A device and method for quickly measuring the porosity and permeability of dense rocks

Abstract

The present application relates to the technical field of shale gas development, and more specifically, to a device and method for rapidly measuring the porosity and permeability of dense rocks. This device and method can, to a certain extent, address the problems of existing pulse attenuation methods for measuring the permeability and porosity of low-permeability rocks, such as complex equipment, inability to perform powdered shale testing, long testing times, and fixed upstream and downstream chamber volumes. The device for rapidly measuring the porosity and permeability of dense rocks includes a gas source, a gas source conversion device, a gas source valve, an air inlet valve, a standard cylinder, a six-way valve, a pressure sensor, a booster valve, a hand-cranked booster pump, an air outlet valve, a vacuum pump, an injection valve, an anti-backflow device, a sample cylinder, a constant-temperature oil bath, an auxiliary heater, and pipelines.

Description

Technical Field

[0001] The present application relates to the technical field of shale gas development, and in particular to a device and method for rapidly measuring the porosity and permeability of dense rocks. Background Art

[0002] Shale gas reservoirs are characterized by strong heterogeneity, large cumulative thickness, small distribution area, relatively low degree of thermal evolution, and diverse organic matter types, which complicates the challenges encountered in shale development. Measuring porosity and permeability, fundamental to understanding the seepage behavior of shale formations, is crucial for addressing these challenges.

[0003] Shale pore throat diameters are often nanometers, making permeability measurement more challenging than for highly permeable media. Existing methods for measuring shale permeability primarily include steady-state and unsteady-state methods. The steady-state method calculates permeability using Darcy's law by measuring the pressure differential and flow rate when the fluid reaches stable flow conditions. Unsteady-state methods, including pulse decay, oscillating pressure, and GRI, derive permeability based on the time-dependent pressure decay at both ends of the sample and corresponding mathematical models. The steady-state and pulse decay methods are commonly used for indoor shale permeability measurements.

[0004] However, the steady-state method for measuring shale permeability requires measuring steady-state flow. Establishing Darcy steady-state flow takes a long time (days or even weeks), and is not suitable for ultra-low permeability shales. The pulse decay method was first proposed by Brace (1968) when testing granite permeability. The dimensionless pressure-time response solution is obtained by calculating the material balance in the upstream and downstream chambers and the core to measure the shale permeability. The conventional pulse decay method for measuring shale permeability is very complex. In addition, there are pressure pulses between the upstream and downstream chambers during the experiment, and there is back suction when testing powdered shale. Therefore, there is an urgent need for an experimental device that is simple and can be used to test powdered shale using the pulse decay method to measure shale permeability and porosity.

[0005] For example, Chinese patent CN107014731B discloses a low-permeability rock gas-liquid dual-drive pressure pulse attenuation permeability test method. The method uses a low-permeability rock gas-liquid dual-drive pressure pulse attenuation permeability test device to measure the permeability and permeability coefficient of low-permeability rocks. However, the method has the following disadvantages: multiple devices, complex installation, cumbersome operation steps, and inability to test powdered shale samples, resulting in a long test time.

[0006] Furthermore, based on Brace's research, Lin et al. (1977) analyzed the effect of upstream and downstream chamber volumes on experimental results. They found that the optimal ratio of upstream and downstream chamber volumes in their experimental setups varied for shale cores of varying volumes. Conventional pulse attenuation method experimental setups for measuring shale permeability and porosity often use cylinders instead of upstream and downstream chambers, with a fixed upstream and downstream chamber volume ratio. Therefore, a device with an adjustable upstream and downstream chamber volume ratio is urgently needed for conventional pulse attenuation method experiments for measuring permeability and porosity in low-permeability rocks.

[0007] Therefore, the existing pulse attenuation method for measuring the permeability and porosity of low-permeability rocks has problems such as complex equipment, inability to perform powdered shale testing, long testing time, and fixed upstream and downstream chamber volumes. Summary of the Invention

[0008] In order to solve the problems of complex equipment, inability to perform powdered shale testing, long testing time, and fixed upstream and downstream chamber volumes in the existing pulse attenuation method for measuring the permeability and porosity of low permeability rocks, the present application provides a device and method for quickly measuring the porosity and permeability of dense rocks.

