A high temperature and high pressure differential stress rock experimental device and control system

Abstract

The present invention is applicable to the field of rock testing technology, and provides a high-temperature and high-pressure differential stress rock experimental device and control system. The experimental device includes a base, a container, a cushion block, a corundum pressure rod, an inner salt jacket, a corundum piston, an axial pressure piston, a graphite furnace, a pyrophyllite jacket, an outer salt jacket, a lead pad, a confining pressure piston, a thermocouple, etc. The corundum piston and the axial pressure piston transmit the axial load to ensure the balanced output of the axial pressure; at the same time, the relatively soft characteristics of the lead pad and the salt jacket are utilized to evenly transmit the circumferential pressure through the deformation of the lead pad and the salt jacket; and the graphite furnace is located in the pyrophyllite jacket, and the pyrophyllite is heat-sintered and has a relatively hard texture, which can provide good protection for the graphite furnace, and the graphite cap is also thick and will not break easily. In addition, in the control system, the output loads in the axial and circumferential directions, as well as the temperature control in the container, can be accurately controlled through the dual PID algorithm, thereby ensuring the accuracy of the experiment.

Description

Technical Field

[0001] The invention belongs to the technical field of rock testing, and in particular relates to a high-temperature and high-pressure differential stress rock experimental device and a control system. Background Art

[0002] Rock mechanics is the science that studies the mechanical properties and deformation laws of rocks under the action of external forces. With the rapid development of the development and utilization of resources such as oil, natural gas, and geothermal energy, and engineering construction, the demand for research on the mechanical properties of rocks is increasing. Especially under high temperature and high pressure conditions, the forces acting on rocks are more complex and severe. Experimental research on rock mechanics under high temperature and high pressure conditions is carried out in a simulated deep underground environment. By applying high temperature and high pressure conditions, the temperature and pressure environment deep in the earth can be simulated, so as to better understand and predict the mechanical behavior of underground rocks. Specifically, the following studies can be carried out through the experimental device:

[0003] Rock mechanical properties: Explore the influence of differential stress on rock mechanical properties under high temperature and high pressure environment, such as the changing patterns of rock strength, elastic modulus, yield limit and other parameters.

[0004] Understanding rock deformation mechanisms: Observe and analyze the deformation behaviors of rocks under different temperature and pressure conditions and differential stresses, including elastic deformation, plastic deformation, creep, etc., to reveal the intrinsic mechanisms of rock deformation and microstructural changes.

[0005] Simulating geological processes: Simulating high temperature, high pressure and differential stress geological environments deep in the earth, such as plate subduction zones and mantle plumes, to study the physical and chemical changes and dynamic processes of rocks under these special conditions, and to provide a basis for understanding the evolution of geological structures.

[0006] The core of the structural design of the experimental device is the balanced pressure and temperature control of the rock sample in the axial and circumferential directions. The current experimental device has unbalanced and unstable axial and circumferential force transmission, and can easily cause the heated graphite furnace to break. Summary of the invention

[0007] In view of the above problems, the purpose of the present invention is to provide a high-temperature and high-pressure differential stress rock experimental device and control system, aiming to solve the above technical problems.

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

[0009] On the one hand, the high temperature and high pressure difference stress rock experimental device comprises a base, on which there is an annular container, in the axial position of the container, a cushion block, a corundum pressure rod, an inner salt jacket, a corundum piston and an axial pressure piston are arranged in sequence from bottom to top, the rock sample is used to be placed in the lower part of the inner salt jacket, and the outer periphery of the lower part of the inner salt jacket is also covered with a nickel protective jacket, and the corundum piston is inserted into the upper part of the inner salt jacket;

[0010] The experimental device also includes a graphite furnace and a graphite cap. A pyrophyllite jacket and an outer salt jacket are respectively arranged between the overall periphery of the inner salt jacket and the corundum pressure rod and the inner wall of the container. The graphite cap is located in the pyrophyllite jacket. The graphite cap is located above the inner salt jacket, the outer salt jacket, the graphite furnace and the pyrophyllite jacket. The corundum piston passes through the graphite cap. A lead pad is also arranged on the top of the graphite cap. A confining pressure piston is arranged above the lead pad.

[0011] A thermal couple is also provided in the pyrophyllite sleeve.

[0012] Furthermore, a circle of insulating sheet is disposed on the base and around the pad.

[0013] Furthermore, a metal ring is provided on the cushion block, and the bottom of the pyrophyllite sleeve extends into the space between the corundum pressure rod and the metal ring, and the metal ring is connected to the bottom of the graphite furnace and the cushion block.

