CN115326662A - Device and method for judging shale gas flow state - Google Patents
Device and method for judging shale gas flow state Download PDFInfo
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- CN115326662A CN115326662A CN202110504856.2A CN202110504856A CN115326662A CN 115326662 A CN115326662 A CN 115326662A CN 202110504856 A CN202110504856 A CN 202110504856A CN 115326662 A CN115326662 A CN 115326662A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/082—Investigating permeability by forcing a fluid through a sample
- G01N15/0826—Investigating permeability by forcing a fluid through a sample and measuring fluid flow rate, i.e. permeation rate or pressure change
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N13/00—Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects
- G01N13/04—Investigating osmotic effects
Abstract
The invention discloses a device and a method for judging shale gas flow state. The invention provides a device for judging shale gas flow state, which comprises: an intermediate container having an inner chamber containing a displacement fluid; the power output device is connected with the inlet of the intermediate container; the inlet of the flow controller is connected with the outlet of the intermediate container; the gas source is connected with the inlet of the flow controller; the core holder is internally provided with a core, and an inlet of the core holder is connected with an outlet of the flow controller through a one-way valve; the confining pressure output device is connected with a confining pressure input port of the rock core holder; an inlet of the liquid receiving device is connected with an outlet of the rock core holder; and a pressure measuring device. The invention also provides a method for judging the shale gas flow state. According to the method, the curve is divided, the pressure range of the shale core entering the transition flow state is determined, and the representation of the matrix gas flow capacity of the shale reservoir is realized.
Description
Technical Field
The invention relates to the technical field of shale gas exploration and development. More particularly, the invention relates to a device and a method for distinguishing shale gas flow state.
Background
Shale gas development potential in China is huge, and the shale gas development potential enters a scale development stage through exploration and development practices of nearly ten years. The shale reservoir has the characteristics of rich organic matter content, micro-nano hole development and the like, so that the occurrence and utilization rules of fluid are complex. Most researches believe that the permeability of the shale matrix is extremely low, the shale matrix basically has no seepage capability, and when gas in micro-nano pores of the shale flows, the space dimension is far smaller than the conventional space dimension, and the flow mechanism is also changed.
At present, for the division of shale gas flow state, darcy flow, slip flow, transition flow and the like are divided mainly according to the division of the Nursen number and the range of the Nursen number, the Darcy flow rule is consistent with the conventional gas reservoir rule, the gas slip effect is mainly influenced by factors such as pressure, temperature, rock pore structure, gas type and the like, the slip effect is more obvious when the temperature is higher and the average pressure is smaller, and the Knudsen diffusion and the like caused by the collision of molecules and the wall surface are required to be considered for the flow of the transition flow state. Due to the complexity of this cross-flow regime, the shale gas flow laws are more difficult to describe.
At present, the flow capacity characterization in the shale experiment still takes Darcy permeability as a main factor, helium or nitrogen is generally adopted as test gas, and the influence of methane gas adsorption on the flow capacity is ignored; the test pressure is generally low, and the test result cannot effectively reflect the flowing capacity of the shale reservoir condition gas, so that the shale gas yield decrement analysis and EUR prediction are greatly influenced.
Therefore, the invention provides a device and a method for judging the shale gas flow state, which aim to solve the problems.
Disclosure of Invention
The invention aims to provide a device for judging the flow state of shale gas.
The invention also aims to provide a method for judging the shale gas flow state.
In order to achieve the purpose, the invention adopts the following technical scheme:
an apparatus for discriminating shale gas flow regime, comprising:
an intermediate container having an inner chamber containing a displacement fluid;
the power output device is connected with the inlet of the middle container and is used for outputting different driving pressures to displace the displacement fluid in the middle container to be transmitted to the rock core in the rock core holder through a pipeline;
the inlet of the flow controller is connected with the outlet of the intermediate container and is used for controlling the flow of the fluid flowing into the core holder;
the gas source is connected with the inlet of the flow controller;
the core holder is internally provided with a core, and the inlet of the core holder is connected with the outlet of the flow controller through a one-way valve;
the confining pressure output device is connected with a confining pressure input port of the core holder and is used for providing confining pressure for the core holder;
an inlet of the liquid receiving device is connected with an outlet of the core holder and is used for connecting liquid to the outlet of the core holder;
pressure measurement apparatus comprising:
the first pressure sensor is arranged between the one-way valve and the inlet of the core holder and used for measuring the gas pressure value of the inlet of the core holder and transmitting the measured gas pressure value of the inlet to the computer;
the second pressure sensor is arranged between the liquid receiving device and the outlet of the core holder and used for measuring the gas pressure value of the outlet of the core holder and transmitting the measured outlet gas pressure value to the computer;
the pressure polling instrument is connected with the first pressure sensor and the second sensor;
and the computer is used for recording the gas pressure value of the inlet and the gas pressure value of the outlet of the core holder in real time and calculating the pressure difference between the inlet and the outlet according to the gas pressure value of the inlet and the gas pressure value of the outlet. It will be appreciated by those skilled in the art that the various components of the apparatus provided by the present invention may be connected by tubing.
