CN114720655A - System and method for simultaneously measuring gas output characteristics of rock cores in different occurrence states - Google Patents

System and method for simultaneously measuring gas output characteristics of rock cores in different occurrence states Download PDF

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CN114720655A
CN114720655A CN202210279383.5A CN202210279383A CN114720655A CN 114720655 A CN114720655 A CN 114720655A CN 202210279383 A CN202210279383 A CN 202210279383A CN 114720655 A CN114720655 A CN 114720655A
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valve
pressure
gas
core holder
constant
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肖前华
王怀林
姜柏材
李嘉豪
丁忠佩
向祖平
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Chongqing University of Science and Technology
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Chongqing University of Science and Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/22—Fuels, explosives
    • G01N33/225—Gaseous fuels, e.g. natural gas
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M3/00—Investigating fluid-tightness of structures
    • G01M3/02—Investigating fluid-tightness of structures by using fluid or vacuum
    • G01M3/04—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point
    • G01M3/06—Investigating fluid-tightness of structures by using fluid or vacuum by detecting the presence of fluid at the leakage point by observing bubbles in a liquid pool
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
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Abstract

The invention discloses a system and a method for simultaneously measuring gas output characteristics of different occurrence states of a rock core, wherein the system comprises a gas collection section, a gas output section and a data acquisition assembly which are connected with each other; the gas collection section simulates the process of flowing from a bottom layer horizontal fracturing network to the vertical shaft, and the gas output section simulates the production process of gas in the stratum vertical shaft under different production systems. The method comprises the steps of system connection, system air tightness detection, system space volume calibration, reservoir gas production process simulation and gas production characteristic calculation of each occurrence state. The system and the method realize quantitative evaluation on the gas production speed of the adsorbed gas, the hole bound gas and the free gas, and provide a new tool for researching the contribution of the gases in different occurrence states to the productivity in the production process. The system and the method simulate the production process under the real reservoir state, and the knowledge obtained by analyzing the experimental data can be directly used for guiding the on-site production of the shale/coal bed methane reservoir.

Description

System and method for simultaneously measuring gas output characteristics of rock cores in different occurrence states
Technical Field
The invention belongs to the technical field of rock core experimental analysis, and particularly relates to a method and a system for simultaneously measuring gas production characteristics of different occurrence states of a reservoir rock core.
Background
Chinese natural gas development report (2021) of the national energy agency indicates that the dense gas reservoir gradually becomes a main contributor to the newly increased reserves of natural gas in China, and shale gas and coal bed gas are the main representatives of the dense gas reservoir. In the gas reservoir, the adsorption gas is the main occurrence form of the gas, and the content can reach 85 percent at most. The development of technologies such as horizontal drilling, hydraulic fracturing and the like promotes the industrial development of compact gas reservoirs, but production gas wells generally have the characteristics of high initial yield and rapid decrease in later period. In order to explore the internal decreasing mechanism of the production yield of the shale/coal bed gas reservoir and provide basic support for the innovation technology, an experimental method for simulating the gas production characteristics of a gas well under the real stratum condition needs to be established urgently, main sources of the yield in different production stages and decreasing rules of the yield are revealed, and data support is provided for modifying and perfecting the development theory of the compact gas reservoir and improving production measures. The existing state of the dense gas reservoir gas comprises adsorbed gas, hole bound gas and free gas, the adsorbed gas desorption speed test comprises an on-site desorption method and an isothermal adsorption method, the former has the problems that the desorption time is long, the gas loss is difficult to calculate, and the result has certain deviation from the actual value. The isothermal adsorption measurement result is usually larger than the real gas content of the reservoir, is mainly used for evaluating the adsorption capacity of the reservoir and is less used for evaluating the gas content; methods for testing gassing characteristics of pore-bound and free gases have not been reported in the literature. In conclusion, a method for simultaneously measuring gas production characteristics of different occurrence states of a reservoir core has not been established.
