A method and device for measuring thermal expansion coefficient of shale under in-situ conversion conditions

Abstract

The present invention provides a method and device for measuring the thermal expansion coefficient of shale under in-situ conversion conditions. The method comprises: processing a shale sample into a rock sample and measuring the size of the rock sample; fixing an optical detector and calibrating an experimental chamber before loading the sample to obtain experimental chamber calibration data; using the optical detector to measure initial projection data of the experimental chamber in the three directions of length, width, and height at room temperature and pressure; applying triaxial pressure to the rock sample using a triaxial pressurizing device; heating the rock sample to an equilibrium temperature point using a constant temperature heating device to determine the temperature difference between the equilibrium temperature point and the normal temperature point; using the optical detector to measure projection data at the equilibrium temperature point; adjusting the fluid pressure in the experimental chamber to the actual fluid pressure of the in-situ conversion using a pressure control system; and calculating the thermal expansion coefficient of the rock sample in the three directions of length, width, and height based on the measured data. The present invention can simultaneously measure the thermal expansion coefficient of shale in three directions under true triaxial pressure, different temperatures, and flow pressures, and with high measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of petroleum exploration, and in particular to a method and device for measuring the thermal expansion coefficient of shale under in-situ conversion conditions. Background Art

[0002] In recent years, shale oil and gas has become a hot topic in unconventional oil and gas exploration and research. In-situ thermal reforming is an effective approach to shale oil recovery. Effectively evaluating the thermal expansion coefficient of shale during in-situ heating and reforming is crucial for protecting heating cables and geological integrity. However, currently, there is a lack of both directly applicable instrumentation and methods for testing the thermal expansion of shale under in-situ temperature and pressure conditions. Research on thermal expansion instruments from companies such as NETZSCH International revealed that currently available equipment either cannot withstand triaxial pressure or high temperatures, or can withstand high temperatures and pressures but not large specimens for multi-directional testing.

[0003] Currently, the main thermal expansion testing methods include strain gauge method, quartz dilatometer method, two-wire method, and optical interferometry method. The strain gauge method has certain limitations under conditions of non-uniform material deformation due to its sensitivity coefficient varying with temperature. The two-wire method, while simple and easy to use, has certain limitations and is mainly applicable to materials such as glass and containers. The optical interferometry method has high requirements for the stability of the optical system and the laser frequency, and the operation is relatively cumbersome. The interferometry method has the highest accuracy in measuring the linear expansion coefficient of materials, but its accuracy is easily affected by factors such as temperature, pressure, and humidity. Therefore, it has strict requirements on the measurement environment and specimen size, and the instrument is expensive and complicated to operate. It is necessary to develop a thermal dilatometer that is simple to operate, meets the conditions and requirements of in-situ geological transformation, can test large samples in multiple directions, and has high accuracy. Summary of the Invention

[0004] The embodiment of the present invention provides a method and device for measuring the thermal expansion coefficient of shale under in-situ conversion conditions, which is used to obtain the true triaxial pressure of shale and simultaneously measure the thermal expansion coefficient of shale in three directions under different temperature and flow pressure conditions with high measurement accuracy.

[0005] In a first aspect, the present application provides a method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions, comprising:

[0006] Processing the shale sample into a cubic rock sample and measuring the size of the rock sample;

[0007] After fixing the optical detector and calibrating the experimental chamber, the sample is loaded to obtain experimental chamber calibration data; the experimental chamber calibration data includes the plane projection distance between the three laser light sources of the optical detector and the corresponding optical positioning holes on the experimental chamber, and the distance between each optical positioning hole and the corresponding projection plate;

[0008] The optical detector is used to measure the initial projection data of the experimental chamber in the three directions of length, width and height at normal temperature and pressure; the initial projection data includes the initial distance between the laser point on the projection board and the laser vertical injection point O in the three directions of length, width and height of the rock sample after the laser passes through the optical positioning hole at normal temperature and pressure;

[0009] Applying triaxial pressure equivalent to the stress under geological conditions to the rock sample by a triaxial pressurizing device;

[0010] According to the set heating conditions and each equilibrium temperature point, the rock sample is heated to the equilibrium temperature point by a constant temperature heating device and the temperature balance is maintained stable, and the temperature difference between the equilibrium temperature point and the normal temperature point is determined;

[0011] The optical detector is used to measure the corresponding projection data of the experimental chamber in the three directions of length, width and height at each equilibrium temperature point to obtain the projection data at the equilibrium temperature point; the projection data at the equilibrium temperature point includes the offset distance of the rock sample on the projection plate after the laser passes through the corresponding optical positioning hole in the three directions of length, width and height;

[0012] Real-time monitoring of the fluid pressure at all temperatures in the experimental chamber, and adjusting the fluid pressure in the experimental chamber to the actual fluid pressure in situ through the pressure control system;

[0013] According to the size of the rock sample, the calibration data of the experimental chamber, the initial projection data of the experimental chamber, and the projection data and corresponding temperature data of each equilibrium temperature point, the thermal expansion coefficient of the rock sample in the three directions of length, width and height at each equilibrium temperature point under the stress under geological conditions and the actual geological fluid pressure is calculated.

[0014] In one or some optional implementations of the embodiments of the present application, based on the size of the rock sample, the calibration data of the experimental chamber, the initial projection data of the experimental chamber, and the projection data and corresponding temperature data of each equilibrium temperature point, the thermal expansion coefficient of the rock sample in the three directions of length, width and height at each equilibrium temperature point under the stress under geological conditions and the actual geological fluid pressure is calculated by the following formula 1:

[0015] The thermal expansion coefficients in three directions can be calculated based on the above parameters. The calculation formula is:

[0016]

[0017] Wherein, a is the length of the rock sample;

[0018] b is the width of the rock sample;

[0019] c is the height of the rock sample;

[0020] αa is the thermal expansion coefficient of the rock sample in the long direction at Ti temperature;

[0021] α b is the thermal expansion coefficient of the rock sample in the wide direction at Ti temperature;

[0022] α c is the thermal expansion coefficient of the rock sample in the high direction at Ti temperature;

[0023] Sa is the plane projection distance between the laser light source and the optical positioning hole in the long direction;

[0024] Sb is the plane projection distance between the laser light source and the optical positioning hole in the width direction;

[0025] Sc is the plane projection distance between the laser light source and the optical positioning hole in the high direction;

[0026] Da is the distance between the optical positioning hole and the projection plate in the long direction;

[0027] Db is the distance between the optical positioning hole and the projection plate in the width direction;

[0028] Dc is the distance between the optical positioning hole and the projection plate in the height direction;

[0029] L 0a The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the long direction;

[0030] L 0b The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the width direction;

[0031] L 0c The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the high direction;

[0032] ΔTi is the temperature difference between the equilibrium temperature point (Ti) and the normal temperature point (To);

[0033] ΔL Tia The offset distance of the laser on the projection board after passing through the optical positioning hole in the long direction;

[0034] ΔL Tib The width direction is the offset distance of the laser on the projection board after passing through the optical positioning hole;

[0035] ΔL Tic It is the offset distance of the laser on the projection board after passing through the optical positioning hole in the high direction.

