Confining pressure control device and operating method thereof

Abstract

A confining pressure control device and an operating method thereof. The confining pressure control device comprises: a fine filter (1), used for filtering a liquid the pressure of which is to be controlled, so as to allow solid impurity particles to settle; a high-precision backpressure device (2), which comprises a backpressure body, the backpressure body being internally provided with an inner chamber and a balanced liquid discharge channel, a piston-type hydraulic balance structure being slidably arranged inside the inner chamber and the balanced liquid discharge channel, the portion of the inner chamber located above the hydraulic balance structure constituting a pressure control chamber (20), the portion of the inner chamber located below the hydraulic balance structure constituting a front-end liquid injection chamber, the backpressure body being communicated with a communication loop (21), a first end of the communication loop (21) being communicated with the front-end liquid injection chamber, and a second end of the communication loop (21) being communicated with the balanced liquid discharge channel; and an automatic constant-pressure pump (3), used for applying a constant pressure to the interior of the pressure control chamber (20). The confining pressure control device can filter liquids the pressure of which is to be controlled, thus achieving pressure regulation, reducing input costs, enabling human-machine separation so as to ensure safety, and also providing higher confining pressure, stable confining pressure and a longer lifespan.

Description

Confining pressure control device and operation method thereof

[0001] Related applications

[0002] This application claims priority to Chinese patent application No. 202311154013.X filed on September 8, 2023, and cites the contents disclosed in the above patent application as part of this application. Technical Field

[0003] The present application relates to the technical field of throttle valves, and in particular to a confining pressure control device and an operating method thereof. Background Art

[0004] With the continuous development of drilling and oil production technology, the depth of drilling is increasing. When the well reaches a certain depth, new supporting downhole tools need to be developed. During the development process of downhole tools, high-pressure confining pressure simulation tests are required. Current confining pressure simulation tests generally use a throttle valve or a throttle valve plus an accumulator to maintain the front-end pressure. This solution has several shortcomings:

[0005] First, the confining pressure that can be simulated is relatively low, and it is difficult to simulate a confining pressure of 60 to 100 MPa.

[0006] Second, it is sensitive to viscosity. The relief valve maintains unstable pressure for fluids with large viscosity changes and low viscosity.

[0007] Third, the working fluid in the confining pressure simulation experiment usually contains sand, which will cause serious wear on the valve core of the throttle valve under the high-speed and high-pressure working environment, thereby causing instability in the confining pressure. At the same time, the wear will greatly reduce the service life of the throttle valve.

[0008] Fourth, the pressure is mostly controlled manually, which makes it difficult to adjust the pressure accurately; and in the case of manual adjustment, human-machine separation cannot be achieved, which poses a certain risk factor.

[0009] The prior art discloses a method for controlling pressure using a hydraulic cylinder, but this method has complex control logic, high hardware requirements, and unstable pressure maintenance when investment is insufficient. In summary, there is currently a lack of a low-cost, stable confining pressure control method.

[0010] Therefore, the applicant, relying on many years of experience and practice in related industries, has proposed a confining pressure control device and an operating method thereof to overcome the defects of the prior art.

[0011] Summary of the Invention

[0012] The purpose of this application is to provide a confining pressure control device and an operating method thereof, so as to overcome the problems in the prior art such as low simulated confining pressure, sensitivity to liquid viscosity, severe wear, and inability to automatically control. This application can filter the liquid to be controlled, achieve pressure regulation with a relatively simple structure, reduce investment costs, and achieve human-machine separation to ensure safety, provide protection for related experiments that need to be carried out under confining pressure conditions, improve the accuracy of the experiments, and provide greater confining pressure, stable confining pressure, and longer life.

[0013] The purpose of this application is achieved by providing a confining pressure control device, comprising:

[0014] Fine filter, used to filter the liquid to be pressure controlled to allow solid impurity particles to settle;

[0015] A high-precision back pressure device includes a back pressure body, in which an inner concave chamber and a balanced liquid outlet channel are arranged, and a piston-type hydraulic balance structure can be slidably arranged in the inner concave chamber and the balanced liquid outlet channel, and the part of the inner concave chamber located above the hydraulic balance structure constitutes a pressure control chamber; the part of the inner concave chamber located below the hydraulic balance structure constitutes a front-end liquid injection chamber; the back pressure body is connected to a connecting circuit, the first end of the connecting circuit is connected to the front-end liquid injection chamber, and the second end of the connecting circuit is connected to the balanced liquid outlet channel, and a back pressure body inlet connected to the fine filter is arranged on the connecting circuit; an automatic constant pressure pump is connected to the pressure control chamber, and the automatic constant pressure pump applies constant pressure to the pressure control chamber, and the hydraulic balance structure slides under the pressure difference between the pressure control chamber and the front-end liquid injection chamber to control the opening of the balanced liquid outlet channel.

[0016] In a preferred embodiment of the present application, the back pressure body includes a valve body, the lower portion of the valve body is sealed and connected to the lower seat, the top end of the valve body is downwardly provided with an inner concave chamber, and the bottom end of the inner concave chamber is downwardly provided with a first communicating hole;

[0017] A valve core cavity is upwardly provided at the bottom end of the lower seat, a second communication hole connected to the first communication hole is upwardly penetrated through the top end of the valve core cavity, a valve core is provided in the valve core cavity, a third communication hole is penetrated through the valve core, the bottom end of the valve core cavity is connected to the lower joint, and a fourth communication hole is penetrated through the lower joint;

[0018] A fifth communicating hole is provided on the side wall of the lower seat and is connected to the second communicating hole. The fifth communicating hole is connected to the second end of the communicating circuit. The first communicating hole, the second communicating hole, the third communicating hole, the fourth communicating hole and the fifth communicating hole are connected to form a balanced liquid outlet channel.

