Salt lake rock core sample permeability coefficient testing device and detection method

Abstract

The invention discloses a salt lake rock core sample permeability coefficient testing device and detection method.The testing device comprises a salt lake rock core permeability sample chamber, a confining pressure controller (18), a constant head water supply barrel (25) and a variable head pipe (26), and the salt lake rock core permeability sample chamber comprises an upper cover (2), an organic glass barrel (3) and a lower cover (4); a base (8), a latex film (11) and a pressurizing cap (7) are sequentially arranged above the lower cover (4) from bottom to top; the latex film (11) is sleeved on the base (8) and the pressurizing cap (7), is tightened by a rubber band and is fastened by a hoop straining ring; and the lower cover (4) is provided with a water inlet and outlet valve interface (13) which is connected with a confining pressure controller and is used for controlling the peripheral annular pressure of the latex film (11), and foot pads (5) for supporting the sample chamber. A permeation test is performed by externally connecting a constant head permeation device or a variable head permeation device, a salt lake rock core sample is put into a latex film and then put into a sample chamber, a certain annular pressure is given to the sample by using a water inlet and outlet valve interface, and lateral permeation is prevented and the permeability of the salt lake rock core sample is improved by controlling the annular pressure. And the unreliable permeability coefficient test result caused by the change of the original structure state of the sample under the action of large external force is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of minerals, and in particular to a test device and a detection method for the permeability coefficient of a salt lake core sample. Background Art

[0002] The permeability coefficient, also known as the hydraulic conductivity, in an isotropic medium, is defined as the unit flow rate under a unit hydraulic gradient, indicating the ease with which a fluid passes through the pore skeleton, and is an index comprehensively reflecting the permeability ability of a soil body. The working principle of the test is Darcy's law of permeability, and the formula is Q = KFh / L, where Q is the seepage flow rate per unit time, F is the cross-sectional area of water flow, h is the total head loss, and L is the length of the seepage path. In China, the general methods for testing the permeability coefficient are the constant head permeability test and the variable head permeability test (applicable to sandy soil samples) in the "Standard for Geotechnical Test Methods" (GB / T50123-2019) or the liquid and gas flowmeter method in the petroleum system (applicable to rock samples). The "Specification for Geological Exploration of Salt Lakes and Salt Minerals" requires the test of the permeability coefficient of the original salt lake core samples (the original structure cannot be damaged). However, the original salt lake core samples are special: their structures are extremely uneven and are changed from their original structural states under external forces, they have strong hygroscopicity and are prone to losing crystal water, which causes changes in composition, they are easy to form sidewall channels, and seepage is concentrated and piping occurs, making the test of the permeability coefficient extremely difficult. The constant head permeability device or variable head permeability device in the "Standard for Geotechnical Test Methods" cannot be used to test the permeability coefficient of the original salt lake core samples. At present, there is no relevant research report on the test equipment and methods for the permeability coefficient of salt lake core samples in China.

[0003] The correct determination of the permeability coefficient of salt lake core samples is of great significance for calculating reserves in salt lake exploration, and helps in the division of aquifers and non-aquifers, the distinction of aquitards, and reserve calculation. Therefore, it is of great significance to study the determination of the permeability coefficient of salt lake core samples.

[0004] However, salt lake core samples are a special type of sample. Their structures are extremely uneven and are changed from their original structural states under external forces, they have strong hygroscopicity and are prone to losing crystal water, which causes changes in composition, they are easy to form sidewall channels, and seepage is concentrated and piping occurs, making the test of the permeability coefficient extremely difficult. Different from other rock and soil samples, they have the characteristics of being easily loose (the internal structure cannot be damaged), poor representativeness (representativeness can only be achieved when reaching a certain volume), internal entrainment of brine, and complex salt mineral composition (the crystal water of some minerals is easily lost), which makes it difficult to determine the permeability coefficient of salt lake cores.

[0005] In the applicant's prior application CN202510363990.3, a salt lake core penetration sample chamber for testing the permeability coefficient of salt lake core samples was proposed. By loading the salt lake core samples into a latex film and then placing them in the sample chamber, a certain confining pressure was applied to the samples through the inlet and outlet valve interfaces. By controlling the magnitude of the confining pressure, lateral seepage was prevented, and the samples were also prevented from being affected by large external forces to change their original structural state, resulting in unreliable test results for the permeability coefficient. Based on this prior application, the present invention proposes a device and a detection method for testing the permeability coefficient of salt lake core samples. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a device and a detection method for testing the permeability coefficient of salt lake core samples. In order to achieve the invention object of the present invention, the following technical solutions are proposed:

[0007] In the first aspect of the present invention, a device for testing the permeability coefficient of salt lake core samples is provided, including a salt lake core penetration sample chamber, a confining pressure controller (18), a constant head water supply bucket (25) and a variable head tube (26). The salt lake core penetration sample chamber includes: an upper cover (2), an organic glass barrel (3) and a lower cover (4). The upper cover (2) and the lower cover (4) fix the organic glass barrel (3) through a fastening rod (1). The upper cover (2) is provided with an exhaust hole (17). Above the lower cover (4), a base (8), a latex film (11) and a pressure cap (7) are arranged in sequence from bottom to top. The latex film (11) is sleeved on the base (8) and the pressure cap (7), tightened by a rubber band and fastened by a hoop. The base (8) with an internal water inlet pipe (14) is fixed in the middle of the lower cover (4). The pressure cap with an internal water outlet pipe (16) is provided with a flange. The flange is fixed by a support rod (6) and the pressure cap (7) is fixed to the lower cover (4). Pressure sensors (15) are arranged on both the water inlet pipe (14) and the water outlet pipe (16). The lower cover (4) is provided with an inlet and outlet valve interface (13) connected to the confining pressure controller and used to control the confining pressure outside the latex film (11), and a foot pad (5) for supporting the sample chamber.

[0008] The inlet and outlet valve interface (13) of the salt lake core penetration sample chamber is connected to the confining pressure controller (18) through a confining pressure water pipe (19). The water inlet pipe (14) is connected to a water pipe (20). The water pipe (20) is respectively connected to the constant head water supply bucket (25), a water supply bucket (30) and the variable head tube (26) through valves (21). The height of the water supply bucket (30) is higher than that of the constant head water supply bucket (25), and the height of the constant head water supply bucket (25) is higher than the top surface of the salt lake core penetration sample chamber.

[0009] In a preferred embodiment of the present invention, water is supplied to the water supply bucket (30) through the pump water pipe (29) by the pump (33). The water supply bucket (30) supplies water to the constant head water supply bucket (25) through the constant head water supply pipe (27). The constant head water supply bucket (25) is provided with an overflow port (28) for maintaining the water level height of the constant head water supply bucket (25); the outlet pipe (16) is connected to the outlet pipe opening (22), and the water outlet is discharged into the container (23) through the outlet pipe opening (22). The beaker (23) is located on the electronic balance (24). The detection results of the electronic balance (24), the pressure sensor (15) on the inlet pipe (14), and the pressure sensor (15) on the outlet pipe (16) are transmitted to the data collector (31) through the data line (32); the variable head pipe (26) refers to a water pipe whose water level height changes during the test.

[0010] In a preferred embodiment of the present invention, the latex film (11) is a semi-transparent latex film, which is beneficial to observing whether side leakage occurs during the penetration test of the salt lake core sample.

[0011] In a preferred embodiment of the present invention, the pressure sensor (15) is respectively arranged on the inlet pipe (14) and the outlet pipe (16) through a tee.

[0012] In a preferred embodiment of the present invention, the pressure sensors (15) arranged on the inlet pipe (14) and the outlet pipe (16) have a fixed height difference or are at the same horizontal height.

[0013] In a preferred embodiment of the present invention, the pipe orifice of the outlet pipe (16) can be adjusted up and down, and the pressure sensor (15) arranged on the outlet pipe (16) cannot be adjusted up and down. Thus, the sample chamber can be applicable to salt lake core samples of different heights without reducing the pressure detection accuracy of the outlet pipe and affecting the detection result of the permeability coefficient.

[0014] On the other hand, the present invention also relates to a method for testing the permeability coefficient of a salt lake core sample, which comprises the following steps: pumping a permeation medium into a large water supply bucket (30) through a pump (33), sleeving the core sample (10) in the middle of a latex film (11), and padding permeable stones (9) above and below; sleeving the latex film (11) on a base (8) and a pressure cap (7), tightening it with a rubber band and fastening it with a hoop; covering an organic glass barrel (3), covering the lid (2) and then tightening the fastening rod (1) to fix the organic glass barrel (3); setting the confining pressure of the salt lake core sample, turning on the confining pressure controller (18), starting to inject brine, tightening the nut of the exhaust hole (17) after the brine is full, starting to apply pressure, opening the valve (21) between the constant head water supply bucket (25) and the water inlet pipe (14) after the confining pressure reaches the set value and stabilizes, discharging the gas in the pipeline, saturating the salt lake core sample with the permeation medium, discharging the gas in the core sample, and starting a constant head permeability test after the solution discharged from the drain pipe (16) stabilizes; after the constant head permeability test is completed, closing the valve (21) between the constant head water supply bucket (25) and the water inlet pipe (14), injecting a certain height of permeation liquid into the variable head pipe (26), opening the valve (21) between the variable head pipe (26) and the water inlet pipe (14), and starting a variable head permeability test.

