High-temperature and high-pressure-difference stress rock experimental device and control system

Abstract

The utility model is applicable to the technical field of rock testing, and provides a high-temperature high-pressure-difference stress rock experimental device and a control system, and the experimental device comprises a base, a container, a cushion block, a corundum compression bar, an inner salt sleeve, a corundum piston, an axial pressure piston, a graphite furnace, a pyrophyllite sleeve, an outer salt sleeve, a lead pad, a confining pressure piston, a thermocouple and the like. Wherein the corundum piston and the axial pressure piston conduct axial load to ensure balanced output of axial pressure; meanwhile, the characteristic that the lead pad and the salt sleeve are soft is utilized, and surrounding pressure is transmitted in a balanced mode through deformation of the lead pad and the salt sleeve; the graphite furnace is located in the pyrophyllite sleeve, pyrophyllite is thermally sintered and hard in texture, the graphite furnace can be well protected, and the graphite cap is thick and cannot be broken easily.

Description

Technical Field

[0001] This utility model belongs to the field of rock testing technology, and in particular relates to a high-temperature and high-pressure differential stress rock experimental device and control system. Background Technology

[0002] Rock mechanics is the science that studies the mechanical properties and deformation laws of rocks under external forces. With the rapid development of resources such as oil, natural gas, and geothermal energy, and in engineering construction, the demand for research on rock mechanical properties is constantly increasing. Especially under high temperature and high pressure conditions, the forces acting on rocks become more complex and severe. Experimental research on rock mechanics under high temperature and high pressure conditions is conducted in simulated deep underground environments. By applying high temperature and high pressure conditions, the temperature and pressure environment deep within the Earth can be simulated, thereby providing a better understanding and prediction of the mechanical behavior of underground rocks. Specifically, the following studies can be conducted using experimental setups:

[0003] Rock mechanical properties: Investigating the influence of differential stress on rock mechanical properties under high temperature and high pressure, such as the variation of parameters like rock strength, elastic modulus, and yield strength.

[0004] Understanding rock deformation mechanisms: Observing and analyzing the deformation behavior of rocks under different temperature and pressure conditions and differential stress, including elastic deformation, plastic deformation, creep, etc., to reveal the intrinsic mechanisms and microstructural changes of rock deformation.

[0005] Simulated geological processes: Simulating geological environments deep within the Earth with high temperature and pressure and differential stress, such as plate subduction zones and mantle plumes, to study the physicochemical changes and dynamic processes of rocks under these special conditions, providing a basis for understanding the evolution of geological structures.

[0006] The core of the experimental device's structural design is the balanced pressure and temperature control of the rock sample in the axial and circumferential directions. The current experimental device has uneven and unstable force transmission in the axial and circumferential directions, which can easily cause the heated graphite furnace to break. Utility Model Content

[0007] In view of the above problems, the purpose of this utility model is to provide a high-temperature and high-pressure differential stress rock experimental device and control system, which aims to solve the above technical problems.

[0008] The present invention adopts the following technical solution:

[0009] On one hand, the high temperature and high pressure differential stress rock experimental device includes a base, on which there is an annular container. From bottom to top, a pad, a corundum pressure rod, an inner salt sleeve, a corundum piston, and an axial pressure piston are arranged in the axial center of the container. The rock sample is placed in the lower part of the inner salt sleeve, and the outer periphery of the lower part of the inner salt sleeve is also covered with a nickel protective sleeve. The corundum piston is inserted into the upper part of the inner salt sleeve.

[0010] The experimental apparatus also includes a graphite furnace and a graphite cap. Pyrophyllite sleeves and outer salt sleeves are respectively provided between the outer periphery of the inner salt sleeve and the corundum pressure rod and the inner wall of the container. The graphite cap is located inside the pyrophyllite sleeve and above the inner salt sleeve, outer salt sleeve, graphite furnace, and pyrophyllite sleeve. The corundum piston extends out of the graphite cap. A lead pad is also provided on the top of the graphite cap, and a confining piston is located above the lead pad.

[0011] The pyrophyll casing also contains a thermocouple.

[0012] Furthermore, an insulating sheet is located on the base and around the outer periphery of the pad.

[0013] Furthermore, the pad has a metal ring, and the bottom of the pyrophyllite sleeve extends into the space between the corundum pressure rod and the metal ring. The metal ring is in communication with the bottom of the graphite furnace and the pad.

