An experimental device for proppant transportation that can automatically eliminate air bubbles

Abstract

The present invention discloses a proppant transportation experimental device capable of automatically eliminating air bubbles, which relates to the research field of proppant transportation in the process of hydraulic fracturing. It includes a sand mixing tank, a connecting pipeline, a reducing pipe, a bypass pipe, a transportation pump, a simulated wellbore, a flat fracture and a waste liquid collection tank. The sand mixing tank is connected to the simulated wellbore through a connecting pipeline. A reducing pipe with an enlarged diameter is arranged on the connecting pipeline. A bypass pipe is arranged at the opening on the top of the reducing pipe. A transportation pump is installed on the connecting pipeline. The simulated wellbore is connected to the flat fracture, and the tail outlet of the flat fracture is connected to a waste liquid collection tank. This invention can eliminate air bubbles during the proppant transportation experiment, improve the accuracy of the proppant transportation experiment in studying the transportation law of proppants in fractures during the hydraulic fracturing process, provide strong support for the research on indoor proppant transportation problems, and is of great significance in this field.

Description

Technical Field

[0001] The present invention relates to the research field of proppant transportation during the hydraulic fracturing process, and particularly relates to an experimental device for proppant transportation that can automatically eliminate bubbles. Background Art

[0002] Hydraulic fracturing pumps fracturing fluid into the formation at a displacement exceeding the formation's fluid absorption capacity, generating high pressure exceeding the formation rock fracture pressure to create fractures in the formation. Continuing to inject the fracturing fluid extends the hydraulic fractures; subsequently, a proppant-carrying fluid is injected to further extend the hydraulic fractures and fill the fractures with proppants. After the pump stops, due to the proppants' support effect on the fracture wall surface, a sand-filled fracture with high conductivity is formed in the formation, thereby achieving the purpose of increasing oil and gas well production. The placement pattern of proppants in the fracture will determine the final form and extension law of the fracture. Therefore, studying the transportation law of proppants in the fracture is of great significance for guiding on-site fracturing construction.

[0003] Currently, the most important method for studying the transportation law of proppants in fractures during the hydraulic fracturing process is the large-scale visual flat fracture experiment. By combining different types of plates into various complex fracture structures, the flow law of proppants in the plates can be studied. The Chinese patents authorized as "A Simulation Experiment Method and Experimental Device for Fracturing Proppant Transportation with Real-Time Variable Sand Ratio" (CN110596319A), "An Experimental Device and Method for Simulating the Transportation of Proppant-Carrying Fluid in Fractures" (CN109812254B), "A Flat Plate and Experimental Device for Simulating the Influence of Uniform Filtration Loss in Reservoirs on Proppant Placement" (CN110952971B), and "An Experimental Bench and Experimental Method for Simulating the Transportation and Placement of Proppants in Fractures of Reservoir Fracturing" (CN111553065A) can all achieve proppant transportation experiments in flat fractures under different working conditions. Currently, relevant literature at home and abroad has also reported experimental results on proppant transportation using flat fractures.

[0004] During the experiment, it was found that a large number of bubbles would soon separate from the mixture of fracturing fluid and proppant entering the flat plate cracks. These bubbles gathered at the top of the flat plate cracks, affecting the flow field characteristics at this location and the final experimental results. The reason for this is that during the preparation of the sand-carrying fluid in the experiment, the mixing tank needs to be continuously stirred, and a large number of bubbles will be drawn into the tank by the agitator. At the same time, during the addition of the proppant, a large number of bubbles will enter the mixing tank with the proppant, which will affect the experimental process. When the mixture enters the flat plate cracks, due to the low average flow velocity, the bubbles will quickly float to the top of the cracks and gather. The movement of bubbles and the mixture of fracturing fluid and proppant in the flat plate cracks is a gas-liquid-solid three-phase flow state, while the proppant transportation process under actual engineering conditions is only the solid-liquid two-phase flow of proppant and fracturing fluid. It can be seen that bubbles will cause inaccuracy in the experiment. Therefore, it is very necessary to design a device to eliminate bubbles for the proppant transportation experiment process. Summary of the invention

[0005] In order to solve the above technical problems, the present invention aims to provide a proppant transport experimental device which can automatically eliminate bubbles during the proppant transport experimental process.