Disclosure of Invention
The invention aims to solve the technical problems that the existing measurement technology for the gas production characteristics of gas in different occurrence states of a reservoir rock core has defects, a convenient and effective measurement method and a convenient and effective measurement system are provided for the measurement of the gas production characteristics of the gas in different occurrence states of the reservoir rock core, and the problems that the desorption time of adsorbed gas is long, the gas loss is difficult to calculate, the gas production characteristics of hole bound gas and free gas cannot be measured in the prior art are solved.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a system for simultaneously measuring gas output characteristics of different occurrence states of a rock core,
comprises a gas collection section, a gas output section and a data acquisition component which are connected with each other;
the gas collecting section comprises a test gas cylinder, a booster pump, an intermediate container, a rock core holder A, a thermostat, a constant-pressure constant-speed pump A, a valve B, a valve C and a valve D;
the test gas cylinder is connected with the inlet of the core holder A through a pipeline, the open end of the intermediate container is connected with the pipeline between the test gas cylinder and the core holder A through a connection point A, the booster pump is arranged on a pipeline between the test gas cylinder and the connection point A, the valve A is arranged on a pipeline between the test gas cylinder and the booster pump, the valve B is arranged on a pipeline between the booster pump and the connection point A, the valve C is arranged on a pipeline between the connection point A and the core holder A, a branch pipe A is arranged on a pipeline between the valve B and the valve C, the valve D is arranged on the branch pipe A, the constant-pressure constant-speed pump A is connected to the cylinder of the core holder A to realize the gas confining pressure displacement in the core holder A, the middle container, the core holder A and pipelines mutually connected between the middle container and the core holder A are arranged in a constant temperature box;
the gas output section comprises a pressure regulating valve, a rock core holder B, a back pressure valve, a back pressure automatic tracking pump, a constant pressure constant speed pump B and a valve E;
the air inlet of the core holder B is communicated with 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 a barrel of the core holder B and an inlet pipeline of the core holder B to form constant pressure displacement of a core in the core holder B; the air inlet of the back pressure valve is connected with the air outlet of the rock core holder B through a pipeline, and the constant-pressure constant-speed pump B is connected to the air inlet side of the back pressure valve; a branch pipe B is arranged on a pipeline connected with the rock core holder B and the back pressure valve, and the valve E is arranged on the branch pipe B;
the data acquisition assembly comprises 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 a pipeline between a valve B and a valve C, the pressure sensor B is arranged on a cylinder of the core holder A to test confining pressure in the core holder A, the pressure sensor C is arranged on a pipeline connected with the core holder A and a pressure regulating valve, the pressure sensor D is arranged on a pipeline between the pressure regulating valve and the core holder B, the pressure sensor E is arranged on a cylinder of the core holder B to test confining pressure in the core holder B, the pressure sensor F is arranged on a pipeline between the core holder B and a back-pressure valve, and an air outlet of the back-pressure valve is connected with 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 with a data terminal, and data of each pressure sensor are recorded through the data terminal;
filling samples of a core research block by the intermediate container, and simulating reservoir characteristics under the conditions of bottom layer temperature and original water saturation by the intermediate container under the action of a test gas cylinder and a booster pump; the gas collection section simulates the process of flowing from a bottom layer horizontal fracturing network to a vertical shaft, and the gas output section simulates the production process of gas in the stratum vertical shaft under different production systems.
The invention also relates to a method for simultaneously measuring the gas output characteristics of different occurrence states of the rock core, which comprises the following steps:
s1, system connection:
connecting and assembling each part of the gas collection section, the gas output section and the data acquisition assembly;
s2, detecting the air tightness of the system;
placing false cores in the core holder A and the core holder B, adopting constant-pressure displacement by the constant-pressure constant-speed pump A and the constant-pressure constant-speed pump B, wherein the displacement pressure is higher than the formation pressure, setting a back pressure valve as the formation pressure, adjusting the pressure of a pressure adjusting valve to the maximum, and keeping the formation temperature by a constant temperature box; opening a valve A, a valve B and a valve C, closing a valve D and a valve E, filling helium with the same pressure value as the formation pressure into the intermediate container, the core holder A and the core holder B by using a booster pump, and closing the valve A and the valve B after the pressure is stable; after standing, observing the numerical values of the pressure sensor A, the pressure sensor C and the pressure sensor E, if the pressure values are not changed, indicating that the system is good in air tightness, and starting an experiment; if the pressure changes, the gas leakage part of the soap soaking water detection system is used for carrying out sealing treatment and then carrying out gas tightness detection again;
s3, system space volume calibration:
volume V of space between pressure regulating valve A and valve B0Calibrating, wherein the valve D is always in a closed state in the whole calibration process; the volume between the valve B and the valve C is V'0The volume between the valve C and the pressure regulating valve is V ″)0Volume of system space V0The calibration steps are as follows:
1) placing a hollow false core into the core holder A, wherein the pore volume of the false core is known as V', and a constant-speed and constant-pressure pump connected with the core holder A is used for displacing at a constant pressure;
2) filling volume V into intermediate container1The non-porous cylinder of (a);
3) closing the valve A, the valve B and the valve C, and closing the pressure regulating valve;
4) opening the valve A and the valve B, filling gas with certain pressure into the intermediate container, closing the valve A and the valve B, and recording the numerical value of the pressure sensor A as P after the reading of the pressure sensor A is stable1；
5) Opening the valve C, recording the reading of the pressure sensor A and the pressure sensor C as P after the reading of the pressure sensor A and the pressure sensor C is stable2；
6) After the pressure regulating valve is adjusted to be emptied into the system, the steps 2), 3), 4) and 5) are repeated, the volume of the filling cylinder of the intermediate container is changed when the steps are repeated each time, and at least 3 groups of data tests are finished;
7) the volume in space and the pressure satisfy the following relation calculated according to Boyle's law:
Figure BDA0003556430110000041
8) 3 sets of data obtained from the test
Figure BDA0003556430110000042
And V1Linear fitting was performed, and V 'was obtained from the intercept and slope, respectively'0、V″0Then volume of space V0Comprises the following steps:
V0＝V′0+V″0；
s4, simulating the production process of reservoir gas:
saturating the sample to be measured according to the real water saturation of the stratum by using the stratum water, wherein the volume of the saturated water is Vw(ii) a The method comprises the following steps: closing the valve B and the valve C, connecting the valve D with a vacuum pump, starting the vacuum pump to vacuumize the system, then closing the valve D and removing the vacuum pump; calculating the stratum water amount to be added into the sample to be measured according to the real stratum water saturation and the core pore volume; the volume V of the formation water is obtained by weighing and calculating by a balancewPlacing a branch pipe A of a valve D in the weighed formation water, opening the valve D until the formation water is completely saturated and enters a container, and standing for later use;
the simulation process comprises the following steps:
1) respectively filling the core sample to be detected in the reservoir into the intermediate container and the core holder A, wherein the total volume of the filled core sample is V, and the pore volume is VpThe displacement pressure value of a constant-pressure constant-speed pump A connected with the rock core holder A is higher than the formation pressure;
2) closing the valve A, the valve B and the valve E, opening the valve C and the valve D, setting the pressure of the pressure regulating valve to be zero, connecting a vacuum pump with the valve D, vacuumizing the system by the vacuum pump, and closing the valve A, the valve B, the valve C, the valve D and the valve E after the vacuum pump finishes vacuumizing;
3) opening a valve A, a valve B and a valve C, injecting gas in a test gas cylinder into the system in a mode of simulating formation constant pressure by using a booster pump, keeping the state to ensure that a rock core sample to be tested in the rock core holder A is fully adsorbed, and then closing the valve A and the valve B;
4) filling a false core in the core holder B, displacing the false core by a constant-pressure constant-speed pump B connected with the core holder B at a constant pressure higher than the formation pressure, setting the size of a back pressure valve as a waste pressure, and then adjusting the size of a pressure regulating valve to enable the outlet flow of the pressure regulating valve to reach a set flow rate;
5) the data terminal starts data recording software and records the count values of the pressure sensors and the gas mass flow at different times;
6) when the outlet flow of the gas mass flowmeter cannot be kept constant at a set flow value, the pressure regulating valve is regulated to be maximum, and data are continuously recorded;
7) stopping the experiment when the pressure sensor C reaches the waste pressure, then opening the valve D and the valve E, discharging all the gas in the system, and recording the total amount of the discharged waste gas by using a flowmeter;
s5, calculating gas production characteristics of the gas in each occurrence state:
combining the definitions of the parts in the system of steps S1-S4, wherein the space volume is V0The apparent volume of the filled core sample in the system is V, and the pore volume of the filled core sample in the middle container and the core holder A is VpThe pressure of the pressure sensor A at any time t is P (t), the gas yield recorded by the gas mass flowmeter at any time t is Q (t), and the time when production is finished is assumed to be tTThe total gas production is Q (t)T) And after production is finished, the residual waste gas quantity of the reservoir is QrWherein Z is a gas compression factor, the simulated formation temperature T of the constant temperature box is the system temperature, R is a universal gas constant, and V isLIs the standard molar volume, M is the gas phase relative molecular mass in the test cylinder, ρaIs the adsorption phase gas density;
then at any time, free gas Q in the systemf(t) a pore-bounding gas Qb(t) adsorption gas Qa(t) the content calculation formula is as follows:
Figure BDA0003556430110000051
Figure BDA0003556430110000052
Qb(t)＝Q(tT)+Q-Q(t)-Qf(t)-Qa(t)
at time t1And time t2The expression formula for calculating the gas production speed of the gas in different occurrence states is as follows:
Figure BDA0003556430110000053
Figure BDA0003556430110000054
Figure BDA0003556430110000061
ultimate recovery of reservoir production ErThe calculation expression is:
Figure BDA0003556430110000062
the system and the method for simultaneously measuring the gas output characteristics of the rock core in different occurrence states realize quantitative evaluation on gas production speed of adsorbed gas, hole bound gas and free gas, and provide a new tool for researching the contribution of the gas in different occurrence states to the productivity in the production process. The system and the method simulate the production process under the real reservoir state, and the knowledge obtained by analyzing the experimental data can be directly used for guiding the on-site production of the shale/coal bed methane reservoir.