[0019] The hydraulic balancing structure includes a piston slidably arranged in an inner concave chamber, the bottom end of the piston is connected to a valve needle, the valve needle is slidably arranged in a first connecting hole and a second connecting hole, and the valve needle passes through the valve body and the lower seat; and the bottom end of the valve needle can block the third connecting hole of the valve core, or can slide away from the third connecting hole to change the opening of the balanced liquid outlet channel.

[0020] In a preferred embodiment of the present application, the connecting circuit includes a U-shaped tube, and the two straight tube portions of the U-shaped tube are horizontally arranged; the first end of the U-shaped tube is connected to the bottom end of the concave chamber, and the second end of the U-shaped tube is connected to the fifth connecting hole and the fine filter.

[0021] In a preferred embodiment of the present application, a tee joint is provided at the second end of the U-shaped tube, the first interface of the tee joint is connected to the U-shaped tube, the second interface of the tee joint constitutes the inlet of the back pressure body, and the third interface of the tee joint is connected to the fifth connecting hole through a straight-through joint.

[0022] In a preferred embodiment of the present application, a sixth communicating hole is provided in the valve body, a first end of the sixth communicating hole is communicated with the first end of the U-shaped tube, and a second end of the sixth communicating hole is communicated with the bottom end of the concave chamber.

[0023] In a preferred embodiment of the present application, the first end of the U-shaped tube is sealed and connected to the sixth connecting hole through a plug and a pressure cap, and the second end of the U-shaped tube is connected to the first interface of the three-way joint through a plug and a pressure cap.

[0024] In a preferred embodiment of the present application, an inner groove is provided at the bottom end of the piston, and the second end of the sixth communicating hole is provided corresponding to the inner groove.

[0025] In a preferred embodiment of the present application, a pressure pad is provided between the valve core and the lower joint.

[0026] In a preferred embodiment of the present application, the maximum working pressure of the high-precision back pressure device is 105 MPa, the confining pressure stability accuracy is ±1 MPa, the working ambient temperature is 0-50°C, and the maximum allowable flow rate is 30 L / min.

[0027] In a preferred embodiment of the present application, the fine filter includes a cylinder body, a filter center hole is set through the cylinder body, a filter liquid inlet is set on the side wall of the cylinder body, the two ends of the filter center hole are sealed and connected to the first cover body and the second cover body respectively, a hollow filter element is arranged axially in the filter center hole, and the two ends of the filter element are placed on the first cover body and the second cover body; a filter annulus is formed between the outer wall of the filter element and the side wall of the filter center hole, and the filter liquid inlet is connected to the filter annulus; a cover body through hole connected to the inner cavity of the filter element is set on the second cover body, and the cover body through hole constitutes the filter liquid outlet, and the liquid to be pressure controlled is filtered through the filter inlet and the filter annulus by the filter element.

[0028] In a preferred embodiment of the present application, the maximum working pressure of the fine filter is 105 MPa, the filtration accuracy is 3 μm, and the maximum allowable flow rate is 30 L / min.

[0029] In a preferred embodiment of the present application, the liquid inlet of the filter is connected to the control valve, and the inlet of the control valve is connected to the four-way joint.

[0030] In a preferred embodiment of the present application, the automatic constant pressure pump is connected to a pressure sensor, and the pressure sensor is used to detect the real-time pressure of the automatic constant pressure pump.

[0031] In a preferred embodiment of the present application, the automatic constant pressure pump is electrically connected to the control chassis.

[0032] In a preferred embodiment of the present application, a right-angle needle valve is provided on the automatic constant pressure pump, and the right-angle needle valve is used to exhaust the automatic constant pressure pump.

[0033] In a preferred embodiment of the present application, the automatic constant pressure pump is controlled by a PLC data acquisition system, with a maximum working pressure of 105 MPa, a displacement range of 0.001 to 42 ml / min, a constant pressure accuracy of ±0.1 MPa, a tracking accuracy of ±0.1 MPa, a pressure tracking speed of 3 MPa / s, and an ambient temperature of 0°C to 50°C.

[0034] In a preferred embodiment of the present application, it also includes a frame, a support plate is set on the frame, and a fine filter, a high-precision back pressure device and an automatic constant pressure pump are set on the support plate.

[0035] The object of the present application can also be achieved as follows: a method for operating a confining pressure control device, comprising: a liquid to be controlled in a controlled pressure system is filtered through a fine filter and then flows into a communication circuit of a high-precision back pressure device, wherein one path of the liquid flows to a fifth communication hole of a lower seat, and another path of the liquid flows to a front-end liquid injection chamber below a piston in an inner concave chamber of a valve body, wherein the pressure at the bottom of the piston is equal to the front-end pressure of the device;

[0036] When the pressure at the bottom of the piston is greater than the pressure applied to the pressure control chamber by the automatic constant pressure pump, the piston is pushed upward and drives the valve needle to move upward, that is, the opening between the valve core and the valve needle increases, so that the outlet area of ​​the balanced liquid outlet channel increases, the high-precision back pressure device releases pressure, and the front end pressure decreases;

[0037] When the pressure at the bottom of the piston is lower than the pressure applied to the pressure control chamber by the automatic constant pressure pump, the piston is pushed downward, driving the valve needle downward, that is, the opening between the valve core and the valve needle is reduced, which reduces the outlet area of ​​the balanced liquid outlet channel, increases the pressure of the high-precision back pressure device, and increases the front end pressure.

