CN111272635A - Rock porosity and permeability combined test device and test method under triaxial condition - Google Patents
Rock porosity and permeability combined test device and test method under triaxial condition Download PDFInfo
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- 239000011435 rock Substances 0.000 title claims abstract description 125
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- 239000011148 porous material Substances 0.000 claims abstract description 41
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- 239000000126 substance Substances 0.000 claims description 8
- 238000000605 extraction Methods 0.000 claims description 7
- 239000008367 deionised water Substances 0.000 claims description 5
- 229910021641 deionized water Inorganic materials 0.000 claims description 5
- 238000007789 sealing Methods 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
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- 239000007789 gas Substances 0.000 description 34
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- 230000006872 improvement Effects 0.000 description 9
- 229910001220 stainless steel Inorganic materials 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
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- 230000006355 external stress Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
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- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention discloses a rock porosity and permeability combined test device and a rock porosity and permeability combined test method under a triaxial condition, wherein the device is used for simultaneously measuring the rock porosity and permeability under a triaxial stress condition, and comprises a pore permeability measuring assembly, a rock core holder (17), a confining pressure loading assembly, an axial pressure loading assembly, a multi-channel data acquisition card (15) and a data storage processing module (16); and the hole permeability measuring assembly, the confining pressure loading assembly and the axial pressure loading assembly are respectively connected with a rock core holder (17). The present invention fully couples porosity and permeability tests together. In the gas diffusion process, according to the pressure values and the differential pressure attenuation curves at the two ends of the rock to be tested, the porosity and the permeability of the rock under certain triaxial stress are obtained according to a porosity calculation formula and a permeability calculation formula respectively, the correlation between the porosity and the permeability of the rock and the stress can be comprehensively analyzed, the testing time is shortened to a certain extent, and the testing efficiency is improved.
Description
Technical Field
The invention relates to the field of engineering geology, in particular to a rock porosity and permeability combined test device and a test method under a triaxial condition.
Background
With the development and utilization of underground energy and space, the basic physical and mechanical properties of underground reservoir rock have significant influence on the safety of underground engineering. The porosity and permeability of the porous rock are used as one of the most basic rock physical parameters to respectively represent the storage space characteristics and the fluid circulation performance of the underground reservoir rock, and the method has important significance for oil and gas resource quantity evaluation and storage capacity evaluation.
The research on the correlation between the rock porosity and the permeability is of great significance for comprehensively mastering the reservoir characteristics of reservoir rocks. In addition, the porosity and permeability of rock are related to the stress state of the reservoir rock. In practical situations, reservoir rock is in a certain stress environment and is under the action of external stress, and the porosity, permeability and the correlation of the porosity and the permeability change along with the change of the reservoir stress.
At present, most of the rock sample testing devices on the market need to separately measure the porosity and the permeability, and a few devices integrate the porosity and permeability testing methods into the same device. However, in practice, step-by-step measurement is required during testing, namely, the porosity is measured first and then the permeability is measured, or the permeability is measured first and then the porosity is measured, and the two methods are not really coupled together for measurement, so that the testing time is prolonged to a certain extent, and the testing efficiency is reduced.
Reference [1] (invention patent "a test apparatus and a test method for porosity and permeability of a low permeability core" of application publication No. CN 106872328A) only applies confining pressure, no axial pressure, and no triaxial condition in the test on porosity and permeability.
Although the reference [2] (patent of invention publication No. CN 107917867A, a multifunctional rock sample testing device) can complete porosity and permeability tests on the same equipment, the porosity and permeability are separately tested, i.e. the porosity is measured first, and the permeability is tested on the basis of the porosity analysis test.
The device proposed in reference [3] (patent publication No. CN 108088778A entitled permeability and porosity testing device for rock-like materials) focuses on integrating a steady-state method and an unsteady-state method in measuring permeability, and porosity measurement is only used as an additional part and is not measured simultaneously.
Reference [4] (patent application publication No. CN 108333091 a "invention of high temperature triaxial pore permeation testing apparatus and method") proposes to use a constant pressure method in measuring the permeability. Under the influence of the measurement range of the constant pressure method, the permeability measurement effect of the device on low-permeability rocks is not ideal. Therefore, there is a need for a testing apparatus and a testing method that can simultaneously measure porosity and permeability in three-axis conditions.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a rock porosity and permeability joint test device under a triaxial condition, and also discloses a rock porosity and permeability joint test method under a triaxial condition.