[0015] The present invention conducts a permeability test by externally connecting a constant head permeability device or a variable head permeability device. The salt lake core sample is placed in a latex film and then put into the sample chamber. A certain confining pressure is applied to the sample through the inlet and outlet valve interface. By controlling the size of the confining pressure, lateral seepage is prevented, and the original structural state of the sample is also prevented from being changed by a large external force, resulting in unreliable test results of the permeability coefficient. Description of the Drawings

[0016] Figure 1 : Schematic structural diagram of a device for testing the permeability coefficient of a salt lake core sample, wherein, 1 - fastening rod; 2 - upper cover; 3 - organic glass barrel; 4 - lower cover; 5 - foot pad; 6 - support rod; 7 - organic glass pressure cap; 8 - organic glass base; 9 - permeable stone; 10 - salt lake core sample; 11 - latex film; 12 - water outlet; 13 - inlet and outlet valve interface; 14 - water inlet pipe; 15 - pressure sensor; 16 - water outlet pipe; 17 - exhaust hole; 18 - confining pressure controller; 19 - confining pressure water pipe; 20 - water pipe; 21 - valve; 22 - water outlet; 23 - container; 24 - electronic balance; 25 - constant head water supply bucket; 26 - variable head pipe; 27 - constant head water supply pipe; 28 - overflow port; 29 - pump water pipe; 30 - water supply bucket; 31 - data collector; 32 - data line; 33 - pump. Detailed Embodiments

[0017] To further illustrate the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following takes a preferred embodiment to elaborate in detail the specific implementation manners, technical solutions, features and their effects of the application according to the present invention. Specific features, structures, or characteristics in the following descriptions can be combined in any suitable form.

[0018] Example 1:

[0019] As Figure 1 shown, the permeability coefficient test device for salt lake core samples includes a salt lake core permeability sample chamber, a confining pressure controller (18), and a set of switchable constant head permeability device and variable head permeability device.

[0020] Among them, the structure of the salt lake core permeability sample chamber includes: an upper cover (2) and a lower cover (4) made of stainless steel fix an organic glass barrel (3) through three fastening rods (1). The upper cover (2) is provided with an exhaust hole (17). Above the lower cover (4), from bottom to top, there are an organic glass base (8), a semi-transparent latex film (11), and an organic glass pressure cap (7) in sequence. The latex film (11) is sleeved on the organic glass base (8) and the organic glass pressure cap (7), tightened by a rubber band and fastened by a hoop. The organic glass base (8) with an internal water inlet pipe (14) is fixed in the middle of the lower cover (4). The upper organic glass pressure cap with an internal water outlet pipe (16) has a cover edge, and the cover edge is fixed and the organic glass pressure cap is fixed through two support rods (6). Pressure sensors (15) are provided on both the water inlet pipe (14) and the water outlet pipe (16). An inlet and outlet water valve interface (13) for controlling the peripheral confining pressure of the latex film (11) and a plurality of feet (5) for placing the entire sample chamber on the table and keeping it stable for cleaning are provided on the lower cover (4).

[0021] Position of the pressure sensor (15): According to Darcy's law and the standards of geotechnical test methods, it is necessary to accurately measure the pressures at the front and rear ends of the core sample. Since the permeation medium is highly corrosive brine, corrosion-resistant pressure sensors need to be selected. However, the probes and volumes of such sensors are relatively large, and it is impossible to design them to be placed at the water outlet end of the water inlet pipe of the plexiglass base and the water inlet end of the water outlet pipe of the pressure cap. Considering the stability of the pressure sensor when measuring the pressures at the front and rear ends of the core sample, a tee is added at the positions of the water inlet pipe and the water outlet pipe at the lower cover of the sample chamber to connect the pressure sensor. At this time, the distance between the placement position of the pressure sensor at the front end of the core sample and the front end of the core sample (the upper edge of the plexiglass base) is fixed. The pressure measured by the pressure sensor minus the pressure generated by this fixed distance is the pressure at the front end of the core sample. The pressure measured at the placement position of the pressure sensor at the rear end of the core sample is the pressure at the rear end of the core sample plus the pressure generated by the distance between the rear end of the core sample and the placement position of the rear-end pressure sensor. According to the U-tube pressure principle, at this time, the water outlet pipe orifice (which can be adjusted up and down) is adjusted to the position of the lower edge of the pressure cap and fixed (since the position of the pressure cap changes with the length of the sample seepage path, the water outlet pipe orifice is designed to be adjustable up and down to fix this distance, so that the pressure measured by the pressure sensor at the rear end of the core sample is relatively stable). Make the pressure generated by the distance from the water outlet pipe orifice to the placement position of the rear-end pressure sensor the same as the pressure generated by the distance between the rear end of the core sample and the placement position of the rear-end pressure sensor. At this time, the pressure measured at the placement position of the pressure sensor at the rear end of the core sample is the pressure at the rear end of the core sample. During the entire core sample permeation test process, the front and rear pressure sensors are less disturbed by the flow of the permeation medium and can accurately measure the pressures at the front and rear ends of the core sample.