[0038] After the front end pressure is increased or decreased and adjusted, it reaches the same pressure as the automatic constant pressure pump, and the upper and lower pressures of the piston are equal and the movement stops;

[0039] When the front pressure changes, the piston repeats the above steps under the action of the upper and lower pressure difference, so that the pressure below the piston is equal to the pressure of the automatic constant pressure pump, achieving dynamic balance of the confining pressure.

[0040] As described above, the confining pressure control device and the operating method thereof of the present application have the following beneficial effects:

[0041] The fine filter of the present application can filter the liquid to be pressure-controlled entering the device, so that the solid impurity particles are settled to prevent them from entering the subsequent structure and causing wear;

[0042] The high-precision back pressure device of the present application controls the opening of the balanced liquid outlet channel through the sliding of a piston-type hydraulic balance structure, and the automatic constant pressure pump provides a constant back pressure to the pressure control chamber above the hydraulic balance structure, thereby realizing pressure regulation. The pressure regulation is automated, and the separation of man and machine is achieved, thereby ensuring safety. The surrounding pressure is adjusted by adjusting the pressure of the automatic constant pressure pump, and the surrounding pressure is larger and more stable, meeting a wider range of simulated surrounding pressures. The high-precision back pressure device is not a high-precision hydraulic device and is insensitive to liquid viscosity, so the pressure stability will not be affected by liquid viscosity. Compared with the surrounding pressure control system controlled by hydraulic pressure, the cost is lower, the control principle is simpler, and the surrounding pressure is more stable.

[0043] In addition, the present application also has ultra-high pressure control capability, based on the linkage control logic of the throttling unit and the balancing unit, ensuring a maximum throttling pressure control of 105Mpa; the interception unit is easy to disassemble, the valve core is easy to repair, and the investment cost of the high-pressure control system is lower; in addition, it can also achieve stepless real-time stable pressure control, based on the piston-type hydraulic balance principle, and realizes the remote control of the constant pressure source instead of the conventional manual or electric control of the valve opening, achieving stepless adjustment while greatly shortening the feedback speed.

[0044] The overall structure of this application is simple, the sealing is good, the adjustment is quick and convenient, and the maintenance is easy. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The following figures are intended only to illustrate and explain the present application and are not intended to limit the scope of the present application.

[0046] Figure 1: is an overall schematic diagram of the confining pressure control device of this application.

[0047] Figure 2 is a three-dimensional structural diagram of the confining pressure control device of the present application.

[0048] FIG3 is a cross-sectional view of the fine filter of the present application.

[0049] Figure 4: Appearance diagram of the fine filter of this application.

[0050] FIG5 is a cross-sectional view of the high-precision back pressure device of the present application.

[0051] Figure 6: Appearance diagram of the high-precision back pressure device of the present application.

[0052] In the picture:

[0053] 1. Fine filter;

[0054] 11. Cylinder body; 12. Filter liquid inlet; 13. First cover; 14. Second cover; 15. Filter element; 16. Sealing ring;

[0055] 2. High-precision back pressure device;

[0056] 20. Pressure control chamber; 21. Connecting circuit; 211. U-shaped tube; 212. Tee joint; 213. Straight joint; 214. Plug; 215. Pressure cap; 22. Valve body; 23. Lower seat; 24. Valve core; 25. Lower joint; 26. Piston; 261. Inner groove; 27. Valve needle; 28. Pressure pad; 29. ​​Upper cover plate;

[0057] 3. Automatic constant pressure pump; 31. Right-angle needle valve;

[0058] 4. Control valve;

[0059] 5. Four-way connector;

[0060] 6. Elbow joint;

[0061] 7. Pressure sensor;

[0062] 8. Control chassis;

[0063] 9. Frame; 91. Pallet. DETAILED DESCRIPTION

[0064] In order to have a clearer understanding of the technical features, purposes and effects of this application, the specific implementation methods of this application are now described with reference to the accompanying drawings.

[0065] The specific embodiments of the present application described herein are only used to explain the purpose of the present application and should not be understood in any way as limiting the present application. Under the guidance of the present application, technicians can conceive of any possible variations based on the present application, which should be considered to fall within the scope of the present application. It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there can be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there can be an intermediate element at the same time. The terms "mounted", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be internal communication between two elements, it can be directly connected, or it can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended only to describe specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0067] As shown in Figures 1 to 6, the present application provides a confining pressure control device, comprising:

[0068] A fine filter 1, used for filtering the liquid to be pressure-controlled to allow solid impurity particles to settle;

[0069] The high-precision back-pressure device 2 includes a back-pressure body, a concave chamber and a balanced liquid outlet channel provided therein, a piston-type hydraulic balancing structure slidably provided in the concave chamber and the balanced liquid outlet channel, the portion of the concave chamber located above the hydraulic balancing structure constituting a pressure control chamber 20; the portion of the concave chamber located below the hydraulic balancing structure constituting a front-end liquid injection chamber; a connecting circuit 21 is connected to the back-pressure body, a first end of the connecting circuit 21 being connected to the front-end liquid injection chamber, a second end of the connecting circuit 21 being connected to the balanced liquid outlet channel, and a back-pressure body inlet connected to the fine filter 1 being provided on the connecting circuit 21;

