CN112730160B - Transient test system for seepage evolution rule of low-permeability coal rock - Google Patents
Transient test system for seepage evolution rule of low-permeability coal rock Download PDFInfo
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- CN112730160B CN112730160B CN202110090029.3A CN202110090029A CN112730160B CN 112730160 B CN112730160 B CN 112730160B CN 202110090029 A CN202110090029 A CN 202110090029A CN 112730160 B CN112730160 B CN 112730160B
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Abstract
The invention discloses a transient test system for a seepage evolution rule of a low-permeability coal rock, which comprises a triaxial core holder, an upstream fluid supply device and a downstream fluid circulation device, wherein the triaxial core holder is provided with a first fluid inlet and a second fluid outlet; the upstream fluid supply device comprises a plurality of upstream gas standard chambers connected in series, the upstream gas standard chamber at the head end is connected with a gas source, and the upstream gas standard chamber at the tail end is connected with a gas inlet port of the triaxial core holder; the downstream fluid circulation device comprises a plurality of downstream gas standard chambers connected in series, the downstream gas standard chamber at the head end is connected with the gas outlet port of the triaxial core holder, and the influence of different volumes on permeability is tested by adjusting the volumes of the upstream and downstream gas standard chambers.
Description
Technical Field
The invention belongs to the technical field of coal rock sample permeability determination simulation test equipment, and particularly relates to a transient test system for a low-permeability coal rock seepage evolution rule.
Background
The statements herein merely provide background information related to the present disclosure and may not necessarily constitute prior art.
The soft low-permeability compact coal seam is generally developed because the coal seam is influenced by the movement of the structure. At present, the inventor finds that when permeability test is carried out on a low-permeability compact coal rock sample, the test period is long, the time consumption is long, the test efficiency is low, and the real simulation degree of the seepage test of the coal rock sample has certain limitation; the permeability of the coal bed is dynamic permeability, is comprehensively influenced by various effects such as gas pressure, effective stress, water content of a reservoir and matrix shrinkage caused by desorption besides self environmental attributes such as the coal bed environment, the development degree and the distribution state of a fracture system and the like, and is one of important parameters influencing yield and mining benefit, so that the accurate measurement of the permeability of the coal bed has important engineering guidance significance for improving the extraction rate of the coal bed gas.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a transient test system for the seepage evolution law of low-permeability coal rocks, which is used for carrying out a transient method measurement seepage evolution law simulation test on low-permeability compact coal rocks, can simulate the gas seepage evolution law in a coal bed more truly, and can reflect the complex process of mutual coupling between coal bed gas migration and coal bed solid deformation more truly, thereby having important engineering guidance significance for improving the extraction rate of coal bed gas.
In order to achieve the purpose, the invention is realized by the following technical scheme:
in a first aspect, an embodiment of the present invention provides a transient test system for a seepage evolution law of a hypotonic coal rock, including a triaxial core holder, an upstream fluid supply device, and a downstream fluid circulation device; the upstream fluid supply device comprises a plurality of upstream gas standard chambers connected in series, the upstream gas standard chamber at the head end is connected with a gas source, and the upstream gas standard chamber at the tail end is connected with a gas inlet port of the triaxial core holder; the downstream fluid circulation device comprises a plurality of downstream gas standard chambers connected in series, the downstream gas standard chamber at the head end is connected with the gas outlet port of the triaxial core holder, and the influence of different volumes on permeability is tested by adjusting the volumes of the upstream and downstream gas standard chambers.
As a further technical scheme, a buffer tank is arranged between the gas source and an upstream gas standard chamber at the head end, a booster pump is arranged between the gas source and the buffer tank, and a pressure gauge and a pressure reducing valve are arranged at a gas source outlet; the inlet and the outlet of the buffer tank are both provided with pneumatic valves, and the buffer tank is also connected with a first pressure sensor; and a pressure reducing valve and a second pressure sensor are arranged between the buffer tank and the upstream gas standard chamber of the head end.
As a further technical scheme, pneumatic valves are arranged at the inlet and the outlet of the upstream gas standard chamber at the head end, and the pneumatic valve is arranged at the outlet of the upstream gas standard chamber at the tail end; the outlet of the upstream gas standard chamber at the head end is also communicated with a vacuum pumping pipeline, the vacuum pumping pipeline is communicated with a vacuum pump, and the vacuum pumping pipeline is provided with a pneumatic valve; the outlet of the upstream gas standard chamber at the head end is also communicated with an upstream emptying pipeline, the upstream emptying pipeline is arranged in parallel with the vacuumizing pipeline, and the upstream emptying pipeline is provided with an upstream emptying stop valve.