[0014] Furthermore, there is a pyrophyllite ring between the outer periphery of the pad and the metal ring and the inner wall of the container, and the pyrophyllite ring is located at the bottom of the outer salt sleeve.

[0015] Furthermore, metal gaskets are provided on both the upper and lower surfaces of the lead pad, and upper and lower circular grooves are opened at the axial center of the lead pad. The bottom of the axial pressure piston is located in the upper circular groove, and the top of the corundum piston is located in the lower circular groove.

[0016] Furthermore, the inner and outer rings at the bottom of the confining piston are both provided with triangular sealing rings.

[0017] On the other hand, the high-temperature and high-pressure differential stress rock experimental control system, including the experimental device, also includes a hydraulic pump station, an industrial control computer, and a power supply. The hydraulic pump station is connected to a confining pressure cylinder and an axial pressure cylinder through two servo valves, each equipped with a displacement sensor and a load sensor. The output end of the confining pressure cylinder is connected to the confining pressure piston, and the output end of the axial pressure cylinder is connected to the axial pressure piston. The industrial control computer is connected to the two servo valves and each sensor. The power supply is connected to a thyristor, which is connected to a graphite furnace through a low-voltage, high-current transformer. The control system also includes a temperature controller, with a thermocouple connected to the temperature controller. The temperature controller is connected to the thyristor through a trigger board, and the data acquisition output port of the temperature controller is connected to the industrial control computer.

[0018] The beneficial effects of this utility model are as follows: In the structural design of this device, the corundum pressure rod, inner salt sleeve, corundum piston, and axial pressure piston are located on the same upward axis to transmit axial load and ensure balanced axial pressure output; at the same time, taking advantage of the relatively soft characteristics of the lead pad and salt sleeve, especially under high temperature conditions, the pressure output by the confining piston is evenly transmitted through the deformation of the lead pad and salt sleeve, making the confining force more uniform; moreover, the graphite furnace is located inside the pyrophyllite sleeve, and the lower pyrophyllite is hot-sintered and relatively hard, which can play a good protective role for the graphite furnace, and the graphite cap is also relatively thick, so it will not easily break. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the high-temperature and high-pressure differential stress rock experimental device provided in this embodiment of the utility model;

[0020] Figure 2 This is a schematic diagram of the high-temperature and high-pressure differential stress rock experimental control system provided in this embodiment of the utility model. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0022] To illustrate the technical solution described in this utility model, specific embodiments are described below.

[0023] like Figure 1 As shown, the high-temperature and high-pressure differential stress rock experimental device provided in this embodiment includes a base 1, an annular container 2 on the base 1, and a pad 3, a corundum pressure rod 4, an inner salt sleeve 5, a corundum piston 6 and an axial pressure piston 7 arranged sequentially from bottom to top in the axial position of the container 2. The rock sample 8 is used to place in the lower part of the inner salt sleeve 5, and a nickel protective sleeve 9 is also provided on the outer periphery of the lower part of the inner salt sleeve 5. The corundum piston 7 is inserted into the upper part of the inner salt sleeve 5. The experimental apparatus also includes a graphite furnace 10 and a graphite cap 21. Pyrophyllite sleeve 11 and outer salt sleeve 12 are respectively provided between the outer periphery of the inner salt sleeve 5 and the corundum pressure rod 4 and the inner wall of the container 2. The graphite furnace 10 is located inside the pyrophyllite sleeve 11, and the graphite furnace cap 21 is located above the inner salt sleeve 5, outer salt sleeve 12, graphite furnace 10, and pyrophyllite sleeve 11. The corundum piston 6 extends out of the graphite cap 21. A lead pad 13 is also provided on the top of the graphite cap 11, and a confining piston 14 is located above the lead pad 13. A thermocouple 15 is also provided inside the pyrophyllite sleeve 11.

[0024] This experimental setup is a high-temperature (1200℃) and high-pressure (3GPa) solid medium rock mechanics experimental device, capable of pressurizing and heating the interior of a container. The container has thick walls, strong resistance to deformation, and can withstand 3GPa high pressure.