[0070] The automatic constant pressure pump 3 is connected to the pressure control chamber. The automatic constant pressure pump applies a constant pressure to the pressure control chamber. The hydraulic balance structure slides under the pressure difference between the pressure control chamber and the front-end liquid injection chamber to control the opening of the balance liquid outlet channel. When the pressure of the front-end pressure-controlled liquid entering the front-end liquid injection chamber through the back-pressure body inlet is lower than the pressure of the automatic constant pressure pump 3, the hydraulic balance structure moves downward, the opening of the balance liquid outlet channel decreases, and the system is pressurized; when the pressure of the front-end pressure-controlled liquid entering the front-end liquid injection chamber through the back-pressure body inlet is higher than the pressure of the automatic constant pressure pump 3, the hydraulic balance structure moves upward, the opening of the balance liquid outlet channel increases, and the system is depressurized, and finally a dynamic balance is achieved to stabilize the front-end pressure. Compared with the hydraulically controlled confining pressure control system, it has lower cost, simpler control principle, and more stable confining pressure. It is also simpler and less complicated than the throttle valve control that requires manual adjustment. The automatic constant pressure pump can be connected to a computer, and computer control can achieve remote control.

[0071] The fine filter 1 is mainly used to prevent the primary desander and the secondary desander (existing technology) from not removing sand thoroughly enough, causing some fine sand particles to flow into the high-precision back pressure device and damage the high-precision back pressure device.

[0072] The fine filter of the present application can filter the liquid to be pressure-controlled entering the device, so that the solid impurity particles are settled to prevent them from entering the subsequent structure and causing wear;

[0073] The high-precision back-pressure device of the present application controls the opening of the balanced liquid outlet channel through the sliding of a piston-type hydraulic balance structure, and the automatic constant-pressure pump provides a constant pressure to the pressure control chamber above the hydraulic balance structure to achieve pressure regulation. The pressure regulation is automated, and the separation of man and machine is achieved to ensure safety. The surrounding pressure is adjusted by adjusting the pressure of the automatic constant-pressure pump. The surrounding pressure is larger and more stable, and a wide range of simulated surrounding pressures can be met. The high-precision back-pressure device is not a high-precision hydraulic device and is insensitive to liquid viscosity, so the pressure stability will not be affected by liquid viscosity. Compared with the surrounding pressure control system controlled by hydraulic pressure, the cost is lower, the control principle is simpler, and the surrounding pressure is more stable.

[0074] The overall structure of this application is simple, the sealing is good, the adjustment is quick and convenient, and the maintenance is easy.

[0075] 5 and 6, the high-precision back pressure device 2 is the core component of the confining pressure control device and adopts a piston-type structural design. The side of the back pressure body is provided with a liquid inlet and the bottom is provided with a liquid outlet.

[0076] The back pressure body includes a valve body 22, the lower portion of the valve body 22 is sealed and connected to a lower seat 23, and an O-ring is used between the valve body 22 and the lower seat 23; a concave chamber is provided downwardly at the top end of the valve body 22, and a first communication hole is provided downwardly through the bottom end of the concave chamber;

[0077] A valve core cavity is provided upward from the bottom end of the lower seat 23. A second communication hole communicating with the first communication hole is provided through the top end of the valve core cavity. A valve core 24 is provided in the valve core cavity. A third communication hole is provided through the valve core 24. The bottom end of the valve core cavity is threadedly connected to a lower joint 25. A fourth communication hole is provided through the lower joint 25. The outlet of the fourth communication hole constitutes a liquid outlet. The lower joint 25 can be connected to a water tank (existing technology).

[0078] A fifth communication hole is provided on the side wall of the lower seat 23 and is connected to the second communication hole (i.e., a liquid outflow channel is designed on the side of the lower seat). The fifth communication hole is connected to the second end of the external communication circuit 21, and the inlet of the fifth communication hole constitutes the liquid inlet. The first communication hole, the second communication hole, the third communication hole, the fourth communication hole, and the fifth communication hole are connected to form a balanced liquid outlet channel.

[0079] The hydraulic balancing structure includes a piston 26 that slides within the concave chamber. The contact surface between piston 26 and the concave chamber is sealed with an O-ring. The bottom end of piston 26 is connected to a valve needle 27, which slides within the first and second communication holes. Valve needle 27 extends through valve body 22 and lower seat 23. The bottom end of valve needle 27 can block the third communication hole of valve core 24 or slide away from the third communication hole to adjust the opening of the balanced liquid outlet channel. Multiple cushions and O-rings are installed on the contact surface between valve needle 27 and valve body 22 to ensure a tight seal.

[0080] The outer diameter of valve needle 27 is slightly smaller than the diameter of the second communicating hole. An annular gap is formed between the outer wall of valve needle 27 and the sidewall of the second communicating hole, allowing liquid to flow downward through the fifth communicating hole and this annular gap. The sealing effect of valve needle 27 on the third communicating hole of valve core 24 changes with its movement, thereby varying the overall opening of the balanced liquid outlet channel.