As a further technical scheme, an upstream gas pressure sensor is arranged at the inlet end of the triaxial core holder, a downstream gas pressure sensor is arranged at the outlet end of the triaxial core holder, and changes of upstream and downstream pressure values are monitored through the upstream and downstream gas pressure sensors.
As a further technical scheme, the triaxial core holder is also connected in parallel with a differential pressure monitoring pipeline, and the differential pressure monitoring pipeline is provided with a differential pressure monitoring sensor, a differential pressure stop valve and a differential pressure pneumatic valve; the triaxial core holder is also connected with an upstream and downstream communication pipeline in parallel, the upstream and downstream communication pipeline communicates an upstream fluid supply device with a downstream fluid circulation device, and the upstream and downstream communication pipeline is provided with a pneumatic valve.
As a further technical scheme, a pneumatic valve is arranged at an inlet of a downstream gas standard chamber at the head end, an outlet of the downstream gas standard chamber at the head end is connected with a downstream emptying pipeline, and a downstream emptying stop valve is arranged on the downstream emptying pipeline; and pneumatic valves are arranged at the inlet and the outlet of the downstream gas standard chamber at the tail end.
As a further technical scheme, the triaxial core holder, the upstream fluid supply device and the downstream fluid circulation device are all arranged in a thermostat, and the thermostat is provided with a temperature sensor; and a displacement sensor is arranged at the end part of the triaxial core holder and used for monitoring the axial deformation of the coal rock sample.
According to a further technical scheme, the triaxial core holder comprises a main steel cylinder, a ring pressure transmission rubber sleeve is arranged in the main steel cylinder, two ends of the ring pressure transmission rubber sleeve are respectively connected with an inlet pressure head and an outlet pressure head, a coal rock sample cavity is formed among the ring pressure transmission rubber sleeve, the inlet pressure head and the outlet pressure head, and a ring pressure application cavity is formed between the ring pressure transmission rubber sleeve and the side wall of the main steel cylinder.
As a further technical scheme, two ends of the annular pressure transmission rubber sleeve are tightly attached to the side wall of the main steel cylinder; the side wall of the main body steel cylinder is provided with a plurality of fluid inlet interfaces which are communicated with the annular pressure applying cavity, and the fluid inlet interfaces are connected with an annular pressure pump so as to inject annular pressure fluid into the triaxial core holder; the side wall of the main body steel cylinder is also provided with a fluid outlet interface which is communicated with the annular pressure applying cavity.
As a further technical scheme, the outer sides of the inlet pressure head and the outlet pressure head are respectively provided with a pressing sleeve structure, and the pressing sleeve structure of the inlet pressure head is provided with a fluid interface connected with an axial pressure pump so as to inject axial pressure fluid into the triaxial core holder; the entry pressure head all link up with the export pressure head and set up the circulation route, and the circulation route of entry pressure head communicates triaxial core holder's inlet port and coal petrography sample chamber, and the circulation route of export pressure head communicates triaxial core holder's outlet port and coal petrography sample chamber.
The embodiment of the invention has the following beneficial effects:
the test system of the invention can carry out transient test aiming at the seepage evolution law of the low-permeability compact coal rock, can carry out seepage tests under the coupling action of a plurality of effects such as different original stresses, different gas pressures, different effective stresses, different temperatures and the like by adjusting the gas pressures at the upstream and the downstream, can simultaneously adjust the volumes of the upstream and the downstream gas standard chambers, can test the influence of different volumes on the permeability, can more truly simulate the gas seepage evolution law in a coal bed, can more truly reflect the complex process of mutual coupling between the gas migration of the coal bed and the solid deformation of the coal bed, can more truly reflect the gas seepage condition of the low-permeability compact coal rock under different loading and unloading stress paths, can more truly simulate the reciprocal process of the effective stresses to the permeability change under different stress environments, can improve the test precision and greatly reduce the test time when the permeability is tested by adopting a transient method for the low-permeability compact coal rock, the test efficiency is improved, and the method has important engineering guidance significance for improving the extraction rate of the coal bed gas.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.
