Proppant transportability testing device and operation method thereof

Abstract

The invention discloses a proppant transportability testing device and an operation method thereof, and belongs to the technical field of oil and gas field yield increase, and the device comprises a liquid supply system, a flat plate visual model system and a measurement and detection system. Meanwhile, the invention further discloses an operation method of the proppant transportability testing device. According to the technical scheme, the migration and laying states of the proppant in a vertical well, a horizontal well and a horizontal crack are simulated through experiments; the sedimentation rule of the propping agent in different fracturing fluids is simulated, and fracturing fluid matching optimization is carried out, so that the novel fracturing fluid and the propping agent are subjected to system test evaluation; and parameters such as construction displacement, fracturing fluid flowback speed and the like are optimized.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field production increase, and relates to a proppant transportability testing device and an operating method thereof. Background Art

[0002] As an unconventional natural gas, shale gas has great development potential. However, shale reservoirs are different from conventional oil and gas reservoirs, and are characterized by low porosity, low permeability, and density. At present, hydraulic fracturing technology is an effective measure to increase injection wells and production wells. Its purpose is to produce sand-filled fractures with high conductivity in the formation, which communicate with natural fractures to form a complex fracture network. The reservoir transformed by hydraulic fracturing can form a complex fracture network structure, which is conducive to the output of natural gas and greatly improves the recovery rate.

[0003] As the fracturing fluid is continuously injected into the target formation, the pressure in the target formation at the bottom of the well continues to rise. When this pressure is higher than the formation pressure near the rock and the tensile strength of the rock mass, the natural fractures in the formation are opened. Continuing to inject fracturing fluid into the formation will form a hydraulic fracture with high conductivity. In this process, the proppant enters the open fracture along with the fracturing fluid, supporting the open fracture. The purpose is to prevent the originally opened fracture from gradually closing under the action of geostress after the pumping procedure stops, resulting in a significant reduction in the fracture conductivity and a significant decrease in oil and gas production capacity. During hydraulic fracturing, geostress acts on the filling fractures, and the compacted proppant porous medium enables the closed fractures to maintain a certain high conductivity, providing a seepage channel for the flow of water and gas in the formation.

[0004] Whether the proppant can be effectively laid during hydraulic fracturing largely determines the success or failure of the operation and the effect of increasing production. At present, the migration and sedimentation laws of proppant are mostly concentrated in theory, lacking the necessary experimental research and relevant complete test equipment. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects existing in the prior art and provide a proppant transportability testing device and an operating method thereof, which simulates the migration and laying state of the proppant in vertical wells, horizontal wells and horizontal cracks through experiments; simulates the sedimentation law of the proppant in different fracturing fluids, optimizes the fracturing fluid matching, and thus conducts systematic testing and evaluation of new fracturing fluids and proppants; and optimizes parameters such as construction displacement and fracturing fluid return speed.

[0006] The embodiment of the present invention is achieved as follows:

[0007] On the one hand, an embodiment of the present invention provides a proppant transportability testing device, including a liquid supply system, a flat visual model system, a measurement and detection system, etc.;

[0008] The liquid supply system is responsible for stirring the fracturing fluid and proppant to make them evenly mixed, and pressurizing the mixed liquid to make it enter the flat-panel visual model system; the flat-panel visual model system is responsible for the transportation of the mixed liquid, and its pipes and plates are made of transparent fully visible PC material, which is convenient for experimenters to observe; the liquid supply system and the flat-panel visual model system are connected by threads; the measurement and detection system is responsible for collecting and measuring the amount of liquid and sand flowing out of the flat-panel visual model system, and collecting the liquid into the mixing tank; the flat-panel visual model system and the measurement and detection system are connected by metal pipes, and the two ends of the metal pipes are connected to the flat-panel visual model system and the measurement and detection system by threads.

[0009] Furthermore, the liquid supply system includes a motor, a sand mixing liquid storage tank, and a screw pump; the sand mixing liquid storage tank is made of stainless steel, with a system for mixing liquid and solid evenly, and has a capacity of 200L; the sand mixing liquid storage tank is designed as a flange structure, and the top is easy to open and add sand, and is easy to prepare and clean. The screw pump uses a general direct-connected pump, the wetted part is 316L stainless steel, and the maximum displacement is 2.5m 3 / h, the maximum working pressure is 1.2MPa. The motor is a variable frequency motor, and the flow rate is accurately controlled by frequency conversion of the inverter.

