Integrated visualization experimental device for proppant delivery and reflux under in-situ environmental conditions

Abstract

The present invention relates to a visual experimental device and method for proppant delivery and reflux under in-situ environmental conditions. The device mainly consists of a control unit, a sand mixing unit, a fracturing fluid pumping unit, a temperature control and hydraulic unit, a fracture flow unit, and a recovery unit. The device body comprises a visual built-in sand delivery panel and an external pressurized box, which applies pressure via a hydraulic device. The temperature control system controls the temperature of the test environment. Springs provided at the joints of the device body during sand delivery and flowback can simulate dynamic changes in fractures. During the sand delivery and flowback process, a displacement meter placed on the sand delivery panel can detect changes in fracture displacement, and flow meters at the liquid pump inlet and outlet monitor fluid flow rate. The present invention can simulate high-temperature and high-pressure environments in formations, detect proppant placement and fracture reflux capacity under different fracture widths and shapes, measure the critical flow rate and sand output during proppant reflux, and observe the proppant sedimentation pattern. The experimental process and results can also be visually observed.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic fracturing, and in particular to a visual experimental device for proppant delivery and reflux under in-situ environmental conditions. Background Art

[0002] Hydraulic fracturing is a key technology for exploiting low-permeability oil and gas reservoirs. The proppant delivery, placement, and return flow processes crucially influence fracturing effectiveness. To further investigate these processes and optimize hydraulic fracturing technology, it is crucial to develop an experimental device capable of simulating the proppant movement characteristics within in-situ fractures.

[0003] This paper proposes a visual experimental device for proppant transport and return flow in situ. This device simulates the actual movement of proppant in formation fractures, including key processes such as transport, placement, and return flow. Through this visual design, researchers can intuitively observe the dynamic behavior of proppant in simulated fractures, thereby gaining a deeper understanding of its movement patterns. Summary of the Invention

[0004] The purpose of this invention is to provide a visual experimental device for proppant delivery and reflux under in situ environmental conditions. The device has a reliable structure and realizes visualization, allowing for more intuitive observation of the experimental process and results. The integrated design of proppant delivery, placement, and reflux simplifies the experimental steps and improves experimental efficiency.

[0005] The technical solution adopted by the present invention is as follows: the device is mainly composed of a control unit, a proppant sand mixing unit, a fracturing fluid pumping unit, a temperature control unit, a hydraulic unit, a fracture flow unit, a detection unit, a proppant reflux and fracturing fluid recovery unit and various pipelines. The main body of the device is provided with a visual built-in sand delivery panel and an external pressurized box, and pressure is applied by the hydraulic unit, and the temperature of the test environment is controlled by the temperature control unit. During the experiment, the displacement meter placed on the visual built-in sand delivery panel can detect the change of fracture displacement, the fluid flow rate is detected in real time by the flow meter placed at the end, and the sand output is monitored by the graduated cylinder and electronic balance of the recovery unit. The present invention can simulate the high temperature and high pressure environment of the formation, and the wall of the fracture has a certain degree of roughness, simulating the irregularity of natural fractures. In the simulated formation environment, the proppant laying situation and the fracture reflux capacity are detected, the critical flow rate and sand output during proppant reflux are measured, and the sedimentation law of the proppant is observed.

[0006] The proppant mixing unit consists of a mixing tank, an agitator, a fracturing fluid tank, and several pipelines. The tank's upper surface is open for adding fracturing fluid and proppant. The liquid outlet is located at the bottom of the tank, the liquid return inlet is located at the top, and the drain port is located at the center of the tank's bottom. A stirrer is fixed to the top to mix the proppant and fracturing fluid.

[0007] The hydraulic unit consists of a hydraulic pump, a pressure block, a protective block, a hydraulic pump pipeline, an external pressure box, a hydraulic valve, and a pressure sensor. A portion of the hydraulic pump pipeline is laid inside the pressure block, which uses hydraulic pressure to apply crack-closing pressure to the simulated crack texture panel. The protective block protects the hydraulic pump pipeline. The hydraulic pump pipeline is laid outside the pressure block, and the ambient pressure is controlled by a control unit.

[0008] The temperature control unit cleverly incorporates seven heating tubes inside the pressurized block, specifically designed to house the heating rods. These seven tubes ensure even heat distribution, preventing localized overheating or uneven temperatures. This design precisely controls the ambient temperature through the control unit, meeting temperature requirements in a variety of complex environments.

