A device and method for measuring the fracture permeability of compacted rock under high temperature and high pressure conditions

Abstract

A kind of high temperature and high pressure conditions under the fracture of compacted rock permeation resistivity measuring device and method, including: core holder, fluid injection system, resistivity measurement system, pressure applying device and heating device;The device can be carried out under the condition of high temperature and high pressure simultaneously, simulate the fluid permeation process of fractured rock under different temperature and pressure conditions, wherein resistivity measurement system can measure the rock resistivity of permeation process in real time.The device has high measurement accuracy, the test result is intuitive, the device structure is simple, the sealing property, corrosion resistance and heat insulation effect are excellent, can be applied to rock fracture permeation resistivity measurement under different conditions, can quantitatively analyze the influence of temperature, pressure, fluid properties and rock fracture on rock permeability and resistivity, establish the mathematical model of the relationship between permeability and resistivity of fractured rock, can provide theoretical basis for geothermal development reservoir permeability resistivity prediction and evaluation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rock fracture seepage and resistivity test, in particular to a device and method for measuring fracture seepage resistivity of dense rock under high temperature and high pressure conditions. BACKGROUND

[0002] Dry hot rock geothermal resources (temperature greater than 180℃) is a typical clean energy, which has a wide distribution range, stable operation and huge reserves, and has a high utilization value. Developing dry hot rock geothermal resources needs to establish an enhanced geothermal system (EGS), which uses the almost constant temperature of deep underground to heat the low-temperature fluid injected into the system and then extracts the high-temperature fluid from the underground to generate electricity for extracting geothermal energy. Establishing an enhanced geothermal system requires hydraulic fracturing of the dry hot rock reservoir to create an artificial fracture network to increase the permeability of the reservoir. The permeability of the reservoir directly affects the operation efficiency and service life of the system, so how to evaluate the permeability of the modified reservoir is one of the key problems in geothermal development. Because the resistivity of rock mass is sensitive to the fluid seepage contained therein, the permeability and resistivity characteristics of rock mass are consistent, and there have been a large number of studies on the relationship between rock resistivity and oil and gas permeability in the field of oil and gas. However, the rocks in the oil and gas field are mostly high-porosity sandstones without fractures, and the temperature and pressure of the oil and gas reservoir are relatively low, while the dry hot rock is a dense granite with very small porosity in a high temperature and high pressure environment.

[0003] In the study of dry hot rock, the key factor affecting the resistivity of rock is no longer porosity, but macroscopic fractures contained in the rock mass. At present, most of the instruments for measuring the resistivity of rock seepage are instruments for measuring the resistivity of rock seepage by gas or other fluids through rock porosity, and there are few instruments for measuring the resistivity of rock seepage. Therefore, there is still a lack of a device for measuring the resistivity of dense rock seepage under high temperature and high pressure conditions to explore the relationship between the fluid permeability and resistivity characteristics of dense rock under high temperature and high pressure conditions. SUMMARY

[0004] The present application solves the problems of the prior art and provides a device and method for measuring the resistivity of dense rock seepage under high temperature and high pressure conditions.

[0005] In order to achieve the above purpose, an embodiment of the present application provides a device for measuring the resistivity of dense rock seepage under high temperature and high pressure conditions, which comprises a core holder, a fluid injection system, a resistivity measurement system, a pressure applying device and a heating device,

[0006] The core holder comprises a metal cylinder and an elastic insulation cylinder, the elastic insulation cylinder is coaxially arranged in the metal cylinder, the openings at both ends of the elastic insulation cylinder are communicated with the openings at both ends of the metal cylinder, and the elastic insulation cylinder is sealingly mounted on both ends of the metal cylinder by sealing members, a gap is arranged between the outer wall of the elastic insulation cylinder and the inner wall of the metal cylinder to form a confining pressure cavity, the confining pressure inlet of the confining pressure cavity is connected with a pressure applying device through a pipeline, a core chamber is arranged in the inner cavity of the elastic insulation cylinder and in the range of the confining pressure cavity, electrodes, insulation blocks and locking members are symmetrically arranged in the inner cavity of the elastic insulation cylinder, from inside to outside, on both sides of the core chamber, the electrodes abut against the end of the core placed in the core chamber, the locking members are fixed on both ends of the metal cylinder to seal both ends of the metal cylinder, and the locking members press the electrodes and the end of the core by pressing the insulation blocks, the middle part of the electrodes, the insulation blocks and the locking members are all provided with through holes for fluid communication, conductive pipes are sealingly mounted in the through holes, the conductive pipes comprise inlet conductive pipes and outlet conductive pipes, one end of each of the inlet conductive pipes and the outlet conductive pipes is connected with an electrode, and the other end of each of the inlet conductive pipes and the outlet conductive pipes extends out of the end of the locking member on each end of the metal cylinder to form a liquid inlet end and a liquid outlet end of the core holder, the liquid inlet end and the liquid outlet end of the core holder are connected with a liquid injection end and a collection end of a fluid injection system respectively, the detection end of the resistivity measuring system is electrically connected with the outlet conductive pipes and the inlet conductive pipes respectively, and the outer side of the metal cylinder is further wrapped with a heat preservation layer, a gap is arranged between the inner wall of the heat preservation layer and the outer wall of the metal cylinder to form a heating zone, and a heating device is mounted in the heating zone.