In order to achieve the aim, the invention provides a rock porosity and permeability combined testing device under a triaxial condition, which is used for simultaneously measuring the rock porosity and permeability under a triaxial stress condition and is characterized by comprising a pore permeability measuring assembly, a rock core holder, a confining pressure loading assembly, an axial pressure loading assembly, a multi-channel data acquisition card and a data storage processing module; the hole permeability measuring assembly, the confining pressure loading assembly and the axial pressure loading assembly are respectively connected with the core holder; wherein the content of the first and second substances,
the pore-permeability measuring assembly is used for measuring the pressure and the pressure difference of the upper end and the lower end of the rock sample to be tested under the triaxial condition;
the core holder is used for fixing a rock sample to be tested and applying confining pressure and axial pressure to the rock sample to be tested;
the confining pressure loading assembly is used for generating confining pressure acting on a rock sample to be tested;
the axial pressure loading assembly is used for generating axial pressure acting on a rock sample to be tested;
the multi-channel data acquisition card is used for acquiring the pressure and the pressure difference measured by the pore permeability measurement assembly and sending the pressure and the pressure difference to the data storage processing module;
and the data storage and processing module is used for simultaneously calculating the porosity and the permeability of the rock sample to be tested based on the pressure and the pressure difference.
As an improvement of the above apparatus, the pore permeability measuring assembly comprises: the device comprises a high-pressure gas cylinder, a first valve, a pore pressure booster pump, a second valve, a first pressure sensor, a differential pressure gauge, a first buffer tank, a third valve, a fourth valve, a fifth valve, a second buffer tank, a sixth valve, a second pressure sensor and a vacuum pump; wherein the content of the first and second substances,
the outlet of the high-pressure gas cylinder is respectively communicated with a first valve and a pore pressure booster pump through pipelines, the pipelines are divided into three paths after passing through a second valve, and the first path is connected with the input end of a first pressure sensor; the second path is connected with one end of the differential pressure gauge; the third path sequentially passes through the first buffer cylinder and the third valve and is communicated with the rock core holder;
the pipeline connected with the other end of the differential pressure gauge is divided into three paths, and the first path is connected with the input end of the second pressure sensor; the second path is communicated with a vacuum pump through a sixth valve; the third path sequentially passes through a second buffer tank and a fifth valve and is communicated with the rock core holder;
a pipeline is arranged between the third valve and the first buffer cylinder and communicated to a position between the fifth valve and the second buffer tank, and a fourth valve is arranged in the middle of the pipeline;
and the data output ends of the first pressure sensor, the differential pressure gauge and the second pressure sensor are connected with a multi-channel data acquisition card.
As an improvement of the device, the core holder comprises a heat-shrinkable tube positioned in the chamber, a fluid extraction port positioned on the outer wall of the chamber, a confining pressure injection hole, an axial pressure injection hole and a fluid injection hole; wherein the content of the first and second substances,
the heat-shrinkable tube seals a rock sample to be tested and then fixes the rock sample in the rock core holder;
the fluid extraction port is communicated with a fifth valve of the pore-permeability measurement assembly through a pipeline;
the confining pressure injection hole is communicated with the confining pressure loading assembly through a pipeline;
the axial pressure injection hole is communicated with the axial pressure loading assembly through a pipeline;
the fluid injection port is in communication with a third valve of the pore permeation measurement assembly via a conduit.
As an improvement of the above apparatus, the confining pressure loading assembly comprises: the device comprises a confining pressure first control valve, a confining pressure booster pump, a confining pressure second control valve and a confining pressure power source;
the confining pressure power source output pipeline is communicated with a confining pressure injection hole of the core holder through a confining pressure second control valve, a confining pressure booster pump and a confining pressure first control valve in sequence; the confining pressure power source is deionized water; the confining pressure booster pump is a high-precision metering pump.
As an improvement of the above apparatus, the axial compression loading assembly includes: the device comprises a first axial pressure control valve, an axial pressure loading pump, a second axial pressure control valve and an axial pressure power source;
the axial pressure power source output pipeline is communicated with an axial pressure injection hole of the core holder through an axial pressure second control valve, an axial pressure booster pump and an axial pressure first control valve in sequence; the shaft pressure power source is deionized water; the axial pressure booster pump is a high-precision metering pump.
