Anisotropic resistivity testing device for sandstones with different water saturations

Abstract

The utility model relates to the technical field of rock physical property test experiment instruments and equipment, and discloses a different water saturation sandstone anisotropic resistivity test device, which comprises a clamping assembly, a dynamic fluid circulation assembly and a resistivity test assembly, the clamping assembly comprises a metal tank body and a rock clamping device, and the rock clamping device is arranged in the metal tank body; the dynamic fluid circulation assembly comprises a water supply unit and a gas supply unit and is used for providing rock saturated pressure and rock longitudinal pressure; the resistivity testing assembly comprises a bridge, at least two metal gaskets and an insulating tube, the at least two metal gaskets are arranged at the two ends of the rock, the insulating tube is arranged on the outer side of the rock, and the bridge is connected with the metal gaskets through wires. The anisotropic resistivity of core samples with different water saturations can be conveniently, quickly and accurately tested, and the relation between the tested resistivity result and anisotropy and different water saturation rates can be directly applied to the fields of geophysical electrical prospecting and the like.

Description

Technical Field

[0001] This application relates to the technical field of instruments and equipment for testing the physical properties of rocks, and in particular to a device for testing the anisotropic resistivity of sandstone with different water saturation. Background Technology

[0002] Mine water hazards are one of the major geological disasters frequently encountered in the mining of various mineral deposits, including coal mines, in my country. They are also a significant factor restricting production activities and sustainable development in mining areas. Mine water hazards typically manifest as outbursts, surges, collapses, and water seepage. For many years, the prevention and control of mine water hazards has been an important topic of concern and research for scientists, engineers, and production workers in related fields.

[0003] Archie first proposed a resistivity structure model for clay-free, pure sandstone. Subsequently, numerous scholars studied resistivity models for various rock and soil types, analyzing the influence of various factors on resistivity. The Archie formula is also a commonly used method for calculating water content in sandstone using resistivity. However, when using the Archie formula, unknown parameters need to be obtained through experimental testing. Many factors influence the variation of rock resistivity, mainly including pore water conductivity, water saturation, mineral types in the rock, and anisotropy. Clarifying the relationship between rock resistivity, water saturation, and anisotropy using experimental methods is helpful for the quantitative interpretation of water-bearing sandstone layers.

[0004] Conducting resistivity anisotropy experiments requires multiple adjustments to the core orientation, making the experimental procedures cumbersome. Secondly, determining the water saturation level of the rock is also a significant challenge. Current methods primarily include immersion, drying, and placing the sample in a constant humidity environment; these are time-consuming and make it difficult to control the rock's water saturation. If resistivity testing is not performed on saturated rocks promptly, the degree of water saturation may decrease. Conventional testing methods or equipment struggle to obtain complete, accurate, and reliable resistivity curves showing the anisotropy of rock resistivity with water saturation.

[0005] Therefore, there is an urgent need for an effective device to prepare sandstone with different water saturation levels and simultaneously test the anisotropic resistivity of the rock to solve the above problems. Utility Model Content

[0006] The purpose of this application is to provide an anisotropic resistivity testing device for sandstone with different water saturation levels, so as to solve the problem that conventional testing methods or equipment are difficult to obtain complete, true and reliable resistivity curves of rock anisotropy with water saturation.

[0007] To achieve the above objectives, the following technical solution is adopted:

[0008] An anisotropic resistivity testing device for sandstone with different water saturation includes a clamping assembly, a dynamic fluid circulation assembly, and a resistivity testing assembly.

[0009] The clamping assembly includes a metal can and a rock clamp, wherein the rock clamp is disposed inside the metal can and is used to clamp and fix the rock.

[0010] The dynamic fluid circulation assembly includes a water supply unit and an air supply unit; wherein, the water supply unit is connected to the rock holder and is used to provide pressure when the rock is saturated with water, and the air supply unit is connected to the metal tank and is used to provide longitudinal pressure to the rock;

[0011] The resistivity testing assembly includes a bridge circuit, at least two metal gaskets, and an insulating tube. The at least two metal gaskets are disposed at both ends of the rock, and the insulating tube is disposed on the outside of the rock to isolate the rock from the metal container. The bridge circuit is connected to the metal gaskets via wires.

[0012] Preferably, in the above-mentioned anisotropic resistivity testing device for sandstone with different water saturation, the water supply unit includes a pressure pump, a first pressure valve, a first fluid container, a second pressure valve, a first pipe, a second pipe, a third pressure valve, a fourth pressure valve, a fifth pressure valve, and a second fluid container; wherein, the pressure pump is connected to the first fluid container through a pipe, and the first pressure valve is installed on the pipe connecting the pressure pump and the first fluid container; the first fluid container is connected to one end of the rock holder through the first pipe, and the other end of the rock holder is connected to the second fluid container through the second pipe; the second pressure valve and the third pressure valve are installed on the first pipe, and the fourth pressure valve and the fifth pressure valve are installed on the second pipe.