Preferably, the pressure measuring device further comprises a third pressure sensor arranged between the confining pressure output device and the core holder and used for measuring the pressure applied to the core holder by the confining pressure pump.
Preferably, the core holder is arranged in an incubator.
Preferably, the liquid receiving device comprises a water tank and a liquid receiving pipe arranged in the water tank; the liquid receiving pipe is connected with an outlet of the core holder.
Preferably, the pipette is a glass tube provided with a scale.
Preferably, a first regulating valve is arranged between the gas source and the flow controller and used for opening and closing the whole experiment process.
Preferably, a second regulating valve is arranged between the intermediate container and the flow controller and used for regulating the gas to enter the core holder at a substantially constant flow rate.
Preferably, the power take-off is an ISCO pump.
Preferably, the confining pressure output device is a confining pressure pump.
Preferably, the gas provided by the gas source is methane.
The invention also provides a method for distinguishing the shale gas flow state by using the device, which comprises the following steps:
taking a core sample, measuring the length and the sectional area of the core sample, and clamping the core sample by using a core holder;
providing methane gas with preset pressure to the core holder by using a gas source to simulate the flow of shale gas, and controlling the flow of the gas input into the core holder by using a flow controller;
applying preset confining pressure to a rock core holder holding a rock core sample through a confining pressure output device;
applying preset confining pressure to a rock core holder holding a rock core sample through a confining pressure output device;
measuring the inlet pressure and the outlet pressure of the core holder by a pressure measuring device, and regulating and controlling an air source and a power output device according to the inlet pressure monitoring value of the core holder to stabilize the inlet pressure;
when the inlet pressure amplitude of the core holder is less than 0.00001MPa/h, measuring the gas flow at the outlet of the core holder by using the liquid receiving device repeatedly for three times at different periods by a water and gas drainage method;
calculating permeability according to a formula (I), drawing permeability and pressure curves and permeability and pressure reciprocal curves, dividing according to a fitting straight line of Darcy flow, and judging the flow form of the shale gas;
in the formula (I), the compound is shown in the specification,
K g represents gas permeability in units of D;
Q v the volume flow of gas in cm is expressed for the output core holder 3 /s；
p 0 The standard atmospheric pressure is expressed, and the value is 0.1MPa;
mu represents the viscosity of the gas output by the gas source, and is related to the gas type, temperature and pressure, and mPa & s;
l represents the length of the core sample and is in cm;
a represents the cross-sectional area of the core sample in cm 2 ；
p 1 The inlet pressure of the core holder is shown in 10 -1 MPa；
p 2 The outlet pressure of the core holder is shown in 10 -1 MPa。
Preferably, the inlet pressure is in the range of 0.1 to 30MPa.
Preferably, the step of regulating and controlling an air source and a power output device to stabilize the inlet pressure according to the inlet pressure monitoring value of the core holder specifically comprises:
a. when the inlet pressure is lower than 1MPa, the gas source outlet is connected with a precision air pressure control regulating valve with the precision of 0.001MPa, and the measuring range of the first pressure sensor is 1MPa and the precision is 1/1000; recording the change condition of the inlet pressure of the core holder, and repeatedly measuring the flow for three times in different periods by adopting a drainage and gas production method when the variation of the inlet pressure is less than 0.00001MPa/h and averaging;
b. when the inlet pressure is higher than 1MPa, the inlet pressure is stabilized by using a power output device and is connected with a first pressure sensor with a corresponding range; and recording the change condition of the inlet pressure of the core holder, and repeatedly measuring the flow for three times in different periods by adopting a drainage and gas production method when the variation of the inlet pressure is less than 0.00001MPa/h and averaging.