[0006] The technical solution of the present invention is as follows:

[0007] A proppant delivery experimental device capable of automatically eliminating bubbles comprises a sand mixing tank, a connecting pipeline, a reducer, a bypass pipe, a delivery pump, a simulated wellbore, a flat fracture and a waste liquid collection tank, wherein the sand mixing tank is connected to the simulated wellbore through a connecting pipeline, a reducer with an enlarged diameter is arranged on the connecting pipeline, a bypass pipe is arranged at an opening at the top of the reducer, a delivery pump is installed on the connecting pipeline, the simulated wellbore is connected to the flat fracture, and a waste liquid collection tank is connected to a tail outlet of the flat fracture.

[0008] Furthermore, the diameter of the reducer , where W is the width of the flow channel in the flat plate crack, and H is the height of the flow channel in the flat plate crack.

[0009] Furthermore, the flat plate crack is composed of two transparent plates, the top and bottom of which are supported and separated by long strip objects.

[0010] Furthermore, the simulated wellbore is a hollow cylinder, and a plurality of holes are opened in the wellbore in the direction of the fracture.

[0011] Furthermore, a valve is provided on the bypass pipe.

[0012] Furthermore, the sand mixing tank is provided with a blade-type agitator, a fracturing fluid inlet pipe and a proppant addition pipe. The blade-type agitator is installed on the top of the sand tank, and the central axis is aligned with the sand mixing tank.

[0013] Furthermore, a flow meter and a pressure gauge are provided at the rear side of the transfer pump.

[0014] Furthermore, the bypass pipe is connected to an antifoaming system.

[0015] Furthermore, the antifoaming system includes an antifoaming tank, a float level gauge arranged at the top of the antifoaming tank, and a drain pipe led out from an opening in the upper part of the antifoaming tank, and an electric control valve is installed on the drain pipe.

[0016] Furthermore, the float level gauge is a magnetic float level gauge.

[0017] The beneficial effects of the present invention include:

[0018] 1. In the present invention, the sand mixing tank uses a carrying sand liquid mixture that stirs and mixes the proppant and the fracturing fluid evenly, and enters the flat fracture device through a transfer pump via a connecting pipeline, a reducer pipe, and a simulated wellbore, and the entire experimental process is completed in the device. Thereafter, the fracturing fluid and part of the proppant flow out of the flat fracture, and finally are collected in the waste liquid collection tank through the connecting pipeline. The reducer pipe is a local component that the carrying sand liquid mixture must flow through during the process of entering the flat fracture. Its structural feature is that the smaller pipe diameter of the connecting pipeline at its front end suddenly changes to a larger pipe diameter. The reducer pipe is horizontally placed, so that air bubbles can float and gather in the reducer pipe, and a bypass pipe that can lead out air bubbles is opened at its top and led upward, so as to effectively collect the air bubbles contained in the mixture.

[0019] 2. In the present invention, in order to further ensure that no air bubble aggregation occurs in the flat fracture during the experimental process, further requirements are made on the diameter of the reducer pipe according to the principle of hydrodynamics. The reason for the air bubbles to float in the fracture is that the flow velocity of the mixture in the fracture is small. If the flow velocity of the mixture in the reducer pipe is less than the flow velocity in the flat fracture, the air bubbles can float and gather in the reducer pipe, and thus be collected by the antifoaming tank. Assuming that the mixture flow rate is Q, the fluid velocity v in the flat fracture is: , in order to satisfy that the flow velocity v1 in the reducer pipe is less than the flow velocity v in the flat fracture, then there is: , that is, it is required: , where D is the pipe diameter of the reducer pipe, W is the width of the flow channel in the flat fracture, and H is the height of the flow channel in the flat fracture.

[0020] 3. In the present invention, the flat fracture is composed of two transparent plates, which is convenient for observation. The top and bottom are supported and separated by long strip-shaped objects, and the top and bottom are supported and separated by long strip-shaped objects to enclose a flow channel in the fracture.

[0021] 4. In the present invention, the simulated wellbore is a hollow cylinder. The fracturing fluid and proppant mixture fills the entire wellbore after flowing into the wellbore during the experiment, and a plurality of holes are opened in the wellbore in the direction of the fracture to simulate the perforation under field conditions.

[0022] 5. In the present invention, a valve is provided on the bypass pipe. When there are fewer bubbles during the experiment, the valve can be closed to stop using the defoaming function.