[0009] The control unit plays a vital role in adjusting the current or operating time of the heating rod according to the preset temperature value or the actual ambient temperature feedback signal, and accurately controlling the ambient temperature and pressure according to the preset pressure value or the actual ambient pressure feedback signal.

[0010] The fracture flow unit is mainly composed of two visual built-in sand delivery panels. The fracturing fluid pump pipeline is fixed to the perforation through a threaded connection. The other end of the pipeline is threadedly connected to the screw pump. After the proppant is mixed with sand, the formed fracturing fluid is pumped into the visual simulated fracture by the screw pump. The transportation and laying status of the proppant under the simulated formation environment can be observed. After the proppant is transported and laid, the fracturing fluid pump inlet valve is closed, the return fluid inlet valve is opened, and the horizontal flow valve is started to carry out the next reflux test.

[0011] The visual internal sand transport panel 18 consists of a simulated crack texture panel and a high-strength quartz glass transparent panel. Both panels are 500mm long and 400mm high. The high-strength quartz glass panel is 100mm thick and can withstand pressures of 100-300MPa. The simulated crack texture panel is made of ferritic stainless steel, which has excellent high-temperature, pressure, and corrosion resistance. The two visual internal sand transport panels are placed in parallel, forming a crack between them, and the crack size is adjustable from 5-10mm. The visual internal sand transport panels are sealed from top to bottom with high-temperature resistant elastomer sealing strips and axially pre-tightened with bolts. The visual internal sand transport panels are installed inside an external protective housing. The liquid pump inlet and proppant return outlet pipelines in the crack between the high-strength quartz glass transparent panel and the simulated crack texture panel are connected to various pipelines through the external pressurized housing.

[0012] The external protection box 22 can withstand a maximum pressure of 500 MPa. Figure 1The protective block 21, the pressure block 20, the simulated crack texture panel 1801 and the high-strength quartz glass transparent panel 1802 are installed in sequence inside, and the sand delivery pipeline and the liquid pump pipeline are connected externally. The sand delivery port and the liquid pump inlet are respectively as follows: Figure 2 As shown, the smooth side of the simulated crack texture panel is spliced ​​with the pressurized block.

[0013] The spring 26 is placed at the horizontal contact point between the visual internal sand transport panel and the external protective box to visualize the dynamic changes in cracks during the experiment, providing a deeper understanding of the crack propagation patterns during sand transport and flowback. These data and results can also provide valuable reference for engineering practice and scientific research.

[0014] The proppant reflux and fracturing fluid recovery unit consists of a waste liquid recovery cylinder, a liquid recovery pipeline, a measuring cylinder 4 and a balance 5. The measuring cylinder and the balance are used to collect and record the proppant reflux situation, and the waste liquid recovery cylinder 34 recovers excess waste liquid.

[0015] The beneficial effects of the present invention are:

[0016] The present invention can simulate an in-situ high-temperature and high-pressure environment, detect the dynamic seam width, simulate the proppant laying situation and reflux capacity under the in-situ pressure and temperature environment, measure the critical flow velocity and sand production during proppant reflux, and observe the sedimentation law of the proppant. In addition, the present invention realizes visualization function, which can more intuitively observe the experimental process and results. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the overall experimental device flow chart provided for the implementation of the present invention.

[0018] Figure 2 Left view of the visual built-in sand transport panel and perforation provided for the implementation of the present invention.

[0019] Figure 3 A partial cross-sectional view of a pressurizing block provided for the implementation of the present invention.

[0020] In the figure: 1. Sand mixing tank, 2. Liquid mixing tank, 3. Backflow liquid storage tank, 4. Measuring cylinder, 5. Balance, 6. Stirring device, 7. Heater, 8. Valve 3, 9. Valve 4, 10. Valve 1, 11. Valve 2, 12. Screw pump, 13. Horizontal flow pump, 14. Cooling pump, 15. Pressure sensor 1, 16. Pressure sensor 2, 17. Back pressure pump, 18. Visual built-in sand transport panel, 1801, Simulated crack texture panel, 1802, High-strength quartz glass transparent panel, 20. Pressure block, 21. Protective block, 22. External protective box, 23. Valve 5, 24. Hydraulic pump, 25. Gas cylinder, 26. Spring, 2701. Control system 1, 2702. Control system 2, 28. Heating pipe, 29. Pressurized pipe, 30. Perforation, 31. Camera, 32. Flow meter 1, 33. Flow meter 2, 34. Waste liquid recovery cylinder, 35. Displacement meter 1, 36. Displacement meter 2. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] On the one hand, if Figure 1 As shown, the present invention provides a visual experimental device for proppant delivery and reflux under in-situ environmental conditions, including a control unit, a proppant sand mixing unit, a fracturing fluid pumping unit, a temperature control unit, a hydraulic unit, a fracture flow unit, a proppant reflux and a fracturing fluid recovery unit.