[0014] Furthermore, a pyrophyllite ring is provided between the overall periphery of the gasket and the metal ring and the inner wall of the container, and the pyrophyllite ring is located at the bottom of the outer salt jacket.

[0015] Furthermore, metal gaskets are arranged on the upper and lower surfaces of the lead pad, and upper and lower circular grooves are opened at the axial position 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, triangular sealing rings are provided on both the inner and outer rings of the bottom of the confining pressure piston.

[0017] On the other hand, the high-temperature and high-pressure difference stress rock experiment control system includes the experimental device, and also includes a hydraulic pump station, an industrial computer and a power supply. The hydraulic pump station is connected to the confining pressure cylinder and the axial pressure cylinder in a one-to-one correspondence through two-way servo valves, wherein 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 computer is connected to the two-way servo valves and each sensor, the power supply is connected to a thyristor, and the thyristor is connected to the graphite furnace through a low-voltage and high-current transformer. The control system also includes a temperature controller, a thermocouple is 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 computer.

[0018] Furthermore, the displacement sensor is used to monitor the output displacement of the cylinder in real time, and the load sensor is used to monitor the output thrust of the cylinder in real time. The data monitored and collected by the sensor is output to the industrial computer in real time after analog-to-digital conversion. The industrial computer calculates the cylinder offset based on the real-time data using the PID algorithm, and controls the change of the oil volume in the upper and lower chambers of the cylinder by controlling the servo valve to form a control closed loop; the temperature controller monitors the temperature in the container in real time through a thermocouple, and transmits the temperature value to the industrial computer through the serial port in real time for recording. The temperature controller detects the temperature and controls the voltage of the graphite furnace in real time through the PID algorithm, trigger board, and thyristor, thereby achieving high-precision control of the temperature in the container, so that the temperature in the container is controlled within the range of ±1°C of the target temperature.

[0019] The beneficial effects of the present invention are as follows: in the structural design of the device, the corundum pressure rod, the inner salt jacket, the corundum piston, and the axial pressure piston are located on the same axis upward, transmitting the axial load to ensure balanced axial pressure output; at the same time, the relatively soft characteristics of the lead pad and the salt jacket are utilized, especially under high temperature conditions, the confining pressure piston outputs pressure, and the deformation of the lead pad and the salt jacket is balanced to transmit the circumferential pressure, so that the circumferential force is more uniform; and the graphite furnace is located in the pyrophyllite jacket, the lower pyrophyllite is heat-sintered and has a relatively hard texture, which can play a good protective role for the graphite furnace, and the graphite cap is also thick and will not break easily. In addition, in the control system, the output loads in the axial and circumferential directions, as well as the temperature control in the container, can be accurately controlled by the dual PID algorithm, thereby ensuring the accuracy of the experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural diagram of a high temperature and high pressure difference stress rock experimental device provided by an embodiment of the present invention;

[0021] Figure 2 It is a schematic diagram of a high-temperature, high-pressure differential stress rock experiment control system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] In order to illustrate the technical solution of the present invention, a specific embodiment is provided below for illustration.

[0024] like Figure 1As shown, the high-temperature and high-pressure differential stress rock experimental device provided in this embodiment includes a base 1, on which is a ring-shaped container 2, and the axial position of the container 2 is provided with a cushion block 3, a corundum pressure rod 4, an inner salt jacket 5, a corundum piston 6 and an axial pressure piston 7 from bottom to top, a rock sample 8 is used to be placed in the lower part of the inner salt jacket 5, and a nickel protective jacket 9 is also provided on the outer periphery of the lower part of the inner salt jacket 5, and the corundum piston 7 is inserted into the upper part of the inner salt jacket 5. The experimental device also includes a graphite furnace 10 and a graphite cap 21. A pyrophyllite sleeve 11 and an outer salt sleeve 12 are respectively arranged between the overall 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 in the pyrophyllite sleeve 11. The graphite furnace cap 21 is located above the inner salt sleeve 5, the outer salt sleeve 12, the graphite furnace 10 and the pyrophyllite sleeve 11, and the corundum piston 6 passes through the graphite cap 21. A lead pad 13 is also provided on the top of the graphite cap 11, and a confining pressure piston 14 is provided above the lead pad 13; there is also a thermocouple 15 in the pyrophyllite sleeve 11.