The invention has the following beneficial effects:
according to the device and the method for judging the shale gas flow state, provided by the invention, the pressure range of the shale core entering the transition flow state is determined by dividing the curve, and the representation of the shale reservoir matrix gas flow capacity is realized.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of an apparatus for discriminating shale gas flow state provided by the present invention;
FIG. 2 is a graph showing the relationship between pressure and permeability in example 1 of the present invention;
FIG. 3 is a graph showing the relationship between the reciprocal pressure and the permeability in example 1 of the present invention;
the device comprises a middle container 1, a power output device 2, a flow controller 3, an air source 4, a first regulating valve 41, a core holder 5, a confining pressure output device 6, a liquid receiving device 7, a water tank 71, a liquid receiving pipe 72, a pressure measuring device 8, a first pressure sensor 81, a second pressure sensor 82, a pressure patrol instrument 83, a computer 84, a third pressure sensor 85, a check valve 9, a thermostat 10 and a second regulating valve 11.
Detailed Description
In order to more clearly illustrate the invention, the invention is further described below in connection with preferred embodiments. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.
The invention provides a device for judging shale gas flow state, which specifically comprises the following components in combination with a figure 1:
an intermediate container 1 having an inner chamber containing a displacement fluid;
the power output device 2 is connected with an inlet of the intermediate container 1 and is used for outputting different driving pressures to displace the displacement fluid in the intermediate container to be transmitted to the rock core in the rock core holder through a pipeline, and specifically can be a power pump, wherein the power pump can be an ISCO pump;
the inlet of the flow controller 3 is connected with the outlet of the intermediate container 1 and is used for controlling the flow of the fluid flowing into the core holder;
the gas source 4 is connected with the inlet of the flow controller 3;
a rock core holder 5 with a rock core is arranged inside, and an inlet of the rock core holder 5 is connected with an outlet of the flow controller 3 through a one-way valve 9;
the confining pressure output device 6 is connected with a confining pressure input port of the core holder 5 and is used for providing confining pressure for the core holder 5, and specifically can be a confining pressure pump;
an inlet of the liquid receiving device 7 is connected with an outlet of the core holder 5 and is used for connecting liquid to an outlet of the core holder 5;
the first pressure sensor 81 is arranged between the check valve 9 and the inlet of the core holder 5 and is used for measuring the gas pressure value of the inlet of the core holder 5 and transmitting the measured gas pressure value of the inlet to the computer 84;
the second pressure sensor 82 is arranged between the liquid receiving device 7 and the outlet of the core holder 5, and is used for measuring the gas pressure value of the outlet of the core holder 5 and transmitting the measured outlet gas pressure value to the computer 84;
a pressure polling instrument 83 connecting the first pressure sensor and the second sensor; the pressure patrols and examines the appearance and is equipped with 8 passageways, can show the pressure-sensitive value in the pressure sensor through the pressure patrols and examines the appearance display.
And a computer 84 for recording the gas pressure value at the inlet and the gas pressure value at the outlet of the core holder in real time and calculating the pressure difference between the inlet and the outlet according to the gas pressure value at the inlet and the gas pressure value at the outlet. The components of the device provided by the invention can be connected through pipelines, for example, the power output device is connected with the inlet of the intermediate container through a pipeline, the inlet of the flow controller is connected with the outlet of the intermediate container through a pipeline, the gas source is connected with the inlet of the flow controller through a pipeline, the inlet of the core holder is connected with the outlet of the flow controller through a one-way valve arranged on a pipeline, the confining pressure output device is connected with the confining pressure input port of the core holder through a pipeline, and the inlet of the liquid receiving device is connected with the outlet of the core holder through a pipeline.
As a preferred embodiment of the present invention, the pressure measuring device 8 further includes a third pressure sensor 85 disposed between the confining pressure output device 6 and the core holder 5, and configured to measure the pressure applied to the core holder by the confining pressure pump.
As a preferred embodiment of the invention, the core holder 5 is arranged in an incubator 10.
According to the invention, methane is used as experimental gas, the core holder is arranged in the incubator, so that the temperature can be kept constant, the density, viscosity and compression factor of the gas can be kept constant, and the experimental data is more stable and accurate.
In a preferred embodiment of the present invention, the liquid receiver 7 includes a water tank 71 and a liquid receiving pipe 72 disposed in the water tank 71; the liquid receiving pipe 72 is connected with the outlet of the core holder 5, and the pipette 72 is a graduated glass tube and is used for reading a gas volume value.