The invention also provides a rock porosity and permeability joint test method under the triaxial condition, which comprises the following steps:
step 1) putting a standard sample with a fixed size into the heat-shrinkable tube, and sealing the standard sample;
step 2) respectively applying confining pressure and axial pressure to the standard sample through a confining pressure loading component and an axial pressure loading component, and keeping the confining pressure and the axial pressure applied to the standard sample at design values;
step 3) vacuumizing an internal pipeline of the pore permeation measurement assembly;
step 4) injecting gas into the pore permeation measurement assembly, and carrying out pipeline volume measurement and calibration;
step 5) closing the confining pressure loading assembly and the axial pressure loading assembly, stopping applying confining pressure and axial pressure on the standard sample, and disassembling the standard sample;
step 6), placing a rock sample to be tested into a heat-shrinkable tube, and sealing the rock sample to be tested, wherein the volume of the rock sample to be tested is V;
step 7) repeating the step 2) and the step 3), respectively applying confining pressure and axial pressure to the rock sample to be tested through the confining pressure loading assembly and the axial pressure loading assembly, and keeping the confining pressure and the axial pressure applied to the rock sample to be tested at design values; vacuumizing the pore-permeation measuring assembly;
step 8) injecting gas into the pore permeation measurement assembly, obtaining a pressure value through a first pressure sensor and a second pressure sensor, obtaining a pressure difference value through a differential pressure gauge, collecting the pressure value and the pressure difference value through a multi-channel data acquisition card, and transmitting the pressure value and the pressure difference value to a data storage processing module;
and 9) calculating the porosity and the permeability by the data storage processing module according to the pressure value, the volume calibrated by the pipeline and the volume of the rock sample to be tested by combining a pressure attenuation curve.
As an improvement of the above method, the step 2) specifically includes:
closing the confining pressure first control valve, opening a confining pressure second control valve, and filling a confining pressure power source into a confining pressure pressurization pump;
closing the second confining pressure control valve and opening the first confining pressure control valve; after a certain confining pressure is applied to the rock sample to be tested, maintaining the confining pressure at a design value;
closing the first control valve of the axial pressure, opening the second control valve of the axial pressure, and filling the power source of the axial pressure to the axial pressure booster pump;
closing the second control valve for axial pressure, and opening the first control valve for axial pressure; and after a certain axial pressure is applied to the rock sample to be tested, the axial pressure is maintained at a design value.
As an improvement of the above method, the step 3) specifically includes:
closing the second valve, keeping the third valve, the fourth valve, the fifth valve and the sixth valve open, opening a vacuum pump to vacuumize the pore-permeation measuring assembly, and closing the vacuum pump when the pressure values displayed by the first pressure sensor and the second pressure sensor are below 0;
if the pressure values displayed by the first pressure sensor and the second pressure sensor are not more than 0 and are kept for more than 2 hours, the vacuumizing is completed; otherwise, continuing to carry out vacuum-pumping treatment.
As an improvement of the above method, the step 4) specifically includes:
closing the vacuum pump and the sixth valve, opening the high-pressure gas cylinder and the first valve, and injecting gas into the pore permeation measurement assembly to measure and calibrate the volume of the pipeline; wherein the content of the first and second substances,
the volume of a pipeline among the second valve, the first pressure sensor, the differential pressure gauge, the first buffer tank, the third valve and the fourth valve is V1;
the volume of the pipeline between the third valve and the bottom surface of the heat-shrinkable tube is V2;
the volume of the pipeline between the top surface of the heat shrinkable tube and the fifth valve is V3;
and the volume of a pipeline among the fourth valve, the fifth valve, the second buffer tank, the second pressure sensor, the differential pressure gauge and the sixth valve is V4.
As an improvement of the above method, the step 8) specifically includes:
keeping the vacuum pump and the sixth valve closed, closing the third valve and the fourth valve, and keeping the fifth valve open; opening a high-pressure gas cylinder and a first valve, injecting gas into the pore pressure booster pump, and closing the high-pressure gas cylinder and the first valve after the pore pressure booster pump is filled with the gas; opening a second valve, injecting gas into a pipeline volume V1 between the second valve, the first pressure sensor, the differential pressure gauge, the first buffer tank, the third valve and the fourth valve, and recording a pressure value P1 of the first pressure sensor and a numerical value DP1 of the differential pressure gauge through a multi-channel data acquisition card after the pressure is stable;
opening a third valve, diffusing the gas in the pipeline with the volume of V1 into the pipeline with the volume of V2 and the rock sample to be tested until the gas reaches the pipeline with the volume of V3 and the pipeline with the volume of V4, slowly attenuating the pressure of the differential pressure gauge at the moment, and recording the pressure attenuation curve S of the differential pressure gauge through a multi-channel data acquisition card;
and after the gas slowly diffuses from the upstream end to the downstream end of the rock sample to be tested and the related pipelines with the volumes of V3 and V4, recording the reading P2 of the second pressure sensor by using the multi-channel data acquisition card when the value of the differential pressure meter is 0.
