Salt lake rock core permeation sample chamber for testing permeation coefficient of salt lake rock core sample

Abstract

The invention discloses a salt lake rock core permeation sample chamber for testing the permeation coefficient of a salt lake rock core sample, the salt lake rock core permeation 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, and the latex film (11) sleeves 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 salt lake rock core sample is put into the latex film and then put into the sample chamber, a certain annular pressure is given to the sample through the water inlet and outlet valve interface, lateral seepage is prevented by controlling the annular pressure, and the situation that the permeability coefficient test result is unreliable due to the fact that the original structure state of the sample is changed under the action of large external force is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of minerals, and particularly to a salt lake core permeation sample chamber for testing the permeability coefficient of salt lake core samples. 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 of the soil mass. 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 the flowing water, h is the total head loss, and L is the length of the seepage path. In China, the permeability coefficient test generally adopts the constant head permeability test and variable head permeability test in the "Standard for Geotechnical Test Methods" (GB / T 50123-2019) (applicable to sandy soil samples) or the liquid and gas flow meter 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: the structure is extremely uneven and is changed from its original structure state under external force, it has strong hygroscopicity and is easy to lose crystal water, which causes changes in composition, is easy to form sidewall channels, and the seepage is concentrated and piping occurs, making the permeability coefficient test 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 is helpful for 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. The structure is extremely uneven and is changed from its original structure state under external force, it has strong hygroscopicity and is easy to lose crystal water, which causes changes in composition, is easy to form sidewall channels, and the seepage is concentrated and piping occurs, making the permeability coefficient test extremely difficult. Different from other rock and soil samples, it has the characteristics of being easy to loosen (the internal structure cannot be damaged), poor representativeness (it has representativeness only when reaching a certain volume), internal entrainment of brine, and complex salt mineral composition (the crystal water of some minerals is very easy to lose), which makes it difficult to determine the permeability coefficient of salt lake cores. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a salt lake core permeation sample chamber for testing the permeability coefficient of salt lake core samples and its usage method. In order to achieve the invention purpose of the present invention, the following technical solutions are proposed:

[0006] In the first aspect of the present invention, a salt lake core permeation sample chamber for testing the permeability coefficient of salt lake core samples is provided, which includes: an upper cover (2), a plexiglass barrel (3) and a lower cover (4). The upper cover (2) and the lower cover (4) fix the plexiglass 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 successively arranged 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 a water inlet and outlet valve interface (13) connected to a confining pressure controller and used for controlling the peripheral confining pressure of the latex film (11) and a foot pad (5) for supporting the sample chamber.

[0007] In a preferred embodiment of the present invention, the latex film (11) is a semi-transparent latex film, which is beneficial to observing whether there is side leakage during the salt lake core sample permeation test.

[0008] In a preferred embodiment of the present invention, the pressure sensors (15) are respectively arranged on the water inlet pipe (14) and the water outlet pipe (16) through tees.

[0009] In a preferred embodiment of the present invention, 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 horizontal height.

[0010] In a preferred embodiment of the present invention, the nozzle 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. Thus, the sample chamber can be applicable to salt lake core samples of different heights without reducing the pressure detection accuracy of the water outlet pipe and affecting the detection result of the permeability coefficient.

[0011] On the other hand, the present invention also relates to a method for testing the permeability coefficient of salt lake core samples, which uses the above-mentioned salt lake core permeation sample chamber. After the salt lake core sample is treated on the side wall, it is loaded into the latex film (11), and water-permeable stones (9) are padded on the upper and lower sides. 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 confining pressure controller is used to apply a confining pressure to the latex film to prevent side seepage, and the water inlet pipe (14) is externally connected to a constant head permeation device or a variable head permeation device for a permeation test.

[0012] In the present invention, a salt lake core sample is placed into a latex film and then into a sample chamber. A certain confining pressure is applied to the sample through the inlet and outlet valve interface. By controlling the magnitude of the confining pressure, lateral seepage is prevented, and the sample is also prevented from being affected by a large external force to change its original structural state, resulting in unreliable test results of the permeability coefficient. Description of the Drawings

[0013] Figure 1 : Schematic structural diagram of a salt lake core permeability sample chamber, wherein, 1 - fastening rod; 2 - upper cover; 3 - plexiglass barrel; 4 - lower cover; 5 - foot pad; 6 - support rod; 7 - plexiglass pressure cap; 8 - plexiglass base; 9 - permeable stone; 10 - salt lake core sample; 11 - latex film; 12 - water outlet; 13 - inlet and outlet valve interface; 14 - inlet pipe; 15 - pressure sensor; 16 - outlet pipe; 17 - exhaust hole. Detailed Embodiments

[0014] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following takes a preferred embodiment to describe in detail the specific implementation manner, technical solution, features and their effects of the application according to the present invention. The specific features, structures, or characteristics in the following descriptions of multiple embodiments can be combined in any suitable form.

[0015] Embodiment 1:

[0016] As Figure 1 shown, the structure of the salt lake core permeability sample chamber includes: the upper cover (2) and the lower cover (4) made of stainless steel fix the plexiglass barrel (3) through three fastening rods (1). The upper cover (2) is provided with an exhaust hole (17). Above the lower cover (4), there are successively arranged from bottom to top a plexiglass base (8), a semi-transparent latex film (11), and a plexiglass pressure cap (7). The latex film (11) is sleeved on the plexiglass base (8) and the plexiglass pressure cap (7), tightened by a rubber band and fastened by a hoop. The plexiglass base (8) with an inlet pipe (14) built-in is fixed in the middle of the lower cover (4). The upper plexiglass pressure cap with an outlet pipe (16) built-in has a cover edge, and the cover edge is fixed and the plexiglass pressure cap is fixed through two support rods (6). Pressure sensors (15) are arranged on both the inlet pipe (14) and the outlet pipe (16); the inlet and outlet valve interface (13) for controlling the confining pressure around the latex film (11) on the lower cover (4) and multiple foot pads (5) for placing the entire sample chamber on the table and keeping it stable for cleaning.

[0017] 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 to connect the pressure sensor at the positions of the water inlet pipe and the water outlet pipe at the lower cover of the sample chamber. 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). This makes 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.

[0018] Use of the salt lake core permeation sample chamber: After the side walls of the salt lake core sample are treated, it is placed in 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 fixed with a hoop. The water inlet and outlet pipe orifices 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, and an external constant head permeation device or variable head permeation device is used for the permeation test.

[0019] The specific embodiments of the present invention disclosed above are only for illustration purposes, 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 permeability sample chamber for testing the permeability coefficient of a salt lake core sample, characterized in that: include: 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); pressure sensors (15) are 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.

2. The salt lake core permeation sample chamber according to claim 1, characterized in that: The latex film (11) is a translucent latex film.

3. The salt lake core permeation sample chamber according to claim 1, 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.

4. The salt lake core permeation sample chamber 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.

5. The salt lake core permeation sample chamber according to claim 1, 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.

6. A method for testing the permeability coefficient of a salt lake core sample, which adopts the salt lake core permeability sample chamber described in any one of claims 1 to 5, and the salt lake core sample is placed in a latex membrane (11) after side wall treatment, and permeable stones (9) are placed on the upper and lower pads. The latex membrane (11) is sleeved on a base (8) and a pressure cap (7) and tightened by a rubber band and fastened with a clamp ring. A confining pressure controller is used to apply annular pressure to the latex membrane to prevent lateral seepage, and a water inlet pipe (14) is externally connected to a constant head permeation device or a variable head permeation device to perform a permeability test.

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