[0013] Preferably, in the above-mentioned anisotropic resistivity testing device for sandstone with different water saturation, the gas supply unit includes an inlet cylinder, an outlet cylinder, a third pipe, a fourth pipe, a sixth pressure valve, and a seventh pressure valve; wherein, the inlet cylinder is connected to the interior of the metal tank through the third pipe, the outlet cylinder is connected to the interior of the metal tank through the fourth pipe, the sixth pressure valve is disposed in the third pipe, and the seventh pressure valve is disposed in the fourth pipe.

[0014] Preferably, in the above-mentioned anisotropic resistivity testing device for sandstone with different water saturation, the resistivity testing component further includes at least two circuit interfaces. The circuit interfaces are disposed on the side wall of the metal tank, the bridge is disposed outside the metal tank, one end of the wire is connected to the bridge, and the other end of the wire passes through the metal tank in a sealed manner through the circuit interface and is connected to the metal gasket.

[0015] Preferably, in the above-mentioned anisotropic resistivity testing device for sandstone with different water saturation, the metal tank and the wire are wrapped with insulating material.

[0016] Preferably, the above-mentioned anisotropic resistivity testing device for sandstone with different water saturation also includes a mass sensor, which is fixed to the bottom of the metal tank and the sensing end of the mass sensor is connected to the insulating tube.

[0017] Preferably, in the above-mentioned anisotropic resistivity testing device for sandstone with different water saturation, the insulating tube is a rubber tube.

[0018] Preferably, in the above-mentioned anisotropic resistivity testing device for sandstone with different water saturation, among the multiple circuit interfaces, the bridge is connected to the metal pad by wires through at least two circuit interfaces for testing the vertical resistivity of the rock, and the bridge is connected to the rock core inside the rock by wires through at least two circuit interfaces for testing the anisotropic resistivity of the rock. The at least two circuit interfaces for testing the anisotropic resistivity of the rock are arranged in a ring array on the metal tank.

[0019] Preferably, in the above-mentioned anisotropic resistivity testing device for sandstone with different water saturation, six circuit interfaces are arranged in a ring array on the metal tank, with each circuit interface spaced 60° apart.

[0020] The beneficial effects of this application are:

[0021] The water-saturated sandstone anisotropic resistivity testing device provided in this application can conveniently, quickly and accurately test the anisotropic resistivity of core samples with different water saturation. The relationship between the test resistivity results and anisotropy and different water saturation can be directly used in fields such as geophysical electrical exploration. Attached Figure Description

[0022] Figure 1 A schematic diagram of a device for testing the anisotropic resistivity of sandstone with different water saturation according to an embodiment of this application is shown.

[0023] Figure 2 It shows according to Figure 1 A-A' cross-sectional view.

[0024] Figure label:

[0025] 1-Pressure pump; 2-First pressure valve; 3-First fluid container; 4-Second pressure valve; 5-Inlet cylinder; 6-Pressure valve 3; 7-Outlet cylinder; 8-Seventh pressure valve; 9-Second fluid container; 10-Fourth pressure valve; 11-Third pressure valve; 12-Insulating tube; 13-Metal tank cavity; 14-Rock holder; 15-Metal gasket; 16-Plug-shaped core sample; 17-Metal tank; 18-Pressure valve; 19-Wheatstone bridge; 20-Seventh circuit interface; 21-Eighth circuit interface; 22-First circuit interface; 23-Second circuit interface; 24-Third circuit interface; 25-Fourth circuit interface; 26-Fifth circuit interface; 27-Sixth circuit interface; 28-Mass sensor; 29-Wire; 30-First pipe; 31-Second pipe; 32-Third pipe; 33-Fourth pipe. Detailed Implementation

[0026] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0027] The specific implementation methods of this application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] This application provides an embodiment of a device for testing the anisotropic resistivity of sandstone with different water saturation levels, such as... Figure 1 As shown, the anisotropic resistivity testing device for sandstone with different water saturation levels includes a clamping assembly, a dynamic fluid circulation assembly, and a resistivity testing assembly. The clamping assembly includes a metal tank 17 and a rock clamp 14, which is disposed inside the metal tank 17 for clamping and fixing the rock. In this embodiment, the rock example is a plunger-shaped core sample 16. The dynamic fluid circulation assembly includes a water supply unit and an air supply unit; wherein, the water supply unit is connected to the rock clamp 14 to provide pressure when the rock is saturated with water, and the air supply unit is connected to the metal tank 17 to provide longitudinal pressure to the rock. The resistivity testing assembly includes a bridge 19, at least two metal gaskets 15, and an insulating tube 12. At least two metal gaskets 15 are disposed at both ends of the plunger-shaped core sample 16, and the insulating tube 12 is disposed on the outside of the plunger-shaped core sample 16 to isolate the rock 12 from the metal tank 17. The bridge 19 is connected to the metal gaskets 15 through wires 29.