[0025] This experimental device is a high temperature (1200°C) and high pressure (3GPa) solid medium rock mechanics experimental equipment, which can realize pressurization and heating inside the container. The wall thickness of the container is relatively thick, the deformation resistance is strong, and it can withstand 3GPa high pressure.

[0026] The base is the bearing seat of the entire device, and there is a pad in the center position on it. The pad is a tungsten carbide pad with high hardness and is not easy to deform. There are corundum pistons and corundum pressure rods in the axial direction, and an inner salt sleeve and a rock sample for the experiment are placed in the middle. The corundum piston and corundum pressure rod are used to transmit axial loads. The axial pressure piston is used to provide an axial load to the sample. In this embodiment, a 5GPa axial load is provided for the sample cavity. The device is also provided with an outer salt sleeve, a talc sleeve, a nickel protective sleeve, a graphite furnace, a graphite cap, a lead block, etc. The graphite furnace provides a 1200°C high temperature environment for the sample cavity, and the output pressure of the confining pressure piston provides a 3GPa confining pressure environment. The nickel protective sleeve 9 is used to protect the sample and the thermocouple, and the thermocouple monitors the sample temperature in real time. The graphite furnace is also annular. Because the lead and salt are relatively soft, especially at high temperatures, the lead pad and the salt sleeve will have circumferential deformation, and the confining pressure is transmitted through deformation, so that the circumferential force is more uniform. There is also an inner salt sleeve located at the top of the rock sample, which can also ensure that the sample cavity is uniformly pressurized. In addition, the lead pad applies uniform pressure to the top of the graphite cap, making it less likely to break.

[0027] In this structure, metal gaskets 19 are provided on the upper and lower surfaces of the lead pad 13. Upper and lower circular grooves are opened at the axial position 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. The inner and outer rings of the bottom of the confining pressure piston 14 are provided with triangular sealing rings 20. The triangular sealing rings and metal gaskets are used to prevent leakage of the pressure transmission cutoff during loading. The lead pad 13 is located entirely on the top surface of the graphite cap. The graphite cap is thickened in design. Even if the graphite cap has some cracks, it does not affect the conductivity. Moreover, when the confining pressure piston is pressurized, the outer side of the graphite cap keeps in contact with the inner wall of the container. The talc sleeve is heat-sintered and has a relatively hard texture. The graphite furnace is located in the talc sleeve, which plays a protective role and prevents the graphite furnace from deforming due to high confining pressure.

[0028] In the above structure, the pad 3 also has a metal ring 17, the bottom of the pyrophyllite sleeve 11 extends to the space between the corundum pressure rod 4 and the metal ring 17, and there is a pyrophyllite ring 18 between the overall 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 the electrode conduction. As shown in the figure, there are two electrodes, one electrode is connected to the container and the other is connected to the base. There is a circle of insulating sheets 16 on the base 1 and located on the periphery of the pad 3, which is used to insulate and isolate the base and the container. One electrode is electrically connected to one end of the graphite furnace through the base, tungsten carbide pad, and metal ring; the other electrode is electrically connected to the other end of the graphite furnace through the container, lead pad, metal gasket, and graphite cap. The power supply of the experimental device adopts low voltage and high current, such as 8V500A. When running, the entire experimental device is located in the protective cover.

[0029] Based on the above experimental device, this embodiment also provides a high temperature and high pressure difference stress rock experimental control system. The whole system includes two parts, a closed-loop hydraulic system and a closed-loop heating system.

[0030] like Figure 2 As shown, the control system includes the experimental device, and also includes a 20MPa hydraulic pump station, an industrial computer and a power supply. The hydraulic pump station is connected to the confining pressure cylinder and the axial pressure cylinder through two-way servo valves in a one-to-one correspondence, wherein 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 computer is connected to the two-way servo valves and each sensor, the power supply is connected to a thyristor, and the thyristor is connected to the graphite furnace through a low-voltage high-current transformer. The control system also includes a temperature controller, a thermocouple is connected to the temperature controller, and 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 computer.

[0031] The hydraulic pump station, servo valve, oil cylinder, sensor, industrial computer and other components form a closed-loop hydraulic system. The displacement sensor is used to monitor the output displacement of the oil cylinder in real time, and the load sensor is used to monitor the output thrust of the oil cylinder in real time. The data collected by the sensor monitoring is output to the industrial computer at a frequency of 500Hz in real time after analog-to-digital conversion. The industrial computer calculates the oil cylinder offset using the PID algorithm based on the real-time data and the set value, and outputs it to the servo valve at a frequency of 500Hz through the digital-to-analog converter and signal amplifier. The servo valve controls the flow of hydraulic oil entering the upper and lower chambers of the oil cylinder to control the oil volume change, forming a control closed loop, and then performing high-precision control of the confining pressure and axial pressure load applied to the high-pressure vessel.

