CN108732061B - Method for identifying desorbed gas and free gas in shale gas output gas - Google Patents

Method for identifying desorbed gas and free gas in shale gas output gas Download PDF

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CN108732061B
CN108732061B CN201710252082.2A CN201710252082A CN108732061B CN 108732061 B CN108732061 B CN 108732061B CN 201710252082 A CN201710252082 A CN 201710252082A CN 108732061 B CN108732061 B CN 108732061B
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gas
pump
volume
valve
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赵春鹏
伦增珉
吕成远
王卫红
潘伟义
刘华
王海涛
赵清民
郎东江
周霞
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China Petroleum and Chemical Corp
Sinopec Exploration and Production Research Institute
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Abstract

The invention belongs to the field of natural gas exploitation, and relates to a method for identifying desorbed gas and free gas in shale gas output gas, which comprises the following steps: 1) volume V was performed on the samples before the experimentSample (A)Mass m measured, for VLower partCalibrating, and setting the temperature T of the constant temperature box as an experimental temperature; 2) closing the valve I and opening the valve III; 3) after the system pressure is stable, recording the initial pressure P through a pressure sensor, and closing a valve III; 4) setting the high-precision plunger pump in a constant pressure mode, setting the pump pressure as a first experimental pressure value, starting to withdraw the pump at the moment, and resetting the accumulated gas production volume of the high-precision plunger pump; 5) opening the valve III and continuing to withdraw the pump; 6) and when the pressure value reaches the first experimental pressure value set by the high-precision plunger pump and is balanced, recording the pressure P', closing the valve III, and repeating the steps 4) to 5). The method can identify the content of desorbed gas and free gas in the produced gas, and simultaneously ensures the reliability of the test result.