[0025] The base serves as the support for the entire device, with a tungsten carbide pad at its center, known for its high hardness and resistance to deformation. Along the axial direction are a corundum piston and a corundum pressure rod, with an inner salt sleeve and the rock sample for the experiment placed in between. The corundum piston and pressure rod transmit axial loads. The axial pressure piston applies an axial load to the sample; in this embodiment, it provides a 5 GPa axial load to the sample chamber. The device also includes an outer salt sleeve, a pyrophyllite sleeve, a nickel protective sleeve, a graphite furnace, a graphite cap, and a lead block. The graphite furnace provides a 1200°C high-temperature environment for the sample chamber, and the confining pressure piston outputs a 3 GPa confining pressure environment. The nickel protective sleeve protects the sample and the thermocouple, which monitors the sample temperature in real time. The graphite furnace is also annular. Due to the relatively soft nature of lead and salt, especially at high temperatures, the lead pad and salt sleeve undergo circumferential deformation, transmitting the confining pressure through deformation and resulting in more uniform circumferential force. The inner salt sleeve, located at the top of the rock sample, also helps ensure uniform pressure within the sample chamber. In addition, the lead pad applies pressure evenly to the top of the graphite cap, making it less prone to breakage.

[0026] In this structure, metal gaskets 19 are provided on both the upper and lower surfaces of the lead pad 13. Upper and lower circular grooves are formed at the axial center of the lead pad 13. The bottom of the axial pressure piston 7 is located in the upper circular groove, and the top of the corundum piston 6 is located in the lower circular groove. Triangular sealing rings 20 are provided on both the inner and outer rings of the bottom of the confining pressure piston 14. The triangular sealing rings and metal gaskets are used to prevent pressure transmission leakage during loading. The lead pad 13 is entirely located on the top surface of the graphite cap. The graphite cap is thickened, so even if there are slight cracks, it will not affect conductivity. Furthermore, when the confining pressure piston is pressurized, the outer side of the graphite cap remains in contact with the inner wall of the container. The pyrophyllite sleeve is hot-sintered and relatively hard. The graphite furnace is located inside the pyrophyllite sleeve, providing protection and preventing deformation of the graphite furnace due to high confining pressure.

[0027] In the above structure, the pad 3 also has a metal ring 17, and the bottom of the pyrophyllite sleeve 11 extends into the space between the corundum pressure rod 4 and the metal ring 17. A pyrophyllite ring 18 is also present between the outer periphery of the pad 3 and the metal ring 17 and the inner wall of the container 2, and the pyrophyllite ring 18 is located at the bottom of the outer salt sleeve 12. The pyrophyllite ring is used to seal the pressure transmission medium and protect the thermocouple. The bottom metal ring 17 is used to seal the pressure transmission medium and ensure electrode conductivity. As shown in the figure, there are two electrodes, one connected to the container and the other to the base. An insulating sheet 16 is located on the base 1 and around the outer periphery of the pad 3, used to insulate the base and the container. One electrode is electrically connected to one end of the graphite furnace through the base, the tungsten carbide pad, and the metal ring; the other electrode is electrically connected to the other end of the graphite furnace through the container, the lead pad, the metal pad, and the graphite cap. The experimental device is powered by a low voltage and high current, such as 8V 500A. During operation, the entire experimental device is located inside a protective cover.

[0028] Based on the above experimental setup, this embodiment also provides a high-temperature and high-pressure differential stress rock experimental control system. The entire system consists of two parts: a closed-loop hydraulic system and a closed-loop heating system.

[0029] like Figure 2 As shown, the control system includes the experimental apparatus, a 20MPa hydraulic pump station, an industrial computer, and a power supply. The hydraulic pump station is connected to a confining pressure cylinder and an axial pressure cylinder via two servo valves, each equipped with a displacement sensor and a load sensor. The output of the confining pressure cylinder is connected to the confining pressure piston, and the output of the axial pressure cylinder is also connected to the axial pressure piston. The industrial computer is connected to the two servo valves and the sensors. The power supply is connected to a thyristor, which is connected to the graphite furnace via a low-voltage, high-current transformer. The control system also includes a temperature controller, with a thermocouple connected to it. The temperature controller is connected to the thyristor via a trigger board, and its data acquisition output port is connected to the industrial computer.