[0022] Use of the salt lake core permeation sample chamber: After the side walls of the salt lake core sample are treated, it is placed into a latex film, with permeable stones placed on the top and bottom. The latex film is sleeved on the cylindrical base and the upper plexiglass cylinder, tightened with a rubber band and fastened with a clamp ring. The water inlet and outlet pipes are connected to the pressure sensor, placed in the sample chamber, and a certain confining pressure is applied to the latex film using a confining pressure controller to prevent side seepage. An external constant head permeation device or variable head permeation device is connected to conduct the permeation test.

[0023] The inlet and outlet valve interfaces (13) of the salt lake core penetration sample chamber are connected to the confining pressure controller (18) through the confining pressure water pipe (19). The inlet water pipe (14) is connected to the water pipe (20). The water pipe (20) is respectively connected to the constant head water supply bucket (25), the water supply bucket (30) and the variable head pipe (26) through the valve (21). The height of the water supply bucket (30) is higher than that of the constant head water supply bucket (25), and the height of the constant head water supply bucket (25) is higher than the top surface of the salt lake core penetration sample chamber. Water is supplied to the water supply bucket (30) through the pump (33) via the pump water pipe (29). The water supply bucket (30) supplies water to the constant head water supply bucket (25) through the constant head water supply pipe (27). The constant head water supply bucket (25) is provided with an overflow port (28) for maintaining the water level height of the constant head water supply bucket (25). The outlet water pipe (16) is connected to the outlet water pipe port (22), and the outlet water is discharged into the container (23) through the outlet water pipe port (22). The beaker (23) is located on the electronic balance (24). The detection results of the electronic balance (24), the pressure sensors (15) on the inlet water pipe (14) and the pressure sensors (15) on the outlet water pipe (16) are transmitted to the data collector (31) through the data line (32). The variable head pipe (26) refers to a water pipe whose water level height changes during the test.

[0024] The test process is as follows: Pump the penetration medium (brine) into the large water supply bucket (30) through the pump (33). Set the core sample (10) in the middle of the latex film (11). Pad permeable stones (9) on the top and bottom. When the cut surface is uneven, level it with coarse quartz sand and then pad the permeable stones (9). Put the latex film (11) on the organic glass cylindrical base (8) and the organic glass cylindrical pressure cap (7), tighten it with a rubber band and fasten it with a hoop. Cover the organic glass barrel (3), cover the stainless steel upper cover (2), and then tighten the fastening rod (1) to fix the organic glass barrel (3). Set the confining pressure of the salt lake core sample (about 15 - 25 KPa), turn on the confining pressure controller (18), start injecting brine. After the brine is filled, tighten the nut of the exhaust hole (17), start pressurizing. After the confining pressure reaches the set value and stabilizes, open the valve (21) between the constant head water supply bucket (25) and the inlet water pipe (14) to discharge the gas in the pipeline, saturate the salt lake core sample with the penetration medium, fully discharge the gas in the core sample. After the solution discharged from the drain pipe (16) stabilizes, start the constant head penetration test. After the constant head penetration test is completed, close the valve (21) between the constant head water supply bucket (25) and the inlet water pipe (14), inject a certain height of penetration liquid into the variable head pipe (26), open the valve (21) between the variable head pipe (26) and the inlet water pipe (14), and start the variable head penetration test.

[0025] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the above-mentioned claims.