Description

Method for identifying desorbed gas and free gas in shale gas output gas
Technical Field
The invention relates to the technical field of natural gas exploitation, in particular to a method for identifying desorbed gas and free gas in shale gas output gas.
Background
At present, shale gas exploration and development in China are in a starting stage, indoor experimental research mainly comprises petrological analysis, geochemical analysis, gas content analysis and the like, physical simulation research is developed and focused on aspects of physical property parameter determination, pore structure characteristics, adsorption experiments, seepage characteristics and the like, dynamic physical simulation research on identification of free gas and desorbed gas in a gas production process is less, and gas production characteristics in different development stages are very important for shale gas yield prediction.
Patent document CN201420640699.3 discloses a shale property tester, which can measure the free gas content and the adsorbed gas content of a shale sample. The patent document CN201410826709.7 obtains the gas content of shale reservoir from two phase states of adsorption state and free state through well logging data. The patent document CN201410335444.0 uses synchrotron radiation light and computer technology to predict the content of free gas and adsorbed gas in shale gas. Patent document CN201610060001.4 establishes a calculation method for shale adsorbed gas and free gas by means of comprehensive overbottom pore permeation, adsorption-sound wave joint measurement and the like. In summary, the existing literature respectively adopts indoor experiments, logging means or numerical methods to respectively calculate the free gas amount and the adsorbed gas amount, and studies the shale gas content. However, the gas content is not equal to the gas production, and in fact, the desorption gas content in the exploitation process is not equal to the adsorption gas content because the desorption curve does not coincide with the adsorption curve.
Disclosure of Invention
The invention aims to provide a method for identifying desorbed gas and free gas in shale gas output gas aiming at the problem that the existing shale gas adsorption and desorption device cannot develop gas production rules.
In order to achieve the above object, the present invention provides a method for identifying desorbed gas and free gas in shale gas output gas, including:
A. after the adsorption experiment is finished, developing a constant pressure exploitation simulation experiment:
1) volume V was performed on the samples before the experimentSample (A)Volume of free space VFromMeasuring mass m, and adding volume V of sample cylinder volume and volume from cylinder volume to pipeline volume between valve I, valve III and sensorLower partCalibrating, and setting the temperature T of the constant temperature box as an experimental temperature;
2) closing the valve I and opening the valve III;
3) after the system pressure formed by the sample cylinder, the piston type intermediate container and the pipeline is stable, recording the initial pressure P through a second pressure sensor, and closing a valve III;
4) setting the high-precision plunger pump in a constant pressure mode, setting the pump pressure as a first experimental pressure value, starting to withdraw the pump at the moment, and resetting the accumulated gas production volume of the high-precision plunger pump after the system pressure is stable;
5) opening the valve III, continuing to withdraw the pump, and acquiring the pumping pressure and the pump withdrawing volume V of the high-precision plunger pump in real time by the data acquisition systemPump and method of operating the sameGas production flow rate and accumulated gas production volume;
6) when the pressure value displayed by the second pressure sensor reaches the first experimental pressure value set by the high-precision plunger pump and is balanced, recording the pressure P', closing the valve III, performing a second pressure point balance test, and repeating the steps 4) -5), and performing a plurality of pressure point balance tests until the last pressure point balance test is finished;
B. data processing:
Figure GDA0002377570930000021
Figure GDA0002377570930000022
Vswimming device＝V-VSolution (II)；
In the formula (I), the compound is shown in the specification,
gas production in cm at V-standard3/g，
VSolution (II)Desorption gas volume in cm under standard conditions3/g，
VSwimming deviceFree gas yield in standard conditions, cm3/g，
P-initial pressure, MPa,
the P' -equilibrium pressure, MPa,
z-the gas compression factor at the initial pressure,
z' -gas compression factor at equilibrium pressure,
Vpump and method of operating the samePump withdrawal volume, cm3，
VLower partSample Cylinder space volume, cm3，
VSample (A)Apparent volume of sample, cm3，
VFrom-volume in free space, cm3，
T-experimental temperature, K,
m-sample mass, g.
According to the method provided by the invention, preferably, in the step 6) of the constant pressure mining simulation experiment, the steps 4) to 5) are repeated, and a plurality of pressure point balance experiments are carried out one by one from high to low.
According to the method provided by the invention, preferably, the high-precision plunger pump has a constant-pressure mode and a constant-flow mode.
According to the method provided by the invention, VFromFor free space volume, see QSH0511-2013, GBT19560-2008 for its definition and determination method. This value was determined before the adsorption experiments were performed.
In the invention, the method is realized by the following experimental device: the device comprises a reference cylinder, a sample cylinder, a thermostat, a back pressure control/yield metering system, a data acquisition system, a valve I, a valve II, a valve III, a first pressure sensor and a second pressure sensor;