Drawings
The contents of the description and the references in the drawings are briefly described as follows:
FIG. 1 is a schematic diagram of a system according to a first embodiment;
FIG. 2 is a system space volume calibration fit of the embodiment;
FIG. 3 shows a dynamic gas production law and cumulative gas production distribution map at different stages of production;
FIG. 4 is a diagram illustrating a gas production rate dynamic change rule of gas in different occurrence states during a production process according to an embodiment;
in the figure: 1 is a test gas cylinder; 2 is a booster pump; 3 is an intermediate container; 4 is a rock core holder A; 5 is a constant temperature cabinet; 6 is a constant pressure 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 rock core holder B; 14 is a back pressure valve; 15 is a back pressure automatic tracking pump; 16 is a constant pressure 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; and 25 is a gas mass flow meter.
Detailed Description
The invention will now be further elucidated with reference to the following non-limiting embodiment in which the drawing is combined. It should be understood that these descriptions are only illustrative and are not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
Example one
As shown in fig. 1, a system for simultaneously measuring gas production characteristics of different occurrence states of a core,
comprises a gas collection section, a gas output section and a data acquisition component which are connected with each other;
the gas collecting section comprises a testing gas bottle 1, a booster pump 2, an intermediate container 3, a core holder A4, a thermostat 5, a constant-pressure constant-speed pump A6, a valve A7, a valve B8, a valve C9 and a valve D10;
the test gas cylinder 1 is connected with the inlet of the core holder A4 through a pipeline, the open end of the intermediate container 3 is connected with 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 a pipeline between the test gas cylinder 1 and a connection point A11, the valve A7 is arranged on a 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 a is provided on the line between the valve B8 and the valve C9, the valve D10 is provided on the branch a, the constant-pressure constant-speed pump A6 is connected to the cylinder of the core holder A4 to realize the gas confining pressure displacement in the core holder A4, the middle container 3, the core holder A4 and pipelines connected with the middle container and the core holder A4 are arranged in the incubator 5;
the gas production section comprises a pressure regulating valve 12, a core holder B13, a back pressure valve 14, a back pressure automatic tracking pump 15, a constant pressure constant speed pump B16 and a valve E17;
the air inlet of the core holder B13 is communicated with 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 a barrel of the core holder B13 and an inlet pipeline of the core holder B13 to form constant pressure displacement of the core in the core holder B13; the air inlet of the back pressure valve 14 is connected with the air outlet of the core holder B13 through a pipeline, and the constant-pressure constant-speed pump B16 is connected to the air inlet side of the back pressure valve 14; a branch pipe B is arranged on a pipeline connected with the core holder B13 and the back pressure valve 14, and the valve E17 is arranged on the branch pipe B;
the data acquisition assembly comprises 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 flowmeter 25; the pressure sensor A19 is arranged on a pipeline between a valve B8 and a valve C9, the pressure sensor B20 is arranged on a cylinder of a core holder A4 to test the confining pressure in a core holder A4, the pressure sensor C21 is arranged on a pipeline connecting the core holder A4 and the pressure regulating valve 12, the pressure sensor D22 is arranged on a pipeline between the pressure regulating valve 12 and a core holder B13, the pressure sensor E23 is arranged on a cylinder of a core holder B13 to test the confining pressure in a core holder B13, the pressure sensor F24 is arranged on a pipeline between a core holder B13 and a back-pressure valve 14, and an air outlet of the back-pressure valve 14 is connected with the gas mass flowmeter 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 flowmeter 25 are respectively connected with the data terminal 18, and data of each pressure sensor are recorded through the data terminal 18;
the middle container 3 is filled with samples of a core research block, and the middle container 3 simulates reservoir characteristics under the conditions of bottom temperature and original water saturation under the action of a test gas cylinder 1 and a booster pump 2; the gas collection section simulates the process of flowing from a bottom layer horizontal fracturing network to a vertical shaft, and the gas output section simulates the production process of gas in the stratum vertical shaft under different production systems.
The experimental method of the system for simultaneously measuring the gas output characteristics of the rock core in different occurrence states comprises the following steps:
s1, system connection:
connecting and assembling each part of the gas collection section, the gas output section and the data acquisition assembly; the pipeline is connected according to fig. 1, and the functions of each part in the experimental process are as follows: the test gas cylinder 1 and the booster pump 2 provide gas with target pressure values in the experiment, the test gas cylinder 1 is filled with methane, the middle container 3 is filled with samples of a research block, and reservoir characteristics under the conditions of formation temperature and original water saturation can be simulated; filling a real reservoir sample in the core holder A4, and simulating the flowing process of real reservoir natural gas from a matrix to a vertical shaft; the component consisting of the pressure regulating valve 12, the core holder B13 and the back pressure valve 14 simulates the production process of gas under different production systems, wherein the core holder B13 is filled with a false core; the gas mass flowmeter 25, the pressure sensor and the data terminal 18 form a data recording part of the system; the constant temperature box 5, the back pressure automatic tracking pump 15 and the constant pressure constant speed pump form a reservoir environment simulation component.
