyle's law, the spatial volume and pressure satisfy the following relationship:

[0027]

[0028] 8) The three sets of data obtained from the test Perform linear fitting with V1, and calculate V′0 and V″0 according to the intercept and slope respectively, then the spatial volume V0 is:

[0029] V0=V′0+V″0;

[0030] S4. Reservoir gas production process simulation:

[0031] Use formation water to saturate the sample to be tested according to the actual water saturation of the formation. The volume of saturated water is V w The steps are as follows: close valve B and valve C, connect valve D to the vacuum pump, start the vacuum pump to evacuate the system, then close valve D and remove the vacuum pump; calculate the amount of formation water to be added to the sample to be tested based on the actual formation water saturation and the core pore volume; use a balance to weigh the calculated formation water volume V w , place the branch pipe A of valve D in the weighed formation water, open valve D until the formation water is fully saturated and enters the container, and let it stand for use;

[0032] The simulation process steps are as follows:

[0033] 1) Fill the reservoir core samples to be tested into the intermediate container and core holder A respectively. The total volume of the core samples is V and the pore volume is V. p , the displacement pressure value of the constant pressure and constant speed pump A connected to the core holder A is higher than the formation pressure;

[0034] 2) Close valve A, valve B and valve E, open valve C and valve D, set the pressure of the pressure regulating valve to zero, connect the vacuum pump to valve D, and use the vacuum pump to evacuate the system. After the vacuum is completed, close valves A, valve B, valve C, valve D and valve E;

[0035] 3) Open valve A, valve B and valve C, use a booster pump to inject the gas in the test gas cylinder into the system in a manner that simulates constant formation pressure, maintain this state so that the core sample to be tested in the core holder A is fully adsorbed, and then close valve A and valve B;

[0036] 4) A dummy core is filled into the core holder B, and a constant pressure and constant speed pump B connected to the core holder B is used for displacement at a constant pressure higher than the formation pressure. The back pressure valve is set to the waste pressure, and then the pressure regulating valve is adjusted to make the outlet flow of the pressure regulating valve reach the set flow rate;

[0037] 5) The data terminal starts the data recording software to record the values ​​of each pressure sensor and gas mass flow meter at different times;

[0038] 6) When the gas mass flow meter outlet flow cannot be constant at the set flow value, adjust the pressure regulating valve to the maximum and continue to record data;

[0039] 7) When the pressure sensor C reaches the waste pressure, stop the experiment, then open valve D and valve E to discharge all the gas in the system, and use a flow meter to record the total amount of waste gas discharged;

[0040] S5. Calculation of gas production characteristics of gases in various occurrence states:

[0041] Combined with the definitions of each part of the system in steps S1-S4, the spatial volume is V0, the apparent volume of the core sample filled in the system is V, and the pore volume of the core sample filled in the intermediate container and the core holder A is V p At any time t, the pressure of pressure sensor A is P(t), and the gas production recorded by the gas mass flow meter at any time t is Q(t). Assume that the time when production ends is t T The total gas production is Q(t T ), after the production is completed, the remaining waste gas volume in the reservoir is Q r , where Z is the gas compression factor, the formation temperature simulated by the thermostat T is the system temperature, R is the universal gas constant, V L is the standard molar volume, M is the relative molecular mass of the gas in the test cylinder, ρ a is the density of adsorbed phase gas;

[0042] At any time, the free gas Q in the system f (t), hole bound gas Q b (t), adsorbed gas Q a (t) The content is calculated as follows:

[0043]

[0044]

[0045] Q b (t) = Q(t T )+QQ(t)-Q f (t)-Q a (t)

[0046] The calculation expression for the gas production rate of gases in different occurrence states between time t1 and time t2 is:

[0047]

[0048]

[0049]

[0050] Ultimate recovery factor of reservoir production E r The calculation expression is:

[0051]

[0052] The system and method of the present invention simultaneously measure the gas production characteristics of different occurrence states of the core, realize the quantitative evaluation of the gas production rate of adsorbed gas, pore-bound gas, and free gas, and provide a new tool for studying the contribution of different occurrence states of gas to production capacity during the production process. The system and method simulate the production process under the real reservoir state, and the knowledge obtained from the experimental data analysis can be directly used to guide the field production of shale / coalbed methane reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The contents expressed in the drawings of the specification and the symbols in the drawings are briefly explained:

[0054] Figure 1 This is a schematic diagram of the system structure of Embodiment 1;

[0055] Figure 2 Example 1 System space volume calibration fitting diagram;

[0056] Figure 3 Example 1 Dynamic gas production rules and cumulative production distribution diagrams at different production stages;

[0057] Figure 4 Example 1 A diagram showing the dynamic change of gas production rate of gases in different states during production;

[0058] In the figure: 1 is a test gas cylinder; 2 is a booster pump; 3 is an intermediate container; 4 is a core holder A; 5 is a constant temperature box; 6 is a constant pressure and constant speed pump A; 7 is a valve A; 8 is a valve B; 9 is a valve C; 10 is a valve D; 11 is a connection point A; 12 is a pressure regulating valve; 13 is a core holder B; 14 is a back pressure valve; 15 is a back pressure automatic tracking pump; 16 is a constant pressure and constant speed pump B; 17 is a valve E; 18 is a data terminal; 19 is a pressure sensor A; 20 is a pressure sensor B; 21 is a pressure sensor C; 22 is a pressure sensor D; 23 is a pressure sensor E; 24 is a pressure sensor F; 25 is a gas mass flow meter. DETAILED DESCRIPTION

[0059] The present invention is further described below with reference to a non-limiting embodiment of the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0060] Embodiment 1

[0061] like Figure 1 As shown in the figure, a system for simultaneously measuring the gas production characteristics of different occurrence states in the core is used.

[0062] It includes a gas collection section, a gas production section and a data acquisition component which are interconnected;

[0063] The gas collection section includes a test gas cylinder 1, a booster pump 2, an intermediate container 3, a core holder A4, a constant temperature box 5, a constant pressure and constant speed pump A6, a valve A7, a valve B8, a valve C9 and a valve D10;

[0064] The test gas cylinder 1 is connected to the inlet of the core holder A4 through a pipeline, the open end of the intermediate container 3 is connected to the pipeline between the test gas cylinder 1 and the core holder A4 through a connection point A11, the booster pump 2 is arranged on the pipeline between the test gas cylinder 1 and the connection point A11, the valve A7 is arranged on the pipeline between the test gas cylinder 1 and the booster pump 2, the valve B8 is arranged on the pipeline between the booster pump 2 and the connection point A11, the valve C9 is arranged on the pipeline between the connection point A11 and the core holder A4, a branch pipe A is arranged on the pipeline between the valve B8 and the valve C9, the valve D10 is arranged on the branch pipe A, the constant pressure and constant speed pump A6 is connected to the cylinder of the core holder A4 to realize the confining pressure displacement of the gas in the core holder A4, and the intermediate container 3 and the core holder A4 and the pipelines connecting them are arranged in a constant temperature box 5;

[0065] The gas production section includes a pressure regulating valve 12, a core holder B13, a back pressure valve 14, a back pressure automatic tracking pump 15, a constant pressure and constant speed pump B16 and a valve E17;

[0066] The air inlet of the core holder B13 is connected to the air outlet of the core holder A4 through a pipeline, and the pressure regulating valve 12 is arranged on the pipeline between the core holder A4 and the core holder B13; the back pressure automatic tracking pump 15 is connected between the core holder B13 cylinder and the inlet pipeline of the core holder B13 to form a constant pressure displacement of the core in the core holder B13; the air inlet of the back pressure valve 14 is connected to the air outlet of the core holder B13 through a pipeline, and the constant pressure and constant speed pump B16 is connected to the air inlet side of the back pressure valve 14; a branch pipe B is arranged on the pipeline connecting the core holder B13 and the back pressure valve 14, and the valve E17 is arranged on the branch pipe B;