As an improvement of the above method, the step 9) is specifically:
calculating the porosity of the rock sample (19) to be tested under triaxial stress by the data storage and processing module (16)
Wherein Vr is the effective pore volume of the rock sample (19) to be tested under the stress condition:
and the data storage processing module (16) calculates the permeability k of the rock sample to be tested (19) through the pressure attenuation curve S of the differential pressure gauge according to a transient pressure pulse method:
from the pressure decay curve S of the differential pressure gauge, based on:
wherein, Δ DP (t) is the pressure decay curve S, Δ P measured by the differential pressure gaugeiCalculating to obtain the slope α of the attenuation curve;
substituting slope α into the following equation:
wherein L is the length of the rock sample to be tested, A is the cross-sectional area of the rock sample to be tested, and mu is the viscosity coefficient of the high-pressure gas; and calculating to obtain the permeability k of the rock sample to be tested.
Compared with the prior art, the invention has the advantages that:
1. the testing device of the present invention fully couples porosity and permeability testing together. In the gas diffusion process, according to the pressure values and the differential pressure attenuation curves at the two ends of the rock to be tested, the porosity and the permeability of the rock under certain triaxial stress are obtained according to a porosity calculation formula and a permeability calculation formula respectively, the correlation between the porosity and the permeability of the rock and the stress can be comprehensively analyzed, the testing time is shortened to a certain extent, and the testing efficiency is improved.
Drawings
FIG. 1 is a schematic structural diagram of a rock porosity and permeability joint test device under a triaxial condition.
Reference numerals
1. High-pressure gas cylinder 2 and first valve
3. Pore pressure booster pump 4 and second valve
5. First pressure sensor 6, differential pressure gauge
7. First buffer tank 8 and third valve
9. Fourth valve 10, fifth valve
11. A second buffer tank 12 and a sixth valve
13. Second pressure sensor 14, vacuum pump
15. Multi-channel data acquisition card 16 and data storage processing module
17. Core holder 18, heat-shrinkable tube
19. Rock sample 20 to be tested and confining pressure first control valve
21. Confining pressure booster pump 22, confining pressure second control valve
23. Confining pressure power source 24 and axial pressure first control valve
25. Axial compression booster pump 26, second control valve for axial compression
27. Axial pressure power source 28, fluid injection port
29. Fluid extraction port 30, axial pressure injection port
31. Confining pressure injection hole
Detailed Description
The invention provides a rock porosity and permeability combined test device and a test method under a triaxial condition.
The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and examples.
Example 1
This embodiment provides a rock porosity permeability joint test device under triaxial condition, as shown in fig. 1, the device includes: the device comprises a pore-permeability measuring assembly, a rock core holder, a confining pressure loading assembly, an axial pressure loading assembly, a multi-channel data acquisition card and a data storage processing module; wherein the hole seepage measurement assembly, the confining pressure loading assembly and the axial pressure loading assembly are connected with the core holder. The data acquisition card is used for acquiring data of the first pressure sensor 5, the second pressure sensor 13 and the differential pressure gauge 6 in the pore permeation test pipeline and transmitting the data to the data storage processing module.
The pore permeability measuring component comprises a high-pressure gas bottle 1, a first valve 2, a pore pressure booster pump 3, a second valve 4, a first pressure sensor 5, a differential pressure gauge 6, a first buffer tank 7, a third valve 8, a fourth valve 9, a fifth valve 10, a second buffer tank 11, a sixth valve 12, a second pressure sensor 13 and a vacuum pump 14; the high-pressure gas cylinder 1 is connected with one end of a first valve 2; the other end of the first valve 2 is connected with one end of a pore pressure booster pump 3; the other end of the pore pressure booster pump 3 is connected with one end of a second valve 4; the other end of the second valve 4 is simultaneously connected with the first pressure sensor 5, one end of the differential pressure gauge 6, one end of the first buffer cylinder 7 and one end of the third valve 8 and one end of the fourth valve 9; the other end of the third valve 8 is connected with a fluid injection port 28 of the core holder 17; the fluid extraction port 29 of the core holder 17 is connected to one end of the fifth valve 10; the other end of the fifth valve 10 is connected with the other end of the fourth valve 9, the second buffer tank 11, one end of the sixth valve 12, the second pressure sensor 13 and the other end of the differential pressure gauge 6; the other end of the sixth valve 6 is connected to a vacuum pump 14.
The core holder 17 is used for fixing a rock sample 19 to be tested and applying confining pressure and axial pressure to the rock sample 19 to be tested; the rock to be tested is sealed by the heat-shrinkable tube 18 and then is fixed in the core holder 17; the heat-shrinkable tube 18 is used for isolating pore fluid pressure from confining pressure and preventing confining pressure media from permeating into rock pores; a confining pressure injection hole 31, an axial pressure injection hole 30, a fluid injection hole 28 and a fluid extraction port 29 are arranged on the outer wall of the core holder 17, wherein the confining pressure injection hole 31 and the axial pressure injection hole 30 are respectively communicated with a confining pressure loading assembly and an axial pressure loading assembly; fluid injection port 28 and fluid withdrawal port 29 communicate with the porosity measurement assembly.