[0007] In the embodiment, the sealing members comprise conical rings, the outer diameter of the large end of the conical ring is matched with the inner diameter of the metal cylinder, the openings at both ends of the metal cylinder are provided with inwardly protruding stop edges, the large ends of the two conical rings abut against the stop edges at both ends of the metal cylinder, and the small ends of the two conical rings are sealingly fixed on the metal cylinder respectively.

[0008] In the embodiment, the cylinder wall of the elastic insulation cylinder is made of rubber.

[0009] In the embodiment, the electrode end surface on the side of the electrode facing the core chamber is provided with a meshed groove. The electrode end surface with the meshed groove ensures close contact with the core, so that the electrode fully contacts the core during fluid seepage.

[0010] In the embodiment, the locking member comprises a bolt and a nut, the nut is coaxially fixed on both ends of the metal cylinder, the outer diameter of the bolt is matched with the diameter of the opening at both ends of the metal cylinder, and the bolt is threadedly connected with the nut.

[0011] In the embodiment, the middle part of the bolt is provided with the through hole, and an insulating rubber sleeve is sleeved on the outer side of the conductive pipe and outside the region of the bolt.

[0012] In the embodiment, the fluid injection system comprises a fluid container, a constant speed and constant pressure pump, an air compressor, a preheater, a first temperature gauge, a back pressure valve, a back pressure pump, a back pressure control gauge and a tail liquid collection container, the outlet of the fluid container is connected with the inlet of the preheater through the constant speed and constant pressure pump, the first temperature gauge is arranged in the preheater, the outlet of the preheater is a liquid injection end of the fluid injection system, a first valve made of insulating material is arranged on the pipeline between the preheater and the constant speed and constant pressure pump, the liquid injection end is connected with the liquid inlet end of the core holder through the pipeline, a second valve made of insulating material is arranged on the pipeline between the liquid injection end and the liquid inlet end of the core holder, the constant speed and constant pressure pump is provided with high pressure air by the air compressor, and a fifth valve is arranged on the pipeline between the air compressor and the constant speed and constant pressure pump.

[0013] The inlet of the back pressure valve is a liquid outlet end of the fluid injection system, the liquid outlet end is connected with the liquid outlet end of the core holder through the pipeline, a third valve made of insulating material is arranged on the pipeline between the liquid outlet end and the liquid outlet end of the core holder, the outlet of the back pressure valve is connected with the tail liquid collection container through the back pressure pump, the control end of the back pressure control gauge is connected with the back pressure pump, and the detection end of the back pressure control gauge is connected with the inlet of the back pressure valve and the outlet end of the back pressure pump.

[0014] In the embodiment, the resistivity measurement system comprises a resistivity measuring instrument and a lead wire, and the resistivity measuring instrument is connected with the outlet conductive pipeline and the inlet conductive pipeline through the lead wire. The resistivity of the core sample is calculated by measuring the resistance value of the two ends of the core sample.

[0015] In the embodiment, the pressure applying device comprises a confining pressure pump and a confining pressure gauge, the confining pressure pump is connected with the confining pressure inlet of the confining pressure cavity through a fourth valve, and the confining pressure gauge is used for detecting the confining pressure value of the confining pressure inlet.

[0016] In the embodiment, the heating device comprises a heating control assembly, an internal temperature control assembly, a heating resistor, a temperature measuring probe and a second temperature gauge, the heating resistor is arranged in a heating area, the heating resistor is electrically connected with the heating control assembly, the temperature measuring probe is electrically connected with the internal temperature control assembly, and the internal temperature control assembly is electrically connected with the second temperature gauge.

[0017] The application also discloses a method for measuring the resistivity of fractured dense rock under high temperature and high pressure conditions.