[0036] In one or some optional implementations of the embodiment of the present application, processing the shale sample into a cubic rock sample and measuring the size of the rock sample includes:

[0037] The specific geological position of the shale sample underground is calibrated, the shale sample is prepared into a cubic rock sample using a waterless wire cutting technology, and the size of the rock sample is measured using a micrometer.

[0038] In one or some optional implementations of the embodiments of the present application, before applying triaxial pressure equivalent to the stress under geological conditions to the rock sample through a triaxial pressurizing device, the three cylinders of the triaxial pressurizing device are respectively fixed to the top surface and two adjacent side surfaces of the experimental chamber.

[0039] In one or some optional implementations of the embodiment of the present application, the optical detector is used to measure the corresponding projection data of the experimental chamber in the three directions of length, width and height at each equilibrium temperature point to obtain the projection data at the equilibrium temperature point, including:

[0040] The optical detector is used to measure the corresponding projection data of the experimental chamber in the three directions of length, width and height at the equilibrium temperature point; the projection data includes the expansion distance of the laser point on the projection board from the laser vertical injection point O in the three directions of length, width and height of the rock sample at the equilibrium temperature point after the laser passes through the optical positioning hole;

[0041] The expansion distance of the laser point on the projection board from the laser vertical injection point O after the laser passes through the optical positioning hole in the length, width and height directions of the rock sample is subtracted from the corresponding initial distance to obtain the offset distance of the rock sample on the projection board after the laser passes through the corresponding optical positioning hole in the length, width and height directions.

[0042] In one or some optional implementations of the embodiments of the present application, heating the rock sample to the equilibrium temperature point by a constant temperature heating device according to the set heating conditions and each equilibrium temperature point and maintaining the temperature equilibrium and stability of the temperature point, and determining the temperature difference between the equilibrium temperature point and the normal temperature point, includes:

[0043] According to the set heating conditions and each equilibrium temperature point, the rock sample is heated by the heating tube of the constant temperature heating device until the temperature reaches the equilibrium temperature point, and the temperature of the equilibrium temperature point is kept stable within a preset time;

[0044] Calculate the temperature difference between each equilibrium temperature point and the normal temperature point.

[0045] In one or some optional embodiments of the present application, the real-time monitoring of the fluid pressure at all temperatures in the experimental chamber and adjusting the fluid pressure in the chamber to in-situ conversion to the actual fluid pressure through the pressure control system include:

[0046] The fluid pressure at all temperatures in the experimental chamber is monitored in real time. When the pressure in the experimental chamber is greater than the actual fluid pressure converted in situ, the fluid is discharged through the pressure control system to reduce the fluid pressure in the experimental chamber until the actual fluid pressure converted in situ is reached.

[0047] In a second aspect, the present application provides a device for measuring the thermal expansion coefficient of shale under in-situ conversion conditions, comprising: an experimental chamber, a triaxial pressurizing device, an optical detector, a constant temperature heating device, and a pressure control system;

[0048] The experimental chamber is used to provide a sealed environment for the rock sample, wherein the rock sample is a cubic rock sample obtained by processing a mud shale sample. The experimental chamber is provided with an optical positioning hole and a projection plate, and the projection plates are respectively arranged on the inner wall of the experimental chamber opposite to the triaxial pressurizing device;

[0049] The triaxial pressure device is respectively connected to the top surface and two adjacent side surfaces of the experimental chamber, and abuts against the top surface and two adjacent side surfaces of the rock sample, and is used to apply triaxial pressure equivalent to the stress under geological conditions to the rock sample;

[0050] The constant temperature heating device is arranged in the experimental chamber, and is used to heat the rock sample to an equilibrium temperature point and keep the temperature of the temperature point balanced and stable;

[0051] The pressure control system is connected to the experimental chamber and is used to monitor the fluid pressure at all temperatures in the experimental chamber in real time and adjust the fluid pressure in the experimental chamber to convert it into actual fluid pressure in situ;

[0052] The optical detector is used to measure the experimental chamber calibration data, the initial projection data and the projection data at the equilibrium temperature point by using laser deep hole scanning.

[0053] In one or some optional implementations of the embodiments of the present application, the experimental chamber is a sealed chamber enclosed by a high-temperature alloy material, and an installation hole that is detachably connected to the experimental chamber is provided on the outer wall of the experimental chamber for placing the rock sample into the experimental chamber.

[0054] In one or some optional implementations of the embodiment of the present application, the triaxial pressurizing device includes three oil cylinders, three pistons, three high-precision pressure sensors and a hydraulic station, and each oil cylinder includes a cylinder head, a cylinder barrel and a piston connecting rod connected in sequence;

[0055] The three cylinder covers are connected to the top surface and two adjacent side surfaces of the experimental chamber via annular flanges;

[0056] The three cylinders are each provided with the high-precision pressure sensor for detecting the liquid pressure in the cylinder in real time;

[0057] The three piston connecting rods extend into the experimental chamber along the length, width and height directions respectively;

[0058] The three pistons are respectively connected to the three piston connecting rods and abut against the top surface and two adjacent side surfaces of the rock sample;

[0059] The three cylinders are connected to the hydraulic station via hydraulic oil pipes.

[0060] In one or some optional implementations of the embodiment of the present application, three support arms are further included;

[0061] Three support arms are provided in the experimental chamber, and the three support arms are respectively arranged parallel to the three pistons. One ends of the three support arms are respectively fixed on the inner wall of the experimental chamber opposite to the three pistons, and the other ends of the three support arms are in contact with the rock sample, and the rock sample is clamped between the support arms and the three pistons.

[0062] In one or some optional implementations of the embodiment of the present application, a copper cooling water jacket is further included;

[0063] The copper cooling water jacket is sleeved on each piston connecting rod, and each copper cooling water jacket is arranged between each cylinder head and the experimental chamber, and is pressed by each cylinder head through the annular flange.

[0064] In one or some optional embodiments of the embodiment of the present application, a pulse heating device is further included, wherein the constant temperature heating device includes a plurality of heating tubes;

[0065] The heating tube is arranged in the experimental chamber, and each heating tube is connected to the pulse heating device, and the pulse heating device is used to perform pulse heating on each heating tube.

[0066] One or some optional implementations of the embodiment of the present application further include a photosensitive sheet and a photosensitive sensor;

[0067] The photosensitive sheet is provided on the surface of each projection plate, and the photosensitive sheet is connected to the photosensor for measuring the projection data at the equilibrium temperature point.