[0029] In this embodiment, the clamping assembly provides the necessary environment for experimental testing. The metal can 17 has a closed internal space, namely the metal can cavity 13. The rock clamp 14 is used to clamp and fix the plunger-shaped rock core sample 16 and is disposed within the metal can cavity 13. The dynamic fluid circulation assembly includes a water supply unit and an air supply unit to provide the pressure of the plunger-shaped rock core sample 16 when it is saturated with water and the longitudinal pressure of the plunger-shaped rock core sample 16, respectively. The resistivity testing assembly is used to test the resistivity of the rock under different conditions. Specifically, the resistance value of the rock under different saturated conditions or different longitudinal pressure conditions is tested using a bridge 19. The bridge 19 is connected to metal gaskets 15 disposed at both ends of the rock through wires 29, thereby forming a detection circuit. The rock resistance value under different rock conditions is measured by the bridge 19, and the rock resistivity under the corresponding condition can be calculated based on the rock resistance value. The insulating tube 12 isolates the plunger-shaped rock core sample 16 from the metal can 17, eliminating the interference of the metal can 17 on the resistance test results. Therefore, the anisotropic resistivity testing device for sandstone with different water saturation provided in this embodiment can conveniently, quickly and accurately test the anisotropic resistivity of core samples with different water saturation.

[0030] In some embodiments, such as Figure 1 As shown, the water supply unit includes a pressure pump 1, a first pressure valve 2, a first fluid container 3, a second pressure valve 4, a first pipe 30, a second pipe 31, a third pressure valve 11, a fourth pressure valve 10, a fifth pressure valve 18, and a second fluid container 9. The pressure pump 1 is connected to the first fluid container 3 through a pipe, and the first pressure valve 2 is installed on the pipe connecting the pressure pump 1 and the first fluid container 3. The first fluid container 3 is connected to one end of a rock clamp 14 through the first pipe 30, and the other end of the rock clamp 14 is connected to the second fluid container 9 through the second pipe 31. The second pressure valve 4 and the third pressure valve 11 are installed on the first pipe 30, and the fourth pressure valve 10 and the fifth pressure valve 18 are installed on the second pipe 31.

[0031] In this embodiment, the pressure of the rock when it is saturated can be controlled by controlling the operating parameters of the pressure pump 1, thereby accelerating the rock saturation process. The second pressure valve 4 is used to control and detect the pressure of the pressure pump and the flow rate of the fluid. The first fluid container 3 is used to supply fluid during the rock saturation process and is connected to the pressure pump 1 and the first pipeline 30. The second fluid container 9 is used to recover fluid during the rock saturation process, thus forming a closed-loop circulating liquid pipeline, which reduces the amount of liquid required for the experiment while meeting the experimental requirements.

[0032] In some embodiments, the gas supply unit includes an inlet cylinder 5, an outlet cylinder 7, a third pipe 32, a fourth pipe 33, a sixth pressure valve 6, and a seventh pressure valve 8; wherein, the inlet cylinder 5 is connected to the interior of the metal tank 17 through the third pipe 32, the outlet cylinder 7 is connected to the interior of the metal tank 17 through the fourth pipe 33, the sixth pressure valve 6 is disposed in the third pipe 32, and the seventh pressure valve 8 is disposed in the fourth pipe 33.

[0033] In this embodiment, the inlet cylinder 5 and the outlet cylinder 7, together with the internal cavity of the metal canister 17, form a closed-loop gas circulation channel through the third pipe 32 and the fourth pipe 33. Both the inlet cylinder 5 and the outlet cylinder 7 are pressure cylinders. When the inlet cylinder 5 and the outlet cylinder 7 are opened, the corresponding gas pressure is provided to the inside of the metal canister 17 according to the different gas pressures inside the cylinders. The longitudinal pressure change of the rock can be controlled by controlling the opening degree of the sixth pressure valve 6 or the seventh pressure valve 8.