The confining pressure loading assembly comprises a confining pressure first control valve 20, a confining pressure booster pump 21, a confining pressure second control valve 22 and a confining pressure power source 23; one end of the confining pressure first control valve 20 is connected with a confining pressure injection hole 31 of the core holder 17, and the other end of the confining pressure first control valve is connected with one end of a confining pressure booster pump 21; the other end of the confining pressure pressurization pump 21 is connected with one end of a confining pressure second control valve 22; the other end of the confining pressure second control valve 22 is connected with a confining pressure power source 23.
The axle pressure loading assembly comprises an axle pressure first control valve 24, an axle pressure loading pump 25, an axle pressure second control valve 26 and an axle pressure power source 27; wherein the axial pressure injection hole 30 on the core holder 17 is connected with one end of the axial pressure first control valve 24; the other end of the first axial pressure control valve 24 is connected with one end of an axial pressure booster pump 25; the other end of the axial pressure booster pump 25 is connected with one end of an axial pressure second control valve 26; the other end of the second control valve 26 is connected to a shaft pressure power source 27.
The multi-channel data acquisition card 15 is respectively connected with the data output end of the first pressure sensor 5, the data output end of the differential pressure gauge 6 and the data output end of the second pressure sensor 13.
The high-pressure gas is helium or nitrogen and is used for measuring the porosity and permeability of the rock sample 19 to be tested;
the confining pressure power source 23 and the axial pressure power source 27 are deionized water;
the hole pressure pressurizing pump 3, the confining pressure pressurizing pump 21, and the axial pressure pressurizing pump 25 are high-precision metering pumps, and perform fluid and pressure control on the injection fluid.
Example 2
In this embodiment, based on the above apparatus, a rock porosity and permeability combined test is performed under a triaxial condition, and the specific method includes the following steps:
step 1: a standard cylindrical stainless steel sample 19 with the diameter of 25mm and the length of 50mm is placed in a core holder 17 and sealed by a heat-shrinkable tube 18 for isolating confining pressure and pore pressure;
step 2: applying certain confining pressure and axial pressure on a stainless steel sample through a confining pressure loading assembly and an axial pressure loading assembly, and then closing the stainless steel sample, so that the confining pressure and the axial pressure are maintained at design values, and surface flow is formed on the surface of the sample when pore pressure is applied in the measurement process;
and step 3: the pore permeation measurement assembly is evacuated. The second valve 4 is closed, the third valve 8, the fourth valve 9, the fifth valve 10 and the sixth valve 12 are kept open, the vacuum pump 14 is opened to evacuate the inside of the measurement pipeline for about 2h, and when the pressures indicated by the first pressure sensor 5 and the second pressure sensor 13 are below 0, the vacuum pump 14 is closed. After standing for a period of time, keeping the first pressure sensor 5 and the second pressure sensor 13 at 0 and below for more than 2 hours, and finishing vacuum pumping; otherwise, continuing to repeat the vacuum-pumping treatment.
And 4, step 4: closing the vacuum pump 14 and the sixth valve 12, opening the high-pressure gas cylinder 1 and the first valve 2, and injecting gas into the porosity measurement system to measure and calibrate the pipeline volume; the volume of a pipeline among the second valve 4, the first pressure sensor 5, the differential pressure gauge 6, the first buffer tank 7, the third valve 8 and the fourth valve 9 is marked as V1; the volume of the line between the third valve 8 and the bottom of the stainless steel sample 19 was designated as V2; the volume of the line between the top surface of the stainless steel sample 19 and the fifth valve 10 was designated as V3; the volume of a pipeline between the fourth valve 9, the fifth valve 10, the second buffer tank 11, the second pressure sensor 13, the differential pressure gauge 6 and the sixth valve 12 is marked as V4;
and 5: closing the confining pressure loading assembly and the axial pressure loading assembly, stopping applying confining pressure and axial pressure, and disassembling the standard sample;
step 6: selecting a natural rock sample 19, processing the rock sample into a cylinder with the diameter of 25mm, measuring the diameter and the height of the cylinder, and calculating to obtain the volume V of the rock sample 19;
and 8: repeating the step 2 and the step 3, applying confining pressure and axial pressure to the rock sample, and vacuumizing the whole system;
and step 9: keeping the vacuum pump 14 and the sixth valve 12 closed, closing the third valve 8 and the fourth valve 9, and keeping the fifth valve 10 open; at the moment, opening the high-pressure gas cylinder 1 and the first valve 2, injecting gas into the pore pressure booster pump, and closing the high-pressure gas cylinder 1 and the first valve 2 after the pore pressure booster pump is filled with the gas; opening the second valve 4, injecting gas into a pipeline volume V1 between the second valve 4, the first pressure sensor 5, the differential pressure gauge 6, the first buffer tank 7, the third valve 8 and the fourth valve 9, and after the pressure is stabilized, recording the pressure value of the first pressure sensor 5 as P1 and the numerical value of the differential pressure gauge 6 as DP1 by using the multi-channel data acquisition card 15;