[0018] a. Core sample preparation:

[0019] Select a complete core from the resource target area, process the core into a cylindrical rock that matches the inner diameter of the elastic insulation cylinder, and further process the core to form the required cracks for the test; measure the height a, radius b, rock fracture surface length L, width D, and fluid viscosity μ of the cylindrical rock, and configure the permeation fluid according to the resistivity of the groundwater or hydraulic fracturing fluid of the resource target area thermal reservoir;

[0020] b. Core sample loading and sealing:

[0021] Place the processed rock into the core chamber, place the electrodes and insulation plate blocks at both ends of the rock, and tightly press the electrodes against the end of the rock through the locking piece;

[0022] c. Test temperature loading:

[0023] Heat the metal cylinder using the heating control assembly and heating resistance, and maintain heating after the temperature display of the temperature probe reaches the set temperature T; control the temperature at the set temperature for more than 1 hour;

[0024] d. Test confining pressure loading:

[0025] Open the fourth valve, control the confining pressure pump to inject high-temperature hydraulic oil into the confining pressure cavity through the confining pressure inlet, and when the confining pressure value on the confining pressure table stabilizes at the test set value P, close the fourth valve to maintain the confining pressure;

[0026] e. Permeation fluid loading and permeation data collection:

[0027] Open the third valve, set the pressure value of the back pressure valve through the back pressure pump, set the outlet pressure P2 of the permeation fluid, set the temperature of the preheater, open the air compressor, constant speed constant pressure pump and fifth valve, the constant speed constant pressure pump passes the permeation fluid in the fluid container into the preheater, opens the second valve to inject the permeation fluid heated to the specified temperature into the core holder, and the tail liquid collection container collects the fluid after the rock high temperature and high pressure seepage, and the constant speed constant pressure pump monitors and collects the injection pressure P1 and fluid flow Q of the injected fluid in real time during the test;

[0028] f. Resistivity data collection:

[0029] Turn on the switch of the resistivity measuring instrument to collect the resistance R of the rock permeation process, and calculate the resistivity p of the sample according to the resistivity calculation formula:

[0030]

[0031] g. Test end:

[0032] Turn off the heating power switch, remove the confining pressure and back pressure, and take out the rock after the device cools down naturally.

[0033] In the embodiment, the steps a-g are repeated under different temperatures, different confining pressures and different fluids to obtain the rock fracture permeability K and the resistivity p under different conditions, and a mathematical model of the relationship between the rock fracture permeability and the resistivity is established.

[0034]

[0035]

[0036] wherein, b e is the equivalent hydraulic opening, K is the permeability.

[0037] The above scheme of the present application has the following beneficial effects:

[0038] 1. The core holder of the device is provided with a special structure, the inner layer of the core holder is an elastic insulating cylinder, and the electrode is sealed and clamped with the end of the rock through a three-section structure of the electrode, the insulating block and the locking piece. The metal pipes are connected through valves made of insulating materials. The whole rock and the seepage fluid in the rock are in an absolutely insulating environment. The rock and the resistivity measurement system form a closed circuit. The contact between the conductive pipe and the metal cylinder is prevented to avoid measurement error. The accuracy of the resistivity measurement result is ensured.

[0039] 2. The core holder of the device further comprises a metal cylinder, the metal cylinder is provided with a heating device outside for providing a high temperature environment for the rock. The metal cylinder and the elastic insulating cylinder form a confining pressure cavity. The pressure in the confining pressure cavity is controlled through a pressure applying device to simulate the state of the rock under high temperature and high pressure in the deep formation. The resistivity measured by the device can accurately reflect the actual state of the rock in the deep formation. The accuracy of the simulation environment is ensured.

[0040] 3. The fluid injection system of the device can control the state of the injected fluid. Through the constant speed and constant pressure pump at the inlet end and the back pressure valve at the outlet end, the permeation pressure of the injected fluid can be set. The temperature of the injected fluid is controlled through the preheater. The temperature and pressure of the injected fluid are controlled to control the phase state of the injected fluid.

[0041] In summary, this invention enables experiments to be conducted under simultaneous high temperature and high pressure conditions, realistically and accurately simulating the temperature and pressure of rocks in the formation environment, and simulating the fluid seepage process of fractured rocks under different temperature and pressure conditions. The resistivity measurement system can measure the rock resistivity in real time during the seepage process, accurately measuring resistivity and thus enabling a more comprehensive study and analysis of the factors influencing rock resistivity. This device can collect data such as fluid inlet pressure, outlet pressure, temperature, confining pressure, and resistivity during the fluid seepage process in rock fractures. By calculating the permeability of fractured rocks under different temperature and confining pressure conditions and the variation law of rock resistivity caused by fluid seepage, a quantitative relationship between fluid permeability and resistivity in fractured rocks under multiple factors can be obtained, and a mathematical model of permeability and resistivity in fractured rocks can be established. This allows for indoor experimental research on the permeability and resistivity variation law of fluid seepage in rock fractures, providing a theoretical basis for resistivity evaluation methods of hot dry rock reservoirs, and offering important theoretical and scientific value for realizing the economical and efficient commercial exploitation of geothermal resources. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the present invention;

[0043] Figure 2 This is a schematic diagram of the core holder of the present invention;

[0044] Figure 3 This is a schematic diagram of the left electrode facet of the present invention.

[0045] Figure 4 This invention relates to the resistivity and permeability of distilled water seepage in fractured granite under different confining pressures at 150°C.