FIG. 1 is a schematic diagram of a test system according to one or more embodiments of the invention;
FIG. 2 is a schematic diagram of a tri-axial core holder according to one or more embodiments of the present disclosure;
in the figure: the mutual spacing or size is exaggerated to show the position of each part, and the schematic diagram is only used for illustration;
wherein, 1 main steel cylinder, 2 inlet pressure heads, 3 outlet pressure heads, 4 sample grooves, 5 annular pressure transfer rubber sleeves, 6 annular pressure applying cavities, 7 coal rock sample cavities, 8 annular pressure high-pressure fluid inlet ports, 9 annular pressure high-pressure fluid outlet ports, 10 upstream fluid injection ports, 11 downstream fluid outflow ports, 12 first pressure sleeves, 13 second pressure sleeves, 14 axial high-pressure fluid ports, 15 high-pressure gas sources, 16 pressure reducing valves, 17 gas booster pumps, 18 high-pressure gas buffer tanks, 19 buffer tank pressure sensors, 20 pressure reducing valves, 21 gas pressure sensors, 22 upstream gas pressure sensors, 23 pressure difference monitoring sensors, 24 downstream gas pressure sensors, 25 downstream emptying stop valves, 26 pressure difference stop valves, 27 pressure difference stop valves, 28 upstream temperature sensors, 29 downstream temperature sensors, 30 upstream emptying stop valves, 31, 32 pressure gauges, 33 axial pressure fluid injection valves, 34 ring pressure fluid injection valve, 35 pneumatic valve, 36 pneumatic valve, 37 pneumatic valve, 38 pneumatic valve, 39 pneumatic valve, 40 gas injection pneumatic valve, 41 pressure difference pneumatic valve, 42 pressure difference pneumatic valve, 43 upstream and downstream communication pneumatic valve, 44 pneumatic valve, 45 pneumatic valve, 46 pneumatic valve, 47 vacuum pneumatic valve, 48 vacuum line, 49 upstream vent line, 50 downstream vent line;
a1 upstream gas standard cell, a2 upstream gas standard cell, B1 downstream gas standard cell, B2 downstream gas standard cell; the core-holding device comprises a C triaxial core holder, a D differential pressure monitoring pipeline, an E axial pressure pump, an F annular pressure pump and a G upstream and downstream communication pipeline.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an", and/or "the" are intended to include the plural forms as well, unless the invention expressly state otherwise, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof;
for convenience of description, the words "up", "down", "left" and "right" in the present invention, if any, merely indicate correspondence with up, down, left and right directions of the drawings themselves, and do not limit the structure, but merely facilitate the description of the invention and simplify the description, rather than indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the invention.
The terms "mounted", "connected", "fixed", and the like in the present invention should be understood broadly, and for example, the terms "mounted", "connected", "fixed", and the like may be fixedly connected, detachably connected, or integrated; the two components can be connected mechanically or electrically, directly or indirectly through an intermediate medium, or connected internally or in an interaction relationship, and the terms used in the present invention should be understood as having specific meanings to those skilled in the art.
As introduced by the background art, the prior art has defects, and in order to solve the technical problems, the invention provides a transient test system for the seepage evolution law of low-permeability coal rocks.
In a typical embodiment of the present invention, as shown in fig. 1, a transient test system for a seepage evolution law of a low-permeability coal rock is provided, which mainly comprises a high-pressure gas source 15, a pressure reducing valve 16, a high-pressure gas buffer tank 18, a pneumatic valve, a gas pressure sensor, a standard chamber, a differential pressure sensor, a stop valve, a three-axis core holder C, a vacuum pump 31, a ring pressure pump F, an axial pressure pump E, and the like.
The triaxial core holder C is used for placing and holding a low-permeability coal rock sample to carry out axial pressure and annular pressure loading and gas seepage test, and the high-pressure gas source 15, the pressure reducing valve 16, the gas booster pump 17, the high-pressure gas buffer tank 18, the buffer tank pressure reducing valve 20, the upstream gas standard chamber A1, the upstream gas standard chamber A2 and the upstream gas pressure sensor 22 are sequentially connected in series and then connected with the gas inlet end of the triaxial core holder C; the gas outlet end of the triaxial core holder C is sequentially connected with a downstream gas pressure sensor 24, a downstream gas standard chamber B2 and a downstream gas standard chamber B1 in series.