step 10: opening the third valve 8, diffusing the gas in the pipeline with the volume of V1 into the pipeline with the volume of V2 and rock pores until the gas in the pipeline with the volume of V3 and the pipeline with the volume of V4, slowly attenuating the pressure of the differential pressure gauge 6 at the moment, and recording the pressure attenuation curve S of the differential pressure gauge 6 through the multi-channel data acquisition card 15;
step 11: after the gas slowly diffuses from the upstream end of the rock 19 to be measured to the downstream end and the related pipelines with the volumes of V3 and V4, the gas pressure in the measuring pipeline reaches balance, the gas pressure in the pipeline can be judged to be balanced according to the fact that the pressure value of the differential pressure gauge 6 is 0, and the reading of the second pressure sensor 13 at the moment is recorded as P2;
step 12: and calculating the porosity of the rock by the data storage and processing module.
Calculating the rock porosity of the rock sample under a certain triaxial stress by the following formula:
wherein Vr is the effective pore volume of the rock under the stress condition, and the calculation formula is as follows:
step 13: calculating the permeability of the rock by a data storage processing module:
according to the transient pressure pulse method, the permeability of the rock is calculated by the pressure attenuation curve of a differential pressure gauge as follows:
wherein: Δ DP (t) is the pressure decay curve S, Δ P measured by the differential pressure gaugeiThe initial pressure difference is adopted, t is the testing time, k is the permeability coefficient of the rock sample to be tested, L is the length of the test piece, and mu is the viscosity coefficient of the high-pressure gas.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and are not limited. Although the present invention has been described in detail with reference to the embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (11)
1. A rock porosity and permeability combined testing device under a triaxial condition is used for simultaneously measuring the rock porosity and permeability under a triaxial stress condition, and is characterized by comprising a pore permeability measuring assembly, a rock core holder (17), a confining pressure loading assembly, an axial pressure loading assembly, a multi-channel data acquisition card (15) and a data storage processing module (16); the hole permeability measuring assembly, the confining pressure loading assembly and the axial pressure loading assembly are respectively connected with a rock core holder (17); wherein the content of the first and second substances,
the pore-permeability measuring assembly is used for measuring the pressure and the pressure difference of the upper end and the lower end of the rock sample to be tested under the triaxial condition;
the core holder (17) is used for fixing a rock sample to be tested and applying confining pressure and axial pressure to the rock sample to be tested;
the confining pressure loading assembly is used for generating confining pressure acting on a rock sample to be tested;
the axial pressure loading assembly is used for generating axial pressure acting on a rock sample to be tested;
the multi-channel data acquisition card (15) is used for acquiring the pressure and the pressure difference measured by the pore permeability measurement assembly and sending the pressure and the pressure difference to the data storage processing module (16);
the data storage and processing module (16) is used for simultaneously calculating the porosity and the permeability of the rock sample to be tested based on the pressure and the pressure difference.
2. The joint rock porosity-permeability test apparatus under triaxial conditions according to claim 1, wherein the pore-permeability measuring assembly comprises: the device comprises a high-pressure gas cylinder (1), a first valve (2), a pore pressure booster pump (3), a second valve (4), a first pressure sensor (5), a differential pressure gauge (6), a first buffer tank (7), a third valve (8), a fourth valve (9), a fifth valve (10), a second buffer tank (11), a sixth valve (12), a second pressure sensor (13) and a vacuum pump (14); wherein the content of the first and second substances,
the outlet of the high-pressure gas bottle (1) is respectively communicated with the first valve (2) and the pore pressure booster pump (3) through pipelines, the pipelines are divided into three paths after passing through the second valve (4), and the first path is connected with the input end of the first pressure sensor (5); the second path is connected with one end of a differential pressure gauge (6); the third path sequentially passes through a first buffer cylinder (7) and a third valve (8) and is communicated with a rock core holder (17);
the pipeline connected with the other end of the differential pressure gauge (6) is divided into three paths, and the first path is connected with the input end of the second pressure sensor (13); the second path is communicated with a vacuum pump (14) through a sixth valve (12); the third path sequentially passes through a second buffer tank (11) and a fifth valve (10) and is communicated with a rock core holder (17);
a pipeline is arranged between the third valve (8) and the first buffer cylinder (7) and communicated to the position between the fifth valve (10) and the second buffer tank (11), and a fourth valve (9) is arranged in the middle of the pipeline;
and the data output ends of the first pressure sensor (5), the differential pressure gauge (6) and the second pressure sensor (13) are connected with a multi-channel data acquisition card (15).