[0046] In the drawings, 101, core chamber; 102, left electrode; 103, right electrode; 104, left insulating pressing block; 105, right insulating pressing block; 106, left conical ring; 107, right conical ring; 108, elastic insulating cylinder; 109, metal cylinder; 110, confining pressure cavity; 111, confining pressure inlet; 112, left nut; 113, right nut; 114, left bolt; 115, right bolt; 116, outlet conductive pipeline; 117, inlet conductive pipeline; 118, insulating rubber sleeve; 201, fluid container; 202, constant-speed constant-pressure pump; 203, air compressor; 204, preheater; 205, first temperature gauge; 206, back pressure valve; 207, back pressure pump; 208, back pressure control gauge; 209, tail liquid collection container; 301, resistivity measuring instrument; 302, wire; 401, confining pressure pump; 402, confining pressure gauge; 501, warming control assembly; 502, internal temperature control assembly; 503, heating resistor; 504, temperature measuring probe; 505, heat preservation layer; 506, second temperature gauge; V1, first valve; V2, second valve; V3, third valve; V4, fourth valve; V5, fifth valve. DETAILED DESCRIPTION

[0047] In order to make the technical problems, technical solutions and advantages of the present application clearer, the following will be described in detail in combination with the drawings and specific embodiments.

[0048] The present application provides a dense rock fracture seepage resistivity measuring device under high temperature and high pressure, aiming at the fact that there are few rock seepage resistivity measuring devices under high temperature and high pressure, and most of the existing test devices can only measure the resistivity of oil and gas seepage of complete high-porosity rock, and the fluid seepage resistivity measurement of dense rock with macroscopic cracks is not considered.

[0049] As shown in Figure 1 The embodiment of the present application provides a dense rock fracture seepage resistivity measuring device under high temperature and high pressure, which comprises a core holder, a fluid injection system, a resistivity measuring system, a pressure applying device and a heating device. The core holder is provided with a core chamber 101, and the two ends of the core chamber 101 are respectively provided with a left electrode 102 and a right electrode 103. The left electrode 102 and the right electrode 103 are in close contact with the core. The outer sides of the left electrode 102 and the right electrode 103 are provided with a left insulating pressing block 104 and a right insulating pressing block 105. The left insulating pressing block 104 and the right insulating pressing block 105 are externally sleeved with a left conical ring 106 and a right conical ring 107. The front ends of the left conical ring 106 and the right conical ring 107 are conical and are sleeved with an elastic insulating cylinder 108. The elastic insulating cylinder 108 is internally used for loading the rock used for experiment. The elastic insulating cylinder 108 tightly wraps the outer sides of the core chamber 101, the left electrode 102 and the right electrode 103,

[0050] The elastic insulation cylinder 108 is externally provided with a metal cylinder 109, in the embodiment, the metal cylinder 109 ensures that the pressure resistance is greater than 50 MPa and the temperature resistance is greater than 250℃, the metal cylinder 109 and the elastic insulation cylinder 108 form a confining pressure cavity 110, the confining pressure cavity 110 is connected with the pressure applying device through a confining pressure inlet 111;

[0051] The left and right insulation pressing blocks 104 and 105 are externally provided with left and right nuts 112 and 113, the left and right nuts 112 and 113 are fixed through left and right bolts 114 and 115, so as to maintain the sealing property of the core chamber 101;

[0052] The bolts, insulation pressing blocks and electrodes are provided with an outlet conductive pipeline 116 and an inlet conductive pipeline 117, the outlet conductive pipeline 116 and the inlet conductive pipeline 117 are externally provided with an insulation rubber sleeve 118, so as to connect the core chamber 101 with the outside world;

[0053] The fluid injection system includes a fluid container 201, a constant-speed constant-pressure pump 202, an air compressor 203, a preheater 204, a first temperature meter 205, a back pressure valve 206, a back pressure pump 207, a back pressure control table 208 and a tail liquid collection container 209, the fluid injection system is used for controlling the temperature, flow and osmotic pressure of the injected fluid;

[0054] The resistivity measuring system includes a resistivity measuring instrument 301 and a wire 302, the resistivity measuring instrument 301 is connected with the outlet conductive pipeline 116 and the inlet conductive pipeline 117 through the wire 302, the resistivity of the core sample is calculated by measuring the resistance value between the two ends of the core sample;

[0055] The pressure applying device includes a confining pressure pump 401 and a confining pressure table 402, the pressure applying device is used for providing and controlling the confining pressure of the core;

[0056] The heating device includes a heating control assembly 501, an internal temperature control assembly 502, a heating resistance 503, a temperature measuring probe 504, a heat preservation layer 505 and a second temperature meter 506, the heating device is used for providing a high-temperature environment for the core.