[0009] The embodiment of the present application is implemented as follows:

[0010] In the first aspect, the present application provides a device for rapidly measuring the porosity and permeability of dense rocks, including a gas source, a gas source conversion device, a gas source valve, an air inlet valve, a standard cylinder, a six-way valve, a pressure sensor, a booster valve, a hand-cranked booster pump, an air outlet valve, a vacuum pump, an injection valve, an anti-backflow device, a sample cylinder, a constant temperature oil bath, an auxiliary heater and pipelines.

[0011] The gas source is connected to the gas source conversion device, the gas source conversion device is connected to the standard cylinder through a pipeline, the gas source valve is located between the gas source conversion device and the pipeline, the air inlet valve is located between the standard cylinder and the pipeline connected to the gas source, the standard cylinder is connected to the six-way valve through a pipeline, the detection end of the pressure sensor is connected to the six-way valve through a bolt, the booster pump is connected to the six-way valve through a pipeline, the booster valve is located between the booster pump and the pipeline, the vacuum pump is connected to the six-way valve through a pipeline, the air outlet valve is located between the vacuum pump and the pipeline, the anti-backflow device is located inside the sample cylinder, and is connected to the air inlet of the sample cylinder, the standard cylinder and the sample cylinder are placed in the constant temperature oil bath, and the auxiliary heater is wrapped around the outside of the pipeline.

[0012] In one possible implementation, the six-way valve includes a first valve connected to the standard cylinder, a second valve connected to the sample cylinder, a third valve connected to the vacuum pump, a fourth valve connected to the booster pump, and fifth and sixth valves that are always kept closed.

[0013] In one possible implementation, the detection end of the pressure sensor converts the collected millivolt signal into a digital communication signal RS232, and then connects to a computer via USB. The computer collects real-time data of pipeline pressure to facilitate adjustment of the pressure in the standard cylinder.

[0014] In a second aspect, the present application provides a method for rapidly measuring the porosity and permeability of dense rocks, comprising:

[0015] A shale powder sample from a deep layer in the Sichuan Basin was dried at 105°C for 50 hours. The mass of the shale sample (powder sample or plunger) was measured, and the volume of the shale sample to be tested was obtained based on its density.

[0016] Fill the sample cylinder with a known volume of shale sample. At the same time, adjust the mechanical locking mechanism to ensure close contact between the sample cylinder and the shale sample, ensuring that the volume in the cylinder other than the apparent volume is minimized.

[0017] Open the vacuum valve and use the vacuum pump to evacuate the experimental device for 600 s;

[0018] Close the vacuum valve and the third valve of the six-way valve, open the air inlet valve, injection valve, and the first, second, and fourth valves on the six-way valve, then open the gas source valve and inflate the device to the preset pressure P0 (5 MPa, 7 MPa, 9 MPa) before proceeding to the next experiment;

[0019] Close the gas source valve, gas injection valve, and air inlet valve, open the booster valve and the third valve on the six-way valve, then use a hand-cranked booster pump to increase the pressure in the standard cylinder by 0.5 MPa, so that there is a pressure pulse of 0.5 MPa in the sample cylinder and the standard cylinder. Record the pressure P1 and proceed to the next step of the experiment;

[0020] Close the intake valve, boost valve, and the third valve on the six-way valve. Open the air injection valve at a rate of 1 / 4 turn per second and record the elapsed time and pressure until the pressure change is less than 200 Pa for 1,200 consecutive seconds (the final pressure is called P2). The test is complete.

[0021] The test data are processed to obtain the shale porosity and permeability.

[0022] In a possible implementation, when performing the step of opening the vacuum valve and evacuating the experimental device for 600 seconds using a vacuum pump, it is also necessary to ensure that the pressure measured by the sensor in the device does not fluctuate by more than 200 Pa within 120 seconds.

[0023] In one possible implementation, when closing the vacuum valve and the third valve of the six-way valve, opening the air intake valve, the injection valve, and the first, second, and fourth valves on the six-way valve, and then opening the air source valve to inflate the device to a preset pressure P0 (5 MPa, 7 MPa, 9 MPa), it is necessary to control the pressure measured by the sensor in the device to not fluctuate by more than 200 Pa within 120 seconds.