[0067] The data acquisition component includes a data terminal 18, a pressure sensor A19, a pressure sensor B20, a pressure sensor C21, a pressure sensor D22, a pressure sensor E23, a pressure sensor F24 and a gas mass flow meter 25; the pressure sensor A19 is arranged on the pipeline between the valve B8 and the valve C9, the pressure sensor B20 is arranged on the cylinder of the core holder A4 to test the confining pressure in the core holder A4, the pressure sensor C21 is arranged on the pipeline connecting the core holder A4 and the pressure regulating valve 12, and the pressure sensor D22 is arranged between the pressure regulating valve 12 and the core holder B1 3, the pressure sensor E23 is arranged on the cylinder of the core holder B13 to test the confining pressure in the core holder B13, the pressure sensor F24 is arranged on the pipeline between the core holder B13 and the back pressure valve 14, and the gas outlet of the back pressure valve 14 is connected to the gas mass flow meter 25 through a pipeline; the pressure sensor A19, the pressure sensor B20, the pressure sensor C21, the pressure sensor D22, the pressure sensor E23, the pressure sensor F24 and the gas mass flow meter 25 are respectively connected to the data terminal 18, and the data of each pressure sensor is recorded through the data terminal 18;

[0068] The intermediate container 3 is filled with samples of the core research block, and the intermediate container 3 simulates the reservoir characteristics under the conditions of bottom temperature and original water saturation under the action of the test gas cylinder 1 and the booster pump 2; the gas collection section simulates the flow process of the bottom horizontal fracture network to the vertical wellbore, and the gas production section simulates the gas production process under different production systems in the vertical wellbore of the formation.

[0069] The above-mentioned systematic experimental method for simultaneously measuring the gas production characteristics of different occurrence states of the core includes the following steps:

[0070] S1. System connection:

[0071] Connect and assemble the gas collection section, gas production section and data acquisition components; Figure 1Connect the pipelines. The functions of each component in the experimental process are as follows: the test gas cylinder 1 and the booster pump 2 provide gas with the target pressure value in the experiment, the test gas cylinder 1 is filled with methane, and the intermediate container 3 is filled with samples of the study block, which can simulate the reservoir characteristics under the conditions of formation temperature and original water saturation; the core holder A4 is filled with real reservoir samples to simulate the flow process of real reservoir natural gas from the matrix to the vertical wellbore; the components composed of the pressure regulating valve 12, the core holder B13, and the back pressure valve 14 simulate the production process of gas under different production systems, among which the core holder B13 is filled with fake cores; the gas mass flow meter 25, the pressure sensor, and the data terminal 18 constitute the data recording component of the system; the constant temperature box 5, the back pressure automatic tracking pump 15, and the constant pressure and constant speed pump constitute the reservoir environment simulation component.

[0072] S2. System air tightness test:

[0073] Put a fake core in the core holder A4 and the core holder B13, and use constant pressure and constant speed pumps A6 and B16 to displace at constant pressure. The displacement pressure is 2MPa higher than the formation pressure. The back pressure valve 14 is set to the formation pressure, and the pressure regulating valve 12 is adjusted to the maximum. The thermostat 5 maintains the formation temperature. Open valves A7, B8 and C9, close valves D10 and E17, and use booster pump 2 to fill helium with the same pressure value as the formation pressure into the intermediate container 3 and the core holder A4 and B13. After the pressure stabilizes, close valves A7 and B8. After standing for 24 hours, observe the values ​​of pressure sensor A19, pressure sensor C21 and pressure sensor E23. If the pressure value does not change, it means that the system is airtight and the experiment begins; if the pressure changes, use soap bubble water to detect the gas leakage of the system, perform sealing treatment and then perform airtightness test again.

[0074] S3. System space volume calibration:

[0075] The volume V0 of the space between the pressure regulating valve 12A and the valve B8 is calibrated. During the entire calibration process, the valve D10 is always in a closed state; the volume between the valve B8 and the valve C9 is V′0, and the volume between the valve C9 and the pressure regulating valve 12 is V″0. The calibration steps are as follows:

[0076] 1. Place a dummy core with a central hole in the core holder A4. The pore volume of the dummy core is known as V′. A constant speed and pressure pump connected to the core holder A4 is used for displacement at a constant pressure of 10 MP.