S2, detecting the airtightness of the system:
pseudo cores are placed in the core holder A4 and the core holder B13, the constant-pressure constant-speed pump A6 and the constant-pressure constant-speed pump B16 adopt constant-pressure displacement, the displacement pressure is higher than the ground pressure by 2MPa, the back pressure valve 14 is set to be the formation pressure, the pressure of the pressure regulating valve 12 is regulated to be the maximum, and the thermostat 5 keeps the formation temperature. Opening the valve A7, the valve B8 and the valve C9, closing the valve D10 and the valve E17, filling helium with the same pressure value as the formation pressure into the intermediate container 3, the core holder A4 and the core holder B13 by using a booster pump 2, and closing the valve A7 and the valve B8 after the pressure is stabilized. After standing for 24 hours, observing the numerical values of the pressure sensor A19, the pressure sensor C21 and the pressure sensor E23, if the pressure values are not changed, indicating that the air tightness of the system is good, and starting an experiment; if the pressure changes, the gas leakage part of the soap soaking water detection system is used for carrying out sealing treatment and then carrying out gas tightness detection again.
S3, system space volume calibration:
volume V of space between pressure regulating valve 12A and valve B80The calibration is carried out, and the valve D10 is always in a closed state in the whole calibration process; the volume between the valve B8 and the valve C9 is V'0The volume between the valve C9 and the pressure regulating valve 12 is V ″0The calibration steps are as follows:
1, placing a hollow false core into a core holder A4, wherein the pore volume of the false core is known as V', and a constant-speed constant-pressure pump connected with a core holder A4 carries out displacement at a constant pressure of 10 MP;
2-way intermediate container 3 with a filling volume V1The non-porous cylinder adopts a stainless steel cylinder;
3, the valve A7, the valve B8 and the valve C9 are closed, and the pressure value of the pressure regulating valve 12 is set to be 0;
4, opening the valve A7 and the valve B8 to fill the gas with certain pressure into the intermediate container 3, closing the valve A7 and the valve B8, and recording the value of the pressure sensor A19 as P after the reading of the pressure sensor A19 is stable1；
5 open valve C9 and record the pressure sensor A19 and pressure sensor C21 readings as P after they stabilize2；
6, after the pressure regulating valve 12 is adjusted to empty the system, repeating the steps 2, 3, 4 and 5, and changing the volume of the column filled in the intermediate container 3 every time of repetition to finish 3 groups of data tests;
7, the space volume and the pressure satisfy the following relation formula according to Boyle's law:
Figure BDA0003556430110000091
8 data of 3 sets obtained from the test
Figure BDA0003556430110000092
And V1Linear fitting was performed, and V 'was obtained from the intercept and slope, respectively'0、V″0Then volume of space V0Comprises the following steps:
V0＝V′0+V′0
the original data of the calibration process of the embodiment are shown in table 1, and the fitting result is shown in fig. 2:
table 1: original data recording table for system space volume calibration process
Figure BDA0003556430110000093
From the fitting formula, it can be seen that:
Figure BDA0003556430110000094
s4, simulating the production process of reservoir gas:
in this example, the water saturation is set to 0 and the saturated water volume VwIs 0. The simulation process comprises the following steps:
1 respectively filling a reservoir rock core sample to be detected into an intermediate container 3 and a rock core holder A4, wherein the total volume of the filled rock core sample is V, and the pore volume of the rock core sample in the intermediate container 3 and the rock core holder A4 is VpThe value of the displacement pressure of a constant-pressure constant-speed pump A6 connected with the core holder A4 is 2MPa higher than the formation pressure, and the displacement pressure is set to be 10MPa in the embodiment;
2, closing the valve A7, the valve B8 and the valve E17, opening the valve C9 and the valve D10, setting the pressure of the pressure regulating valve 12 to be zero, connecting the vacuum pump with the valve D10, vacuumizing the system for 24 hours by the vacuum pump, and closing the valve A7, the valve B8, the valve C9, the valve D10 and the valve E17 after the vacuum pump finishes vacuumizing;
3, opening a valve A7, a valve B8 and a valve C9, injecting methane gas in the test gas cylinder 1 into the system in a constant pressure 8MPa mode by using a booster pump 2, keeping the state, and closing a valve A7 and a valve B8 after fully adsorbing the core sample to be tested in the core holder A4 for 24 hours;
4, filling a false core into the core holder B13, displacing the false core by a constant-pressure constant-speed pump B16 connected with the core holder B13 at a constant pressure of 10MPa, setting the size of the back pressure valve 14 to be 1MPa, and then adjusting the size of the pressure regulating valve 12 to enable the outlet flow of the pressure regulating valve 12 to reach a set flow rate;
5, the data terminal 18 starts data recording software and records the numerical values of each pressure sensor and the gas mass flowmeter 25 at different time;
6 when the outlet flow of the gas mass flowmeter 25 cannot be kept constant at the set flow value, adjusting the pressure regulating valve 12 to be maximum, and continuing to record data;
7 stopping the experiment when the pressure sensor C21 reaches the waste pressure, then opening the valve D10 and the valve E17, discharging all the gas in the system, and recording the total amount of the discharged waste gas by using a flowmeter;
the original data records of the experimental process are shown in the table 2, and the gas production characteristics are shown in the figure 3.