[0024] In one possible implementation, after closing the gas source valve, the gas injection valve, and the gas inlet valve, the boost valve and the third valve on the six-way valve are opened. Then, a hand-cranked boost pump is used to increase the pressure in the standard cylinder by 0.5 MPa, so that a pressure pulse of 0.5 MPa exists in the sample cylinder and the standard cylinder. When recording the pressure P1, it is necessary to control the pressure measured by the sensor in the device to not fluctuate by more than 200 Pa within 120 seconds.

[0025] In one possible implementation, processing the test data to obtain shale porosity and permeability further includes:

[0026] By formula , calculate the pore volume of powdered shale;

[0027] The porosity calculation formula is: ;

[0028] The volume fraction F is calculated using the following formula: R (t):

[0029] ;

[0030] Among them, 1-F R (t) represents the fraction of the amount of gas that enters the shale particle from the starting point to time t relative to the final amount of gas that enters the particle when equilibrium is reached, K c is the ratio of the volume outside the sample in the standard cylinder and the sample cylinder to the pore volume of the sample, is the average gas density at P1, is the gas density at P0, is the gas density at P(t);

[0031] Taking the logarithm of the volume coefficient, we can get ln(F R (t)) is:

[0032] ;

[0033] The permeability k is calculated according to the following relationship:

[0034] ;

[0035] Where μ is the viscosity of the gas, cg is the compression factor.

[0036] The technical solution provided by this application can achieve at least the following beneficial effects:

[0037] The method provided in the present application for rapidly measuring the porosity and permeability of dense rocks uses a hydraulic cylinder with a mechanical locking mechanism to replace the standard cylinder and sample cylinder in a conventional experimental device. The volume of the hydraulic cylinder is variable, and the cylinder is then locked by a mechanical locking device, thereby achieving a change in the volume ratio of the upstream and downstream cavities of the experimental device; an anti-backflow device is added to the pipeline port where the injection valve leads to the sample cylinder to achieve testing of powdered shale samples; at the same time, the present application uses a gas source conversion device, which makes it more convenient to change the gas source for different experiments and the experimental operation steps are also simpler; and, compared with the conventional pulse attenuation method for measuring the permeability and porosity of low-permeability rocks, the present method has no specific requirements for the shape and volume of the shale sample, and the test accuracy is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0039] Figure 1 It is a schematic structural diagram of a device for rapidly measuring the porosity and permeability of dense rocks, shown in an exemplary embodiment of the present application.

[0040] Figure 2 It is a structural schematic diagram of an anti-backflow device shown in an exemplary embodiment of the present application.

[0041] Figure 3 It is a flow chart of a method for rapidly measuring the porosity and permeability of dense rocks shown in an exemplary embodiment of the present application.

[0042] Figure 4 This is a deep shale sample ln(F in the Sichuan Basin shown in an exemplary embodiment of the present application. R Schematic diagram of the (t)-t function.

[0043] Reference numerals:

[0044] 1. Gas source; 2. Gas source conversion device; 3. Standard cylinder; 4. Gas source valve; 5. Inlet valve; 6. Six-way valve; 7. Pressure sensor; 8. Computer; 9. Hand-cranked booster pump; 10. Booster valve; 11. Vacuum pump; 12. Outlet valve; 13. Sample cylinder; 14. Pipeline. DETAILED DESCRIPTION

[0045] In order to make the purpose, implementation methods and advantages of the present application clearer, the exemplary implementation methods of the present application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only part of the embodiments of the present application, not all of the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0046] It should be noted that the brief descriptions of terms in this application are only for the purpose of facilitating the understanding of the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood according to their ordinary and usual meanings.

[0047] In the specification and claims of this application and the accompanying drawings, the terms "first," "second," "third," etc. are used to distinguish similar or similar objects or entities, and are not necessarily intended to limit a particular order or sequence, unless otherwise noted. It should be understood that the terms used in this manner are interchangeable under appropriate circumstances.

[0048] The terms "comprise," "include," and "have," and any variations thereof, are intended to cover but not exclude inclusion; for example, a product or device comprising a list of components is not necessarily limited to all the components expressly listed but may include other components not expressly listed or inherent to such product or device.

[0049] Before explaining the method for rapidly measuring the porosity and permeability of dense rocks provided in the embodiment of the present application, the application scenario and implementation environment of the embodiment of the present application are first introduced.

[0050] Shale gas reservoirs are characterized by strong heterogeneity, large cumulative thickness, small distribution area, relatively low degree of thermal evolution, and diverse organic matter types, which complicates the challenges encountered in shale development. Measuring porosity and permeability, fundamental to understanding the seepage behavior of shale formations, is crucial for addressing these challenges.