[0010] Furthermore, the flat visual model system includes an inlet simulated well network, a flat visual model, connecting pipelines, etc. The inlet of the flat visual model system uses a high-strength transparent fully visible PC tube model to simulate vertical wells and horizontal wells, each with a length of 1 meter and an inner diameter of 40 mm. The arc radius of the connection between the vertical well and the horizontal well is 0.5 meters. The vertical well, horizontal well, etc. are all connected and sealed with stainless steel flanges; the PC visual flat panel is fully transparent.

[0011] Furthermore, the inlet simulation well network adopts a high-strength transparent PC material with an inner diameter of 40mm and a thickness of 5mm. The holes are evenly perforated on the upper and lower sides of the pipe wall, and the hole diameter is 150mm, so that the solid particle mixture is evenly injected into the model, and the hole diameter is adjustable. Different prompts are set at different positions on the top of the inlet simulation wellbore. By rotating the wellbore, different prompt signs are aligned with each other, and the wellbores with different numbers of perforations are aligned with the fracture surface. The hole diameter is designed according to the wellbore diameter to ensure that the hole diameter is much larger than the proppant particle size, so that the proppant can enter the fracture smoothly. In addition, the gap between the inner and outer cylinders is smaller than the proppant particle size, so that the proppant will not enter the gap between the inner and outer cylinders, preventing sand from settling and getting stuck, and the wellbore cannot rotate.

[0012] Furthermore, the flat visual model is mainly composed of 3 PC full-visible cover plates, PC visual flat plate, sealing strip, middle pad, 1 entry simulated wellbore, entry joint, outlet joint, etc. The flat visual model mainly uses rough visualized PC plates with different representative rock surface features to simulate horizontal fractures in the formation; the size of the flat visual model is 1000×300mm, the crack width is 2-10mm, and the crack width can be adjusted by pads; the flat visual model as a whole is composed of 3 models, with a total length of 900mm, a height of 1100mm (excluding joint height), and a thickness of 100m; the overall maximum pressure resistance of the flat visual model is 1MPa.

[0013] Furthermore, the measuring and detecting system includes a flow meter, a pressure sensor, and a digital secondary instrument. The liquid flow meter uses the FLDC series electromagnetic flowmeter with a flow range of 2.83m 3 / h, withstand pressure 1.6MPa, accuracy 0.5%, 4-20mA output current, can be collected by computer through instrument RS485 interface, and there is a separate instrument to display on the control panel, which can display instantaneous flow and cumulative flow. The pressure sensor is Senex brand, with a range of 1MPa and an accuracy of ±0.1%FS. The pressure value is directly displayed by the secondary instrument and can communicate with the computer through the RS232 interface.

[0014] On the other hand, an embodiment of the present invention provides an operating method of a proppant transportability testing device, comprising: step 1, different proppants and fracturing fluid enter a stirring tank, and are stirred by a motor to form a two-phase mixture, and the two-phase mixture enters a vertical well and a horizontal well through an inlet and outlet valve and an injection pump;

[0015] Step 2, entering the horizontal fracture model. At this time, the proppant particles will migrate along a certain trajectory in the parallel plate under the action of gravity, buoyancy, resistance and horizontal carrying force, especially the shear force at the perforation. Most of the proppant particles will eventually settle to the bottom of the fracture, and a small part will be taken away from the end of the fracture. The outflowing fracturing fluid mixture enters two discharge channels through the outlet of the horizontal fracture model;

[0016] Step 3: The mixture is filtered to separate solid particles and liquid, and the liquid is returned to the mixing tank;

[0017] Step 4: When the test device is working, the second flow channel is closed and the first flow channel is opened. When the entire test device reaches a dynamic equilibrium state, the first flow channel is closed and the second flow channel is opened to conduct experimental testing.

[0018] Furthermore, in step 2, of the two discharge channels, the first channel is composed of a pipeline connected by a valve, and the second channel is a pipeline composed of a filter and a flow meter.

[0019] Furthermore, the two flow channel outlets are both connected to the stirring tank, and the pipeline connection forms a whole closed loop, which can realize the circulation of the proppant and fracturing fluid mixture inside the test device.