The high pressure gas source may be stored in a cylinder.
The high-pressure gas source 15 is externally provided with a pressure gauge 32 for monitoring a gas pressure inlet and an outlet and a pressure reducing valve 16 for adjusting the pressure of the outlet, an output pipeline of the high-pressure gas source is connected with the high-pressure gas buffer tank 18, the output pipeline of the high-pressure gas source is provided with a gas booster pump 17, and the gas booster pump is arranged between the pressure reducing valve 16 and the high-pressure gas buffer tank 18 and used for boosting gas.
The inlet of the high-pressure gas buffer tank 18 is provided with a pneumatic valve 35, the outlet of the high-pressure gas buffer tank 18 is provided with a pneumatic valve 36, the high-pressure gas buffer tank 18 is also provided with a buffer tank pressure sensor 19 for monitoring the gas pressure in the buffer tank, and the high-pressure gas buffer tank is mainly used for storing the gas after being pressurized by the gas booster pump.
The outlet of the high-pressure gas buffer tank 18 is provided with a pressure reducing valve 20 and a gas pressure sensor 21 which are respectively responsible for regulating the outlet pressure of the gas flowing into the gas standard chamber from the outlet of the buffer tank and monitoring the regulated outlet pressure. The pressure reducing valve and the gas pressure sensor are matched to adjust and monitor the outlet pressure of the high-pressure gas buffer tank, so that the gas pressure required by the test can reach an accurate numerical value.
In an alternative embodiment, a plurality of upstream gas standard chambers are arranged, the plurality of upstream gas standard chambers are connected in series, the upstream gas standard chamber at the head end is connected with an outlet of the high-pressure gas buffer tank 18, and the upstream gas standard chamber at the tail end is connected with a gas inlet port of the triaxial core holder; in this embodiment, two gas standard chambers are provided, namely an upstream gas standard chamber a1 and an upstream gas standard chamber a2, an outlet of the high-pressure gas buffer tank 18 is connected with the upstream gas standard chamber a1, and the upstream gas standard chamber a1 is connected with the upstream gas standard chamber a 2.
In this embodiment, the definition of the head end and the tail end is: along the flow direction of the test fluid, the test fluid passes first as a head end and then as a tail end.
The air-operated valve 37 is arranged at the inlet of the upstream gas standard chamber A1, and the air-operated valve 38 is arranged at the outlet of the upstream gas standard chamber A1, so that the operation process of gas pressure regulation can be simplified, and the safe operation of the whole system can be ensured.
An inlet of the upstream gas standard chamber A2 is connected with a vacuumizing pipeline 48 and an upstream emptying pipeline 49 in parallel, and the vacuumizing pipeline 48 is connected with an inlet of the upstream gas standard chamber A2 after being connected with the upstream emptying pipeline 49 in parallel.
The vacuum-pumping pipeline 48 is provided with a vacuum-pumping pneumatic valve 47 which is connected with the vacuum pump 31 in series and is mainly used for vacuumizing the pipeline before the test is started so as to prevent the existence of other gases from influencing the test precision; the upstream vent line 49 is provided with an upstream vent stop valve 30 which can be used to regulate the gas pressure in the upstream standard cell during the test and the venting of the entire system after the test is completed.
An outlet of the upstream gas standard chamber A2 is communicated with an air inlet port of the triaxial core holder C, an outlet side of the upstream gas standard chamber A2 is provided with an air-operated valve 39, and an upstream gas pressure sensor 22 is arranged between an outlet of the upstream gas standard chamber A2 and the air inlet port of the triaxial core holder C and used for monitoring the gas pressure value of the air inlet end of the triaxial core holder C.
The gas injection pneumatic valve 40 is arranged in front of a gas inlet port of the triaxial core holder C, and is closed when the air pressure of the system is balanced, so that the gas injection pneumatic valve can be opened after upstream pulse pressure can be accurately applied to reach a specified value, a seepage test is carried out, and the change of upstream and downstream pressure difference is monitored in real time to calculate the permeability.