[0068] In one or some optional embodiments of the embodiments of the present application, each piston connecting rod is provided with an observation groove, each observation groove is provided with the optical positioning hole, and the laser emitted by the optical detector passes through the observation groove, the optical positioning hole, the oil cylinder, the piston, the experimental chamber and the projection plate in sequence.

[0069] In one or some optional implementations of the embodiment of the present application, the pressure control system includes a pressure control pump, a pressure control valve, a gas-liquid separation tank and a cold trap;

[0070] The experimental chamber is connected to one end of the pressure control valve, the other end of the pressure control valve is connected to the gas-liquid separation tank and the cold trap in sequence, and the fluid in the experimental chamber flows to the pressure control valve, the gas-liquid separation tank and the cold trap in sequence;

[0071] The pressure control pump is connected to the pressure control valve and is used to control the opening of the pressure control valve and to adjust the fluid pressure in the experimental chamber to convert the actual fluid pressure in situ.

[0072] In one or some optional implementations of the embodiments of the present application, a data acquisition system is also included for detecting and collecting the temperature of the experimental chamber, the pressure data of the pressure control system and the triaxial pressurizing device, and controlling the pressure control system, the constant temperature heating device, the optical detector and the triaxial pressurizing device.

[0073] In one or some optional implementations of the embodiment of the present application, a peripheral auxiliary device is further included, connected to the data acquisition system;

[0074] The peripheral auxiliary equipment receives the temperature of the experimental chamber, the pressure data of the pressure control system and the triaxial pressurizing device collected by the data acquisition system, and records the calibration data of the experimental chamber, the initial projection data of the experimental chamber, and the projection data and corresponding temperature data of each equilibrium temperature point, and calculates the thermal expansion coefficient of the rock sample in the three directions of length, width and height at each equilibrium temperature point under the stress under geological conditions and the actual geological fluid pressure.

[0075] In one or some optional implementations of the embodiment of the present application, the high-temperature alloy material is GH4169 high-alloy steel.

[0076] In one or some optional implementations of the embodiment of the present application, an insulation layer is provided on the outer wall of the experimental chamber, and the insulation layer is formed by filling with insulation material.

[0077] The beneficial effects of the above technical solutions provided by the embodiments of the present application include at least:

[0078] An embodiment of the present invention proposes a method and device for measuring the thermal expansion coefficient of mud shale under in-situ transformation conditions, wherein a triaxial pressure device is used to apply triaxial pressure equivalent to the stress under geological conditions to the rock sample, the rock sample is heated to an equilibrium temperature point by a constant temperature heating device and the temperature balance of the temperature point is maintained stable, the fluid pressure at all temperatures in the experimental chamber is monitored in real time, and the fluid pressure in the chamber is adjusted to the actual fluid pressure of the in-situ transformation by a pressure control system, thereby truly restoring the formation pressure, temperature and fluid pressure conditions during the in-situ transformation of mud shale under the actual formation. Under these conditions, the experimental chamber calibration data, the initial projection data of the experimental chamber and the equilibrium temperature point projection data are measured by an optical detector, and the thermal expansion coefficient of the rock sample in three directions is calculated corresponding to the temperature data and the rock sample size. The obtained thermal expansion coefficient can truly reflect the thermal expansion coefficient of the rock sample under formation conditions, and the measurement accuracy is high.

[0079] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present application can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings.

[0080] The technical solution of the present application is further described in detail below through the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0082] Figure 1 Flow chart of a method for measuring thermal expansion coefficient of shale under in-situ conversion conditions in an embodiment of the present invention;

[0083] Figure 2 Schematic diagram of the structure of a device for measuring thermal expansion coefficient under in-situ conversion conditions of shale in an embodiment of the present invention;

[0084] Figure 3 This is a schematic diagram of the specific structure of a device for measuring the thermal expansion coefficient under in-situ conversion conditions of shale in an embodiment of the present invention;

[0085] Figure 4 Schematic diagram of the cross-sectional structure of an experimental chamber of a device for measuring thermal expansion coefficient under in-situ conversion conditions of shale in an embodiment of the present invention;

[0086] Figure 5Schematic diagram of optical detection calculation of thermal expansion coefficient measuring device under the condition of in-situ conversion of shale in an embodiment of the present invention;

[0087] Description of reference numerals:

[0088] 1. Experimental chamber; 2. Triaxial pressurizing device; 3. Optical detector; 4. Constant temperature heating device; 5. Pressure control system; 6. Rock sample; 7. Optical positioning hole; 8. Projection board; 9. Cylinder; 10. Piston; 11. Heating tube; 12. Insulation layer; 13. Cylinder head; 14. Cylinder barrel; 15. Piston connecting rod; 16. Cylinder control port; 17. Hydraulic station; 18. Copper cooling water jacket; 19. Pulse heating device; 20. Observation tank; 21. Photosensitive film; 22. Pressure control pump; 23. Pressure control valve; 24. Peripheral auxiliary equipment; 25. Support arm; 26. Gas-liquid separation tank. DETAILED DESCRIPTION

[0089] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clearly understood, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention. All other embodiments proposed by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0090] It should be understood that, in the description of the embodiments of the present invention, all directional indication terms, such as "up," "down," "left," "right," "front," "back," etc., indicate positions or positional relationships based on the positions and positional relationships shown in the accompanying drawings or the positions or positional relationships in which the inventive product is typically placed when in use. These terms are intended only to simplify the description of the present invention and do not explicitly or implicitly indicate that the devices, elements, or components referred to must have a specific position or specific directional structure, and should not be construed as limiting the present invention. They are only used to explain the relative positional relationships and movement conditions between the components shown in the accompanying drawings. When the specific posture changes, the directional indication may also change accordingly.

[0091] Furthermore, ordinal numbers such as "first" and "second" in this disclosure are used solely for distinction purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. The terms "first" and "second" may explicitly or implicitly indicate at least one of the technical features. In this disclosure, "plurality" means at least two, i.e., two or more, unless otherwise expressly specified; and "at least one" means one, one, or more.

[0092] In the present invention, unless otherwise clearly stipulated and limited, the terms "install", "set", "connect", "fix", "screw" and the like should be understood in a broad sense. For example, it can mean that the positional relationship between components is relatively fixed, or that the components are physically fixedly connected. It can be a detachable connection or an integrated structure. It can be a mechanical connection or an electrical signal connection. It can be a direct connection or an indirect connection through an intermediate medium or component. It can be the internal connection of two elements or the interaction relationship between two elements. Unless otherwise clearly defined in the specification, other understandings may not achieve the corresponding functions or effects. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0093] The controllers and control circuits involved in the present invention are conventional control technologies or units known to those skilled in the art. For example, the control circuits of the controllers can be implemented by those skilled in the art using existing technologies, such as simple programming. Regarding software or programs that work with hardware to achieve control results, if the description does not provide a detailed description of the software or program control process involved, then the existing technologies or conventional technologies known to those skilled in the art are used. The power supply also uses the existing technologies described above, and the main technical point of the present invention is to improve the mechanical device. Therefore, the present invention will not further describe the specific circuit control relationships and circuit connections.