[0057] The core holder forms a sealed space through the elastic insulation cylinder 108, the left electrode 102, the right electrode 103, the left insulation block 104, the right insulation block 105, the left tapered ring 106, the right tapered ring 107, the left nut 112, the right nut 113, the left bolt 114 and the right bolt 115, and the rock used for experiments is placed in the sealed space. The elastic insulation cylinder is made of high-temperature and high-pressure resistant material, is not easy to be damaged in a high-temperature and high-pressure environment, can avoid corrosion of experimental fluid, and can be used multiple times in experiments. The left electrode 102 and the right electrode 103 are meshed groove end faces, which are tightly combined with the end face of the core, thereby reducing the error of resistivity measurement. The left insulation block 104 and the right insulation block 105 are made of high-temperature and high-pressure resistant insulation materials. In this embodiment, the high-temperature and high-pressure resistant insulation materials can be ceramic materials such as alumina ceramic or silicon nitride ceramic or polytetrafluoroethylene. The left insulation block 104 and the right insulation block 105 and the elastic insulation cylinder 108 constitute an insulated sealed space, so that the current can only flow from the inlet conductive pipeline 117 to the outlet conductive pipeline 116. The metal cylinder 109 is sleeved outside the elastic insulation cylinder 108, and the confining pressure cavity 110 exists between the metal cylinder 109 and the elastic insulation cylinder 108. When the confining pressure cavity 110 is filled with confining pressure oil, the rock in the elastic insulation cylinder 108 will be subjected to confining pressure. The fluid injection system can provide the core holder with output pressure, flow rate and temperature stable permeation fluid. The resistivity measurement system can measure the resistance value of the core between the inlet conductive pipeline 117 and the outlet conductive pipeline 116 of the core holder in real time. The pressure applying device is used to apply pressure to the confining pressure cavity 110 of the device and control it. The heating device can provide a high-temperature environment for the core holder and control the temperature.

[0058] The fluid injection system is connected with the inlet and outlet pipelines through heat-insulated stainless steel high-pressure pipelines.

[0059] The fluid container 201, the constant-speed constant-pressure pump 202 and the preheater 204 are sequentially connected through pipelines, and the outlet of the preheater is connected with the inlet conductive pipeline 117.

[0060] The constant-speed constant-pressure pump 202 is connected with the air compressor 203, and the air compressor 203 provides high-pressure air for the constant-speed constant-pressure pump 202.

[0061] The first valve V1 is used for controlling the fluid sent into the preheater 204 by the constant speed and pressure pump 202, so as to ensure that the fluid in the preheater 204 can be heated sufficiently, and the second valve V2 is used for controlling the fluid in the preheater 204 to enter the inlet conductive pipeline 117, and the second valve V2 is made of electrically insulating plastic, so that the electric circuit between the inlet conductive pipeline 117 and the preheater 204 is broken, and the error of the resistivity measurement is reduced.

[0062] The outlet conductive pipeline 116, the back pressure valve 206, the back pressure pump 207 and the tail liquid collecting container 209 are connected by pipelines, the third valve V3 is arranged between the outlet pipeline 116 and the back pressure valve 206, the third valve V3 is made of electrically insulating material, so as to reduce the error of the resistivity measurement. The back pressure valve 206 and the back pressure pump 207 can control the outlet pressure of the experimental fluid, so as to lift the system pressure, and the pressure condition of the fluid in the ground can be simulated truly.

[0063] The fluid injection system is used for storing the fluid required by the experimental seepage process by the fluid container 201, the constant speed and pressure pump 202 is used for controlling the injection pressure and flow of the injected fluid, and the fluid is injected into the preheater 204, heated to a specified temperature, and then enters the inlet conductive channel 117, the fluid enters the outlet conductive channel 116 after seepage in the core chamber 101, and then enters the back pressure valve 206 through the third valve V3, and finally flows into the tail liquid collecting container 209 to complete the experiment.

[0064] The resistivity measuring instrument 301 is connected with the inlet conductive pipeline 117 and the outlet conductive pipeline 116 through the wire 302, the insulating rubber sleeve 118 is wrapped around the left bolt 114 and the right bolt 115, and the resistivity measuring instrument 301, the wire 302, the inlet conductive pipeline 117, the right electrode 103, the core, the left electrode 102 and the outlet conductive pipeline 116 form a closed circuit.

[0065] The resistivity measuring instrument 301 is connected to both ends of the rock through the conductive and conductive pipelines, and can accurately measure the resistivity of both ends of the rock in real time.

[0066] The confining pressure pump 401 is connected to the confining pressure cavity 110 through the fourth valve V4, the confining pressure inlet 111 is arranged on the metal cylinder 109, and the confining pressure meter 402 reads the confining pressure value through the confining pressure inlet 111.

[0067] The fourth valve V4 is a confining valve, the confining pump 401 is controlled by the fourth valve V4, the confining pump 401 can apply pressure to the confining cavity 110 and provide confining pressure for the rock, and the confining table 402 can monitor the confining pressure in real time.