In an optional embodiment, a plurality of downstream gas standard chambers are arranged, the downstream gas standard chambers are connected in series, and the downstream gas standard chamber at the head end is connected with the gas outlet port of the triaxial core holder C; in this embodiment, two gas standard chambers are provided, namely a downstream gas standard chamber B1 and a downstream gas standard chamber B2, an air outlet port of the triaxial core holder C is communicated with the downstream gas standard chamber B1, and the downstream gas standard chamber B1 is communicated with the downstream gas standard chamber B2.
And a downstream gas pressure sensor 24 is arranged between the gas outlet port of the triaxial core holder C and the downstream gas standard chamber B1 and is used for monitoring the gas pressure value of the gas outlet port of the triaxial core holder C.
The inlet of the downstream gas standard chamber B1 is provided with a pneumatic valve 44, and the inlet of the downstream gas standard chamber B2 is provided with a pneumatic valve 45 for changing the upstream and downstream test calculated volume in the test process; the outlet of the downstream gas standard chamber B2 is provided with a pneumatic valve 46.
The outlet of the downstream gas standard chamber B1 is also communicated with a downstream vent pipeline 50 which is provided with a downstream vent stop valve 25 which can be used for adjusting the gas pressure of the downstream standard chamber in the test process and the gas venting of the whole system after the test is finished.
In the scheme of the application, two standard chambers are arranged upstream and downstream, wherein the volumes of a1 and B1 are approximately the same, and the volumes of a2 and B2 are approximately the same, when system volume calibration is performed, the volume of a pipeline is numerically included, namely the volume of an upstream reservoir (for example, the volume of the upstream standard chamber a2 is numerically the sum of the volumes of all pipelines between the upstream end of a sample in a core holder and the standard chamber a2 and the volume of the standard chamber), and the size of the upstream reservoir volume needs to be considered when permeability calculation is performed.
In the scheme of the application, the volumes of the two upstream and downstream standard chambers are set to be different, so that permeability test conditions under different volumes can be provided, and the constant volume pulse attenuation method test and the variable volume pulse attenuation method test can be performed.
The measurement range of the constant volume pulse attenuation method has certain limitation, generally 2 orders of magnitude, and cannot meet the measurement requirement of large range or large range change of permeability. And by adopting a variable-volume pulse attenuation method, the volume of a proper standard chamber can be adjusted according to the requirement of a tested piece, so that the measuring range is expanded within proper measuring time and can reach 6 orders of magnitude theoretically.
The three-axis core holder C is connected with a pressure difference monitoring pipeline D and an upstream and downstream communicating pipeline G in parallel, the pressure difference monitoring pipeline D is connected with the air inlet end and the air outlet end of the three-axis core holder, and the upstream and downstream communicating pipeline G is connected with the air inlet end and the air outlet end of the three-axis core holder.
When the initial value of the gas pressure is dynamically balanced when the test is started, the upstream and downstream communication pipelines are opened, so that the time for the gas pressure to reach balance can be shortened.
After the experiment, need all arrange the clean with the air in the system, no matter open upstream gas drain or the gaseous drain of low reaches, open the valve of upper and lower stream intercommunication pipeline and can both be fast effectual with the test gas exhaust in the system.
The pressure difference monitoring pipeline D is used for monitoring the pressure difference of upstream and downstream gases, the pressure difference monitoring pipeline D is sequentially connected with a pressure difference pneumatic valve 41, a pressure difference stop valve 26, a pressure difference monitoring sensor 23, a pressure difference stop valve 27 and a pressure difference pneumatic valve 42 in series, and the pressure difference monitoring sensor 23 is mainly used for monitoring the initial pressure difference at the two ends of the upstream and the downstream and the change condition of the pressure difference in the test process when the permeability of a coal rock sample is tested by a transient method, so that the seepage process that the upstream and the downstream pressures gradually reach balance can be intuitively reflected. The differential pressure pneumatic valve and the differential pressure stop valve can protect the differential pressure monitoring sensor from exceeding the test range.
The pressure difference monitoring pipeline can monitor that the maximum small pulse of the applied gas pressure in the test process is not more than 2MPa, and can accurately control the numerical value of the pressure difference through the valve, so that the small pulse of the applied gas pressure is the same in the gas boosting process of each stage, and the test precision is improved.
The upstream and downstream communication pipeline G communicates the upstream and downstream, and the upstream and downstream communication pipeline G is provided with an upstream and downstream communication pneumatic valve 43, which is mainly used for quickly balancing the gas pressure of the whole system before the test starts and quickly deflating the whole system after the test starts.