[0081] The valve needle 27 moves up and down following the piston 26 to control the opening size of the balanced liquid outlet channel, and when the piston 26 is at the bottom of the concave chamber, it cooperates with the valve core 24 to just seal the balanced liquid outlet channel.

[0082] To enable dynamic adjustment of the valve opening, the valve core 24 of the high-precision back-pressure device 2 is constructed of a lower material hardness than the valve needle 27. This provides a cushioning effect and ensures a tight seal when the liquid outlet is closed, preventing liquid leakage. Due to prolonged erosion by water flow, the valve core 24 will wear out and require replacement. To replace the valve core 24, simply unscrew the lower connector 25 to remove it.

[0083] An O-ring is provided at the position where the valve core 24 contacts the lower seat 23 .

[0084] This application has stable control and a simple structure. It adopts a piston-type structural design. A valve needle 27 is installed at the bottom of the piston 26, and an automatic constant pressure pump is connected to the top of the piston 26. A liquid inlet is set on the side of the back pressure body, and a liquid outlet is set at the bottom. When the liquid inlet pressure is higher than the pressure at the top of the piston 26, the piston pushes up, the opening of the balance liquid outlet channel increases, and the system automatically relieves pressure. When the liquid inlet pressure is lower than the pressure at the top of the piston 26, the piston presses down, the opening of the balance liquid outlet channel decreases, and the system pressurizes, eventually achieving dynamic balance and stabilizing the front-end pressure. Compared with hydraulically controlled confining pressure control systems, this system has lower costs, simpler control principles, and more stable confining pressure. It is also simpler and less complicated than a throttle valve control that requires manual adjustment.

[0085] Further, as shown in Figures 5 and 6, the connecting loop 21 includes a U-shaped tube 211, and the two straight tube portions of the U-shaped tube 211 are horizontally arranged; the first end of the U-shaped tube 211 is connected to the bottom end of the concave chamber, that is, the front end liquid injection cavity, and the second end of the U-shaped tube 211 is connected to the fifth connecting hole and the fine filter 1.

[0086] Further, as shown in Figures 5 and 6, a tee joint 212 is provided at the second end of the U-shaped tube 211, the first interface of the tee joint 212 is connected to the U-shaped tube 211, the second interface of the tee joint 212 constitutes the inlet of the back pressure body, and the third interface of the tee joint 212 is connected to the fifth connecting hole through a straight joint 213 (external wire straight joint).

[0087] Furthermore, as shown in FIG5 , a sixth communicating hole is provided in the valve body 22 , a first end of the sixth communicating hole is communicated with a first end of the U-shaped tube 211 , and a second end of the sixth communicating hole is communicated with a bottom end of the concave chamber.

[0088] Furthermore, the first end of the U-shaped tube 211 is sealed and connected to the sixth communication hole through a plug 214 and a pressure cap 215, and the second end of the U-shaped tube is connected to the first interface of the three-way connector through a plug 214 and a pressure cap 215. The plug 214 seals to prevent liquid leakage and the pressure cap 215 is used for decoration.

[0089] Furthermore, as shown in FIG5 , an inner groove 261 is provided at the bottom end of the piston 26 (i.e., the lower portion of the piston 26 is hollowed out), and the second end of the sixth communication hole is disposed corresponding to the inner groove 261. When the piston 26 is located at the bottom of the inner concave chamber, a cavity is provided to ensure that liquid can flow along the U-shaped tube 211 to the bottom of the piston.

[0090] 5, a pressure pad 28 is provided between the valve core 24 and the lower connector 25 to further cushion the movement of the valve needle 27. A liquid through hole is provided through the pressure pad 28 to ensure smooth liquid flow.

[0091] Furthermore, as shown in FIG5 , the top end of the concave chamber is sealed and connected with an upper cover plate 29 , and an automatic constant pressure pump 3 is connected to the upper cover plate 29 to apply a constant pressure thereto.

[0092] Furthermore, the maximum working pressure of the high-precision back pressure device is 105MPa, the confining pressure stability accuracy is ±1MPa, the working ambient temperature is 0-50°C, and the maximum allowable flow rate is 30L / min.

[0093] Further, as shown in Figures 3 and 4, the fine filter 1 includes a cylinder body 11, a filter center hole is set through the cylinder body 11, a filter liquid inlet 12 is set on the side wall of the cylinder body 11, and the two ends of the filter center hole are sealed and connected to the first cover body 13 and the second cover body 14 respectively. A hollow filter element 15 is axially arranged in the center hole of the filter, and the two ends of the filter element 15 are mounted on the first cover body 13 and the second cover body 14; a filter annulus is formed between the outer wall of the filter element 15 and the side wall of the center hole of the filter, and the filter liquid inlet 12 is connected with the filter annulus; a cover through hole connected to the inner cavity of the filter element 15 is set on the second cover body 14, and the cover through hole constitutes the filter liquid outlet, and the liquid to be pressure-controlled is filtered through the filter liquid inlet 12 and the filter annulus by the filter element 15.