Table 2: original data recording table of pressure and flow in production process
Figure BDA0003556430110000101
Figure BDA0003556430110000111
As can be seen from the table 2 and the figure 3, the production is switched to the attenuation production after the stable production time is 13.8 hours, and the attenuation production is 36.4 hours, so that the characteristics of shale gas reservoir production, such as yield attenuation blocks and long production period, are integrally reproduced.
S5, calculating gas production characteristics of the gas in each occurrence state:
combining parts of the system in steps S1-S4Definition of where the space volume is V0The apparent volume of the core sample filled in the system is V, and the pore volume of the core sample filled in the middle container 3 and the core holder A4 is VpThe pressure of the pressure sensor A19 at any time t is P (t), the gas yield recorded by the gas mass flowmeter 25 at any time t is Q (t), and the time when production is finished is assumed to be tTThe total gas production is Q (t)T) And after production is finished, the residual waste gas quantity of the reservoir is QrWherein Z is a gas compression factor, the simulated formation temperature T of the constant temperature box 5 is the system temperature, R is a universal gas constant, and V isLM is the gas phase relative molecular mass, ρ, of the gas cylinder under test 1, in standard molar volumeaIs the adsorption phase gas density;
then at any time, free gas Q in the systemf(t) a pore-bounding gas Qb(t) adsorption gas Qa(t) the content calculation formula is as follows:
Figure BDA0003556430110000112
Figure BDA0003556430110000113
Qb(t)＝Q(tT)+Q-Q(t)-Qf(t)-Qa(t)
at time t1And time t2The expression formula for calculating the gas production speed of the gas in different occurrence states is as follows:
Figure BDA0003556430110000121
Figure BDA0003556430110000122
Figure BDA0003556430110000123
ultimate recovery of reservoir production ErThe calculation expression is:
Figure BDA0003556430110000124
the gas production rate and ultimate recovery ratio calculation data of the gas in different occurrence states in the production process are shown in the table 3, and the gas production rate dynamic distribution diagram is shown in the table 4.
Table 3: calculation results of gas production speed and recovery ratio of gas in different occurrence states in production process
Figure BDA0003556430110000125
As can be seen from table 3 and fig. 4, the present embodiment realizes the separation of the gas production rate of the gas in different occurrence states, reveals the contribution of the gas in different occurrence states to the production rate in the production process of the gas reservoir, provides a technical means for researching the influence of the gas production characteristics of the reservoir under different production systems, and also provides an indoor simulation method for optimizing the production system of the gas reservoir.
The pressure sensor, the data terminal 18 and the related processing, sending and receiving programs of the software and the like are routine technical choices of technicians in the field, belong to the prior art, can obtain a technical scheme without creative labor, and do not belong to the object protected by the invention.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, when used in the orientation or positional relationship indicated in the figures, are used merely for convenience in describing the invention and to simplify the description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered as limiting. Furthermore, the appearances of the terms "first," "second," and the like, if any, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to imply that the number of indicated features is essential. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that unless otherwise explicitly stated or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly, e.g., as being fixed or detachable or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

Claims (5)

1. The system for simultaneously measuring the gas output characteristics of different occurrence states of the rock core is characterized in that,
comprises a gas collection section, a gas output section and a data acquisition component which are connected with each other;
the gas collection section comprises a test gas cylinder (1), a booster pump (2), an intermediate container (3), a core holder A (4), a thermostat (5), a constant-pressure 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 with an inlet of a core holder A (4) through a pipeline, an open end of the middle container (3) is connected with a pipeline between the test gas cylinder (1) and the core holder A (4) through 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), the valve B (8) is arranged on the pipeline 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, and the constant-speed pump A (6) is connected with a cylinder of the core holder A (4) to realize the core holder A (4) 4) The internal gas is displaced in a confining pressure manner, and the intermediate container (3), the rock core holder A (4) and pipelines mutually connected with the intermediate container and the rock core holder A are arranged in a constant temperature box (5);
the gas production section comprises a pressure regulating valve (12), a rock core holder B (13), a back pressure valve (14), a back pressure automatic tracking pump (15), a constant pressure constant speed pump B (16) and a valve E (17);
the air inlet of the core holder B (13) is communicated with 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 a cylinder body of the core holder B (13) and an inlet pipeline of the core holder B (13) to form constant pressure displacement of a core in the core holder B (13); the air inlet of the back pressure valve (14) is connected with 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 a pipeline connected with the rock 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 assembly 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 flowmeter (25); the pressure sensor A (19) is arranged on a pipeline between the valve B (8) and the valve C (9), the pressure sensor B (20) is arranged on the cylinder body of the 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 connected with the core holder A (4) and the pressure regulating valve (12), the pressure sensor D (22) is arranged on a pipeline between the pressure regulating valve (12) and the core holder B (13), the pressure sensor E (23) is arranged on the cylinder body 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 a pipeline between the core holder B (13) and the back pressure valve (14), the gas outlet of the back-pressure valve (14) is connected with a gas mass flowmeter (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 flowmeter (25) are respectively connected with a data terminal (18), and data of each pressure sensor are recorded through the data terminal (18);
the middle container (3) is filled with samples of a core research block, and the middle container (3) simulates reservoir characteristics under the conditions of bottom layer temperature and original water saturation under the action of a test gas cylinder (1) and a booster pump (2); the gas collection section simulates the process of flowing from a bottom layer horizontal fracturing network to a vertical shaft, and the gas output section simulates the production process of gas in the stratum vertical shaft under different production systems.