In a further scheme, the volumes of the upstream gas standard chamber A1 and the upstream gas standard chamber A2 are respectively 50ml and 5 ml; the volumes of the downstream gas standard chamber B1 and the downstream gas standard chamber B2 are 50ml and 5ml respectively. The gas standard chamber is mainly used for selecting various combinations of the calculated volumes of the upstream container and the downstream container when the permeability is measured and calculated by a transient method, and is an innovation of the test system.
As shown in fig. 2, the triaxial core holder C mainly comprises a main body steel cylinder 1, an inlet pressure head 2, an outlet pressure head 3, a ring pressure transfer rubber sleeve 5, a first pressure sleeve 12, a second pressure sleeve 13 and the like.
The first pressing sleeve and the second pressing sleeve can be made of steel.
The inlet pressure head and the outlet pressure head are respectively positioned at the left end and the right end of the main body steel cylinder 1 for plugging, and the main body steel cylinder 1, the inlet pressure head and the outlet pressure head jointly enclose a sample groove 4 for placing a coal rock sample.
The main part steel cylinder internally mounted has the ring crush transmission gum cover 5 of parcel coal petrography sample, and the ring crush transmission gum cover both ends are connected with entry pressure head, export pressure head respectively to cut apart into the ring crush with coal petrography sample groove and apply chamber 6 and coal petrography sample chamber 7, form the "sandwich" structure of closely combining with the coal petrography sample.
The annular pressure transmission rubber sleeve 5, the inlet pressure heads and the outlet pressure heads at two ends of the annular pressure transmission rubber sleeve surround a long-strip-shaped coal rock sample cavity, the length of a sample placed in the coal rock sample cavity is 50mm-80mm, the diameter of the sample is phi 25mm, and the porous grain stainless steel cushion blocks with different calibrated lengths are used, so that the requirements of samples with different lengths in a range permission can be met.
An annular pressure applying cavity 6 is formed between the annular pressure transmission rubber sleeve 5 and the main body steel cylinder 1, 3 annular high-pressure fluid connectors which are right opposite to the annular pressure applying cavity are arranged on the outer wall of the main body steel cylinder, and when the annular pressure transmission rubber sleeve is specifically arranged, one side of the outer wall of the main body steel cylinder is provided with an annular pressure high-pressure fluid outlet connector 9 which is used for connecting an annular pressure fluid discharge plug so as to discharge gas in the annular pressure applying cavity after a test is finished; two ring pressure high pressure fluid inlet ports 8 are arranged on the other side of the outer wall of the main steel cylinder and used for being connected with an external ring pressure pump pipeline so as to apply ring pressure to the injected ring pressure high pressure fluid and avoid damaging a ring pressure transmission rubber sleeve. The ring pressure is transmitted to the coal rock sample because the ring pressure transmission rubber sleeve can deform under the pressure.
And an annular pressure fluid injection valve 34 is arranged between the annular pressure pump F and the annular pressure high-pressure fluid inlet interface 8 and can inject annular pressure fluid into the triaxial core holder.
The inlet pressure head is connected with an upstream fluid injection port 10, the upstream fluid injection port 10 is arranged at an air inlet port of the triaxial core holder, the inlet pressure head is provided with a circulation passage in a penetrating way, the circulation passage is connected with the upstream fluid injection port, and the upstream fluid injection port 10 is communicated with the coal rock sample cavity 7 through the circulation passage; the outlet pressure head is connected with a downstream fluid outlet 11, the downstream fluid outlet 11 is arranged at an air outlet port of the triaxial core holder, the outlet pressure head is provided with a circulation passage in a penetrating manner, the circulation passage is connected with the downstream fluid outlet, and the downstream fluid outlet 11 is communicated with the coal rock sample cavity 7 through the circulation passage.
The outer sides of the inlet pressure head and the outlet pressure head are respectively provided with a pressing sleeve structure, specifically, the outer sides of the inlet pressure head and the outlet pressure head are sleeved with a second pressing sleeve 13, the outer side of the second pressing sleeve 13 is sleeved with a first pressing sleeve 12, and the first pressing sleeves of the inlet pressure head and the outlet pressure head are fixed at the end part of the main steel cylinder; an axial high-pressure fluid interface 14 is arranged on the outer wall of a first pressing sleeve of the inlet pressure head, an axial pressure pump E is communicated with the axial high-pressure fluid interface 14, an axial pressure fluid injection valve 33 is arranged between the axial pressure pump E and the axial high-pressure fluid interface 14, and axial pressure fluid can be injected into the triaxial core holder.