[0051] Shale pore throat diameters are often nanometers, making permeability measurement more challenging than for highly permeable media. Existing methods for measuring shale permeability primarily include steady-state and unsteady-state methods. The steady-state method calculates permeability using Darcy's law by measuring the pressure differential and flow rate when the fluid reaches stable flow conditions. Unsteady-state methods, including pulse decay, oscillating pressure, and GRI, derive permeability based on the time-dependent pressure decay at both ends of the sample and corresponding mathematical models. The steady-state and pulse decay methods are commonly used for indoor shale permeability measurements.

[0052] However, the steady-state method for measuring shale permeability requires measuring steady-state flow. Establishing Darcy steady-state flow takes a long time (days or even weeks), and is not suitable for ultra-low permeability shales. The pulse decay method was first proposed by Brace (1968) when testing granite permeability. The dimensionless pressure-time response solution is obtained by calculating the material balance in the upstream and downstream chambers and the core to measure the shale permeability. The conventional pulse decay method for measuring shale permeability is very complex. In addition, there are pressure pulses between the upstream and downstream chambers during the experiment, and there is back suction when testing powdered shale. Therefore, there is an urgent need for an experimental device that is simple and can be used to test powdered shale using the pulse decay method to measure shale permeability and porosity.

[0053] For example, Chinese patent CN107014731B discloses a low-permeability rock gas-liquid dual-drive pressure pulse attenuation permeability test method. The method uses a low-permeability rock gas-liquid dual-drive pressure pulse attenuation permeability test device to measure the permeability and permeability coefficient of low-permeability rocks. However, the method has the following disadvantages: multiple devices, complex installation, cumbersome operation steps, and inability to test powdered shale samples, resulting in a long test time.

[0054] Furthermore, based on Brace's research, Lin et al. (1977) analyzed the effect of upstream and downstream chamber volumes on experimental results. They found that the optimal ratio of upstream and downstream chamber volumes in their experimental setups varied for shale cores of varying volumes. Conventional pulse attenuation method experimental setups for measuring shale permeability and porosity often use cylinders instead of upstream and downstream chambers, with a fixed upstream and downstream chamber volume ratio. Therefore, a device with an adjustable upstream and downstream chamber volume ratio is urgently needed for conventional pulse attenuation method experiments for measuring permeability and porosity in low-permeability rocks.

[0055] Therefore, in order to solve the problems existing in the existing pulse attenuation method for measuring the permeability and porosity of low permeability rocks, such as complex equipment, inability to perform powdered shale testing, long testing time, and fixed upstream and downstream chamber volumes, there is an urgent need for an experimental device with a simple device, which can perform powdered shale testing, has a short testing time, and an adjustable upstream and downstream chamber volume ratio, as well as a method for its use.

[0056] Based on this, the present application provides a device and method for quickly measuring the porosity and permeability of dense rocks, using a hydraulic cylinder with a mechanical locking mechanism to replace the standard cylinder and sample cylinder in a conventional experimental device. The volume of the hydraulic cylinder is variable, and the cylinder is locked by a mechanical locking device, thereby achieving a change in the volume ratio of the upstream and downstream cavities of the experimental device; an anti-backflow device is added to the pipeline port where the injection valve enters the sample cylinder (mechanical locking hydraulic cylinder 2) to achieve testing of powdered shale samples; at the same time, the present invention uses a gas source conversion device, which makes it more convenient to change the gas source for different experiments, and the experimental operation steps are also simpler; and, compared with the conventional pulse attenuation method for measuring the permeability and porosity of low permeability rocks using a shale plunger experiment, the present invention uses powdered shale samples, which increases the contact area between the experimental gas and the shale sample, and shortens the test time.

[0057] Next, the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems will be described in detail through embodiments and in conjunction with the accompanying drawings. The various embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, not all of them.

[0058] Figure 1 It is a schematic structural diagram of a device for rapidly measuring the porosity and permeability of dense rocks, shown in an exemplary embodiment of the present application.