In a preferred embodiment of the present invention, a first regulating valve 41 is disposed between the gas source 4 and the flow controller 3 for controlling the flow rate of the gas source.
In a preferred embodiment of the present invention, a second regulating valve 11 is provided between the intermediate container 1 and the flow rate controller 3.
The invention also provides a method for distinguishing the shale gas flow state by using the device, which comprises the following steps:
s101, taking a core sample, measuring the length and the sectional area of the core sample, and clamping the core sample by using a core holder 5;
s102, providing high-pressure gas with preset pressure to the core holder 5 by using the gas source 4 to simulate the flow of shale gas, and controlling the flow of the gas input into the core holder 5 through the flow controller 3;
s103, applying preset confining pressure to the core holder 5 clamped with the core sample through the confining pressure output device 6;
s104, measuring the inlet pressure and the outlet pressure of the core holder 5 through a pressure measuring device 8, and starting or closing a power output device 2 to control the pressure range of the inlet pressure according to the inlet pressure of the core holder 5, wherein the specific range can be 0.1-30 MPa; when the inlet pressure is lower than 1MPa, the power output device is not started, and the inlet pressure of the core holder is directly controlled by a control gas source; when the inlet pressure is not lower than 1MPa, the power output device and the intermediate container are used for realizing the control of the pressure;
s105, measuring the liquid flow at the outlet of the rock core holder by using a liquid receiving device 7 through a drainage gas production method;
the accurate control of the experimental pressure is difficult to realize only by a single means, and needs to be regulated and controlled in multiple stages:
a. when the inlet pressure is lower than 1MPa, the first regulating valve 41 selects a precise air pressure control regulating valve with the precision of 0.001MPa, and the first pressure sensor 81 selects the range of 1MPa and the precision of 1/1000. And (3) recording the change condition of the inlet pressure of the core holder by using a pressure polling instrument 83, and repeatedly measuring the flow for three times at different periods by adopting a drainage gas production method and averaging when the pressure amplitude of the inlet is smaller than 0.00001MPa/h after 24-48 h.
b. When the pressure is higher than 1MPa, the ISCO pump and the intermediate container are used for stabilizing the pressure, and the pressure sensor with the corresponding measuring range is connected. Likewise, to ensure that the flow reaches steady state, the measurement error is reduced, and the flow is measured three times repeatedly over a period of time.
The drainage method comprises the following specific processes: connect the liquid receiving pipe with the experimental apparatus exit, fill water in the test tube and back-off to the basin of filling water equally, guarantee not have the air in the test tube, will connect liquid pipe insert test tube bottom, after the experiment begins, because density is different, inject into gas gradually in the test tube, get rid of water gradually, through the gas volume that the different time of measurement got into the test tube, calculate the gas flow, obtain Qv.
S106, calculating permeability according to a formula (I), drawing permeability and pressure curves and permeability and pressure reciprocal curves, dividing according to a fitting straight line of Darcy flow, and judging the flow form of the shale gas;
in the formula (I), the compound is shown in the specification,
K g represents gas permeability in units of D;
Q v the volume flow of gas in cm is expressed for the output core holder 3 /s；
p 0 The standard atmospheric pressure is expressed, and the value is 0.1MPa;
mu represents the viscosity of the gas output by the gas source, and is related to the gas type, temperature and pressure, and mPa & s;
l represents the length of the core sample and is in cm;
a represents the cross-sectional area of the core sample in cm 2 ；
p 1 The inlet pressure of the core holder is expressed in 10 -1 MPa；
p 2 The outlet pressure of the core holder is shown in 10 -1 MPa。
As a preferred embodiment of the present invention, formula (I) is obtained by integrating formula (II) and formula (III);
pM＝ρRT(III)；
in the formulae (II) and (III),
v represents a gas flow rate m/s;
Q m the gas mass flow of the output core holder is expressed, and the unit is kg/s;
r represents the constant of the gas output by the gas source, and the value is 8.314J/(mol.K);
a represents the cross-sectional area of the core sample in cm 2 ；
ρ represents a gas density kg/m 3 ；
p represents a pressure Pa;
m represents a molar mass;
t represents temperature in K.