An LVDT displacement sensor is arranged at the left end head of the triaxial core holder and used for monitoring axial deformation of the coal rock sample.
The high-pressure gas buffer tank, the upstream gas standard chamber A1, the upstream gas standard chamber A2, the upstream gas pressure sensor, the triaxial core holder, the differential pressure monitoring pipeline, the downstream gas pressure sensor, the downstream gas standard chamber B1, the downstream gas standard chamber B2, a pneumatic valve for controlling a pipeline switch, a pressure reducing valve, a stop valve and the like are jointly placed in the incubator, the upstream temperature sensor 28 and the downstream temperature sensor 29 are respectively arranged to jointly monitor the temperature of the whole system, the temperature change range of the incubator is room temperature-150 ℃, so that the temperature is kept in a constant state during constant temperature test, and the temperature can be adjusted in a change range according to the needs of the test during variable temperature test.
The triaxial core holder is provided with the two annular pressure fluid injection ports, so that the three annular pressure fluid injection ports can be used for discharging internal air when an annular pressure cavity is pressurized, annular pressure fluid is injected inwards through one annular pressure fluid injection port, the plug is loosened through the other annular pressure fluid injection port, the internal air is continuously discharged along with the continuous injection of high-pressure fluid, and when the annular pressure fluid overflows from the injection port, the air in the annular pressure cavity is completely discharged, so that the subsequent pressure loading is continuously carried out after the plug is screwed down; the sample groove can be used for placing a sample with the length of 50mm-80 mm; the end head in direct contact with the two ends of the sample and the stainless steel cushion block are both made into porous grains, so that gas can fully flow in or out from the end face of the sample, and the seepage condition of coal and rock is reflected more truly.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A transient test system for a seepage evolution rule of a low-permeability coal rock is characterized by comprising a triaxial core holder, an upstream fluid supply device and a downstream fluid circulation device; the upstream fluid supply device comprises two upstream gas standard chambers connected in series, the upstream gas standard chamber at the head end is connected with a gas source, and the upstream gas standard chamber at the tail end is connected with a gas inlet port of the triaxial core holder; the downstream fluid circulation device comprises two downstream gas standard chambers connected in series, the downstream gas standard chamber at the head end is connected with the gas outlet port of the triaxial core holder, and the influence of different volumes on permeability is tested by adjusting the volumes of the upstream and downstream gas standard chambers; the volumes of the two standard chambers at the upstream are set to be different, and the volumes of the two standard chambers at the downstream are also set to be different;
the inlet and the outlet of the upstream gas standard chamber at the head end are both provided with pneumatic valves, and the outlet of the upstream gas standard chamber at the tail end is provided with a pneumatic valve; the outlet of the upstream gas standard chamber at the head end is also communicated with a vacuum pumping pipeline, the vacuum pumping pipeline is communicated with a vacuum pump, and the vacuum pumping pipeline is provided with a pneumatic valve; the outlet of the upstream gas standard chamber at the head end is also communicated with an upstream emptying pipeline, the upstream emptying pipeline is arranged in parallel with the vacuumizing pipeline, and the upstream emptying pipeline is provided with an upstream emptying stop valve;
a buffer tank is arranged between the gas source and the upstream gas standard chamber at the head end, a booster pump is arranged between the gas source and the buffer tank, and a pressure gauge and a pressure reducing valve are arranged at the outlet of the gas source; the inlet and the outlet of the buffer tank are both provided with pneumatic valves, and the buffer tank is also connected with a first pressure sensor; a pressure reducing valve and a second pressure sensor are arranged between the buffer tank and an upstream gas standard chamber at the head end;
the triaxial core holder is also connected with a differential pressure monitoring pipeline in parallel, and the differential pressure monitoring pipeline is provided with a differential pressure monitoring sensor, a differential pressure stop valve and a differential pressure pneumatic valve; the triaxial core holder is also connected with an upstream and downstream communication pipeline in parallel, the upstream and downstream communication pipeline communicates an upstream fluid supply device with a downstream fluid circulation device, and the upstream and downstream communication pipeline is provided with a pneumatic valve;
the triaxial core holder comprises a main body steel cylinder, wherein a ring pressure transfer rubber sleeve is arranged in the main body steel cylinder, two ends of the ring pressure transfer rubber sleeve are respectively connected with an inlet pressure head and an outlet pressure head, a coal rock sample cavity is formed among the ring pressure transfer rubber sleeve, the inlet pressure head and the outlet pressure head, and a ring pressure applying cavity is formed between the ring pressure transfer rubber sleeve and the side wall of the main body steel cylinder; the side wall of the main body steel cylinder is provided with a plurality of fluid inlet interfaces which are communicated with the annular pressure applying cavity, and the fluid inlet interfaces are connected with an annular pressure pump so as to inject annular pressure fluid into the triaxial core holder; the outer sides of the inlet pressure head and the outlet pressure head are respectively provided with a pressing sleeve structure, and the pressing sleeve structure of the inlet pressure head is provided with a fluid interface to be connected with an axial pressure pump so as to inject axial pressure fluid into the triaxial core holder.