[0023] The proppant sand mixing unit includes a sand mixing tank 1, a liquid preparation tank 2, an agitator 6, a screw pump 12 and a valve 10 connected in sequence. The liquid preparation tank 2 is used to prepare fracturing fluid. An agitator is fixed on the top of the sand mixing tank 1 for mixing the proppant and the fracturing fluid. The screw pump 12 is connected to the perforation end 30 of the visual built-in sand delivery panel. A pipe at the output end of the visual built-in sand delivery panel 18 is connected to the fracturing fluid and proppant recovery cylinder 34, and another pipe is connected to the measuring cylinder 4 and the balance 5.

[0024] The monitoring unit includes a camera 31, a flow meter 1 32 and a flow meter 2 33. The camera 31 is used to monitor the changes in the proppant laying state during the fracturing fluid pumping process and the backflow process of the fracture flow unit. The flow meter 1 32 is placed between the screw pump 12 and the visual built-in sand transport panel 18. The flow meter 2 33 is set between the output end of the visual built-in sand transport panel 18 and the proppant reflux and fracturing fluid recovery unit.

[0025] Among them, see Figure 2The visual built-in sand transport panel 18 is composed of a simulated crack texture panel 1801 and a high-strength quartz glass transparent panel 1802. The two panels play the role of pressure bearing and visualization respectively; the heating pipe and pressurized liquid pump pipeline are laid as follows Figure 3 shown.

[0026] A visual experimental device for proppant transportation and reflux under in-situ environmental conditions includes a fracturing proppant migration and placement process and a fracturing fluid flowback proppant reflux process.

[0027] Simulating the formation environment: The heating rod is heated by the temperature control system and placed in the evenly laid heating pipes to heat and keep the simulated environment warm. The valve 5 23 is opened, the gas cylinder 25 and the hydraulic pump 24 are turned on, and the pressure of the simulated environment is controlled by the hydraulic system. The spring set at the connection between the external protective box and the internal sand conveying panel simulates the dynamic changes of the fracture during the sand conveying and return flow process.

[0028] The fracturing fluid pumping process: Pour the proppant in the sand mixing tank 1 into the liquid preparation tank 2 to prepare the fracturing fluid, and stir it through the stirring device 6. Open valve 10, close the valve at the output end of the visual built-in sand conveying panel, which is to close the recovery unit valve 3 8. This valve is only opened when recovering waste liquid and cleaning experimental instruments at the end of the experiment, and the proppant reflux detection pipeline valve 4 9. This valve is only opened when testing the proppant reflux. Open the screw pump 12 to inject the fully mixed fracturing fluid and proppant into the visual built-in sand conveying panel 18 through the perforation 30. The flow meter 32 measures the fluid flow in the pipeline. After the sand-carrying fluid passes through the visual built-in sand conveying panel 18 and the proppant settles to form a sand bank, it is discharged through the output end into the fracturing fluid recovery cylinder 34. After the sand-carrying fluid is pumped in, close the screw pump 12.

[0029] Flowback fluid pumping process: After the sand-carrying fluid is pumped in, shut down the screw pump and close valve 1. Maintain the closing pressure and the pressure within the fracture to allow the proppant to settle freely, simulating a shut-in. After the well is shut in, open valve 2 11 at the flowback fluid input port, start the horizontal flow pump, and pump flowback fluid from the pump inlet. During this time, close valve 3 8 and open valve 4 9. Observe the changes in the proppant placement and record the backflow volume. End the experiment. Stop the pump, close all valves, cool down and depressurize, and clean the experimental equipment.

[0030] In the description of the present invention, it should be understood that if there are terms such as up, down, left, right, inside, outside, radial, etc. indicating an orientation or positional relationship, these are based on the orientation or positional relationship shown in the accompanying drawings, rather than indicating or implying that the device or element referred to must have a characteristic orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on this patent.

[0031] The above-described embodiments merely represent specific implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of protection of the present application. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the technical concept of the present application, and all such variations and improvements fall within the scope of protection of the present application.