[0020] Furthermore, in step 2, pressure sensors are provided at the inlet and outlet of the horizontal fracture model to measure the inlet and outlet pressures of the horizontal fracture model. The inlet and outlet pressure differences are changed by adjusting the opening sizes of the inlet and outlet valves, and the migration, settlement and laying states of the proppant in the horizontal simulated fractures are tested under different pump pressures to optimize the pump pressure parameters.

[0021] Furthermore, in step 3, the filter is used to filter out solid particles in the discharged mixture, so that the flow meter can directly measure the fracturing fluid discharge volume and indirectly measure parameters such as the backflow rate of the fracturing fluid. At the same time, the test device can simulate and optimize parameters such as the ratio of different proppants and different fracturing fluids, proppant particle size, concentration, etc.

[0022] The beneficial effects of the embodiments of the present invention are:

[0023] The present invention provides a proppant transportability testing device and an operating method thereof, which can simulate the migration of proppant in vertical wells, horizontal wells, and horizontal fractures, directly observe the proppant laying state and simulate the laying state of different proppant in the same fracturing fluid, grasp the sedimentation law of proppant in different fracturing fluids, and optimize the fracturing fluid matching; optimize the construction displacement, fracturing fluid return speed and other parameters; test and evaluate new fracturing fluids and proppants. It is specifically reflected in the following aspects:

[0024] 1. The testing device provided by the present invention can effectively simulate and optimize the migration and settlement rules of the proppant in the crack and the laying state of different construction displacement, pump pressure, sand-liquid ratio, proppant particle size, viscosity and other parameters.

[0025] 2. The existing device only performs proppant transport tests on a single horizontal fracture model. The test device provided by the present invention is equipped with a vertical well, a horizontal well, and a horizontal fracture model, and can provide a complete set of test processes and devices, which can perform a relatively complete and systematic test on the migration, settlement and laying status of the proppant in the fracture.

[0026] 3. During the hydraulic fracturing operation, the construction displacement and pump pressure will directly change the horizontal migration speed and sedimentation speed of the proppant particles in the fracture, thereby changing the migration time in the fracture and affecting the length of the proppant sedimentation distance. This test device adjusts the construction displacement and inlet pump pressure by adjusting the opening size of the outlet valve V1 of the mixing tank and the outlet valve V2 of the injection pump to simulate the migration, sedimentation and laying of the proppant under different construction displacements and pump pressures.

[0027] 4. The test device provided by the present invention is provided with a dynamic balance circuit, that is, before the working test, the V4 valve is opened and the V5 valve is closed, and the reflux liquid flows back to the stirring tank through the V4 valve. When the whole device reaches dynamic balance, the V4 valve is closed and the V5 valve is opened, and the liquid flows back to the stirring tank through the filter and the flow meter. The test is carried out after the device reaches a balanced state, which can ensure that the test results are more accurate, reduce test errors, and accurately optimize the construction parameters, the selection of proppants, etc.

[0028] 5. Due to the mutual interference between particles, when the proppant particles in the sand-carrying fluid settle, interference settling will occur. The higher the sand-to-liquid ratio, the greater the viscosity of the sand-carrying fluid, which causes the buoyancy and settling resistance of the proppant particles in the sand-carrying fluid to increase, and the settling speed is slower. This test device reasonably modulates the mixing ratio of different fracturing fluid concentrations, components, etc. and different proppant types, particle sizes, and viscosities, and selects the best ratio through corresponding tests to solve different fracturing sand-carrying problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a flow chart of a method for operating a proppant transportability testing device of the present invention;

[0031] Figure 2 is a top view of a wellbore perforation schematic diagram of the present invention;