[0059] In an exemplary embodiment, Figure 1 As shown, a device for quickly measuring the porosity and permeability of dense rocks is provided, which includes a gas source, a gas source conversion device 2, a gas source valve 4, an air inlet valve 5, a standard cylinder 3, a six-way valve 6, a pressure sensor 7, a booster valve 10, a hand-cranked booster pump 9, an air outlet valve 12, a vacuum pump 11, an injection valve, an anti-backflow device, a sample cylinder 13, a constant temperature oil bath, an auxiliary heater and a pipeline 14.

[0060] The gas source is connected to the gas source conversion device, the gas source conversion device is connected to the standard cylinder through a pipeline, the gas source valve is located between the gas source conversion device and the pipeline, the air inlet valve is located between the standard cylinder and the pipeline connected to the gas source, the standard cylinder is connected to the six-way valve through a pipeline, the detection end of the pressure sensor is connected to the six-way valve through a bolt, the booster pump is connected to the six-way valve through a pipeline, the booster valve is located between the booster pump and the pipeline, the vacuum pump is connected to the six-way valve through a pipeline, the air outlet valve is located between the vacuum pump and the pipeline, the anti-backflow device is located inside the sample cylinder, and is connected to the air inlet of the sample cylinder, the standard cylinder and the sample cylinder are placed in the constant temperature oil bath, and the auxiliary heater is wrapped around the outside of the pipeline.

[0061] Figure 2 It is a structural schematic diagram of an anti-backflow device shown in an exemplary embodiment of the present application.

[0062] In one possible implementation, the specific components of the device include an air source, an air source conversion device, an air source valve, an air inlet valve, a standard cylinder (mechanically locked hydraulic cylinder 1), a six-way valve (the six-way valve includes valve 1 connected to the standard cylinder (mechanically locked hydraulic cylinder 1), valve 2 connected to the sample cylinder (mechanically locked hydraulic cylinder 2), valve 3 connected to the vacuum pump, valve 4 connected to the booster pump, and valves 5 and 6 that are always kept closed), a pressure sensor, a booster valve, a hand-cranked booster pump (compared to an electronic booster pump, the experimental cost is greatly reduced), an air outlet valve, a vacuum pump, an injection valve, an anti-backflow device, a sample cylinder (mechanically locked hydraulic cylinder 2), a constant temperature oil bath, an auxiliary heater and pipelines.

[0063] The installation structure is as follows:

[0064] The air source is connected to the air source conversion device, and the air source conversion device is connected to the mechanical locking hydraulic cylinder 1 through a pipeline; the air source valve is located between the air source conversion device and the pipeline; the air source conversion device is used for air source replacement; the air inlet valve is located between the standard cylinder (mechanical locking hydraulic cylinder 1) and the pipeline connected to the air source; the standard cylinder (mechanical locking hydraulic cylinder 1) is connected to the six-way valve through a pipeline; the detection end of the pressure sensor is connected to the six-way valve through a bolt, and the detection end converts the collected millivolt signal into a digital communication signal RS232, and then connects to the computer through USB. The computer collects real-time data of the pipeline pressure, which is convenient for adjusting the pressure in the mechanical locking hydraulic cylinder 1; the booster pump is connected to the six-way valve through a pipeline; the booster valve is located between the hand-cranked booster pump and the pipeline; the vacuum pump is connected to the six-way valve through a pipeline; the air outlet valve is located between the vacuum pump and the pipeline.

[0065] like Figure 2 As shown, the anti-backflow device is located inside the sample cylinder and connected to the air inlet of the sample cylinder; the standard cylinder (mechanically locked hydraulic cylinder 1) and the sample cylinder (mechanically locked hydraulic cylinder 2) are placed in the constant temperature oil bath to ensure that the temperatures of the two are stable; the auxiliary heater is wrapped around the outside of the pipeline to maintain the pipeline temperature stable.

[0066] It should be understood that, although the various steps in the flowcharts involved in the above-described embodiments are displayed in sequence according to the instructions, these steps are not necessarily executed in the order indicated. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the above-described embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0067] Corresponding to the aforementioned embodiment of the device for rapidly measuring the porosity and permeability of dense rock, and adopting the same technical concept, the present application also provides an embodiment of a method for rapidly measuring the porosity and permeability of dense rock.

[0068] Figure 3 It is a flow chart of a method for rapidly measuring the porosity and permeability of dense rocks shown in an exemplary embodiment of the present application.