Claims

1. A method for testing a visual experimental device for proppant transport and reflux under in-situ environmental conditions, characterized in that: The experimental device includes a control unit, a proppant mixing unit, a fracturing fluid pumping unit, a temperature control unit, a hydraulic unit, a fracture flow unit, a recovery unit, and a pipeline unit; the proppant mixing unit includes a sand mixing tank, a liquid preparation tank, an agitator, a screw pump, and a valve 1 connected in sequence. The liquid preparation tank is used to prepare the fracturing fluid. The agitator is fixed on the top of the sand mixing tank and is used to mix the proppant and the fracturing fluid. The screw pump is connected to the perforation end of the sand delivery panel. A pipeline at the output end of the sand delivery panel is connected to the fracturing fluid and proppant recovery cylinder, and another pipeline is connected to the graduated cylinder and the balance. The hydraulic unit includes a hydraulic pump, a pressure block, a protective block, a liquid pump pipeline, an external protective box, a hydraulic valve, and a pressure sensor. A portion of the liquid pump pipeline is laid inside the pressure block, and the liquid pump pipeline is laid outside the pressure block. The ambient pressure is controlled by the control unit; The temperature control unit is provided with 7 heating tubes for placing heating rods inside the pressure block; The sand conveying panel consists of a high-strength transparent quartz glass panel and a simulated crack texture panel made of ferritic stainless steel. The two internal sand conveying panels are placed in parallel, forming a crack between them. The crack changes dynamically during the experiment via a spring. The spring is set at the horizontal contact point between the visual internal sand conveying panel and the external protective box. The internal sand conveying panel is inserted into the external pressurized box. The sand conveying panel is sealed from top to bottom with high-temperature resistant elastomer sealing strips and axially pre-tightened with bolts. The liquid pump inlet and proppant reflux outlet pipelines in the crack between the high-strength transparent quartz glass panel and the simulated crack texture panel are connected to various pipelines through the external pressurized box. The protective block, pressurizing block, simulated crack texture panel and high-strength quartz glass transparent panel are installed in sequence inside the external pressurized box, and the sand conveying pipeline and liquid pump pipeline are externally connected. Among them, the smooth side of the simulated crack texture panel is spliced ​​with the pressurizing block; Valve 1 and valve 2 are set on the inlet pipeline of the visual built-in sand conveying panel. The sand mixing tank, liquid preparation tank, stirring device, screw pump, valve 1 and valve 2 are connected to the perforation end of the visual built-in sand conveying panel in sequence; the return liquid storage tank, heater, horizontal flow pump and valve 2 are connected to the perforation end of the visual built-in sand conveying panel in sequence; the outlet end of the visual built-in sand conveying panel is connected to the back pressure pump, cooling pump, valve 3 and waste liquid recovery tank in sequence; at the same time, the outlet end of the visual built-in sand conveying panel is connected to the back pressure pump, cooling pump, valve 4, measuring cylinder and balance in sequence; The test involves the following steps: S1: Pour the proppant in the sand mixing tank into the liquid preparation tank to prepare the fracturing fluid, and stir it through the stirring device, open valve 1, close the valve at the output end of the visual built-in sand delivery panel, which is to close the recovery unit valve 3, where valve 3 is only opened at the end of the experiment to recover waste liquid and clean the experimental equipment, and the proppant reflux detection pipeline valve 4 is only opened when testing the proppant reflux; S2: Start the screw pump to inject the fully mixed fracturing fluid and proppant into the visual built-in sand delivery panel through the perforation. The flow meter measures the fluid flow in the pipeline. After the sand-carrying fluid passes through the visual built-in sand delivery panel and the proppant settles to form a sand bank, it is discharged into the fracturing fluid recovery cylinder through the output end. After the sand-carrying fluid is pumped in, turn off the screw pump. S3: Flowback fluid pumping process: After the sand-carrying fluid is pumped in, shut down the screw pump and close valve 1, maintain the closing pressure and the pressure in the seam, and allow the proppant to settle freely, simulating a shut-in. After the well is shut in, open valve 2 at the flowback fluid input end, start the horizontal flow pump, and pump the flowback fluid in from the liquid pump inlet. During this period, close valve 3 and open valve 4. S4: Observe the changes in the proppant laying conditions through the detection unit and record the reflux volume, end the experiment, stop the pump, close all valves, reduce the temperature and pressure, and clean the experimental equipment.

2. The testing method of the integrated visualization experimental device for proppant transport and reflux under in-situ environmental conditions according to claim 1, wherein the recovery unit consists of a waste liquid recovery cylinder, a liquid recovery pipeline, a measuring cylinder and a balance. The measuring cylinder and balance are used to collect and record the proppant reflux situation, and the waste liquid recovery cylinder recovers excess waste liquid.

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