[0030] A closed-loop hydraulic system is composed of a hydraulic pump station, servo valves, cylinders, sensors, and an industrial control computer. Displacement sensors monitor the output displacement of the cylinders in real time, while load sensors monitor the output thrust of the cylinders in real time. The data collected by the sensors is converted from analog to digital and output to the industrial control computer in real time at a frequency of 500Hz. The industrial control computer calculates the cylinder offset using a PID algorithm based on the real-time data and set values. This offset is then output to the servo valve at the same frequency of 500Hz via a digital-to-analog converter and signal amplifier. The servo valve controls the flow rate of hydraulic oil entering the upper and lower chambers of the cylinder, thus controlling the oil quantity and forming a closed-loop control system. This allows for high-precision control of the confining pressure and axial pressure loads applied to the high-pressure vessel.

[0031] A closed-loop heating system is composed of a temperature controller, a trigger board, a silicon controlled rectifier (SCR), a low-voltage high-current transformer, a power supply, and an industrial control computer. The temperature controller monitors the temperature inside the container in real time via thermocouples and transmits the temperature value to the industrial control computer for recording via a serial port. The temperature controller detects the temperature and uses a PID algorithm, trigger board, and SCR to control the voltage applied to the graphite furnace inside the container in real time, thereby achieving high-precision temperature control within the container and keeping the temperature within the target temperature range of ±1℃.

[0032] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A high-temperature, high-pressure differential stress rock experimental apparatus, characterized in that, The device includes a base with an annular container. From bottom to top, the container has a pad, a corundum pressure rod, an inner salt sleeve, a corundum piston, and an axial pressure piston. Rock samples are placed in the lower part of the inner salt sleeve, which is also covered with a nickel protective sleeve. The corundum piston is inserted into the upper part of the inner salt sleeve. The experimental apparatus also includes a graphite furnace and a graphite cap. Pyrophyllite sleeves and outer salt sleeves are respectively provided between the outer periphery of the inner salt sleeve and the corundum pressure rod and the inner wall of the container. The graphite furnace is located inside the pyrophyllite sleeve, and the graphite cap is located above the inner salt sleeve, outer salt sleeve, graphite furnace, and pyrophyllite sleeve. The corundum piston extends out of the graphite cap, and a lead pad is provided on the top of the graphite cap. A confining piston is located above the lead pad. The pyrophyllite casing also contains a thermocouple.

2. The high-temperature and high-pressure differential stress rock experimental apparatus as described in claim 1, characterized in that, An insulating sheet is located on the base and around the outer periphery of the pad.

3. The high-temperature and high-pressure differential stress rock experimental apparatus as described in claim 2, characterized in that, The pad also has a metal ring, and the bottom of the pyrophyllite sleeve extends into the space between the corundum pressure rod and the metal ring. The metal ring is connected to the bottom of the graphite furnace and the pad.

4. The high-temperature and high-pressure differential stress rock experimental apparatus as described in claim 3, characterized in that, There is also a pyrophyllite ring between the outer periphery of the pad and the metal ring and the inner wall of the container, and the pyrophyllite ring is located at the bottom of the outer salt sleeve.

5. The high-temperature and high-pressure differential stress rock experimental apparatus as described in claim 4, characterized in that, Metal gaskets are provided on both the upper and lower surfaces of the lead pad. Upper and lower circular grooves are opened at the axial center of the lead pad. The bottom of the axial pressure piston is located in the upper circular groove, and the top of the corundum piston is located in the lower circular groove.

6. The high-temperature and high-pressure differential stress rock experimental apparatus as described in claim 5, characterized in that, The confining piston has triangular sealing rings on both its inner and outer bottom rings.

7. A high-temperature, high-pressure differential stress rock experimental control system, characterized in that, The control system includes the experimental apparatus as described in any one of claims 1-6, and further includes a hydraulic pump station, an industrial control computer, and a power supply. The hydraulic pump station is connected to a confining pressure cylinder and an axial pressure cylinder through two servo valves, each servo valve corresponding to the other. Both cylinders are equipped with displacement sensors and load sensors. The output end of the confining pressure cylinder is connected to the confining pressure piston, and the output end of the axial pressure cylinder is connected to the axial pressure piston. The industrial control computer is connected to the two servo valves and each sensor. The power supply is connected to a thyristor, which is connected to a graphite furnace through a low-voltage, high-current transformer. The control system also includes a temperature controller, with a thermocouple connected to the temperature controller. The temperature controller is connected to the thyristor through a trigger board, and the data acquisition output port of the temperature controller is connected to the industrial control computer.

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