3. The rock porosity and permeability combined test device under the triaxial condition of claim 1, wherein the core holder (17) comprises a heat-shrinkable tube (18) positioned inside the chamber, a fluid extraction port (29) positioned on the outer wall of the chamber, a confining pressure injection hole (31), an axial pressure injection hole (30) and a fluid injection hole (28); wherein the content of the first and second substances,
the heat-shrinkable tube (18) seals a rock sample (19) to be tested and then fixes the rock sample in the core holder (17);
the fluid extraction port (29) is communicated with a fifth valve (10) of the pore-permeability measurement assembly through a pipeline;
the confining pressure injection hole (31) is communicated with the confining pressure loading assembly through a pipeline;
the axial pressure injection hole (30) is communicated with the axial pressure loading assembly through a pipeline;
the fluid injection port (28) is in communication with the third valve (8) of the pore-permeability measurement assembly via a conduit.
4. The joint rock porosity and permeability test device under triaxial conditions of claim 3, wherein the confining pressure loading assembly comprises: a confining pressure first control valve (20), a confining pressure booster pump (21), a confining pressure second control valve (22) and a confining pressure power source (23);
the output pipeline of the confining pressure power source (23) is communicated with a confining pressure injection hole (31) of the core holder (17) through a confining pressure second control valve (22), a confining pressure booster pump (21) and a confining pressure first control valve (20) in sequence; the confining pressure power source (23) is deionized water; the confining pressure pressurization pump (21) is a high-precision metering pump.
5. The joint rock porosity and permeability test unit under triaxial conditions of claim 3, wherein the axial compression loading assembly comprises: the device comprises a first axial pressure control valve (24), an axial pressure loading pump (25), a second axial pressure control valve (26) and an axial pressure power source (27);
the output pipeline of the axial pressure power source (27) is communicated with an axial pressure injection hole (30) of the core holder (17) through an axial pressure second control valve (26), an axial pressure booster pump (25) and an axial pressure first control valve (24) in sequence; the axial pressure power source (27) is deionized water; the axial pressure booster pump (25) is a high-precision metering pump.
6. A rock porosity and permeability joint test method under triaxial conditions, which is realized based on the device of one of claims 1 to 5, and comprises the following steps:
step 1) putting a standard sample with a fixed size into the heat-shrinkable tube (18), and sealing the standard sample;
step 2) respectively applying confining pressure and axial pressure to the standard sample through a confining pressure loading component and an axial pressure loading component, and keeping the confining pressure and the axial pressure applied to the standard sample at design values;
step 3) vacuumizing an internal pipeline of the pore permeation measurement assembly;
step 4) injecting gas into the pore permeation measurement assembly, and carrying out pipeline volume measurement and calibration;
step 5) closing the confining pressure loading assembly and the axial pressure loading assembly, stopping applying confining pressure and axial pressure on the standard sample, and disassembling the standard sample;
step 6), placing a rock sample (19) to be tested into the heat-shrinkable tube (18), and sealing the rock sample (19) to be tested, wherein the volume of the rock sample (19) to be tested is V;
step 7) repeating the step 2) and the step 3), respectively applying confining pressure and axial pressure to the rock sample (19) to be tested through the confining pressure loading assembly and the axial pressure loading assembly, and keeping the confining pressure and the axial pressure applied to the rock sample to be tested at design values; vacuumizing the pore-permeation measuring assembly;
step 8) injecting gas into the pore permeation measurement assembly, obtaining pressure values through a first pressure sensor (5) and a second pressure sensor (13), obtaining pressure difference values through a differential pressure gauge (6), collecting the pressure values and the pressure difference values through a multi-channel data acquisition card (15), and transmitting the pressure values and the pressure difference values to a data storage processing module;
and 9) calculating the porosity and the permeability by the data storage processing module according to the pressure value, the volume calibrated by the pipeline and the volume of the rock sample (19) to be tested by combining a pressure attenuation curve.