[0069] In an exemplary embodiment, Figure 3 As shown, the method for rapidly measuring the porosity and permeability of dense rocks includes the following steps:

[0070] Step 100: Dry a powdered shale sample from a deep layer in the Sichuan Basin at 105°C for 50 hours, measure the mass of the shale sample (powder or plunger), and obtain the volume of the shale sample to be tested based on its density.

[0071] Step 200: Fill a known volume of shale sample into a sample cylinder. At the same time, adjust the mechanical locking mechanism to ensure close contact between the sample cylinder and the shale sample, ensuring that the volume in the cylinder other than the apparent volume is minimized.

[0072] Step 300: Open the vacuum valve and use a vacuum pump to evacuate the experimental device for 600 seconds.

[0073] Step 400: Close the vacuum valve and the third valve of the six-way valve, open the air inlet valve, injection valve, and the first, second, and fourth valves on the six-way valve, then open the air source valve to inflate the device to the preset pressure P0 (5 MPa, 7 MPa, 9 MPa) and proceed to the next experiment.

[0074] Step 500: Close the gas source valve, gas injection valve, and air inlet valve, open the boost valve and the third valve on the six-way valve, then use a hand-cranked boost pump to increase the pressure in the standard cylinder by 0.5 MPa, so that there is a pressure pulse of 0.5 MPa in the sample cylinder and the standard cylinder. Record the pressure P1 and proceed to the next step of the experiment.

[0075] Step 600: Close the intake valve, boost valve, and the third valve on the six-way valve. Open the gas injection valve at a rate of 1 / 4 turn per second and record the elapsed time and pressure until the pressure change is less than 200 Pa for 1,200 consecutive seconds (the final pressure is called P2). The test is complete.

[0076] Step 700: Process the experimental data to obtain shale porosity and permeability.

[0077] Figure 4 1 is a schematic diagram of the ln(FR(t))-t function of a deep shale sample in the Sichuan Basin, shown in an exemplary embodiment of the present application.

[0078] In a possible implementation, the data processing process is as follows:

[0079] By formula , calculate the pore volume of powdered shale;

[0080] Temperature: 40℃ Sample water saturation: 0%

[0081]

[0082] The porosity calculation formula is: ;

[0083] The volume fraction FR(t) is calculated using the following formula:

[0084] ;

[0085] Among them, 1-F R (t) represents the fraction of the amount of gas that enters the shale particle from the starting point to time t relative to the final amount of gas that enters the particle when equilibrium is reached, K c is the ratio of the volume outside the sample in the standard cylinder and the sample cylinder to the pore volume of the sample, is the average gas density at P1, is the gas density at P0, is the gas density at P(t);

[0086] Take the logarithm of the volume coefficient as Figure 4 As shown, ln(FR(t)) is:

[0087] ;

[0088] The permeability k is calculated according to the following relationship:

[0089] ;

[0090] Where μ is the viscosity of the gas, cg is the compression factor.

[0091] The specific definition of the method for rapidly measuring the porosity and permeability of dense rocks can be found in the above definition of the device for rapidly measuring the porosity and permeability of dense rocks, which will not be repeated here.

[0092] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The embodiments described above merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for rapidly measuring the porosity and permeability of dense rocks, characterized in that: include: A deep shale sample from the Sichuan Basin was dried at 105°C for 50 hours, and the mass of the shale sample was measured. The volume of the shale sample to be tested was obtained based on its density. Fill the sample cylinder with a known volume of shale sample. At the same time, adjust the mechanical locking mechanism to ensure close contact between the sample cylinder and the shale sample, ensuring that the volume in the cylinder other than the apparent volume is minimized. Open the vacuum valve and use the vacuum pump to evacuate the experimental device for 600 s; Close the vacuum valve and the third valve of the six-way valve, open the air inlet valve, injection valve, and the first, second, and fourth valves on the six-way valve, then open the air source valve to inflate the device to a preset pressure P0 of 5 MPa, 7 MPa, or 9 MPa before proceeding to the next step of the experiment. Close the gas source valve, gas injection valve, and air inlet valve, open the booster valve and the third valve on the six-way valve, and then use a hand-cranked booster pump to increase the pressure in the standard cylinder by 0.5 MPa, so that there is a pressure pulse of 0.5 MPa in the sample cylinder and the standard cylinder. Record the pressure P1 and proceed to the next step of the experiment. Close the intake valve, boost valve, and the third valve on the six-way valve, and open the air injection valve at a rate of 1 / 4 turn per second. Record the elapsed time and pressure until the pressure change is less than 200 Pa within 1200 seconds. The final pressure is called P2, and the test is complete. The test data is processed to obtain the shale porosity and permeability; The test data is processed to obtain shale porosity and permeability, including: By formula , calculate the pore volume of powdered shale ; The porosity calculation formula is: ; The volume fraction F is calculated using the following formula: R (t): ； Among them, 1-F R (t) represents the fraction of the amount of gas that enters the shale particle from the starting point to time t relative to the final amount of gas that enters the particle when equilibrium is reached, K c is the ratio of the volume outside the sample in the standard cylinder and the sample cylinder to the pore volume of the sample, is the average gas density at P1, is the gas density at P0, is the gas density at P(t); Taking the logarithm of the volume fraction, we can get ln(F R (t)) is: ； The permeability k is calculated according to the following relationship: ； Where μ is the viscosity of the gas, c g is the compression factor.