Concretely, the formula (II) is substituted into the formula (III) to obtain
In a preferred embodiment of the invention, in step S103, when the inlet pressure is lower than 1MPa, the first regulating valve uses a precise air pressure control regulating valve with the precision of 0.001MPa, the first pressure sensor uses a pressure sensor with the range of 1MPa and the precision of 1/1000, and the pressure patrol instrument is used for recording the change condition of the inlet pressure of the core holder;
when the pressure is higher than 1MPa, the power output device and the intermediate container are used for stabilizing the pressure, the first pressure sensor selects the pressure sensor with the corresponding range according to the requirement, and the pressure patrol instrument is used for recording the change condition of the inlet pressure of the core holder.
In step S105, when the pressure variation at the inlet of the core holder is less than 0.00001MPa/h after 24h to 48h, in order to ensure that the flow reaches a steady state and reduce the measurement error, the drainage method is used to repeatedly measure the liquid flow at the outlet of the core holder 5 three times by using the liquid receiving device 7 in a time-sharing manner, and the average value is obtained.
The present invention will be further described with reference to the following examples.
Example 1
The embodiment provides a method for distinguishing the flow state of shale gas, which uses the device shown in fig. 1, and comprises the following steps:
1) Taking a core sample, measuring the length and the sectional area of the core sample, and clamping the core sample by using a core holder;
2) Providing high-pressure gas with preset pressure to the core holder by using a gas source to simulate the flow of shale gas, and controlling the flow of the gas input into the core holder by using a flow controller;
3) Applying preset confining pressure to a rock core holder holding a rock core sample through a confining pressure output device;
4) Measuring the inlet pressure and the outlet pressure of the core holder by a pressure measuring device, when the inlet pressure is 0.1-1 MPa, not starting a power output device, directly controlling the inlet pressure of the core holder by a control air source, using a precise air pressure control regulating valve with the precision of 0.001MPa as a first regulating valve, using a pressure sensor with the range of 1MPa and the precision of 1/1000 as the first pressure sensor, and recording the change condition of the inlet pressure of the core holder by using a pressure patrol instrument;
when the inlet pressure is more than or equal to 1MPa and less than or equal to 30MPa, the power output device and the intermediate container are used for controlling the pressure, the first pressure sensor selects the pressure sensor with the corresponding range as required, and the pressure patrol instrument is used for recording the change condition of the inlet pressure of the core holder;
5) When the pressure variation of the inlet of the core holder is less than 0.00001MPa/h after 24-48 h, repeatedly measuring the liquid flow of the outlet of the core holder for three times by using a liquid receiving device in a drainage and gas production method in time intervals and averaging;
the average here means: by the drainage gas production method, when the same gas volume is measured, the time is used to obtain a more stable and constant outlet flow value Qv, because the outlet flow value is measured only 1 time in the experimental process and cannot be reliable.
6) Substituting the data obtained in the step 2) and the data obtained in the step 5) into a formula (I) to calculate permeability, drawing a permeability and pressure curve (shown in figure 2) and a permeability and pressure reciprocal curve (shown in figure 3), dividing according to a fitting straight line of Darcy flow, and judging the flow form of shale gas;
as shown in fig. 2, the permeability values exhibited two-step characteristics. The permeability slowly increases with decreasing pressure, and after reaching a certain pressure, the permeability rapidly increases. It can be judged that when the average pressure is gradually reduced to an extremely low pressure level (< 1 MPa), the permeability value is significantly increased by more than 1 order of magnitude, which indicates that the flow is gradually changed from darcy flow to transition flow, the knudsen diffusion effect in the transition flow is correspondingly enhanced, the molecular motion characteristic is significant, and the core flow capacity is enhanced.
It can be seen from the curve of the reciprocal average pressure (fig. 3) that the permeability value shows a three-stage characteristic, non-linear seepage occurs in both the low-pressure stage and the high-pressure stage, and only in the middle stage, the reciprocal average pressure and the permeability show a better linear relationship, which conforms to the gas slip rule. The high-pressure section has high gas flow rate, the high-speed non-Darcy effect causes nonlinear seepage characteristics, when the pressure is lower, the large change amplitude of the permeability is mainly caused by that the gas flow state changes under the low pressure, the mean molecular free path increases along with the reduction of the pressure, when the pressure is reduced to a certain degree, the gas flow state is converted into a transition flow state, and the Knudsen diffusion effect increases to enable the permeability to be rapidly increased.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (10)
1. A device for distinguishing shale gas flow state, which is characterized in that the device comprises:
an intermediate container having an inner chamber containing a displacement fluid;
the power output device is connected with the inlet of the intermediate container;
a flow controller, an inlet of the flow controller is connected with an outlet of the intermediate container;
the gas source is connected with the inlet of the flow controller;
the core holder is internally provided with a core, and the inlet of the core holder is connected with the outlet of the flow controller through a one-way valve;
the confining pressure output device is connected with the confining pressure input port of the rock core holder;
an inlet of the liquid receiving device is connected with an outlet of the rock core holder; and
pressure measurement apparatus comprising:
a first pressure sensor disposed between the check valve and the inlet of the core holder;
the second pressure sensor is arranged between the liquid receiving device and the outlet of the rock core holder;
the pressure polling instrument is connected with the first pressure sensor and the second sensor;
and a computer.