[0077] 2. Filling the intermediate container 3 with a non-porous column having a volume of V1, wherein the non-porous column is a stainless steel column;

[0078] 3. Close valve A7, valve B8 and valve C9, and set the pressure value of pressure regulating valve 12 to 0;

[0079] 4. Open valve A7 and valve B8 to fill the intermediate container 3 with gas of a certain pressure, then close valve A7 and valve B8, and wait for the reading of pressure sensor A19 to stabilize and record its value as P1;

[0080] 5 Open valve C9, and wait for the readings of pressure sensor A19 and pressure sensor C21 to stabilize and record their values ​​as P2;

[0081] 6. After adjusting the pressure regulating valve 12 to vent the system, repeat steps 2, 3, 4, and 5. Change the volume of the column filled in the intermediate container 3 each time, and complete 3 sets of data tests;

[0082] 7 According to Boyle's law, the volume and pressure of space satisfy the following relationship:

[0083]

[0084] 8. The three sets of data obtained from the test Perform linear fitting with V1, and calculate V′0 and V″0 according to the intercept and slope respectively, then the spatial volume V0 is:

[0085] V0=V′0+V′0

[0086] The original data of the calibration process of this embodiment is shown in Table 1, and the fitting results are shown in Figure 2 :

[0087] Table 1: Original data record table of system space volume calibration process

[0088]

[0089] From the fitting formula, we can know:

[0090] S4. Reservoir gas production process simulation:

[0091] In this embodiment, the water saturation is set to 0, and the saturated water volume V w is 0. The simulation process steps are as follows:

[0092] 1 Fill the reservoir core sample to be tested into the intermediate container 3 and the core holder A4 respectively. The total volume of the core sample is V, and the pore volume of the core sample in the intermediate container 3 and the core holder A4 is V. p , the displacement pressure value of the constant pressure and constant speed pump A6 connected to the core holder A4 is 2MPa higher than the formation pressure. In this embodiment, the displacement pressure is set to 10MPa;

[0093] 2 Close valve A7, valve B8 and valve E17, open valve C9 and valve D10, set the pressure of pressure regulating valve 12 to zero, connect the vacuum pump to valve D10, and use the vacuum pump to evacuate the system for 24 hours. After the vacuum is completed, close valves A7, valve B8, valve C9, valve D10 and valve E17;

[0094] 3. Open valve A7, valve B8 and valve C9, and use booster pump 2 to inject methane gas in test gas cylinder 1 into the system at a constant pressure of 8 MPa. Keep this state to allow the core sample to be fully adsorbed in core holder A4 for 24 hours, then close valve A7 and valve B8;

[0095] 4. Fill the core holder B13 with a fake core, and the constant pressure and constant speed pump B16 connected to the core holder B13 displaces the core at a constant pressure of 10 MPa. The back pressure valve 14 is set to 1 MPa, and then the pressure regulating valve 12 is adjusted to make the outlet flow of the pressure regulating valve 12 reach the set flow rate;

[0096] 5 The data terminal 18 starts the data recording software to record the values ​​of each pressure sensor and the gas mass flow meter 25 at different times;

[0097] 6 When the outlet flow of the gas mass flow meter 25 cannot be kept constant at the set flow value, adjust the pressure regulating valve 12 to the maximum and continue to record data;

[0098] 7 When the pressure sensor C21 reaches the waste pressure, stop the experiment, then open valve D10 and valve E17 to discharge all the gas in the system, and use a flow meter to record the total amount of waste gas discharged;

[0099] The original data of the experimental process are recorded in Table 2, and the gas production characteristics are recorded in Figure 3 .

[0100] Table 2: Raw data record of pressure and flow during production

[0101]

[0102]

[0103] Through Table 2 and Figure 3 It can be seen that after the stable production time was 13.8 hours, it turned into attenuation production and the attenuation production lasted for 36.4 hours, which overall reproduced the characteristics of shale gas reservoir production with large production attenuation and long production period.