2. The method for rapidly measuring the porosity and permeability of dense rocks according to claim 1, wherein: When opening the vacuum valve and using the vacuum pump to evacuate the experimental device for 600 seconds, the pressure measured by the sensor in the device must not fluctuate by more than 200 Pa within 120 seconds.

3. The method for rapidly measuring the porosity and permeability of dense rocks according to claim 2, wherein: When closing the vacuum valve and the third valve of the six-way valve, opening the air inlet valve, injection valve and the first, second and fourth valves on the six-way valve, and then opening the gas source valve to inflate the device to the preset pressure P0, The pressure measured by the sensor in the control device must not fluctuate more than 200 Pa within 120 seconds; The preset pressure P0 is 5Mpa, 7Mpa or 9Mpa.

4. The method for rapidly measuring the porosity and permeability of dense rocks according to claim 1, wherein: After closing the gas source valve, gas injection valve, and air inlet valve, open the booster valve and the third valve on the six-way valve. Then, use a hand-cranked booster pump to increase the pressure in the standard cylinder by 0.5 MPa, so that there is a pressure pulse of 0.5 MPa in the sample cylinder and the standard cylinder. When recording the pressure P1 step, the pressure measured by the sensor in the control device shall not fluctuate by more than 200 Pa within 120 seconds.

5. The method for rapidly measuring the porosity and permeability of dense rocks according to claim 1, wherein the method uses a device for rapidly measuring the porosity and permeability of dense rocks, characterized in that: The device includes an air source, an air source conversion device, an air source valve, an air inlet valve, a standard cylinder, a six-way valve, a pressure sensor, a booster valve, a hand-cranked booster pump, an air outlet valve, a vacuum pump, an injection valve, an anti-backflow device, a sample cylinder, a constant temperature oil bath, an auxiliary heater and pipelines; The gas source is connected to the gas source conversion device, the gas source conversion device is connected to the standard cylinder through a pipeline, the gas source valve is located between the pipeline connecting the gas source conversion device and the standard cylinder, the air inlet valve is located between the pipeline connecting the standard cylinder and the gas source, the standard cylinder is connected to the six-way valve through a pipeline, the detection end of the pressure sensor is connected to the six-way valve through a bolt, the booster pump is connected to the six-way valve through a pipeline, the booster valve is located between the pipeline connecting the booster pump and the six-way valve, the vacuum pump is connected to the six-way valve through a pipeline, the air outlet valve is located between the pipeline connecting the vacuum pump and the six-way valve, the anti-backflow device is located inside the sample cylinder, and is connected to the air inlet of the sample cylinder, the standard cylinder and the sample cylinder are placed in the constant temperature oil bath, and the auxiliary heater is wrapped around the outside of the pipeline.

6. The method for rapidly measuring the porosity and permeability of dense rocks according to claim 5, wherein: The six-way valve includes a first valve connected to the standard cylinder, a second valve connected to the sample cylinder, a third valve connected to the vacuum pump, a fourth valve connected to the booster pump, and fifth and sixth valves that are always kept closed.

7. The method for rapidly measuring the porosity and permeability of dense rocks according to claim 5, wherein: The detection end of the pressure sensor converts the collected millivolt signal into a digital communication signal RS232, and then connects it to a computer via USB. The computer collects real-time data of the pipeline pressure to facilitate the adjustment of the pressure in the standard cylinder.

Images