[0094] The disclosure of the present invention provides many different embodiments or examples for realizing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and settings of specific examples are described in the present invention. Of course, they are merely examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0095] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0096] Example 1

[0097] See Figure 1 The present application provides a method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions, comprising:

[0098] Step S1: Process the shale sample into a cubic rock sample and measure the size of the rock sample.

[0099] In this embodiment, shale samples can be collected by coring through drilling. The coring method can be conventional coring or pressure coring, which is not limited herein. The collected shale samples are full-diameter core samples.

[0100] In this example, the collected shale samples were calibrated to their specific underground geological location. Waterless wire cutting technology was used to prepare the shale samples into cubic rock specimens. The length, height, and width of the rock specimens ranged from 45 mm to 55 mm. In practical applications, the rock specimen dimensions can be adjusted based on actual needs. The rock specimens can be polished using a polishing machine to achieve a smooth and flat surface. A micrometer was used to accurately measure the rock specimen dimensions, namely, the length a, width b, and height c.

[0101] Step S2: Fix the optical detector and calibrate the experimental chamber, then load the sample and obtain the experimental chamber calibration data; the experimental chamber calibration data includes the plane projection distances Sa, Sb and Sc between the three laser light sources of the optical detector and the corresponding optical positioning holes on the experimental chamber, as well as the distances Da, Db and Dc between each optical positioning hole and the corresponding projection plate.

[0102] Step S3: Use an optical detector to measure the initial projection data of the experimental chamber in the length, width and height directions at normal temperature and pressure; the initial projection data includes the initial distance L between the laser point on the projection board and the laser vertical injection point O after the laser emitted by the laser light source passes through the optical positioning hole in the length, width and height directions of the rock sample at normal temperature and pressure. 0a , L 0b and L 0c .

[0103] Step S4: applying triaxial pressures Pa, Pb, and Pc equivalent to the stress under geological conditions to the rock sample through a triaxial pressurizing device.

[0104] In this embodiment, before applying triaxial pressure equivalent to the stress under geological conditions to the rock sample through the triaxial pressurizing device, the three oil cylinders of the triaxial pressurizing device are respectively fixed to the top surface and two adjacent side surfaces of the experimental chamber.

[0105] In this embodiment, a triaxial pressure equivalent to the stress under geological conditions is applied to the rock sample by driving the cylinder of the triaxial pressurizing device to push the piston (or piston plate), thereby obtaining a triaxial pressure consistent with the ground stress conditions. The specific ground stress can be obtained from regional information or geological data (average rock density * burial depth * gravity constant), ensuring that the rock sample meets the underground in-situ stress conditions of mud shale, thereby restoring the pressure environment of the actual formation, so that the thermal expansion coefficient obtained by subsequent calculation can better reflect the actual thermal expansion coefficient of mud shale in the formation, and the calculation precision and accuracy are higher.

[0106] Step S5: According to the set heating conditions and each equilibrium temperature point Ti, the rock sample is heated to the equilibrium temperature point Ti by a constant temperature heating device and the temperature balance of the temperature point is kept stable, and the temperature difference ΔTi between the equilibrium temperature point Ti and the normal temperature point To is determined.

[0107] In this embodiment, by setting a heating program, according to the set heating conditions and each equilibrium temperature point Ti, the rock sample is heated by the heating tube of the constant temperature heating device until the temperature reaches the equilibrium temperature point Ti, and the temperature balance of the equilibrium temperature point Ti is maintained stable within a preset time. The corresponding temperature difference ΔTi between each equilibrium temperature point Ti and the normal temperature point To is calculated, that is, ΔTi=Ti-To, where Ti is the equilibrium temperature point and To is the normal temperature point.

[0108] Step S6: Use an optical detector to measure the corresponding projection data of the experimental chamber in the three directions of length, width and height at each equilibrium temperature point to obtain the projection data at the equilibrium temperature point Ti; the projection data at the equilibrium temperature point Ti includes the offset distance ΔL of the rock sample on the projection plate after the laser passes through the corresponding optical positioning hole in the three directions of length, width and height. Tia , ΔL Tib and ΔL Tic .

[0109] In this embodiment, the projection data includes the expansion distance L of the laser point on the projection board from the laser vertical injection point O in the length, width and height directions of the rock sample at the equilibrium temperature point Ti after the laser passes through the optical positioning hole. Tia , L Tib and L Tic After the laser passes through the optical positioning hole in the length, width and height directions of the rock sample, the expansion distance L between the laser point on the projection board and the laser vertical injection point O is Tia , L Tib and L Tic The corresponding initial distance L 0a , L 0b and L 0c The difference is calculated to obtain the offset distance ΔL of the rock sample on the projection plate after the laser passes through the corresponding optical positioning hole in the length, width and height directions. Tia , ΔL Tib and ΔL Tic .

[0110] Step S7: Real-time monitoring of the fluid pressure at all temperatures in the experimental chamber, and adjusting the fluid pressure in the experimental chamber to the actual fluid pressure P in situ through the pressure control system li .

[0111] In this embodiment, high-pressure oil and gas will be generated inside the shale after being exposed to high temperature, which is the main factor in the formation of cracks and deformation inside the rock. In order to accurately measure the thermal expansion coefficient of the rock sample under high temperature and high pressure, the experimental chamber is in a sealed state to withstand a certain pressure. When the internal pressure is too high, in order to ensure the safety of the experiment, the pressure in the experimental chamber needs to be adjusted through the pressure control system. Specifically, by real-time monitoring of the fluid pressure at all temperatures in the experimental chamber, when the pressure in the experimental chamber is greater than the actual fluid pressure P in situ conversion, the pressure in the experimental chamber is adjusted. li When the fluid is discharged through the pressure control system, the fluid pressure in the experimental chamber is reduced until the actual fluid pressure P is converted in situ. li It can not only ensure the safety of the experiment, but also make the fluid pressure in the experimental chamber in the actual fluid pressure P converted in situ. li , which can restore the actual fluid pressure of the in-situ transformation of mud shale in the actual formation, so that the thermal expansion coefficient obtained by subsequent calculation can better reflect the actual thermal expansion coefficient of mud shale in the formation, and the calculation precision and accuracy are higher.