2. The transient testing system for the seepage evolution law of the hypotonic coal rock according to claim 1, wherein an upstream gas pressure sensor is arranged at the inlet end of the triaxial core holder, a downstream gas pressure sensor is arranged at the outlet end of the triaxial core holder, and changes of upstream and downstream pressure values are monitored through the upstream and downstream gas pressure sensors.
3. The transient testing system for the seepage evolution law of the hypotonic coal rock as claimed in claim 1, wherein a pneumatic valve is arranged at an inlet of the downstream gas standard chamber at the head end, an outlet of the downstream gas standard chamber at the head end is connected with a downstream emptying pipeline, and the downstream emptying pipeline is provided with a downstream emptying stop valve; and pneumatic valves are arranged at the inlet and the outlet of the downstream gas standard chamber at the tail end.
4. The transient testing system for the seepage evolution law of the hypotonic coal rock according to claim 1, wherein the triaxial core holder, the upstream fluid supply device and the downstream fluid circulation device are all arranged in a constant temperature box, and the constant temperature box is provided with a temperature sensor; and a displacement sensor is arranged at the end part of the triaxial core holder and used for monitoring the axial deformation of the coal rock sample.
5. The transient test system for the seepage evolution law of the hypotonic coal rock as claimed in claim 1, wherein the side wall of the main steel cylinder is further provided with a fluid outlet port communicated with the annular pressure applying cavity.
6. The transient testing system for the seepage evolution law of low-permeability coal rocks as claimed in claim 1, wherein the inlet pressure head and the outlet pressure head are both provided with a circulation passage in a penetrating manner, the circulation passage of the inlet pressure head is communicated with the air inlet port of the triaxial core holder and the coal rock sample cavity, and the circulation passage of the outlet pressure head is communicated with the air outlet port of the triaxial core holder and the coal rock sample cavity.
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| CN103616322B (en) * | 2013-11-25 | 2016-05-11 | 中国石油天然气股份有限公司 | Tight rock permeability unstable state assay method |
| CN103969165B (en) * | 2014-04-30 | 2017-05-24 | 东北大学 | Device and method for simultaneously testing permeability of compact rocks under transient state and steady state |
| CN105675469B (en) * | 2016-01-25 | 2018-03-06 | 中国矿业大学 | Rock Full-automatic gas permeability test system and measuring method |
| CN206410978U (en) * | 2017-01-18 | 2017-08-15 | 西南石油大学 | A kind of tight rock gas phase relative permeability measurement apparatus |
| CN109470616B (en) * | 2018-10-31 | 2021-11-23 | 重庆大学 | Multifunctional seepage testing system for rock |
| CN210155008U (en) * | 2019-07-09 | 2020-03-17 | 中国石油大学胜利学院 | Triaxial coal petrography gas single-phase seepage flow experimental apparatus under residual water state |
| CN110987764B (en) * | 2019-12-25 | 2021-02-26 | 重庆大学 | Long coal rock sample gas-liquid seepage test system |
| CN111929223B (en) * | 2020-09-24 | 2022-11-18 | 山东科技大学 | Device and method for quickly and accurately measuring seepage rule of gas in compact rock core |
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