2. The apparatus for discriminating shale gas flow regime of claim 1, wherein the pressure measurement apparatus further comprises a third pressure sensor disposed between the confining pressure output apparatus and the core holder.
3. The apparatus for discriminating shale gas flow regime of claim 1, wherein the core holder is disposed in a thermostat.
4. The apparatus for discriminating the flow state of shale gas according to claim 1, wherein the liquid receiving apparatus comprises a water tank and a liquid receiving pipe disposed in the water tank; the liquid receiving pipe is connected with an outlet of the core holder.
5. The apparatus for discriminating shale gas flow state according to claim 1, wherein a first regulating valve is disposed between the gas source and the flow controller.
6. The apparatus for discriminating shale gas flow regime of claim 1, wherein a second regulating valve is disposed between the intermediate vessel and the flow controller.
7. The apparatus for discriminating shale gas flow regimes of claim 1, wherein the power take off is an ISCO pump.
8. The apparatus for discriminating the flow state of shale gas according to claim 1, wherein the confining pressure output device is a confining pressure pump.
9. A method for discriminating the flow state of shale gas, which uses the apparatus for discriminating the flow state of shale gas according to any one of claims 1 to 8, comprising the steps of:
taking a core sample, measuring the length and the sectional area of the core sample, and clamping the core sample by using a core holder;
providing methane gas with preset pressure to the core holder by using a gas source to simulate the flow of shale gas, and controlling the flow of the gas input into the core holder by using a flow controller;
applying preset confining pressure to a rock core holder holding a rock core sample through a confining pressure output device;
measuring the inlet pressure and the outlet pressure of the core holder by a pressure measuring device, and regulating and controlling an air source and a power output device according to the inlet pressure monitoring value of the core holder to stabilize the inlet pressure;
when the variation of the inlet pressure of the core holder is less than 0.00001MPa/h, the liquid receiving device is repeatedly used for three times at different periods to measure the gas flow at the outlet of the core holder by a water and gas drainage method;
calculating permeability according to a formula (I), drawing permeability and pressure curves and permeability and pressure reciprocal curves, dividing according to a fitting straight line of Darcy flow, and judging the flow form of the shale gas;
in the formula (I), the compound is shown in the specification,
K g represents gas permeability in units of D;
Q v the volume flow of gas in cm is expressed for the output core holder 3 /s；
p 0 The standard atmospheric pressure is expressed, and the value is 0.1MPa;
mu represents the viscosity of the gas output by the gas source, and is related to the gas type, temperature and pressure, and mPa & s;
l represents the length of the core sample and is in cm;
a represents the cross-sectional area of the core sample in cm 2 ；
p 1 The inlet pressure of the core holder is expressed in 10 -1 MPa；
p 2 The outlet pressure of the core holder is shown in 10 -1 MPa。
10. The method for discriminating the shale gas flow state according to claim 9, wherein the pressure range of the inlet pressure is 0.1-30 MPa;
preferably, the step of regulating and controlling an air source and a power output device to stabilize the inlet pressure according to the inlet pressure monitoring value of the core holder specifically comprises:
a. when the inlet pressure is lower than 1MPa, the gas source outlet is connected with a precision air pressure control regulating valve with the precision of 0.001MPa, and the measuring range of the first pressure sensor is 1MPa and the precision is 1/1000; recording the change condition of the inlet pressure of the core holder, and repeatedly measuring the flow for three times in different periods by adopting a drainage and gas production method when the variation of the inlet pressure is less than 0.00001MPa/h and averaging;
b. when the inlet pressure is higher than 1MPa, the inlet pressure is stabilized by using a power output device and is connected with a first pressure sensor with a corresponding range; and recording the change condition of the inlet pressure of the core holder, and repeatedly measuring the flow for three times in different periods by adopting a drainage and gas production method when the variation of the inlet pressure is less than 0.00001MPa/h and averaging.
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