[0112] Step S8: Based on the dimensions of the rock sample (i.e., length a, width b, and height c), the experimental chamber calibration data, the initial projection data of the experimental chamber, and the projection data and corresponding temperature data at each equilibrium temperature point Ti, the thermal expansion coefficient of the rock sample in the three directions of length, width, and height at each equilibrium temperature point Ti under geological conditions and actual geological fluid pressure is calculated.

[0113] In one embodiment, see Figure 5 According to the size of the rock sample, the calibration data of the experimental chamber, the initial projection data of the experimental chamber, the projection data of each equilibrium temperature point Ti and the corresponding temperature data, the thermal expansion coefficient of the rock sample in the three directions of length, width and height at each equilibrium temperature point Ti under geological stress and actual geological fluid pressure is calculated by the following formula 1:

[0114]

[0115] Wherein, a is the length of the rock sample;

[0116] b is the width of the rock sample;

[0117] c is the height of the rock sample;

[0118] α a is the thermal expansion coefficient of the rock sample in the long direction at Ti temperature;

[0119] α b is the thermal expansion coefficient of the rock sample in the wide direction at Ti temperature;

[0120] α c is the thermal expansion coefficient of the rock sample in the high direction at Ti temperature;

[0121] Sa is the plane projection distance between the laser light source and the optical positioning hole in the long direction;

[0122] Sb is the plane projection distance between the laser light source and the optical positioning hole in the width direction;

[0123] Sc is the plane projection distance between the laser light source and the optical positioning hole in the high direction;

[0124] Da is the distance between the optical positioning hole and the projection plate in the long direction;

[0125] Db is the distance between the optical positioning hole and the projection plate in the width direction;

[0126] Dc is the distance between the optical positioning hole and the projection plate in the height direction;

[0127] L 0a The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the long direction;

[0128] L 0b The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the width direction;

[0129] L 0c The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the high direction;

[0130] ΔTi is the temperature difference between the equilibrium temperature point (Ti) and the normal temperature point (To);

[0131] ΔL Tia The offset distance of the laser on the projection board after passing through the optical positioning hole in the long direction;

[0132] ΔL Tib The width direction is the offset distance of the laser on the projection board after passing through the optical positioning hole;

[0133] ΔL Tic It is the offset distance of the laser on the projection board after passing through the optical positioning hole in the high direction.

[0134] Example 2

[0135] See Figures 2 to 4 , the present application provides a device for measuring the thermal expansion coefficient of shale under in-situ conversion conditions, comprising: an experimental chamber 1, a triaxial pressurizing device 2, an optical detector 3, a constant temperature heating device 4 and a pressure control system 5;

[0136] The experimental chamber 1 is used to provide a sealed environment for the rock sample 6, wherein the rock sample 6 is a cubic rock sample 6 obtained by processing a mudstone sample. The experimental chamber 1 is provided with an optical positioning hole 7 and a projection plate 8. The projection plate 8 is respectively provided on the inner wall of the experimental chamber 1 opposite to the triaxial pressurizing device 2.

[0137] The triaxial pressure device 2 is respectively connected to the top surface and two adjacent side surfaces of the experimental chamber 1, and abuts against the top surface and two adjacent side surfaces of the rock sample 6, and is used to apply triaxial pressure equivalent to the stress under geological conditions to the rock sample 6;

[0138] The constant temperature heating device 4 is provided in the experimental chamber 1 and is used to heat the rock sample 6 to an equilibrium temperature point and keep the temperature of the temperature point balanced and stable;

[0139] The pressure control system 5 is connected to the experimental chamber 1 and is used to monitor the fluid pressure at all temperatures in the experimental chamber 1 in real time and adjust the fluid pressure in the experimental chamber 1 to convert it into the actual fluid pressure in situ;

[0140] The optical detector 3 is arranged above the triaxial pressing device 2 and is used to measure the calibration data of the experimental chamber, the initial projection data and the projection data at the equilibrium temperature point.

[0141] In one embodiment, see Figure 4 The experimental chamber 1 is a sealed chamber enclosed by a high-temperature alloy material. The experimental chamber 1 can be cylindrical in shape, with an outer diameter of 400 mm and a height of 400 mm. An insulation layer 12 is provided on the outer wall of the experimental chamber 1 and is filled with insulation material. The high-temperature alloy material can be GH4169 high-alloy steel. The high-temperature alloy material is not specifically limited herein, as long as it can withstand high temperatures and prevent deformation of the experimental chamber 1 due to high temperatures.

[0142] In this embodiment, a mounting hole (not shown) is provided on the outer wall of the experimental chamber 1, which is detachably connected to the experimental chamber 1 and is used to place the rock sample 6 into the experimental chamber 1. The shape of the mounting hole is not limited and can be circular, square, or other shapes. The mounting hole preferably adopts a detachable method such as threading or snap fasteners to facilitate the installation and removal of the rock sample 6. At the same time, the mounting hole should be sealed with the experimental chamber 1 to prevent leakage of the internal medium and ensure the sealing effect of the experimental chamber 1.

[0143] In one embodiment, see Figure 3 and Figure 4The triaxial pressurizing device 2 comprises three cylinders 9, three pistons 10, three high-precision pressure sensors (not shown), and a hydraulic station 17. Each cylinder 9 comprises a cylinder head 13, a cylinder barrel 14, and a piston connecting rod 15, all connected in sequence. Three support arms 25 are positioned within the experimental chamber. These are arranged parallel to the three pistons 10, with one end fixed to the inner wall of the experimental chamber 1 opposite the three pistons 10. The other ends of the three support arms 25 abut against and secure the rock sample 6. The rock sample 6 is clamped between the support arms 25 and the three pistons 10, ensuring that, of the six surfaces of the rock sample, only the three surfaces in contact with the pistons 10 are free from spatial displacement. The remaining three surfaces are restricted by their attachment to the support arms 25. Therefore, when the rock sample expands, it expands in the opposite direction of the pressure applied by the pistons 10, that is, toward the pistons 10. It is noteworthy that the size and position of the support arms 25 should not affect the projection of the laser light emitted by the optical detector 3 onto the projection board 8. Here, there is no specific limitation on the shape of the support arm 25 , as long as it can fix the three surfaces of the rock sample 6 .