[0023] 6. In the present invention, a vane stirrer, a fracturing fluid inlet pipe, and a proppant addition pipe are provided on the sand mixing tank. The vane stirrer is installed at the top of the sand tank, and its central axis is aligned with the sand mixing tank. It is used to prepare the sand-carrying fluid required for the experiment. First, the fracturing fluid and the proppant are respectively injected through the fracturing fluid inlet pipeline and the proppant addition pipe, and then the proppant and the fracturing fluid are stirred and mixed into a uniform mixture by the stirring mechanism.

[0024] 7. In the present invention, a flow meter and a pressure gauge are provided behind the delivery pump, which are used to measure the flow rate of the sand-carrying fluid mixture and the inlet and outlet pressures, facilitating adjustment.

[0025] 8. In the present invention, the bypass pipe is connected to a defoaming system, whose function is to collect or discharge the bubbles floating up from the variable-diameter pipe.

[0026] 9. In the present invention, the defoaming system includes a defoaming tank, an electric control valve, a float level gauge, a float ball, and a drain pipe. Its function is to collect the bubbles floating up from the variable-diameter pipe. When the bubbles accumulate to a certain height, they are automatically discharged through the electric control valve, and then the valve is closed to continue collecting the bubbles from the subsequent variable-diameter pipe.

[0027] 10. In the present invention, a magnetic float level gauge can be selected for the float level gauge in the defoaming system. The liquid level is automatically characterized by the up and down movement of the float ball, and then a 4-20 mA electrical signal is output to the electric control valve. When the position of the gas-liquid interface is relatively high, the float ball rises to the high position, the electric control valve closes, and the bubbles in the variable-diameter pipe continuously rise and flow through the bypass pipe into the defoaming tank for accumulation. Part of the liquid in the defoaming tank will flow back to the variable-diameter pipe to form an exchange with the gas phase, and the liquid level continuously drops. As more and more gas phases enter the defoaming tank, the liquid level of the defoaming tank 7 continuously drops. When the float ball drops to a certain position, the electrical signal of the magnetic float level gauge is triggered, the electric control valve opens, and the gas phase in the defoaming tank is continuously discharged through the discharge pipe, and the liquid level in the tank continuously rises. When the liquid level in the tank rises to a certain position, the float level gauge triggers the defoaming system to work, and the electric control valve closes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described in detail below in conjunction with the specification drawings and specific embodiments, where:

[0029] Figure 1 is a schematic structural diagram of the experimental device of a certain embodiment of the present invention.

[0030] Figure 2 is a schematic structural diagram of the defoaming system in the closed state of a certain embodiment of the present invention.

[0031] Figure 3 It is a schematic structural diagram of the elimination system in the working state of a certain embodiment of the present invention.

[0032] In the figure: 1, fracturing fluid inlet pipe; 2, proppant addition pipe; 3, stirring mechanism; 4, sand mixing tank; 5, valve; 6, bypass pipe; 7, defoaming tank; 8, electric control valve; 9, drain pipe; 10, reducing pipe; 11, delivery pump; 12, flowmeter; 13, pressure gauge; 14, simulated wellbore; 15, flat fracture; 16, waste liquid collection tank; 17, float level gauge; 18, upper liquid level interface; 19, float; 20, lower liquid level interface. Specific embodiments

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention.

[0034] Unless otherwise defined, the technical terms or scientific terms used in the disclosure of the present invention should have the ordinary meaning understood by those of ordinary skill in the field to which the disclosure of the present invention pertains. The use of words such as "including" or "comprising" in the disclosure of the present invention means that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. "Upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0035] Embodiment 1

[0036] As a preferred embodiment of the present invention, this embodiment provides an experimental device for transporting proppant that can automatically eliminate bubbles, including a sand mixing tank 4, a connecting pipeline, a reducing pipe 10, a bypass pipe 6, a delivery pump 11, a simulated wellbore 14, a flat fracture 15, and a waste liquid collection tank 16. The sand mixing tank 4 is connected to the simulated wellbore 14 through a connecting pipeline. A reducing pipe 10 with an enlarged diameter is provided on the connecting pipeline. A bypass pipe 6 is provided at the top opening of the reducing pipe 10. A delivery pump 11 is installed on the connecting pipeline. The simulated wellbore 14 is connected to the flat fracture 15, and the tail outlet of the flat fracture 15 is connected to a waste liquid collection tank 16.