[0094] The central axis of the fine filter 1 is vertically arranged, with the second cover 14 serving as the upper cover and the first cover 13 serving as the lower cover. The first and second covers 13, 14 of the fine filter 1 are connected to the cylinder body 11 using an interference fit and are sealed with an O-ring and a sealing retaining ring 16. A groove designed to fit the dimensions of a filter element 15 is provided between the first and second covers 13, 14. The filter element 15 is an ultra-high-pressure filter element, with both ends of the filter element 15 mounted in the grooves of the first and second covers 13, 14 and sealed with O-rings. The liquid to be pressure-controlled enters the fine filter 1 through the filter inlet 12. After being filtered by the filter element 15, solid impurity particles settle on the first cover 13 outside the filter element 15. The filtered liquid is then discharged through the cover through-hole in the second cover 14, which is connected to the high-precision back-pressure device 2.

[0095] Furthermore, the maximum working pressure of the fine filter 1 is 105 MPa, the filtration accuracy is 3 μm, and the maximum allowable flow rate is 30 L / min.

[0096] In view of the defects of the existing technology that is sensitive to viscosity and easy to wear, the present application makes it easy and quick to disassemble and assemble the parts that need to be replaced. In order to realize the dynamic adjustment of the valve opening, the valve core of the high-precision back pressure device has a lower material hardness than the valve needle. It will wear out under the erosion of water flow for a long time and needs to be replaced. When replacing the valve core, you only need to unscrew the lower joint to remove the valve core. The filter element of the fine filter needs to be replaced after long-term use. You only need to open the first cover 13 (lower cover) of the fine filter 1, pull out the filter element, insert the new valve core into the center hole of the filter, and then tighten the first cover 13.

[0097] Furthermore, as shown in FIG. 1 and FIG. 2 , the filter liquid inlet 12 is connected to the control valve 4 , and the control valve 4 can open and close the channel for the liquid to flow into the fine filter 1 .

[0098] The inlet of the control valve 4 is connected to the four-way joint 5. One interface of the four-way joint 5 is connected to the system where the pressure-controlled liquid is located, one interface can be connected to other experimental equipment, one interface serves as a safety pressure relief valve of the system to discharge pressure when necessary to ensure safety, and one interface is connected to the control valve 4.

[0099] In order to facilitate the connection between the control valve 4 and the fine filter 1 , the inlet of the fine filter 1 is connected to the elbow joint 6 .

[0100] Furthermore, as shown in FIG1 , the automatic constant pressure pump 3 is connected to a pressure sensor 7 , and the pressure sensor 7 is used to detect the real-time pressure of the automatic constant pressure pump 3 .

[0101] Furthermore, as shown in FIG. 1 and FIG. 2 , the automatic constant pressure pump 3 is electrically connected to the control box 8 .

[0102] The automatic constant pressure pump 3 is used to provide a constant pressure to the pressure control chamber 20 above the piston 26. The automatic constant pressure pump 3 can be operated on the LCD panel of the control box 8 or connected to a computer for control. A pressure sensor 7 is provided on the upper part of the automatic constant pressure pump 3 to detect the real-time pressure of the automatic constant pressure pump 3.

[0103] Furthermore, as shown in FIG2 , a right-angle needle valve 31 is provided on the automatic constant pressure pump 3 , and the right-angle needle valve 31 is used to exhaust the automatic constant pressure pump 3 .

[0104] When the automatic constant pressure pump 3 is in use, the right-angle needle valve 31 must be opened first to exhaust the gas in the cavity under liquid pressure, otherwise the automatic constant pressure pump 3 will be affected in providing constant pressure. After the gas is exhausted, the right-angle needle valve 31 is closed.

[0105] Furthermore, the automatic constant pressure pump 3 is controlled by a PLC data acquisition system, with a maximum working pressure of 105 MPa, a displacement range of 0.001 to 42 ml / min, a constant pressure accuracy of ±0.1 MPa, a tracking accuracy of ±0.1 MPa, a pressure tracking speed of 3 MPa / s, and an ambient temperature of 0°C to 50°C.

[0106] The operating process of the confining pressure control device of the present application when combined with a simulation experiment requiring confining pressure (controlled pressure system) is as follows: turn on the water pump (existing technology) external to the controlled pressure system, wait for the liquid flow to stabilize and the liquid enters the control valve 4, turn on the automatic constant pressure pump 3, open the right-angle needle valve 31 on the automatic constant pressure pump 3 and close it after the gas is emptied, and the entire system can work normally.

[0107] Furthermore, as shown in FIG2 , the confining pressure control device of the present application further includes a frame 9 , on which a support plate 91 is provided, and on which a fine filter 1 , a high-precision back pressure device 2 and an automatic constant pressure pump 3 are provided.

[0108] The wall of the fine filter 1 is provided with supporting feet, which are connected to the frame 9 by threads; the lower seat 23 of the high-precision back pressure device 2 is placed on the support plate 91, so that the high-precision back pressure device 2 can cooperate with the fine filter 1; the control box 8 for controlling the automatic constant pressure pump 3 is also installed on the frame 9.

[0109] Each component is independently processed, with low production cost, and is uniformly assembled on the frame 9. The structure is safe and reliable, and the two components cooperate with each other, making it easy to assemble and disassemble, avoiding the extra cost caused by disassembling the overall structure. The adjustment is quick and convenient, and the maintenance is easy.

[0110] The present invention has a reliable structure and strong sealing performance. Sealing rings are installed at key design positions of the device (matching positions between various parts) to ensure sealing performance, thereby achieving a higher confining pressure.