[0144] For details, see Figure 4The three cylinder covers 13 are connected to the top surface and two adjacent side surfaces of the experimental chamber 1 through annular flanges. The three piston connecting rods 15 extend into the experimental chamber 1 along the length, width and height directions respectively. The three pistons 10 are connected to the three piston connecting rods 15 respectively. The free ends of the three pistons 10 abut against the top surface and two adjacent side surfaces of the rock sample 6 respectively, and the other three surfaces of the rock sample 6 abut against the support arms 25, so that the rock sample 6 is clamped between the support arms 25 and the three pistons 10. Cylinder control ports 16 are provided on the three cylinder barrels 14. The cylinder control ports 16 connect the cylinder barrels 14 to the hydraulic station 17 through hydraulic oil pipes. A high-precision pressure sensor is provided in the cylinder barrel 14, which can transmit the hydraulic pressure value in the cylinder barrel 14 to the hydraulic station 17. During operation, hydraulic station 17 delivers pressurized oil into cylinder 14 via a hydraulic oil pipe, causing piston connecting rod 15 to move under hydraulic pressure, thereby driving piston 10 toward rock sample 6. This applies triaxial pressure equivalent to the stress under geological conditions to rock sample 6. Rock sample 6 expands toward piston 10, changing the hydraulic pressure within cylinder 14 and causing a deviation. A high-precision pressure sensor detects this change in hydraulic pressure and transmits it to the hydraulic station, which adjusts the hydraulic pressure within cylinder 14 to eliminate the deviation, ensuring that the rock sample is always subjected to a constant triaxial pressure. At this point, piston connecting rod 15 drives piston 10 away from rock sample 6. In other words, rock sample 6 expands under in-situ conversion conditions, "pushing" piston 10. The distance piston 10 moves represents the amount of expansion of rock sample 6 in that direction. By applying triaxial pressure equivalent to the stress under geological conditions to rock sample 6, the actual formation pressure conditions can be restored, allowing the subsequently measured thermal expansion coefficient of the rock sample to better reflect the thermal expansion coefficient of shale in the actual formation, resulting in higher precision and accuracy.

[0145] In one embodiment, see Figure 4 Each piston connecting rod 15 is sheathed with a copper cooling water jacket 18. Each copper cooling water jacket 18 is located between each cylinder head 13 and the test chamber 1 and is compressed by each cylinder head 13 via an annular flange. The copper cooling water jacket 18 prevents deformation of the test chamber 1 at high temperatures, which could affect the seal between the test chamber 1 and the oil cylinder 9.

[0146] In one embodiment, see Figure 3 and Figure 4The constant temperature heating device 4 includes a pulse heating device 19. A plurality of heating tubes 11 are arranged in the experimental chamber 1. Each heating tube 11 is connected to the pulse heating device 19 through an orifice (not shown in the figure) opened on the experimental chamber 1. The pulse heating device 19 is used to heat each heating tube 11 so that the experimental chamber 1 reaches the equilibrium temperature point and maintains the temperature balance and stability. The orifice needs to be sealed with a high-temperature resistant glue. The high-temperature resistant glue can be a heat-resistant epoxy glue, a phenolic resin glue, a silicone glue, etc. The type of high-temperature resistant glue is not limited here, as long as it can achieve a good sealing effect, and the sealing effect of the experimental chamber 1 is guaranteed. Preferably, 12 heating tubes 11 are arranged in the experimental chamber 1, and the heating power of each heating tube 11 is 1.5KW, and the maximum temperature that can be reached is 600°C.

[0147] In one embodiment, see Figure 4 Each piston connecting rod 15 is provided with an observation slot 20, and each observation slot 20 is provided with an optical positioning hole 7. Specifically, the observation slot 20 is connected to the piston connecting rod 15. When the rock sample 6 expands, the optical positioning hole 7 moves with the piston connecting rod 15. The laser light emitted by the optical detector 3 passes through the observation slot 20, the optical positioning hole 7, the oil cylinder 9, the piston 10, the experimental chamber 1, and the projection plate 8 in sequence. It is worth noting that the position of the laser light source is fixed. When the rock sample 6 expands, the laser light source does not move with the piston connecting rod 15.

[0148] See Figure 4 Each projection panel 8 is provided with a photosensitive sheet 21 connected to a photosensor (not shown). Made of a photosensitive material, the sheet 21 senses changes in light intensity and transmits the resulting light signal to the photosensor, which measures projection data at the equilibrium temperature.

[0149] When using, refer to Figure 4 and Figure 5 Taking the oil cylinder 9 on the right as an example, the oil cylinder 9 applies leftward pressure to the rock sample 6. Under the action of this pressure, the rock sample 6 expands to the right, and the piston connecting rod 15 drives the piston 10 and the observation slot 20 to move to the right. The optical positioning hole 7 located in the observation slot 20 moves to the right. The value of its movement can be used to characterize the expansion amount of the rock sample 6 in this direction. The calibration data of the experimental chamber, the initial projection data and the projection data at the equilibrium temperature point are measured by the optical detector 3 in combination with the photosensitive sheet 21 and the photosensitive sensor. The thermal expansion coefficient of the rock sample 6 in this direction is calculated according to the above formula (1).

[0150] In one embodiment, see Figure 3 , the pressure control system 5 includes a pressure control pump 22, a pressure control valve 23, a gas-liquid separation tank 26 and a cold trap (not shown in the figure);

[0151] The experimental chamber 1 is connected to one end of the pressure control valve 23 through a drain pipe, and the other end of the pressure control valve 23 is connected to the gas-liquid separation tank 26 and the cold trap in sequence. The fluid in the experimental chamber 1 flows to the pressure control valve 23, the gas-liquid separation tank 26 and the cold trap in sequence;

[0152] The pressure control pump 22 is connected to the pressure control valve 23 and is used to control the opening of the pressure control valve 23 to adjust the fluid pressure in the experimental chamber 1 to convert the actual fluid pressure in situ.

[0153] Since high-pressure oil and gas will be generated inside the mud shale at high temperature, the fluid pressure in the experimental chamber 1 will change. In order to keep the experimental chamber 1 always in the actual fluid pressure of the in-situ conversion. Figure 3 By real-time monitoring of the fluid pressure at all temperatures within experimental chamber 1, when the pressure within experimental chamber 1 exceeds the actual fluid pressure of in-situ conversion, pressure control valve 23 is opened via pressure control pump 22 to discharge the fluid within experimental chamber 1, thereby reducing the fluid pressure within experimental chamber 1 to the actual in-situ conversion fluid pressure. This method not only controls the pressure within experimental chamber 1 within a reasonable range to ensure experimental safety, but also ensures that the fluid pressure within experimental chamber 1 is within the actual in-situ conversion fluid pressure, thereby restoring the actual in-situ conversion fluid pressure of shale in the actual formation. This allows the calculated thermal expansion coefficient to better reflect the actual thermal expansion coefficient of shale in the formation, resulting in higher precision and accuracy.