7. The joint test method for rock porosity and permeability under triaxial conditions according to claim 6, wherein the step 2) specifically comprises:
closing the confining pressure first control valve (20), opening a confining pressure second control valve (22), and filling a confining pressure power source (23) into a confining pressure booster pump (21);
closing the second control valve (22) of the confining pressure and opening the first control valve (20) of the confining pressure; after a certain confining pressure is applied to the rock sample (19) to be tested, the confining pressure is maintained at a design value;
closing the first control valve (24) of the axial pressure, opening the second control valve (26) of the axial pressure, and filling the axial pressure power source (27) into the axial pressure booster pump (25);
closing the second control valve (26) for axial pressure, and opening the first control valve (24) for axial pressure; after a certain axial pressure is applied to the rock sample (19) to be tested, the axial pressure is maintained at a design value.
8. The joint test method for rock porosity and permeability under triaxial conditions according to claim 7, wherein the step 3) specifically comprises:
closing the second valve (4), keeping the third valve (8), the fourth valve (9), the fifth valve (10) and the sixth valve (12) open, opening a vacuum pump (14) to vacuumize the pore-permeability measuring assembly, and closing the vacuum pump (14) when the pressure values displayed by the first pressure sensor (5) and the second pressure sensor (13) are below 0;
if the pressure values displayed by the first pressure sensor (5) and the second pressure sensor (13) are not more than 0 and are kept for more than 2 hours, the vacuumizing is completed; otherwise, continuing to carry out vacuum-pumping treatment.
9. The joint test method for rock porosity and permeability under triaxial conditions according to claim 8, wherein the step 4) specifically comprises:
closing the vacuum pump (14) and the sixth valve (12), opening the high-pressure gas cylinder (1) and the first valve (2), and injecting gas into the pore permeation measurement assembly to measure and calibrate the volume of the pipeline; wherein the content of the first and second substances,
the volume of a pipeline among the second valve (4), the first pressure sensor (5), the differential pressure gauge (6), the first buffer tank (7), the third valve (8) and the fourth valve (9) is V1;
the volume of the pipeline between the third valve (8) and the bottom surface of the heat shrinkable tube (18) is V2;
the volume of the pipeline between the top surface of the heat shrinkable tube (18) and the fifth valve (10) is V3;
the volume of a pipeline between the fourth valve (9), the fifth valve (10), the second buffer tank (11), the second pressure sensor (13), the differential pressure gauge (6) and the sixth valve (12) is V4.
10. The joint test method for rock porosity and permeability under triaxial conditions according to claim 9, wherein the step 8) specifically comprises:
keeping the vacuum pump (14) and the sixth valve (12) closed, closing the third valve (8) and the fourth valve (9), and keeping the fifth valve (10) open; opening the high-pressure gas cylinder (1) and the first valve (2), injecting gas into the pore pressure booster pump (3), and closing the high-pressure gas cylinder (1) and the first valve (2) after the pore pressure booster pump is filled with the gas; opening a second valve (4), injecting gas into a pipeline volume V1 among the second valve (4), a first pressure sensor (5), a differential pressure gauge (6), a first buffer tank (7), a third valve (8) and a fourth valve (9), and recording a pressure value P1 of the first pressure sensor (5) and a numerical value DP1 of the differential pressure gauge (6) through a multi-channel data acquisition card (15) after the pressure is stabilized;
opening a third valve (8), diffusing the gas in the pipeline with the volume of V1 into the pipeline with the volume of V2 and the rock sample to be tested (19) until the gas reaches the pipeline with the volume of V3 and the volume of V4, slowly attenuating the pressure of the differential pressure gauge (6) at the moment, and recording the pressure attenuation curve S of the differential pressure gauge (6) through a multi-channel data acquisition card (15);
after the gas slowly diffuses from the upstream end to the downstream end of the rock sample (19) to be tested and the related pipelines with the volume V3 and the volume V4, when the value of the differential pressure gauge (6) is 0, the reading P2 of the second pressure sensor (13) is recorded through the multi-channel data acquisition card (15).
11. The joint test method for rock porosity and permeability under triaxial conditions according to claim 10, wherein the step 9) is specifically as follows:
calculating the porosity of the rock sample (19) to be tested under triaxial stress by the data storage and processing module (16)
Wherein Vr is the effective pore volume of the rock sample (19) to be tested under the stress condition:
and the data storage processing module (16) calculates the permeability k of the rock sample to be tested (19) through the pressure attenuation curve S of the differential pressure gauge according to a transient pressure pulse method:
from the pressure decay curve S of the differential pressure gauge, based on:
wherein, Δ DP (t) is the pressure decay curve S, Δ P measured by the differential pressure gaugeiCalculating to obtain the slope α of the attenuation curve;
substituting slope α into the following equation:
wherein L is the length of the rock sample (19) to be tested, A is the cross-sectional area of the rock sample (19) to be tested, and mu is the viscosity coefficient of the high-pressure gas; and calculating the permeability k of the rock sample (19) to be tested.
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