[0032] The closed-loop heating system is composed of a temperature controller, a trigger board, a thyristor, a low-voltage high-current transformer, a power supply, an industrial computer, etc. The temperature controller monitors the temperature in the container in real time through a thermocouple, and transmits the temperature value to the industrial computer in real time through a serial port for recording. The temperature controller detects the temperature and controls the voltage applied to the graphite furnace inside the container in real time through a PID algorithm, a trigger board, and a thyristor, thereby achieving high-precision control of the temperature in the container, so that the temperature in the container is controlled within the range of ±1°C of the target temperature.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high temperature and high pressure differential stress rock experimental device, characterized in that: The invention comprises a base, wherein the base is provided with an annular container, wherein a cushion block, a corundum pressure rod, an inner salt jacket, a corundum piston and an axial pressure piston are sequentially arranged in the axial center position of the container from bottom to top, wherein the rock sample is placed in the lower part of the inner salt jacket, and the outer periphery of the lower part of the inner salt jacket is also covered with a nickel protective jacket, and the corundum piston is inserted into the upper part of the inner salt jacket; The experimental device also includes a graphite furnace and a graphite cap. A pyrophyllite jacket and an outer salt jacket are respectively arranged between the overall periphery of the inner salt jacket and the corundum pressure rod and the inner wall of the container. The graphite furnace is located in the pyrophyllite jacket. The graphite cap is located above the inner salt jacket, the outer salt jacket, the graphite furnace and the pyrophyllite jacket. The corundum piston passes through the graphite cap. A lead pad is also arranged on the top of the graphite cap. A confining pressure piston is arranged above the lead pad. A thermal couple is also provided in the pyrophyllite sleeve.

2. The high temperature and high pressure difference stress rock experimental device according to claim 1, characterized in that: A circle of insulating sheets is arranged on the base and located on the outer periphery of the cushion block.

3. The high temperature and high pressure difference stress rock experimental device as claimed in claim 2, characterized in that: The cushion block is also provided with a metal ring, the bottom of the pyrophyllite sleeve extends into the space between the corundum pressure rod and the metal ring, and the metal ring is connected with the bottom of the graphite furnace and the cushion block.

4. The high temperature and high pressure difference stress rock experimental device as claimed in claim 3, characterized in that: A pyrophyllite ring is provided between the overall outer periphery of the cushion block and the metal ring and the inner wall of the container, and the pyrophyllite ring is located at the bottom of the outer salt jacket.

5. The high temperature and high pressure difference stress rock experimental device as claimed in claim 4, characterized in that: The upper and lower surfaces of the lead pad are both provided with metal gaskets, and the axial position of the lead pad is provided with upper and lower circular grooves, 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 difference stress rock experimental device as claimed in claim 5, characterized in that: The inner and outer rings of the bottom of the confining pressure piston are both provided with triangular sealing rings.

7. A high temperature and high pressure differential stress rock experiment control system, characterized in that: The control system includes the experimental device as described in any one of claims 1 to 6, and also includes a 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 in a one-to-one correspondence through two-way servo valves, wherein 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 computer is connected to the two-way servo valves and each sensor, the power supply is connected to a thyristor, and the thyristor is connected to a graphite furnace through a low-voltage and high-current transformer, the control system also includes a temperature controller, a thermocouple is 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 computer.

8. The high temperature and high pressure difference stress rock experiment control system according to claim 7, characterized in that: The displacement sensor is used to monitor the output displacement of the oil cylinder in real time, and the load sensor is used to monitor the output thrust of the oil cylinder in real time. The data monitored and collected by the sensor is output to the industrial computer in real time after analog-to-digital conversion. The industrial computer calculates the cylinder offset using the PID algorithm based on the real-time data, and controls the servo valve to control the change of the oil volume in the upper and lower chambers of the oil cylinder to form a control closed loop; the temperature controller monitors the temperature in the container in real time through a thermocouple, and transmits the temperature value to the industrial computer in real time through a serial port for recording. The temperature controller detects the temperature and controls the voltage of the graphite furnace in real time through the PID algorithm, the trigger board, and the thyristor, thereby realizing high-precision control of the temperature in the container, so that the temperature in the container is controlled within the range of ±1°C of the target temperature.

Images