[0068] The heating resistor 503 is arranged outside the metal cylinder 109, the heat preservation layer 505 is arranged outside the heating resistor 503 and the metal cylinder 109, a sealed through port is arranged on the metal cylinder 109 and is provided with the temperature measuring probe 504, the heating control assembly 501 is electrically connected with the heating resistor 503, and the internal temperature control assembly 502 is electrically connected with the temperature measuring probe 504.

[0069] The heating control assembly 501 can control the on-off of the heating resistor 503 to heat the core holder, the internal temperature control assembly 502 can monitor the temperature in real time through the temperature measuring probe 504, and the heat preservation layer 505 can keep the temperature in the core chamber at a high temperature.

[0070] The high-temperature and high-pressure dense rock fracture seepage resistivity measuring device has the following specific operation process:

[0071] 1. Core sample preparation: complete cores are selected from a resource target area, the cores are processed into cylindrical sample rocks in a laboratory, and a wire cutting instrument or a Brazil splitting device is used to process the sample into a sample containing various types of cracks.

[0072] 2. Core sample loading and sealing: the processed rock is placed in the core chamber 101, the left electrode 102, the right electrode 103, the left insulation plate pressing block 104 and the right insulation pressing block 105 are arranged at both ends of the rock, and then the left nut 112 and the left bolt 114, the right nut 113 and the right bolt 115 are tightened to fix and seal the core holder.

[0073] 3. Test temperature loading: the power switch is turned on, the metal cylinder 109 is heated by the heating control assembly 501 and the heating resistor 503, and the heat is indirectly conducted to the rock in the core chamber 101, the heating process needs to last for a period of time, the temperature of the temperature measuring probe is kept at the set temperature after the temperature display reaches the set temperature, the temperature is controlled at the set temperature for more than one hour, so that the temperature of the rock inside is also reached. The temperature data T is read by the temperature display of the temperature measuring probe.

[0074] 4. Test confining pressure loading: open the fourth valve V4, use the confining pressure pump 401 to inject high-temperature resistant hydraulic oil into the confining pressure cavity 110 through the confining pressure inlet 111, and the hydraulic oil will fluctuate the confining pressure after being heated. Fine adjustment is needed, and the fourth valve V4 is closed when the confining pressure value on the confining pressure table 402 is stable at the test set value. The confining pressure data P is read by the confining pressure table.

[0075] 5. Permeation fluid loading and permeation data collection: open the third valve V3, use the back pressure pump 207 to set the pressure value of the back pressure valve 206, and set the outlet pressure of the permeation fluid. Set the temperature of the preheater 204, open the air compressor 203 and the fifth valve V5, use the constant speed and constant pressure pump 202 to pass the permeation fluid in the fluid container 201 into the preheater 204, open the second valve V2 to inject the permeation fluid heated to the specified temperature into the core holder for testing, and the tail liquid collection container 209 collects the fluid after high-temperature and high-pressure seepage through the rock. The constant speed and constant pressure pump 202 can monitor and collect the injection pressure and flow rate of the injected fluid in real time during the test. The fluid inlet pressure P1 and the fluid flow rate Q are read by the constant speed and constant pressure pump, and the fluid outlet pressure P2 is read by the back pressure table.

[0076] 6. Resistivity data collection: open the resistivity meter switch to monitor and collect the resistivity of the rock during the permeation process, collect the rock resistance R, and calculate the rock resistivity p.

[0077] 7. Test end: turn off the heating power switch, unload the confining pressure and back pressure, and take out the test sample after the device is naturally cooled.

[0078] 8. Post-processing of collected data: the collected data include temperature T, confining pressure P, fluid inlet pressure P1, fluid outlet pressure P2, fluid flow rate q, and rock resistance R. According to the above measurement data and the height a, radius b, rock fracture surface length L, width D, and fluid viscosity μ of the core sample, the resistivity p of the sample can be calculated according to the resistivity calculation formula.

[0079]

[0080] 9. Repeat the above steps to perform rock fracture seepage tests under different temperatures, different confining pressures, and different fluid actions, obtain rock fracture permeability and resistivity data under different conditions, compare and analyze the influence of temperature, confining pressure, and fluid characteristics on the rock fracture permeation characteristics and resistivity characteristics, and establish a mathematical model of the relationship between rock fracture permeability and resistivity.

[0081]

[0082]

[0083] Wherein, according to Darcy's law and cubic law, the equivalent hydraulic opening degree b of rock fissure can be calculated e Permeability K, such as Figure 4 As shown in the figure, the relationship between the resistivity and the permeability of the fissured granite under the condition of 150 DEG C and different confining pressures is shown.