[0034] In some embodiments, such as Figure 1 As shown, the anisotropic resistivity testing device for sandstone with different water saturation also includes a mass sensor 28, which is fixed to the bottom of the metal tank 17. The sensing end of the mass sensor 28 is connected to the insulating tube 12 and is used to monitor the change in core mass during the water saturation process.

[0035] In some embodiments, the position of the mass sensor 28 can be perpendicular to the placement of the anisotropic resistivity testing device for sandstone with different water saturation levels, thereby ensuring the accuracy of the measured core weight change data.

[0036] In some embodiments, the insulating tube 12 is a rubber tube.

[0037] In some embodiments, such as Figure 1 As shown, the resistivity testing assembly also includes at least two circuit interfaces, which are located on the side wall of the metal can 17. The bridge 19 is located outside the metal can 17. One end of the wire 29 is connected to the bridge 19, and the other end of the wire 29 passes through the metal can 17 in a sealed manner through the circuit interface and is connected to the metal gasket 15.

[0038] To ensure the overall sealing of the metal can 17 and the transmission effect of the wire 29, and to avoid the metal can 17 affecting the transmission of the wire, the metal can 17 and the wire 29 are wrapped with insulating material.

[0039] In some embodiments, multiple circuit interfaces are arranged in a ring array on the metal tank. As an example only, eight circuit interfaces are provided, of which two are used to test the vertical resistivity of the rock and six are used to test the anisotropic resistivity of the rock.

[0040] like Figure 2As shown, each of the six circuit interfaces is spaced 60° apart. The six circuit interfaces are the first circuit interface 22, the second circuit interface 23, the third circuit interface 24, the fourth circuit interface 25, the fifth circuit interface 26, and the sixth circuit interface 27. The bridge 19 is connected to the internal rock core through wires via the first circuit interface 22, the second circuit interface 23, the third circuit interface 24, the fourth circuit interface 25, the fifth circuit interface 26, and / or the sixth circuit interface 27, for measuring the anisotropic resistivity of the rock.

[0041] like Figure 1 As shown, the two circuit interfaces are the seventh circuit interface 20 and the eighth circuit interface 21, respectively. The bridge 19 is connected to the metal pad 15 through the seventh circuit interface 20 and the eighth circuit interface 21 in sequence by wires, and is used to test the vertical resistivity of the rock.

[0042] This application also provides a method for using the anisotropic resistivity testing device for sandstone with different water saturation levels as described above, which includes the following steps:

[0043] (1) Cut the collected rock samples into standard 25*50mm plunger-shaped core samples 16, dry them using microwave method, and record the mass of the plunger sample every 8 hours. When the mass change of the sample between two tests is less than 0.001g, it is considered that the sample is completely dry and the mass m1 is recorded.

[0044] (2) Place the plunger-shaped core sample 16 inside the insulating tube 12 of the test device, place metal shims 15 on the top and bottom of the plunger-shaped core sample 16, and fix it with rock clamp 14, and record the mass m2 measured by the mass sensor 28.

[0045] (3) Open the air inlet bottle-5 and pressure valve-6 to determine the sample confining pressure; open the pressure pump 1, first pressure valve 2, second pressure valve 4, and third pressure valve 11 to inject the fluid from the first fluid container 3 into the plunger-shaped core sample 16, close the third pressure valve 11, and record the mass m3 measured by the mass sensor 28.

[0046] (4) Turn on the power to the bridge 19, connect the bridge clamps to the seventh circuit interface 20 and the eighth circuit interface 21 respectively, and record the resistance value R displayed by the bridge. Calculate the rock resistivity under this condition, where r is the sample cross-sectional radius of 12.5 mm and L is the sample length of 50 mm. Connect the bridge clamp to the first circuit interface 22 and the second circuit interface 23 respectively, and record the resistance value R1 displayed by the bridge at 0° azimuth. Calculate the rock resistivity under this condition, where r is the radius of the metal gasket cross-section (2 mm) and L is the sample diameter (25 mm). For the 60° azimuth resistance test, connect the fourth circuit interface 25 and the sixth circuit interface 27 to the bridge 19. For the 120° azimuth resistance test, connect the third circuit interface 24 and the fifth circuit interface 26 to the bridge. Record the resistance value R2 displayed by the 60° azimuth bridge and the resistance value R3 displayed by the 120° azimuth bridge. Calculate the rock resistivity under this condition, where r is the cross-sectional radius of the metal gasket (2 mm) and L is the sample diameter (25 mm).

[0047] (5) Open the third pressure valve 11 to continue to saturate the rock with water; after saturation, close the third pressure valve 11 and record the mass m3 measured by the mass sensor 28; repeat step (4).