[0154] In one embodiment, see Figure 3 The device for measuring the thermal expansion coefficient under in-situ conversion conditions of mudstone also includes a data acquisition system (not shown in the figure) and peripheral auxiliary equipment 24, and the data acquisition system is connected to the peripheral auxiliary equipment 24. The data acquisition system is used to detect and collect the temperature of the experimental chamber 1, the pressure data of the pressure control system 5 and the triaxial pressurizing device 2, and control the pressure control system 5, the constant temperature heating device 4, the optical detector 3 and the triaxial pressurizing device 2. The temperature, pressure and control of each pump in the experiment can be collected and controlled by the data acquisition system. The peripheral auxiliary equipment 24 receives the temperature of the experimental chamber 1, the pressure data of the pressure control system 5 and the triaxial pressurizing device 2 collected by the data acquisition system, and records the calibration data of the experimental chamber, the initial projection data of the experimental chamber, and the projection data and corresponding temperature data of each equilibrium temperature point. According to formula (1), the thermal expansion coefficient of the rock sample 6 in the three directions of length, width and height at each equilibrium temperature point under geological stress and actual geological fluid pressure is calculated.

[0155] Those skilled in the art should understand that the above embodiments of the present invention are described in detail, and specific examples are used herein to elaborate on the principles and implementation methods of the present invention. It should be understood that the description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, those skilled in the art are not used to limit the scope of protection of the present invention based on the ideas of the present invention. Any modifications, equivalent replacements, improvements, etc. made based on the specific implementation methods and application scope of the present invention within the spirit and principles of the present invention should be included in the scope of protection of the present invention. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions, characterized in that: include: Processing the shale sample into a cubic rock sample and measuring the size of the rock sample; After fixing the optical detector and calibrating the experimental chamber, the sample is loaded to obtain experimental chamber calibration data; the experimental chamber calibration data includes the plane projection distance between the three laser light sources of the optical detector and the corresponding optical positioning holes on the experimental chamber, and the distance between each optical positioning hole and the corresponding projection plate; Using the optical detector to measure the initial projection data of the experimental chamber in the three directions of length, width and height at normal temperature and pressure; The initial projection data includes the initial distance between the laser point on the projection board and the laser vertical injection point O in the length, width and height directions of the rock sample after the laser passes through the optical positioning hole at normal temperature and pressure; Applying triaxial pressure equivalent to the stress under geological conditions to the rock sample by a triaxial pressurizing device; According to the set heating conditions and each equilibrium temperature point, the rock sample is heated to the equilibrium temperature point by a constant temperature heating device and the temperature balance is maintained stable, and the temperature difference between the equilibrium temperature point and the normal temperature point is determined; The optical detector is used to measure the corresponding projection data of the experimental chamber in the three directions of length, width and height at each equilibrium temperature point to obtain the projection data at the equilibrium temperature point; the projection data at the equilibrium temperature point includes the offset distance of the rock sample on the projection plate after the laser passes through the corresponding optical positioning hole in the three directions of length, width and height; Real-time monitoring of the fluid pressure at all temperatures in the experimental chamber, and adjusting the fluid pressure in the experimental chamber to the actual fluid pressure in situ through the pressure control system; According to the size of the rock sample, the calibration data of the experimental chamber, the initial projection data of the experimental chamber, and the projection data and corresponding temperature data of each equilibrium temperature point, the thermal expansion coefficient of the rock sample in the three directions of length, width and height at each equilibrium temperature point under geological conditions and actual geological fluid pressure is calculated.

2. The method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions according to claim 1, characterized in that: According to the size of the rock sample, the calibration data of the experimental chamber, the initial projection data of the experimental chamber, and the projection data and corresponding temperature data of each equilibrium temperature point, the thermal expansion coefficient of the rock sample in the three directions of length, width and height at each equilibrium temperature point under geological stress and actual geological fluid pressure is calculated by the following formula (1): The thermal expansion coefficients in three directions can be calculated based on the above parameters. The calculation formula is: Wherein, a is the length of the rock sample; b is the width of the rock sample; c is the height of the rock sample; α a is the thermal expansion coefficient of the rock sample in the long direction at Ti temperature; α b is the thermal expansion coefficient of the rock sample in the wide direction at Ti temperature; α c is the thermal expansion coefficient of the rock sample in the high direction at Ti temperature; Sa is the plane projection distance between the laser light source and the optical positioning hole in the long direction; Sb is the plane projection distance between the laser light source and the optical positioning hole in the width direction; Sc is the plane projection distance between the laser light source and the optical positioning hole in the high direction; Da is the distance between the optical positioning hole and the projection plate in the long direction; Db is the distance between the optical positioning hole and the projection plate in the width direction; Dc is the distance between the optical positioning hole and the projection plate in the height direction; L 0a The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the long direction; L 0b The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the width direction; L 0c The distance between the laser point on the projection board and the laser vertical incident point O after the laser passes through the optical positioning hole in the high direction; ΔTi is the temperature difference between the equilibrium temperature point Ti and the normal temperature point To; ΔL Tia The offset distance of the laser on the projection board after passing through the optical positioning hole in the long direction; ΔL Tib The width direction is the offset distance of the laser on the projection board after passing through the optical positioning hole; ΔL Tic It is the offset distance of the laser on the projection board after passing through the optical positioning hole in the high direction.

3. The method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions according to claim 1, characterized in that: Processing the shale sample into a cubic rock sample and measuring the size of the rock sample includes: The specific geological position of the shale sample underground is calibrated, the shale sample is prepared into a cubic rock sample using a waterless wire cutting technology, and the size of the rock sample is measured using a micrometer.

4. The method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions according to claim 1, characterized in that: Before applying triaxial pressure equivalent to the stress under geological conditions to the rock sample through a triaxial pressurizing device, the three oil cylinders of the triaxial pressurizing device are respectively fixed to the top surface and two adjacent side surfaces of the experimental chamber.

5. The method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions according to claim 1, characterized in that: The method of measuring the corresponding projection data of the experimental chamber in the three directions of length, width and height at each equilibrium temperature point using the optical detector to obtain the projection data at the equilibrium temperature point includes: The optical detector is used to measure the corresponding projection data of the experimental chamber in the three directions of length, width and height at the equilibrium temperature point; the projection data includes the expansion distance of the laser point on the projection board from the laser vertical injection point O in the three directions of length, width and height of the rock sample at the equilibrium temperature point after the laser passes through the optical positioning hole; The expansion distance of the laser point on the projection board from the laser vertical injection point O after the laser passes through the optical positioning hole in the length, width and height directions of the rock sample is subtracted from the corresponding initial distance to obtain the offset distance of the rock sample on the projection board after the laser passes through the corresponding optical positioning hole in the length, width and height directions.

6. The method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions according to claim 1, characterized in that: According to the set heating conditions and each equilibrium temperature point, the rock sample is heated to the equilibrium temperature point by a constant temperature heating device and the temperature of the temperature point is kept stable and balanced, and the temperature difference between the equilibrium temperature point and the normal temperature point is determined, including: According to the set heating conditions and each equilibrium temperature point, the rock sample is heated by the heating tube of the constant temperature heating device until the temperature reaches the equilibrium temperature point, and the temperature of the equilibrium temperature point is kept stable within a preset time; Calculate the corresponding temperature difference between each equilibrium temperature point and the normal temperature point.