[0084] The above is the preferred embodiment of the present application, it should be noted that for those skilled in the art, without departing from the principles of the present application, can also make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A device for measuring the resistivity of seepage through fractures in dense rock under high temperature and high pressure conditions, characterized in that, It includes a core holder, a fluid injection system, a resistivity measurement system, a pressure application device, and a heating device; The core holder includes a metal cylinder (109) and an elastic insulating cylinder (108). The elastic insulating cylinder (108) is coaxially arranged inside the metal cylinder (109). The openings at both ends of the elastic insulating cylinder (108) are connected to the openings at both ends of the metal cylinder (109). The two ends of the elastic insulating cylinder (108) are sealed and installed on the two ends of the metal cylinder (109) by sealing elements. A gap is provided between the outer wall of the elastic insulating cylinder (108) and the inner wall of the metal cylinder (109) to form a confining pressure cavity (110). The confining pressure inlet (111) of the confining pressure cavity (110) is connected to a pressure application device through a pipeline. A core chamber (101) is provided in the inner cavity of the elastic insulating cylinder (108) within the range of the confining pressure cavity (110). Electrodes, insulating blocks, and locking devices are symmetrically arranged from the inside to the outside on both sides of the core chamber (101) in the inner cavity of the elastic insulating cylinder (108). The electrodes abut against the ends of the rocks placed in the core chamber (101). The locking devices are fixed to both ends of the metal cylinder (109) to seal both ends of the metal cylinder (109). The locking devices press the electrodes against the ends of the rocks by pressing the insulating blocks. The electrodes, insulating blocks, and locking devices are all provided with interconnected supply channels in the middle. A through hole for fluid inflow is provided, and a conductive pipe is sealed and installed inside the through hole. The conductive pipe includes an inlet conductive pipe (117) and an outlet conductive pipe (116). One end of the inlet conductive pipe (117) and the outlet conductive pipe (116) are respectively connected to two electrodes, and the other end extends from the ends of the locking parts at both ends of the metal cylinder (109) to form the inlet and outlet ends of the core holder. The inlet and outlet ends of the core holder are respectively connected to the injection end and the collection end of the fluid injection system. The detection end of the resistivity measurement system is electrically connected to the outlet conductive pipe (116) and the inlet conductive pipe (117) respectively. The outside of the metal cylinder (109) is also wrapped with a heat insulation layer (505). A gap is provided between the inner wall of the heat insulation layer (505) and the outer wall of the metal cylinder (109) to form a heating zone. A heating device is installed in the heating zone. The electrode end face facing the core chamber (101) is provided with a mesh groove; the resistivity measurement system includes a resistivity measuring instrument (301) and a wire (302), and the resistivity measuring instrument (301) is connected to the outlet conductive pipe (116) and the inlet conductive pipe (117) respectively through the wire (302).

2. The device for measuring the resistivity of seepage through fractures in dense rock under high temperature and high pressure conditions according to claim 1, characterized in that, The sealing element includes a conical ring, the outer diameter of the large end of the conical ring is matched with the inner diameter of the metal cylinder (109), the two ends of the metal cylinder (109) are provided with inwardly protruding flanges, the large ends of the two conical rings abut against the flanges at both ends of the metal cylinder (109), and the two ends of the elastic insulating cylinder (108) are respectively sealed and fixed on the small ends of the conical rings.

3. The device for measuring the resistivity of seepage through fractures in dense rock under high temperature and high pressure conditions according to claim 1, characterized in that, The wall of the elastic insulating cylinder (108) is made of rubber.

4. The device for measuring the resistivity of seepage through fractures in dense rock under high temperature and high pressure conditions according to claim 1, characterized in that, The locking component includes a bolt and a nut. The nut is coaxially fixed at both ends of the metal cylinder (109). The outer diameter of the bolt matches the opening diameter at both ends of the metal cylinder (109). The bolt is threaded onto the nut.

5. The device for measuring the resistivity of seepage through fractures in dense rock under high temperature and high pressure conditions according to claim 4, characterized in that, The bolt has a through hole in the middle, and the conductive pipe is covered with an insulating sleeve (118) on the outside of the area where the bolt is located.