the back pressure control/yield metering system comprises a piston type intermediate container, a valve IV and a high-precision plunger pump which are connected in sequence;
the reference cylinder, the sample cylinder, the piston type intermediate container and the high-precision plunger pump are sequentially connected, and the reference cylinder, the sample cylinder and the high-precision plunger pump are respectively connected with the data acquisition system; the valve I is positioned between the reference cylinder and the sample cylinder, and the valve III is positioned between the sample cylinder and the piston type intermediate container; a first pressure sensor is located between the reference cylinder and the data acquisition system and a second pressure sensor is located between the sample cylinder and the data acquisition system.
The valve II is connected with the reference cylinder.
According to the method provided by the invention, the experimental device adopted in the operation steps can be used for carrying out isothermal adsorption and desorption experiments, and the experimental steps and the data processing process thereof are referred to as Q/SH0511-2013 shale isothermal adsorption-desorption curve determination method.
The technical scheme of the invention has the following beneficial effects: the exploitation experiment of the method can simulate the production process of the desorbed gas and the free gas in the depressurization exploitation process, an experiment data processing method is established, the content of the desorbed gas and the free gas in the produced gas can be identified, the accurate pressure control and the accurate metering of the gas yield under the conditions of high temperature and high pressure are realized by combining the plunger pump and the piston type intermediate container, and the reliability of the test result is ensured.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts throughout.
Fig. 1 shows a schematic diagram of an experimental device for identifying desorbed gas and free gas in shale gas produced gas.
Fig. 2 shows the cumulative gas production versus pressure for the desorbed gas and free gas from the shale gas produced in example 1.
The numbers in the above figures are illustrated as follows:
1-valve I; 2-a first pressure sensor; 3-valve II; 4-reference cylinder; 5-sample cylinder; 6-piston type intermediate vessel; 7-a second pressure sensor; 8-valve III; 9-valve IV; 10-high precision plunger pump; 11-a constant temperature box; 12-data acquisition system.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein.
Example 1
The method for identifying the desorbed gas and the free gas in the shale gas output gas is implemented by adopting the experimental device for identifying the desorbed gas and the free gas in the shale gas output gas shown in fig. 1, and comprises the following steps:
A. after the adsorption experiment is finished, developing a constant pressure exploitation simulation experiment:
1) volume V was performed on the samples before the experimentSample (A)Volume of free space VFromMass m, measured as the sum V of the volume of the sample cylinder 5 and the volume of the lines between the cylinder to the valve I1, the valve III8, the second pressure sensor 7Lower partCalibrating, and setting the temperature T of the constant temperature box 11 as an experimental temperature;
Vsample (A)，cm3 VFrom，cm3 VLower part，cm3 Mass, g T，℃
759.11 104.91 831.18 1960.8 82
2) Closing valve 1I, opening valve III 8;
3) after the system pressure formed by the sample cylinder 5, the piston type intermediate container 6 and the pipeline is stabilized, recording the initial pressure P through the second pressure sensor 7, and closing the valve III 8;
4) setting the high-precision plunger pump 10 to be in a constant pressure mode, setting the pump pressure to be a first experimental pressure value, starting to withdraw the pump at the moment, and resetting the accumulated gas production volume of the high-precision plunger pump 10 after the system pressure is stable;
5) the valve III8 is opened, the pump is continuously withdrawn, and the data acquisition system 12 acquires the pumping pressure and the pump withdrawal volume V of the high-precision plunger pump 10 in real timePump and method of operating the sameGas production flow rate and accumulated gas production volume;
6) when the pressure value displayed by the second pressure sensor 7 reaches the first experimental pressure value set by the high-precision plunger pump 10 and is balanced, recording the pressure P', closing the valve III8, performing a second pressure point balance test, and repeating the steps 4) -5), and performing a plurality of pressure point balance tests until the last pressure point balance test is finished;
B. data processing:
Figure GDA0002377570930000061
Figure GDA0002377570930000062
Vswimming device＝V-VSolution (II)；
In the formula (I), the compound is shown in the specification,
gas production in cm at V-standard3/g，
VSolution (II)Desorption gas volume in cm under standard conditions3/g，
VSwimming deviceFree gas yield in standard conditions, cm3/g，
P-initial pressure, MPa,
the P' -equilibrium pressure, MPa,
z-the gas compression factor at the initial pressure,
z' -gas compression factor at equilibrium pressure,
Vpump and method of operating the samePump withdrawal volume, cm3，
VLower partSample Cylinder space volume, cm3，
VSample (A)Apparent volume of sample, cm3，
VFrom-volume in free space, cm3，
T-experimental temperature, K,
m-sample mass, g.
The experimental results are shown in fig. 2 below, and it can be seen from the results shown in the figure that the content of desorbed gas and free gas in the produced gas can be identified by the processing method of the present invention, so as to provide support for mining mode optimization, capacity prediction and dynamic analysis.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims (3)