7. The method for measuring the thermal expansion coefficient of shale under in-situ conversion conditions according to claim 1, characterized in that: The real-time monitoring of the fluid pressure at all temperatures in the experimental chamber and adjusting the fluid pressure in the chamber to the actual fluid pressure in situ through the pressure control system include: The fluid pressure at all temperatures in the experimental chamber is monitored in real time. When the pressure in the experimental chamber is greater than the actual fluid pressure converted in situ, the fluid is discharged through the pressure control system to reduce the fluid pressure in the experimental chamber until the actual fluid pressure converted in situ is reached.

8. A device for measuring the thermal expansion coefficient of shale under in-situ conversion conditions, characterized in that: Including: experimental chamber, triaxial pressurizing device, optical detector, constant temperature heating device, pressure control system, data acquisition system and peripheral auxiliary equipment; The experimental chamber is used to provide a sealed environment for the rock sample, wherein the rock sample is a cubic rock sample obtained by processing a mud shale sample. The experimental chamber is provided with an optical positioning hole and a projection plate, and the projection plates are respectively arranged on the inner wall of the experimental chamber opposite to the triaxial pressurizing device; The triaxial pressure device is respectively connected to the top surface and two adjacent side surfaces of the experimental chamber, and abuts against the top surface and two adjacent side surfaces of the rock sample, and is used to apply triaxial pressure equivalent to the stress under geological conditions to the rock sample; The triaxial pressurizing device includes three oil cylinders, three pistons, three high-precision pressure sensors and a hydraulic station. Each oil cylinder includes a cylinder head, a cylinder barrel and a piston connecting rod connected in sequence. The three cylinder covers are connected to the top surface and two adjacent side surfaces of the experimental chamber via annular flanges; The three cylinders are each provided with the high-precision pressure sensor for detecting the liquid pressure in the cylinder in real time; Three piston connecting rods extend into the experimental chamber along the length, width and height directions respectively; The three pistons are respectively connected to three piston connecting rods, and abut against the top surface and two adjacent side surfaces of the rock sample; The three cylinders are connected to the hydraulic station through hydraulic oil pipes; The constant temperature heating device is provided in the experimental chamber and is used to heat the rock sample to an equilibrium temperature point and maintain the temperature equilibrium and stability; The pressure control system is connected to the experimental chamber and is used to monitor the fluid pressure at all temperatures in the experimental chamber in real time and adjust the fluid pressure in the experimental chamber to convert it into actual fluid pressure in situ; The optical detector is used to measure the experimental chamber calibration data, initial projection data and projection data at the equilibrium temperature point by using laser deep hole scanning; The data acquisition system is used to detect and collect the temperature of the experimental chamber, the pressure data of the pressure control system and the triaxial pressurizing device, and control the pressure control system, the constant temperature heating device, the optical detector and the triaxial pressurizing device; The peripheral auxiliary equipment is connected to the data acquisition system; The peripheral auxiliary equipment receives the temperature of the experimental chamber, the pressure data of the pressure control system and the triaxial pressurizing device collected by the data acquisition system, and records the calibration data of the experimental chamber, the initial projection data of the experimental chamber, and the projection data and corresponding temperature data of each equilibrium temperature point, and calculates the thermal expansion coefficient of the rock sample in the three directions of length, width and height at each equilibrium temperature point under the stress under geological conditions and the actual geological fluid pressure.

9. The device for measuring the thermal expansion coefficient of shale under in-situ conversion conditions according to claim 8, characterized in that: The experimental chamber is a sealed chamber enclosed by a high-temperature alloy material. An installation hole detachably connected to the experimental chamber is provided on the outer wall of the experimental chamber for placing the rock sample into the experimental chamber.

10. The device for measuring thermal expansion coefficient of shale under in-situ conversion conditions according to claim 9, characterized in that: Also included are three support arms; Three support arms are provided in the experimental chamber, and the three support arms are respectively arranged parallel to the three pistons. One ends of the three support arms are respectively fixed on the inner wall of the experimental chamber opposite to the three pistons, and the other ends of the three support arms are in contact with the rock sample, and the rock sample is clamped between the support arms and the three pistons.

11. The device for measuring thermal expansion coefficient of shale under in-situ conversion conditions according to claim 10, characterized in that: Also includes a copper cooling water jacket; The copper cooling water jacket is sleeved on each piston connecting rod. Each copper cooling water jacket is arranged between each cylinder head and the experimental chamber and is pressed by each cylinder head through the annular flange.

12. The device for measuring thermal expansion coefficient of shale under in-situ conversion conditions according to claim 11, characterized in that: It also includes a pulse heating device, wherein the constant temperature heating device includes a plurality of heating tubes; Each heating tube is arranged in the experimental chamber, and each heating tube is connected to the pulse heating device, and the pulse heating device is used to perform pulse heating on each heating tube.

13. The device for measuring thermal expansion coefficient of shale under in-situ conversion conditions according to claim 12, characterized in that: Also included are a photosensitive sheet and a photosensitive sensor; The photosensitive sheet is provided on the surface of each projection plate, and the photosensitive sheet is connected to the photosensitive sensor for measuring the projection data at the equilibrium temperature point.

14. The device for measuring thermal expansion coefficient of shale under in-situ conversion conditions according to claim 13, characterized in that: An observation slot is provided on each piston connecting rod, and an optical positioning hole is provided in each observation slot. The laser emitted by the optical detector passes through the observation slot, the optical positioning hole, the oil cylinder, the piston, the experimental chamber and reaches the projection board in sequence.

15. The device for measuring thermal expansion coefficient of shale under in-situ conversion conditions according to claim 14, characterized in that: The pressure control system includes a pressure control pump, a pressure control valve, a gas-liquid separation tank and a cold trap; The experimental chamber is connected to one end of the pressure control valve, the other end of the pressure control valve is connected to the gas-liquid separation tank and the cold trap in sequence, and the fluid in the experimental chamber flows to the pressure control valve, the gas-liquid separation tank and the cold trap in sequence; The pressure control pump is connected to the pressure control valve and is used to control the opening of the pressure control valve and to adjust the fluid pressure in the experimental chamber to convert the actual fluid pressure in situ.

16. The device for measuring thermal expansion coefficient of shale under in-situ conversion conditions according to any one of claims 9 to 15, characterized in that: The high-temperature alloy material is GH4169 high-alloy steel.

17. The device for measuring thermal expansion coefficient of shale under in-situ conversion conditions according to claim 16, characterized in that: An insulation layer is provided on the outer wall of the experimental chamber, and the insulation layer is formed by filling with insulation material.

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