2. The method for simultaneously measuring the gas output characteristics of the rock core in different occurrence states is characterized by comprising the following steps of:
s1, system connection:
connecting and assembling each part of the gas collection section, the gas output section and the data acquisition assembly;
s2, detecting the air tightness of the system;
s3, system space volume calibration: the volume V of the space between the pressure regulating valve (12) A and the valve B (8)0Calibrating;
s4, simulating the production process of reservoir gas:
saturating the sample to be measured according to the real water saturation of the stratum by using the stratum water, wherein the volume of the saturated water is Vw；
The simulation process comprises the following steps:
1) respectively filling the core sample to be detected in the reservoir into an intermediate container (3) and a core holder A (4), wherein the total volume of the filled core sample is V, and the pore volume is VpThe displacement pressure value of a constant-pressure constant-speed pump A (6) connected with the rock core holder A (4) is higher than the formation pressure;
2) closing the valve A (7), the valve B (8) and the valve E (17), opening the valve C (9) and the valve D (10), setting the pressure of the pressure regulating valve (12) to be zero, connecting the vacuum pump with the valve D (10), vacuumizing the system by the vacuum pump, and closing the valve A (7), the valve B (8), the valve C (9), the valve D (10) and the valve E (17) after the vacuum pump finishes vacuumizing;
3) opening a valve A (7), a valve B (8) and a valve C (9), injecting gas in a testing gas cylinder (1) into the system in a mode of simulating formation constant pressure by using a booster pump (2), keeping the state, and closing the valve A (7) and the valve B (8) after fully adsorbing a core sample to be tested in a core holder A (4);
4) filling a false core into the core holder B (13), displacing by a constant-pressure constant-speed pump B (16) connected with the core holder B (13) at a constant pressure higher than the formation pressure, setting the size of a back-pressure valve (14) as a waste pressure, and then adjusting the size of a pressure regulating valve (12) to enable the outlet flow of the pressure regulating valve (12) to reach a set flow rate;
5) the data terminal (18) starts data recording software and records the numerical values of the pressure sensors and the gas mass flowmeter (25) at different times;
6) when the outlet flow of the gas mass flowmeter (25) cannot be kept constant at a set flow value, the pressure regulating valve (12) is regulated to the maximum value, and data are continuously recorded;
7) stopping the experiment when the pressure sensor C (21) reaches the waste pressure, then opening a valve D (10) and a valve E (17), completely discharging the gas in the system, and recording the total amount of the discharged waste gas by using a flowmeter;
s5, calculating gas production characteristics of the gas in each occurrence state:
combining the definitions of the parts in the system of steps S1-S4, wherein the space volume is V0The apparent volume of the core sample filled in the system is V, and the pore volume of the core sample filled in the middle container (3) and the core holder A (4) is VpThe pressure of the pressure sensor A (19) at any time t is P (t), the gas production amount recorded by the gas mass flowmeter (25) at any time t is Q (t), and the time when production is finished is assumed to be tTThe total gas production is Q (t)T) And after production is finished, the residual waste gas quantity of the reservoir is QrWherein Z is a gas compression factor, the simulated formation temperature T of the constant temperature box (5) is the system temperature, R is a universal gas constant, and V isLM is the gas phase relative molecular mass in the test cylinder (1), ρ, for the standard molar volumeaIs the adsorption phase gas density;
then at any time, free gas Q in the systemf(t) a pore-bounding gas Qb(t) adsorbed gas Qa(t) the content calculation formula is as follows:
Figure FDA0003556430100000041
Figure FDA0003556430100000042
Qb(t)＝Q(tT)+Q-Q(t)-Qf(t)-Qa(t)
at time t1And time t2The expression formula for calculating the gas production speed of the gas in different occurrence states is as follows:
Figure FDA0003556430100000043
Figure FDA0003556430100000044
Figure FDA0003556430100000045
ultimate recovery of reservoir production ErThe calculation expression is:
Figure FDA0003556430100000046
3. the method of claim 2, wherein the airtightness detecting step in step S2 is as follows: placing false cores in a core holder A (4) and a core holder B (13), adopting constant-pressure displacement by a constant-pressure constant-speed pump A (6) and a constant-pressure constant-speed pump B (16), wherein the displacement pressure is higher than the formation pressure, setting a back pressure valve (14) to be the formation pressure, adjusting the pressure of a pressure adjusting valve (12) to be the maximum, and keeping the formation temperature by a constant temperature box (5); opening a valve A (7), a valve B (8) and a valve C (9), closing a valve D (10) and a valve E (17), filling helium with the same pressure value as the formation pressure into the intermediate container (3), the core holder A (4) and the core holder B (13) by using a booster pump (2), and closing the valve A (7) and the valve B (8) after the pressure is stable; observing the numerical values of the pressure sensor A (19), the pressure sensor C (21) and the pressure sensor E (23) after standing, if the pressure values are not changed, indicating that the system is good in air tightness, and starting an experiment; if the pressure changes, the gas leakage part of the soap soaking water detection system is used for carrying out sealing treatment and then carrying out gas tightness detection again.