[0032] Figure 3 It is a front view of a schematic diagram of wellbore perforation of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] like Figure 1As shown, the proppant transportability test device is mainly composed of a liquid supply system, a flat visual model system, a measurement and detection system, etc. Different proppants and fracturing fluids enter the stirring tank 5, and are stirred by a motor to form a two-phase mixture. The two-phase mixture enters the vertical well 2 and the horizontal well 3 through the inlet and outlet valves V1 and the injection pump 8, and then enters the horizontal fracture model 4. At this time, the proppant particles will move along a certain trajectory in the parallel plate under the action of gravity, buoyancy, resistance and horizontal carrying force, especially the shear force at the perforation. Most of the proppant particles will eventually settle to the bottom of the fracture, and a small part will be taken away from the end of the fracture. The outflowing fracturing fluid mixture enters the discharge flow channel through the outlet of the horizontal fracture model. The first flow channel is composed of a pipeline connected by the V4 valve, and the second flow channel is composed of a pipeline composed of a filter 7 and a flow meter. The mixture is separated by the filter 7. The solid particles and liquid, and the liquid flows back to the stirring tank 5. The outlets of the two flow channels are both connected to the stirring tank 5, and the pipeline connection is a whole closed loop, which can realize the circulation of the proppant and fracturing fluid mixture inside the test device. When the test device is working, the second flow channel is closed and the first flow channel is opened. When the entire test device reaches a dynamic equilibrium state, the first flow channel is closed, and the second flow channel is opened at this time to conduct experimental tests. The inlet and outlet of the horizontal fracture model are both provided with pressure sensors for measuring the inlet and outlet pressures of the horizontal fracture model. By adjusting the opening size of the inlet and outlet valves to change the different pressure differences of the inlet and outlet, the migration, sedimentation and laying state of the proppant in the horizontal simulated fracture under different pump pressures are tested to optimize the pump pressure parameters. The filter is mainly used to filter the solid particles discharged from the mixture, so that the flow meter 6 can directly measure the displacement of the fracturing fluid and indirectly measure the parameters such as the backflow speed of the fracturing fluid. At the same time, the test device can simulate and optimize the parameters such as the ratio of different proppants and different fracturing fluids, the particle size of the proppant, and the concentration of the proppant.

[0035] The liquid supply system is mainly composed of a motor, a mixing tank, a valve, a liquid injection pump, a pressure sensor and a safety valve 1. The outlet of the mixing tank is equipped with an outlet valve V1, and the outlet of the liquid injection pump is provided with valves V2 and V3. The outlet of the valve V2 is equipped with a pressure sensor and a safety valve. The pressure sensor is used to measure the inlet pressure of the mixture when it enters the wellhead. The function of the safety valve is to ensure that the output pump pressure of the liquid injection pump is within the controllable pressure range to ensure the safety of the device.

[0036] like Figure 2As shown, the inlet simulation well network adopts a high-strength transparent PC material of Φ40 (inner diameter) × 5mm (thickness), and holes are evenly perforated on the upper and lower sides of the pipe wall. The hole diameter is 1.5cm, so that the solid particle mixture is evenly injected into the model, and the hole diameter is adjustable. Different prompts are set at different positions on the top of the inlet simulation wellbore. Through the rotating device 13, different prompt signs are aligned with each other to ensure that the 9 wellbores with different perforations are aligned with the fracture surface. The hole diameter is designed according to the wellbore diameter to ensure that the hole diameter is much larger than the proppant particle size, so that the proppant can enter the fracture 12 smoothly. In addition, the gap between the inner tube 10 and the outer tube 11 is smaller than the proppant particle size, so that the proppant will not enter the gap between the inner and outer tubes, and prevent sand from getting stuck and the wellbore from being unable to rotate.

[0037] like Figure 3 As shown, the size of the flat visual model is 1000×300mm, the seam width is 2-10mm, and the seam width can be adjusted by a pad; the flat visual model as a whole is composed of 3 models, with a total length of 900mm, a height of 1100mm (excluding the joint height), and a thickness of 100mm; the maximum pressure resistance of the flat visual model as a whole is 1MPa.

[0038] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A proppant transportability testing device, characterized in that: Including liquid supply system, flat visual model system, measurement and detection system; The liquid supply system is used to stir the fracturing fluid and proppant to make them evenly mixed, and pressurize the mixed liquid to make it enter the flat-panel visual model system; the flat-panel visual model system is responsible for the transportation of the mixed liquid, and its pipes and plates are all made of transparent and fully visible PC materials, which is convenient for experimental personnel to observe; the liquid supply system and the flat-panel visual model system are connected by threads; the measurement and detection system is responsible for collecting and measuring the amount of liquid and sand flowing out of the flat-panel visual model system, and collecting the liquid into the mixing tank; The flat panel visual model system is connected with the measuring and detecting system through a metal pipe, and both ends of the metal pipe are connected with the flat panel visual model system and the measuring and detecting system through threads.

2. The proppant transportability testing device according to claim 1, characterized in that: The liquid supply system includes a motor, a sand mixing liquid storage tank, and a screw pump; the sand mixing liquid storage tank is made of stainless steel and has a system for stirring liquid and solid mixing; the sand mixing liquid storage tank is a flange type structure; the screw pump is a universal direct-connected pump, and the motor is a variable frequency motor.