Claims

1. A salt lake core sample permeability coefficient testing device, comprising a salt lake core permeability sample chamber, a confining pressure controller (18), a constant head water supply barrel (25) and a variable head pipe (26), wherein the salt lake core permeability sample chamber comprises: The upper cover (2), the organic glass barrel (3) and the lower cover (4), the upper cover (2) and the lower cover (4) fix the organic glass barrel (3) through a fastening rod (1), the upper cover (2) is provided with an exhaust hole (17), and the upper part of the lower cover (4) is provided with a base (8), a latex film (11) and a pressure cap (7) in sequence from bottom to top, the latex film (11) is sleeved on the base (8) and the pressure cap (7) and is tightened by a rubber band and a clamp ring; the base has a built-in water inlet pipe (14) (8) is fixed in the middle of the lower cover (4), and a pressure cap with a built-in water outlet pipe (16) is provided with a cover edge, and the cover edge is fixed by a support rod (6) and the pressure cap (7) is fixed to the lower cover (4); a pressure sensor (15) is provided on the water inlet pipe (14) and the water outlet pipe (16); the lower cover (4) is provided with an inlet and outlet valve interface (13) connected to the confining pressure controller and used to control the peripheral ring pressure of the latex membrane (11) and a pad (5) for supporting the sample chamber; The inlet and outlet valve interface (13) of the salt lake core permeability sample chamber is connected to the confining pressure controller (18) through the confining pressure water pipe (19), the inlet pipe (14) is connected to the water pipe (20), and the water pipe (20) is connected to the constant water head water supply barrel (25), the water supply barrel (30) and the variable water head pipe (26) through the valve (21) respectively; the height of the water supply barrel (30) is higher than the constant water head water supply barrel (25), and the height of the constant water head water supply barrel (25) is higher than the top surface of the salt lake core permeability sample chamber; the variable water head pipe (26) refers to a water pipe whose water level changes during the test process.

2. The salt lake core sample permeability testing device according to claim 1, characterized in that: Water is supplied to a water supply bucket (30) through a pump water pipe (29) by a pump (33), and the water supply bucket (30) supplies water to a constant water supply bucket (25) through a constant water supply pipe (27). The constant water supply bucket (25) is provided with an overflow port (28) for maintaining the water level of the constant water supply bucket (25); the water outlet pipe (16) is connected to the water outlet pipe port (22), and the water is discharged into the container (23) through the water outlet pipe port (22). The beaker (23) is located on an electronic balance (24), and the detection results of the electronic balance (24), the pressure sensor (15) on the water inlet pipe (14) and the pressure sensor (15) on the water outlet pipe (16) are transmitted to a data acquisition device (31) through a data line (32).

3. The salt lake core sample permeability testing device according to claim 1 or 2, characterized in that: The latex film (11) is a translucent latex film.

4. The salt lake core sample permeability testing device according to claim 1 or 2, characterized in that: The pressure sensor (15) is respectively arranged on the water inlet pipe (14) and the water outlet pipe (16) through a tee.

5. The salt lake core sample permeability testing device according to claim 3, characterized in that: The pressure sensors (15) arranged on the water inlet pipe (14) and the water outlet pipe (16) have a fixed height difference or are at the same level.

6. The salt lake core sample permeability testing device according to claim 1 or 2, characterized in that: The pipe mouth of the water outlet pipe (16) can be adjusted up and down, and the pressure sensor (15) arranged on the water outlet pipe (16) cannot be adjusted up and down.

7. A method for testing the permeability coefficient of a salt lake core sample, which uses the salt lake core sample permeability coefficient testing device described in any one of claims 1 to 6, and comprises the following steps: pumping a permeable medium into a large water supply barrel (30) through a pump (33), inserting the core sample (10) into the middle of a latex film (11), and padding the upper and lower parts with permeable stones (9); putting the latex film (11) on a base (8) and a pressure cap (7) and tightening it with a rubber band and a clamping ring; covering the organic glass barrel (3), covering the lid (2), and then tightening the tightening rod (1) to fix the organic glass barrel (3); setting the ring pressure of the salt lake core sample, turning on the confining pressure controller (18), and starting to inject brine until the brine is filled Then tighten the nut of the exhaust hole (17) and start to apply pressure. After the confining pressure reaches the set value and stabilizes, open the valve (21) between the constant head water supply barrel (25) and the water inlet pipe (14) to discharge the gas in the pipeline, saturate the salt lake core sample with the permeable medium, discharge the gas in the core sample, and start the constant head permeability test after the solution discharged from the drainage pipe (16) stabilizes; after the constant head permeability test is completed, close the valve (21) between the constant head water supply barrel (25) and the water inlet pipe (14), inject a certain height of permeable liquid into the variable head pipe (26), open the valve (21) between the variable head pipe (26) and the water inlet pipe (14), and start the variable head permeability test.

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