[0048] (6) Repeat steps (4) and (5) until a saturated plunger-shaped sample is obtained. Record the mass m measured by mass sensor 28. If the difference between the mass m and the previous saturated mass is less than 0.001 g, the rock is considered completely saturated. After each saturation, the water saturation S of the rock is recorded. w can be Calculations show that m i This represents the saturation mass each time.

[0049] (7) When the test rock is completely saturated with water, turn off the pressure pump 1, turn off the first pressure valve 2, turn off the second pressure valve 4; turn off the power supply of the bridge 19; turn off the sixth pressure valve 6, open the seventh pressure valve 8, and recover the gas; open the fifth pressure valve 18 and the fourth pressure valve 10, and recover the fluid to the second fluid container 9; open the core holder 14, take out the metal gasket 15, and take out the plunger-shaped core sample 16.

[0050] The above embodiments are only used to illustrate this application and are not intended to limit this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this application. Therefore, all equivalent technical solutions also fall within the scope of this application, and the patent protection scope of this application should be defined by the claims.

Claims

1. A device for testing anisotropic resistivity of sandstone with different water saturation, characterized in that, The device comprises a clamping assembly, a dynamic fluid circulation assembly and a resistivity testing assembly; The clamping assembly comprises a metal tank and a rock clamp, the rock clamp is arranged inside the metal tank and used for clamping and fixing the rock; The dynamic fluid circulation assembly comprises a water supply unit and a gas supply unit; the water supply unit is connected with the rock clamp and used for providing pressure when the rock is saturated with water; the gas supply unit is connected with the metal tank and used for providing longitudinal pressure of the rock; The resistivity testing assembly comprises a bridge, at least two metal pads and an insulating tube; the at least two metal pads are arranged at two ends of the rock; the insulating tube is arranged outside the rock and used for isolating the rock and the metal tank; the bridge is connected with the metal pads through wires.

2. The varying water saturation sandstone anisotropy resistivity test apparatus of claim 1, wherein, The water supply unit comprises a pressure pump, a first pressure valve, a first fluid container, a second pressure valve, a first pipeline, a second pipeline, a third pressure valve, a fourth pressure valve, a fifth pressure valve and a second fluid container; the pressure pump is connected with the first fluid container through a pipeline; the first pressure valve is arranged on the pipeline connected with the first fluid container; one end of the first fluid container is connected with one end of the rock clamp through the first pipeline; the other end of the rock clamp is connected with the second fluid container through the second pipeline; the second pressure valve and the third pressure valve are arranged on the first pipeline; the fourth pressure valve and the fifth pressure valve are arranged on the second pipeline.

3. The varying water saturation sand anisotropy resistivity test apparatus of claim 1, wherein, The gas supply unit comprises an air inlet bottle, an air outlet bottle, a third pipeline, a fourth pipeline, a sixth pressure valve and a seventh pressure valve; the air inlet bottle is communicated with the inside of the metal tank through the third pipeline; the air outlet bottle is communicated with the inside of the metal tank through the fourth pipeline; the sixth pressure valve is arranged on the third pipeline; the seventh pressure valve is arranged on the fourth pipeline.

4. The varying water saturation sand anisotropy resistivity test apparatus of claim 1, wherein, The resistivity testing assembly further comprises at least two circuit interfaces; the circuit interfaces are arranged on the sidewall of the metal tank; the bridge is arranged outside the metal tank; one end of the wire is connected with the bridge; the other end of the wire is connected with the metal pads through the circuit interfaces and penetrates the metal tank in a sealed manner.

5. The varying water saturation sand anisotropy resistivity test apparatus of claim 4, wherein, The metal tank and the wire are wrapped with an insulating material.

6. The varying water saturation sand anisotropy resistivity test apparatus of claim 1, wherein, A mass sensor is further arranged; the mass sensor is fixed on the bottom of the metal tank; a sensing end of the mass sensor is connected with the insulating tube.

7. The varying water saturation sand anisotropy resistivity test apparatus of claim 1 wherein, The insulating tube is a rubber tube.

8. The varying water saturation sand anisotropy resistivity test apparatus of claim 4, wherein, In the plurality of circuit interfaces, the bridge is connected with the metal pads through at least two circuit interfaces by wires, used for testing vertical resistivity of the rock; the bridge is connected with the rock core inside the rock through at least two circuit interfaces by wires, used for testing anisotropic resistivity of the rock; the at least two circuit interfaces for testing the anisotropic resistivity of the rock are arranged on the metal tank in a layout mode of a ring array.

9. The varying water saturation sand anisotropy resistivity test apparatus of claim 4, wherein, The circuit interfaces arranged on the metal tank in the layout mode of the ring array are six; each circuit interface is spaced by 60°.

Images