[0111] The present application also provides an operating method of a confining pressure control device as follows:

[0112] The pressure-controlled liquid in the controlled pressure system is filtered by the fine filter 1 and flows into the communication circuit 21. One path of the liquid flows to the fifth communication hole of the lower seat 23, and the other path of the liquid flows to the front end liquid injection cavity of the inner concave chamber of the valve body 22 (below the piston 26, generally directly injected into the inner groove 261 of the piston 26). The pressure at the bottom of the piston 26 is equal to the front end pressure of the device, that is, the pressure of the controlled pressure system.

[0113] When the pressure at the bottom of the piston 26 is greater than the pressure applied to the pressure control chamber 20 by the automatic constant pressure pump 3, the piston 26 is pushed upward and drives the valve needle 27 to move upward, thereby increasing the outlet area of ​​the balanced liquid outlet channel. That is, the opening between the valve core 24 and the valve needle 27 increases, the high-precision back pressure device 2 is relieved, and the front end pressure is reduced.

[0114] When the pressure at the bottom of the piston 26 is lower than the pressure applied to the pressure control chamber 20 by the automatic constant pressure pump 3, the piston 26 is pushed downward, driving the valve needle 27 downward, reducing the outlet area of ​​the balanced liquid outlet channel, that is, the opening between the valve core 24 and the valve needle 27 is reduced, the high-precision back pressure device 2 is pressurized, and the front end pressure increases;

[0115] After the front-end pressure is increased or decreased, it will reach a pressure equal to that of the automatic constant pressure pump 3. At this time, the upper and lower pressures of the piston 26 are equal, that is, the pressures of the pressure control chamber 20 and the front-end liquid injection chamber are equal, thereby stopping the movement, and the opening between the valve core 24 and the valve needle 27 remains unchanged. The front-end pressure is equal to the pressure of the automatic constant pressure pump 3.

[0116] Once the front-end pressure (pressure of the controlled pressure system) changes, the piston 26 will continuously repeat the above steps under the action of the upper and lower pressure differences, so that the pressure below the piston 26 (front-end liquid injection chamber), that is, the front-end pressure of the system, is equal to the pressure of the automatic constant pressure pump 3, thereby achieving dynamic balance of the confining pressure.

[0117] As described above, the confining pressure control device and the operating method thereof of the present application have the following beneficial effects:

[0118] The fine filter of the present application can filter the liquid to be pressure-controlled entering the device, so that the solid impurity particles are settled to prevent them from entering the subsequent structure and causing wear;

[0119] The high-precision back pressure device of the present application controls the opening of the balanced liquid outlet channel through the sliding of a piston-type hydraulic balance structure, and the automatic constant pressure pump provides a constant back pressure to the pressure control chamber above the hydraulic balance structure, thereby realizing pressure regulation. The pressure regulation is automated, and the separation of man and machine is achieved, thereby ensuring safety. The surrounding pressure is adjusted by adjusting the pressure of the automatic constant pressure pump, and the surrounding pressure is larger and more stable, meeting a wider range of simulated surrounding pressures. The high-precision back pressure device is not a high-precision hydraulic device and is insensitive to liquid viscosity, so the pressure stability will not be affected by liquid viscosity. Compared with the surrounding pressure control system controlled by hydraulic pressure, the cost is lower, the control principle is simpler, and the surrounding pressure is more stable.

[0120] The overall structure of this application is simple, the sealing is good, the adjustment is quick and convenient, and the maintenance is easy.

[0121] The above description is only an illustrative embodiment of the present application and is not intended to limit the scope of the present application. Any equivalent changes and modifications made by any person skilled in the art without departing from the concept and principle of the present application shall fall within the scope of protection of the present application.

Claims

1. A confining pressure control device, characterized in that: include, Fine filter, used to filter the liquid to be pressure controlled to allow solid impurity particles to settle; A high-precision back-pressure device comprises a back-pressure body, wherein an inner concave chamber and a balanced liquid outlet channel are arranged in the back-pressure body, wherein a piston-type hydraulic balance structure can be slidably arranged in the inner concave chamber and the balanced liquid outlet channel, wherein the portion of the inner concave chamber located above the hydraulic balance structure constitutes a pressure control chamber; the portion of the inner concave chamber located below the hydraulic balance structure constitutes a front-end liquid injection chamber; the back-pressure body is connected with a connecting circuit, wherein a first end of the connecting circuit is connected with the front-end liquid injection chamber, and a second end of the connecting circuit is connected with the balanced liquid outlet channel, wherein a back-pressure body inlet connected with the fine filter is arranged on the connecting circuit; an automatic constant pressure pump is connected with the pressure control chamber, wherein the automatic constant pressure pump applies a constant pressure to the pressure control chamber, and the hydraulic balance structure slides under the pressure difference between the pressure control chamber and the front-end liquid injection chamber to control the opening of the balanced liquid outlet channel.