6. The resistivity measuring device for seepage flow in dense rock fractures under high temperature and high pressure conditions according to any one of claims 1 to 5, characterized in that, The fluid injection system includes a fluid container (201), a constant speed and constant pressure pump (202), an air compressor (203), a preheater (204), a first temperature gauge (205), a back pressure valve (206), a back pressure pump (207), a back pressure control gauge (208), and a tail liquid collection container (209). The outlet of the fluid container (201) is connected to the inlet of the preheater (204) through the constant speed and constant pressure pump (202). The preheater (204) is equipped with a first temperature gauge (205), and the outlet of the preheater (204) is... The injection end of the fluid injection system is provided with a first valve (V1) on the pipeline between the preheater (204) and the constant speed and pressure pump (202). The injection end is connected to the inlet end of the core holder through a pipeline. A second valve (V2) made of insulating material is installed on the pipeline between the injection end and the inlet end of the core holder. The constant speed and pressure pump (202) provides high-pressure air through an air compressor (203). A fifth valve (V5) is provided on the pipeline between the air compressor (203) and the constant speed and pressure pump (202). The inlet of the back pressure valve (206) is the outlet of the fluid injection system. The outlet is connected to the outlet of the core holder through a pipeline. A third valve (V3) made of insulating material is installed on the pipeline between the outlet and the outlet of the core holder. The outlet of the back pressure valve (206) is connected to the tail liquid collection container (209) through the back pressure pump (207). The detection end of the back pressure control gauge (208) is connected to the inlet of the back pressure valve (206) and the outlet of the back pressure pump (207) respectively. The control end of the back pressure control gauge (208) is connected to the back pressure pump (207).

7. The resistivity measuring device for seepage flow in dense rock fractures under high temperature and high pressure conditions according to claim 6, characterized in that, The pressure application device includes a confining pressure pump (401) and a confining pressure gauge (402). The confining pressure pump (401) is connected to the confining pressure inlet (111) of the confining pressure cavity (110) through a fourth valve (V4). The confining pressure gauge (402) is used to detect the confining pressure value at the confining pressure inlet (111).

8. The device for measuring the resistivity of seepage through fractures in dense rock under high temperature and high pressure conditions according to claim 7, characterized in that, The heating device includes a heating control component (501), an internal temperature control component (502), a heating resistor (503), a temperature probe (504), and a second temperature meter (506). The heating resistor (503) is arranged in the heating zone and is electrically connected to the heating control component (501). The temperature probe (504) is electrically connected to the internal temperature control component (502), and the internal temperature control component (502) is electrically connected to the second temperature meter (506).

9. A method for measuring the resistivity of seepage flow in fractured dense rock under high temperature and high pressure conditions, utilizing the resistivity measuring device for seepage flow in fractured dense rock under high temperature and high pressure conditions as described in claim 8, characterized in that... Includes the following steps: a. Core sample preparation: Complete rock cores are selected from the resource target area and processed into cylindrical rocks that match the inner diameter of the elastic insulating cylinder (108). The rock cores are further processed to form the cracks required for the test. The height a, radius b, rock fracture surface length L, width D and fluid viscosity μ of the cylindrical rock are measured. The permeation fluid is configured according to the resistivity of groundwater or hydraulic fracturing fluid in the thermal reservoir of the resource target area. b. Core sample loading and sealing: The processed rock is placed in the core chamber (101), the electrode and the insulating plate block are placed at both ends of the rock, and the electrode is pressed tightly at the end of the rock by the locking device; c. Test temperature loading: The metal cylinder (109) is heated using the heating control component (501) and the heating resistor (503). After the temperature probe (504) shows that the temperature has reached the set temperature T, the heating is maintained and the temperature is controlled at the set temperature for more than 1 hour. d. Confining pressure loading during testing: Open the fourth valve (V4) and control the confining pressure pump (401) to inject high-temperature hydraulic oil into the confining pressure cavity (110) through the confining pressure inlet (111). When the confining pressure value on the confining pressure gauge (402) stabilizes at the test set value P, close the fourth valve (V4) to maintain the confining pressure. e. Permeation fluid loading and permeation data acquisition: Open the third valve (V3), set the pressure value of the back pressure valve (206) through the back pressure pump (207), set the outlet pressure P2 of the permeate fluid, set the temperature of the preheater (204), turn on the air compressor (203), the constant speed and constant pressure pump (202) and the fifth valve (V5), the constant speed and constant pressure pump (202) introduces the permeate fluid in the fluid container (201) into the preheater (204), open the second valve (V2) to inject the permeate fluid heated to the specified temperature into the core holder, and at the same time the tail liquid collection container (209) collects the fluid after it has undergone high temperature and high pressure seepage through the rock. During the test, the constant speed and constant pressure pump (202) monitors and collects the injection pressure P1 and the fluid flow rate Q of the injected fluid in real time. f. Resistivity data acquisition: Turn on the resistivity meter (301) to collect the resistance R during the rock permeation process. The resistivity ρ of the sample can be calculated according to the resistivity calculation formula: ； g. End of experiment: Turn off the heating power switch, remove the confining pressure and back pressure, and remove the rock after the device has cooled down naturally.

10. The method for measuring the resistivity of seepage flow in dense rock fractures under high temperature and high pressure conditions according to claim 9, characterized in that, By repeating the above steps ag under different temperatures, confining pressures, and fluid conditions, the rock fracture permeability K and resistivity ρ under different conditions are obtained, and a mathematical model of the relationship between rock fracture permeability and resistivity is established: ； ； Among them, b e Where K is the equivalent hydraulic aperture and K is the permeability.

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