1. A method for identifying desorbed gas and free gas in shale gas produced gas is characterized by utilizing an experimental device, wherein the experimental device comprises: the device comprises a reference cylinder (4), a sample cylinder (5), a thermostat (11), a back pressure control/yield metering system, a data acquisition system (12), a valve I (1), a valve II (3), a valve III (8), a first pressure sensor (2) and a second pressure sensor (7);
the back pressure control/yield metering system comprises a piston type intermediate container (6), a valve IV (9) and a high-precision plunger pump (10) which are connected in sequence;
the reference cylinder (4), the sample cylinder (5), the piston type intermediate container (6) and the high-precision plunger pump (10) are connected in sequence; the reference cylinder (4), the sample cylinder (5) and the high-precision plunger pump (10) are respectively connected with the data acquisition system (12); the valve I (1) is located between the reference cylinder (4) and the sample cylinder (5); the valve III (8) is located between the sample cylinder (5) and the piston-type intermediate container (6); the first pressure sensor (2) is located between the reference cylinder (4) and the data acquisition system (12); the second pressure sensor (7) is located between the sample cylinder (5) and the data acquisition system (12); the valve II (3) is connected with the reference cylinder (4); the reference cylinder (4), the sample cylinder (5), the piston-type intermediate container (6) are located in the incubator (11);
the method comprises the following steps:
A. after the adsorption experiment is finished, developing a constant pressure exploitation simulation experiment:
1) volume V was performed on the samples before the experimentSample (A)Volume of free space VFromMeasuring mass m, and adding volume V of sample cylinder (5) and pipeline volumes from cylinder to valve I (1), valve III (8) and second pressure sensor (7)Lower partCalibrating, and setting the temperature T of the constant temperature box (11) as an experimental temperature;
2) closing the valve I (1) and opening the valve III (8);
3) after the system pressure formed by the sample cylinder (5), the piston type intermediate container (6) and the pipeline is stabilized, recording the initial pressure P through a second pressure sensor (7), and closing a valve III (8);
4) setting the high-precision plunger pump (10) to be in a constant pressure mode, setting the pump pressure to be a first experimental pressure value, starting to withdraw the pump at the moment, and resetting the accumulated gas production volume of the high-precision plunger pump (10) after the system pressure is stable;
5) opening valve III (8), continuing to withdraw the pump, and collecting data (12)) The volume V of the pumping pressure and the pump withdrawal of the high-precision plunger pump (10) is acquired in real timePump and method of operating the sameGas production flow rate and accumulated gas production volume;
6) when the pressure value displayed by the second pressure sensor (7) reaches the first experiment pressure value set by the high-precision plunger pump (10) and is balanced, recording the pressure P', closing the valve III (8), performing a second pressure point balance test, and repeating the steps from 4) to 5), and performing a plurality of pressure point balance tests until the last pressure point balance test is finished;
B. data processing:
Figure FDA0002377570920000021
Figure FDA0002377570920000022
Vswimming device＝V-VSolution (II)；
In the formula (I), the compound is shown in the specification,
gas production in cm at V-standard3/g，
VSolution (II)Desorption gas volume in cm under standard conditions3/g，
VSwimming deviceFree gas yield in standard conditions, cm3/g，
P-initial pressure, MPa,
the P' -equilibrium pressure, MPa,
z-the gas compression factor at the initial pressure,
z' -gas compression factor at equilibrium pressure,
Vpump and method of operating the samePump withdrawal volume, cm3，
VLower partSample Cylinder space volume, cm3，
VSample (A)Apparent volume of sample, cm3，
VFrom-volume in free space, cm3，
T-experimental temperature, K,
m-sample mass, g.
2. The method as claimed in claim 1, wherein in the step 6) of the constant pressure mining simulation experiment, the steps 4) to 5) are repeated, and a plurality of pressure point balance tests are carried out one by one from high to low.
3. The method according to claim 1, wherein the high precision plunger pump (10) has a constant pressure mode and a constant flow mode.
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CN110146425A (en) * 2019-05-16 2019-08-20 中国地质大学（武汉） A kind of quantitative assessment experimental provision of shale High Pressure Absorption gas componant
CN110608975A (en) * 2019-09-23 2019-12-24 中国地质大学（武汉） Gas content testing device and testing method and application thereof
CN111175176B (en) * 2020-01-06 2022-04-26 重庆科技学院 Automatic calibration system for volume of shale isothermal adsorption experiment cylinder
CN112924354B (en) * 2021-01-22 2022-09-20 西南石油大学 Shale reservoir stress sensitivity experiment evaluation method based on gas diffusion coefficient
CN114047105B (en) * 2021-11-15 2022-11-15 东北石油大学 Device and method for testing porosity of high-pressure helium shale

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