3. The proppant transportability testing device according to claim 1, characterized in that: The flat-panel visual model system includes an inlet simulated well network, a flat-panel visual model, and connecting pipelines; the inlet of the flat-panel visual model system uses a high-strength transparent fully visible PC pipe model to simulate vertical wells and horizontal wells, and the vertical wells and horizontal wells are all connected and sealed with stainless steel flanges; the PC visual flat panel is fully transparent.

4. The proppant transportability testing device according to claim 1, characterized in that: The inlet simulation well network adopts high-strength transparent PC material with an inner diameter of 40mm and a thickness of 5mm. Perforations are evenly perforated on the upper and lower sides of the pipe wall, and the hole diameter is 150mm, so that the solid particle mixture is evenly injected into the model; different prompts are set at different positions on the top of the inlet simulation wellbore, and the wellbore is rotated; the hole diameter is designed according to the wellbore diameter to ensure that the proppant enters the crack smoothly, and the gap between the inner tube and the outer tube is smaller than the support particle diameter.

5. The proppant transportability testing device according to claim 1, characterized in that: The flat-panel visual model includes three PC fully visible cover plates, a PC visible flat plate, a sealing strip, an intermediate pad, an inlet simulated wellbore, an inlet joint, and an outlet joint; the flat-panel visual model uses a rough visualized PC plate with different representative rock surface features to simulate horizontal cracks in the formation, and the crack width is adjusted by pads; the flat-panel visual model as a whole is composed of three models.

6. The proppant transportability testing device according to claim 1, characterized in that: The measuring and detecting system includes a flow meter, a pressure sensor, and a digital secondary instrument; the liquid flow meter adopts the FLDC series electromagnetic flow, which is collected by the computer through the instrument RS485 interface, and a separate instrument is displayed on the control panel; the pressure value is directly displayed by the secondary instrument and communicates with the computer through the RS232 interface.

7. A method for operating the proppant transportability testing device according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Different proppants and fracturing fluid enter a mixing tank, and are stirred by a motor to form a two-phase mixture, and the two-phase mixture enters a vertical well and a horizontal well through an inlet and outlet valve and an injection pump; Step 2, enter the horizontal fracture model. At this time, the proppant particles will move along a certain trajectory in the parallel plate under the action of gravity, buoyancy, resistance and horizontal carrying force, especially the shear force at the perforation. Most of the proppant particles will eventually settle to the bottom of the fracture, and a small part will be taken away from the end of the fracture. The outflowing fracturing fluid mixture enters two discharge channels through the outlet of the horizontal fracture model; Step 3: The mixture is filtered to separate solid particles and liquid, and the liquid is returned to the mixing tank; Step 4: When the test device is working, the second flow channel is closed and the first flow channel is opened. When the entire test device reaches a dynamic equilibrium state, the first flow channel is closed and the second flow channel is opened to conduct experimental testing.

8. The method for operating the proppant transportability testing device according to claim 7, characterized in that: In step 2, of the two discharge flow channels, the first flow channel is composed of a pipeline connected by a valve, and the second flow channel is a pipeline composed of a filter and a flow meter.

9. The method for operating the proppant transportability testing device according to claim 8, characterized in that: The two flow channel outlets are both connected to the stirring tank, and the pipeline connection forms a whole closed loop, which is used to realize the circulation of the proppant and fracturing fluid mixture inside the test device.

10. The method for operating the proppant transportability testing device according to claim 7, characterized in that: In step 2, pressure sensors are provided at the inlet and outlet of the horizontal fracture model to measure the inlet and outlet pressures of the horizontal fracture model. The inlet and outlet pressure differences are changed by adjusting the opening sizes of the inlet and outlet valves. The migration, settlement and laying states of the proppant in the horizontal simulated fractures are tested under different pump pressures to optimize the pump pressure parameters.

11. The method for operating the proppant transportability testing device according to claim 7, characterized in that: In step 3, the filter is used to filter out solid particles in the mixture, so that the flow meter can directly measure the fracturing fluid discharge volume and indirectly measure the backflow velocity parameters of the fracturing fluid. At the same time, the test device can simulate and optimize the ratios of different proppants and different fracturing fluids, proppant particle sizes, and concentration parameters.

Images