[0104] S5. Calculation of gas production characteristics of gases in various occurrence states:

[0105] Combined with the definitions of each part of the system in steps S1-S4, the spatial volume is V0, the apparent volume of the core sample filled in the system is V, and the pore volume of the core sample filled in the intermediate container 3 and the core holder A4 is V p At any time t, the pressure of pressure sensor A19 is P(t), and the gas production recorded by gas mass flow meter 25 is Q(t). Assume that the time when production ends is t T The total gas production is Q(t T ), after the production is completed, the remaining waste gas volume in the reservoir is Q r , where Z is the gas compression factor, the formation temperature simulated by the thermostat 5 T is the system temperature, R is the universal gas constant, V L is the standard molar volume, M is the relative molecular mass of the gas in the test cylinder 1, ρ a is the density of adsorbed phase gas;

[0106] At any time, the free gas Q in the system f (t), hole bound gas Q b (t), adsorbed gas Q a (t) The content is calculated as follows:

[0107]

[0108]

[0109] Q b (t) = Q(t T )+QQ(t)-Q f (t)-Q a (t)

[0110] The calculation expression for the gas production rate of gases in different occurrence states between time t1 and time t2 is:

[0111]

[0112]

[0113]

[0114] Ultimate recovery factor of reservoir production E r The calculation expression is:

[0115]

[0116] The calculation data of gas production rate and final recovery rate of gas in different occurrence states during production are shown in Table 3, and the dynamic distribution diagram of gas production rate is shown in Figure 4 .

[0117] Table 3: Calculation results of gas production rate and recovery rate of gases in different occurrence states during production

[0118]

[0119] Through Table 3 and Figure 4 It can be seen that this embodiment realizes the separation of gas production in different occurrence states, reveals the contribution of gases in different occurrence states to production during gas reservoir production, provides a technical means for studying the influence of reservoir gas production characteristics under different production systems, and also provides an indoor simulation method for optimizing gas reservoir production systems.

[0120] The pressure sensor, data terminal 18 and its software and other related processing, sending and receiving programs of the present invention are conventional technical choices of those skilled in the art, belong to the prior art, and are technical solutions that can be obtained without creative labor. They are not the objects protected by the present invention.

[0121] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, if the terms "first", "second", etc. appear, they are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0122] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

Claims

1. A system for simultaneously measuring the gas production characteristics of different occurrence states of the core, characterized in that: It includes a gas collection section, a gas production section and a data acquisition component which are interconnected; The gas collection section comprises a test gas cylinder (1), a booster pump (2), an intermediate container (3), a core holder A (4), a constant temperature box (5), a constant pressure and constant speed pump A (6), a valve A (7), a valve B (8), a valve C (9) and a valve D (10); The test gas cylinder (1) is connected to the inlet of the core holder A (4) via a pipeline, the open end of the intermediate container (3) is connected to the pipeline between the test gas cylinder (1) and the core holder A (4) via a connection point A (11), the booster pump (2) is arranged on the pipeline between the test gas cylinder (1) and the connection point A (11), the valve A (7) is arranged on the pipeline between the test gas cylinder (1) and the booster pump (2), and the valve B (8) is arranged between the booster pump (2) and the connection point A (11). The valve C (9) is arranged on the pipeline between the connection point A (11) and the core holder A (4), a branch pipe A is arranged on the pipeline between the valve B (8) and the valve C (9), the valve D (10) is arranged on the branch pipe A, the constant pressure and constant speed pump A (6) is connected to the cylinder of the core holder A (4) to achieve confining pressure displacement of gas in the core holder A (4), and the intermediate container (3) and the core holder A (4) and the pipelines connecting them are arranged in a constant temperature box (5); The gas production section comprises a pressure regulating valve (12), a core holder B (13), a back pressure valve (14), a back pressure automatic tracking pump (15), a constant pressure and constant speed pump B (16) and a valve E (17); The air inlet of the core holder B (13) is connected to the air outlet of the core holder A (4) through a pipeline, and the pressure regulating valve (12) is arranged on the pipeline between the core holder A (4) and the core holder B (13); the back pressure automatic tracking pump (15) is connected between the core holder B (13) cylinder and the inlet pipeline of the core holder B (13) to form a constant pressure displacement of the core in the core holder B (13); the air inlet of the back pressure valve (14) is connected to the air outlet of the core holder B (13) through a pipeline, and the constant pressure constant speed pump B (16) is connected to the air inlet side of the back pressure valve (14); a branch pipe B is arranged on the pipeline connecting the core holder B (13) and the back pressure valve (14), and the valve E (17) is arranged on the branch pipe B; The data acquisition component comprises a data terminal (18), a pressure sensor A (19), a pressure sensor B (20), a pressure sensor C (21), a pressure sensor D (22), a pressure sensor E (23), a pressure sensor F (24) and a gas mass flow meter (25); the pressure sensor A (19) is arranged on a pipeline between valves B (8) and valves C (9); the pressure sensor B (20) is arranged on a cylinder of a core holder A (4) to test the confining pressure in the core holder A (4); the pressure sensor C (21) is arranged on a pipeline connecting the core holder A (4) and a pressure regulating valve (12); the pressure sensor D (22) is arranged on a pipeline connecting the pressure regulating valve (12) and the core holder B (4); (13), the pressure sensor E (23) is arranged on the cylinder of the core holder B (13) to test the confining pressure in the core holder B (13), the pressure sensor F (24) is arranged on the pipeline between the core holder B (13) and the back pressure valve (14), and the gas outlet of the back pressure valve (14) is connected to the gas mass flow meter (25) through a pipeline; the pressure sensor A (19), the pressure sensor B (20), the pressure sensor C (21), the pressure sensor D (22), the pressure sensor E (23), the pressure sensor F (24) and the gas mass flow meter (25) are respectively connected to the data terminal (18), and the data of each pressure sensor is recorded through the data terminal (18); The intermediate container (3) is filled with samples of the core research block, and the intermediate container (3) simulates reservoir characteristics under the conditions of bottom temperature and original water saturation under the action of the test gas cylinder (1) and the booster pump (2); The gas collection section simulates the flow process of the bottom horizontal fracture network to the vertical wellbore, and the gas production section simulates the production process of gas under different production systems in the vertical wellbore of the formation.