2. The confining pressure control device according to claim 1, characterized in that: The back pressure body comprises a valve body, the lower part of the valve body is sealed and connected to the lower seat, the top end of the valve body is downwardly provided with the inner concave chamber, and the bottom end of the inner concave chamber is downwardly provided with a first communication hole; A valve core cavity is upwardly arranged at the bottom end of the lower seat, a second communication hole connected to the first communication hole is upwardly penetrated through the top end of the valve core cavity, a valve core is arranged in the valve core cavity, a third communication hole is penetrated through the valve core, the bottom end of the valve core cavity is connected to the lower joint, and a fourth communication hole is penetrated through the lower joint; A fifth communicating hole penetrating to the second communicating hole is provided on the side wall of the lower seat, the fifth communicating hole is connected to the second end of the communicating loop, and the first communicating hole, the second communicating hole, the third communicating hole, the fourth communicating hole and the fifth communicating hole are connected to form the balanced liquid outlet channel; The hydraulic balance structure includes a piston slidably disposed in the inner concave chamber, the bottom end of the piston is connected to a valve needle, the valve needle is slidably disposed in the first connecting hole and the second connecting hole, the valve needle penetrates the valve body and the lower seat; and the bottom end of the valve needle can block the third connecting hole of the valve core, or can slide away from the third connecting hole to change the opening of the balanced liquid outlet channel.

3. The confining pressure control device according to claim 2, characterized in that: The communication loop includes a U-shaped tube, and two straight tube parts of the U-shaped tube are arranged horizontally; the first end of the U-shaped tube is connected to the bottom end of the concave chamber, and the second end of the U-shaped tube is connected to the fifth communication hole and the fine filter.

4. The confining pressure control device according to claim 3, characterized in that: A three-way joint is provided at the second end of the U-shaped tube, a first interface of the three-way joint is connected to the U-shaped tube, a second interface of the three-way joint constitutes the inlet of the return pressure body, and a third interface of the three-way joint is connected to the fifth connecting hole through a straight joint.

5. The confining pressure control device according to claim 4, characterized in that: A sixth communicating hole is disposed in the valve body, a first end of the sixth communicating hole is communicated with a first end of the U-shaped tube, and a second end of the sixth communicating hole is communicated with a bottom end of the concave chamber.

6. The confining pressure control device according to claim 5, characterized in that: The first end of the U-shaped tube is sealed and connected to the sixth connecting hole through a plug and a pressure cap, and the second end of the U-shaped tube is connected to the first interface of the three-way joint through a plug and a pressure cap.

7. The confining pressure control device according to claim 6, characterized in that: An inner groove is arranged at the bottom end of the piston, and the second end of the sixth communicating hole is arranged corresponding to the inner groove.

8. The confining pressure control device according to claim 2, characterized in that: A pressure pad is arranged between the valve core and the lower joint.

9. The confining pressure control device according to claim 2, characterized in that: The fine filter comprises a cylinder body, a filter center hole is provided through the cylinder body, a filter liquid inlet is provided on the side wall of the cylinder body, two ends of the filter center hole are respectively sealed and connected to a first cover body and a second cover body, a hollow filter element is axially provided in the filter center hole, and two ends of the filter element are mounted on the first cover body and the second cover body; a filter annulus is formed between the outer wall of the filter element and the side wall of the filter center hole, and the filter liquid inlet is connected with the filter annulus; a cover body through hole connected with the inner cavity of the filter element is provided on the second cover body, and the cover body through hole forms a filter liquid outlet, and the liquid to be pressure controlled passes through the filter liquid inlet and the filter annulus and is filtered by the filter element.

10. The confining pressure control device according to claim 9, characterized in that: The liquid inlet of the filter is connected to a control valve, and the inlet of the control valve is connected to a four-way joint.

11. The confining pressure control device according to claim 2, characterized in that: The automatic constant pressure pump is connected to a pressure sensor, and the pressure sensor is used to detect the real-time pressure of the automatic constant pressure pump.

12. The confining pressure control device according to claim 11, characterized in that: The automatic constant pressure pump is electrically connected to the control cabinet.

13. The confining pressure control device according to claim 11, characterized in that: A right-angle needle valve is arranged on the automatic constant pressure pump, and the right-angle needle valve is used for exhausting the automatic constant pressure pump.

14. The confining pressure control device according to claim 2, characterized in that: It also includes a frame, on which a support plate is arranged, and on which the fine filter, the high-precision back pressure device and the automatic constant pressure pump are arranged.

15. An operating method of the confining pressure control device according to any one of claims 2 to 14, characterized in that: include: The pressure controlled liquid of the controlled pressure system is filtered by the fine filter and flows into the connecting circuit of the high-precision back pressure device. One path of liquid flows to the fifth connecting hole of the lower seat, and the other path of liquid flows to the front end liquid injection cavity below the piston in the inner concave cavity of the valve body. The pressure at the bottom of the piston is equal to the pressure at the front end of the device; When the pressure at the bottom of the piston is greater than the pressure applied to the pressure control chamber by the automatic constant pressure pump, the piston is pushed upward and drives the valve needle to move upward, that is, the opening between the valve core and the valve needle increases, so that the outlet area of ​​the balanced liquid outlet channel increases, the high-precision back pressure device releases pressure, and the front end pressure decreases; When the pressure at the bottom of the piston is less than the pressure applied to the pressure control chamber by the automatic constant pressure pump, the piston is pushed downward to drive the valve needle downward, that is, the opening between the valve core and the valve needle is reduced, so that the outlet area of ​​the balanced liquid outlet channel is reduced, the high-precision back pressure device is pressurized, and the front end pressure is increased; After the front end pressure is increased or decreased and adjusted, it reaches the pressure equal to that of the automatic constant pressure pump, and the upper and lower pressures of the piston are equal and stop moving; When the front pressure changes, the piston repeats the above steps under the action of the upper and lower pressure difference, so that the pressure below the piston is equal to the pressure of the automatic constant pressure pump, achieving dynamic balance of the confining pressure.

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