4. The method according to claim 2, characterized in that in step S3, the valve D (10) is always in the closed state during the whole calibration process; the volume between valve B (8) and valve C (9) is V'0The volume between the valve C (9) and the pressure regulating valve (12) is V ″)0Volume of system space V0The calibration steps are as follows:
1) placing a hollow false core into the core holder A (4), wherein the pore volume of the false core is known as V', and a constant-speed constant-pressure pump connected with the core holder A (4) performs displacement at constant pressure;
2) the intermediate container (3) is filled with a volume V1The non-porous cylinder of (a);
3) closing the valve A (7), the valve B (8) and the valve C (9), and closing the pressure regulating valve (12);
4) opening the valve A (7) and the valve B (8) to fill gas with certain pressure into the intermediate container (3), closing the valve A (7) and the valve B (8), and recording the numerical value of the pressure sensor A (19) as P after the reading of the pressure sensor A (19) is stable1；
5) The valve C (9) is opened and the pressure sensor A (19) and the pressure sensor C (21) record their values as P after their readings stabilize2；
6) After the pressure regulating valve (12) is adjusted to empty the system, the steps 2), 3), 4) and 5) are repeated, the volume of the column filled in the intermediate container (3) is changed when the steps are repeated each time, and at least 3 groups of data tests are completed;
7) the volume in space and the pressure satisfy the following relation calculated according to Boyle's law:
Figure FDA0003556430100000051
8) 3 sets of data obtained from the test
Figure FDA0003556430100000052
And V1Linear fitting was performed, and V 'was obtained from the intercept and slope, respectively'0、V″0Then volume of space V0Comprises the following steps:
V0＝V′0+V″0。
5. the method as claimed in claim 2, wherein the step of saturating the core sample to be tested with formation water according to true water saturation of the formation in step S4 is as follows: closing the valve B (8) and the valve C (9), connecting the valve D (10) with a vacuum pump, starting the vacuum pump to vacuumize the system, and then closing the valve D (10) and removing the vacuum pump; calculating the stratum water amount to be added in the sample to be measured according to the real stratum water saturation and the core pore volume; the volume V of the formation water is obtained by weighing and calculating by a balancewPlacing a branch pipe A of a valve D (10) in the weighed formation water, opening the valve D (10) until the formation water is fully saturated, entering a container, and standing for later use.
CN202210279383.5A 2022-03-21 2022-03-21 System and method for simultaneously measuring gas output characteristics of rock cores in different occurrence states Pending CN114720655A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116482329A (en) * 2023-03-09 2023-07-25 西南石油大学 Gas reservoir in-situ conversion hydrogen production experiment simulation device and application method
CN117147414A (en) * 2023-11-01 2023-12-01 中国矿业大学 Device and method for determining occurrence of water in shale organic and inorganic pores

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116482329A (en) * 2023-03-09 2023-07-25 西南石油大学 Gas reservoir in-situ conversion hydrogen production experiment simulation device and application method
CN116482329B (en) * 2023-03-09 2023-11-24 西南石油大学 Gas reservoir in-situ conversion hydrogen production experiment simulation device and application method
CN117147414A (en) * 2023-11-01 2023-12-01 中国矿业大学 Device and method for determining occurrence of water in shale organic and inorganic pores
CN117147414B (en) * 2023-11-01 2023-12-29 中国矿业大学 Device and method for determining occurrence of water in shale organic and inorganic pores

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