2. A method for simultaneously measuring the gas production characteristics of different occurrence states of a core, based on the system for simultaneously measuring the gas production characteristics of different occurrence states of a core according to claim 1, characterized in that: The steps include: S1. System connection: connect and assemble the gas collection section, gas production section and data acquisition components; S2. System air tightness test; S3, system space volume calibration: calibrate the space volume V0 between the pressure regulating valve (12) A and the valve B (8); S4. Reservoir gas production process simulation: Use formation water to saturate the sample to be tested according to the actual water saturation of the formation. The volume of saturated water is V w ; The simulation process steps are as follows: 1) Fill the reservoir core sample to be tested into the intermediate container (3) and the core holder A (4) respectively, with the total volume of the core sample being V and the pore volume being V. p , the displacement pressure value of the constant pressure and constant speed pump A(6) connected to the core holder A(4) is higher than the formation pressure; 2) Close valve A (7), valve B (8) and valve E (17), open valve C (9) and valve D (10), set the pressure of the pressure regulating valve (12) to zero, connect the vacuum pump to valve D (10), and evacuate the system with the vacuum pump. After completion, close valves A (7), valve B (8), valve C (9), valve D (10) and valve E (17); 3) Open valve A (7), valve B (8) and valve C (9), use the booster pump (2) to inject the gas in the test gas cylinder (1) into the system in a manner that simulates the constant pressure of the formation, maintain this state so that the core sample to be tested in the core holder A (4) is fully adsorbed, and then close valve A (7) and valve B (8); 4) A dummy core is filled into the core holder B (13), and a constant pressure and constant speed pump B (16) connected to the core holder B (13) is used to displace the core at a constant pressure higher than the formation pressure. The back pressure valve (14) is set to a waste pressure, and then the pressure regulating valve (12) is adjusted to make the outlet flow of the pressure regulating valve (12) reach the set flow rate; 5) The data terminal (18) starts the data recording software to record the values ​​of each pressure sensor and the gas mass flow meter (25) at different times; 6) When the outlet flow rate of the gas mass flow meter (25) cannot be kept constant at the set flow rate value, adjust the pressure regulating valve (12) to the maximum and continue to record data; 7) When the pressure sensor C (21) reaches the waste pressure, stop the experiment, then open valve D (10) and valve E (17) to discharge all the gas in the system, and use a flow meter to record the total amount of waste gas discharged; S5. Calculation of gas production characteristics of gases in various occurrence states: Combined with the definitions of each part of the system in steps S1-S4, the spatial volume is V0, the apparent volume of the core sample filled in the system is V, and the pore volume of the core sample filled in the intermediate container (3) and the core holder A (4) is V p At any time t, the pressure of pressure sensor A (19) is P(t), and the gas production recorded by gas mass flow meter (25) at any time t is Q(t). Assume that the time when production ends is t T The total gas production is Q(t T ), after the production is completed, the remaining waste gas volume in the reservoir is Q r , where Z is the gas compressibility factor, the formation temperature simulated by the thermostat (5) is T, the system temperature, R is the universal gas constant, V L is the standard molar volume, M is the relative molecular mass of the gas in the test cylinder (1), ρ a is the density of adsorbed phase gas; At any time, the free gas Q in the system f (t), hole bound gas Q b (t), adsorbed gas Q a (t) The content is calculated as follows: Q b (t)=Q(t T )+Q-Q(t)-Q f (t)-Q a (t) The calculation expression for the gas production rate of gases in different occurrence states between time t1 and time t2 is: Ultimate recovery factor of reservoir production E r The calculation expression is:

3. The method according to claim 2, characterized in that The air tightness detection steps in step S2 are as follows: a dummy core is placed in the core holder A (4) and the core holder B (13); a constant pressure constant speed pump A (6) and a constant pressure constant speed pump B (16) are used for constant pressure displacement, the displacement pressure is higher than the formation pressure, the back pressure valve (14) is set to the formation pressure, the gate pressure of the pressure regulating valve (12) is adjusted to the maximum, and the thermostatic box (5) maintains the formation temperature; valves A (7), B (8) and C (9) are opened, valves D (10) and E (17) are closed, and a booster pump (2) is used. Fill the intermediate container (3), core holder A (4) and core holder B (13) with helium gas of the same pressure as the formation pressure. After the pressure stabilizes, close valve A (7) and valve B (8). After standing, observe the values ​​of pressure sensor A (19), pressure sensor C (21) and pressure sensor E (23). If the pressure value does not change, it means that the system is airtight and the experiment can be started. If the pressure changes, use soapy water to detect the gas leakage of the system, perform sealing treatment and then perform airtightness test again.

4. The method according to claim 2, characterized in that In step S3, during the entire calibration process, valve D (10) is always in a closed state; the volume between valve B (8) and valve C (9) is V′0, and the volume between valve C (9) and pressure regulating valve (12) is V″0. The system space volume V0 calibration steps are as follows: 1) A through-hole dummy core is placed in the core holder A (4), the pore volume of the dummy core being a known V′, and a constant speed and pressure pump connected to the core holder A (4) is used to displace the core at a constant pressure; 2) filling the intermediate container (3) with a non-porous column having a volume of V1; 3) Close valve A (7), valve B (8) and valve C (9), and close the pressure regulating valve (12); 4) Open valve A (7) and valve B (8) to fill the intermediate container (3) with gas at a certain pressure, then close valve A (7) and valve B (8), and wait for the reading of pressure sensor A (19) to stabilize and record the value as P1; 5) Open valve C (9), wait for the readings of pressure sensor A (19) and pressure sensor C (21) to stabilize and record their values ​​as P2; 6) Adjust the pressure regulating valve (12) to vent the system and repeat steps 2), 3), 4), and 5), changing the volume of the column filled in the intermediate container (3) each time, and complete at least 3 sets of data tests; 7) According to Boyle's law, the spatial volume and pressure satisfy the following relationship: 8) The three sets of data obtained from the test Perform linear fitting with V1, and calculate V′0 and V″0 according to the intercept and slope respectively, then the spatial volume V0 is: V0=V′0+V″0.

5. The method according to claim 2, characterized in that In step S4, the steps of using formation water to saturate the core sample to be tested according to the actual water saturation of the formation are as follows: close valve B (8) and valve C (9), connect valve D (10) to the vacuum pump, start the vacuum pump to evacuate the system, then close valve D (10) and remove the vacuum pump; calculate the amount of formation water to be added to the sample to be tested according to the actual water saturation of the formation and the pore volume of the core; use a balance to weigh the calculated formation water volume V w , place the branch pipe A of valve D (10) in the measured formation water, open valve D (10) until the formation water is completely saturated and enters the container, and then let it stand for use.

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