[0037] This embodiment has a simple structure and is easy to operate. It can collect the bubbles contained in the mixture in the reducing pipe 10 and then discharge them through the bypass pipe 6, reducing the influence of bubbles during the proppant transportation experiment and improving the accuracy of the proppant transportation experiment in studying the transportation law of proppant in fractures during hydraulic fracturing.

[0038] Embodiment 2

[0039] As another preferred embodiment of the present invention, referring to the appended drawings of the specification Figures 1-3 , the present invention provides a proppant transportation experimental device with automatic bubble elimination, including a fracturing fluid inlet pipe 1, a proppant addition pipe 2, a stirring mechanism 3, a sand mixing tank 4, a valve 5, a bypass pipe 6, a reducer 10, a transfer pump 11, a flowmeter 12, a pressure gauge 13, an anti-foaming system, a simulated wellbore 14, a flat fracture 15, an outlet valve 5, a waste liquid collection tank 16 and connecting pipelines, wherein the anti-foaming system includes an anti-foaming tank 7, a float level gauge 17, a float 19, an emptying pipe 9, and an electric control component.

[0040] The main function of the sand mixing tank 4 is to fully stir and mix the fracturing fluid and proppant added to the tank through the stirring mechanism 3. The tank is a cylindrical container, and a vane-type stirrer with a motor is installed at the top of the sand tank, and its central axis is aligned with the sand mixing tank 4, which can fully stir the mixture in the tank. The outlet of the sand mixing tank 4 is located at the bottom of the tank body, and at the same time, the sand tank is placed higher than other components of the experimental device.

[0041] The valve 5 is a ball valve, and during the experiment, the flow can be cut off and the flow rate can be adjusted through it.

[0042] The transfer pump 11 meets the needs of transporting the solid-liquid two-phase flow mixture, and is selected as a single-screw pump, and the displacement and head are directly selected according to the requirements of the experimental device.

[0043] The flowmeter 12 is an electromagnetic flowmeter 12, and during the experiment, the flow rate of the fracturing fluid and proppant mixture can be measured in real time.

[0044] The pressure gauge 13 is a metal pressure gauge 13, and during the experiment, it instantaneously displays the pressure at the outlet of the pump and the outlet of the flat fracture 15.

[0045] The simulated wellbore 14 is a hollow cylinder made of metal material. For example, Figure 1 a hole is opened in the middle of the left side to introduce the fracturing fluid and proppant mixture, and holes can be opened on the right side according to the experimental requirements to simulate the on-site perforation conditions. At the same time, the direction of the opened hole is directly opposite to the inlet direction of the flat fracture 15, and the size is adapted to the width of the flow channel in the middle of the flat fracture 15.

[0046] The front and back of the flat fracture 15 are made of PC boards, and the top and bottom are supported and separated by long strip-shaped PC board strips. The width of the long strip-shaped object is exactly the width of the simulated fracture required for the experiment. At the same time, the entire fracture plate is fixed by a metal frame on the outside, and the end of the fracture is connected to a slotted wellbore, and the discharged liquid flows out through the hole at the top of the right wellbore.

[0047] The variable-diameter pipe 10 is made of metal material, with a pipe diameter of D and a pipe length of L. An opening is made at the top to connect the vertical bypass pipe 6. In order to effectively separate the bubbles contained in the mixture in the variable-diameter pipe 10, its diameter is determined according to the calculation method in the specification. Assuming that the height of the flow channel in the crack of the flat crack 15 is 30 cm and the width of the flow channel in the crack is 6 mm, the diameter of the variable-diameter pipe 10 is

[0048]

[0049] On the basis of the above calculation, select the corresponding series pipe diameter greater than the calculated value in accordance with the national standard.

[0050] The function of the bypass pipe 6 is to allow the bubbles gathered at the top of the variable-diameter pipe 10 to float smoothly to the defoaming system, and part of the liquid in the defoaming tank 7 can be exchanged into the pipeline. In order to reduce the resistance generated by factors such as surface tension during the floating process of the bubbles, the diameter of the bypass pipe 6 can be taken to be greater than 20 mm. When the valve 5 on this pipeline is closed, the function of the defoaming system stops being used, and when it is opened, the function of the defoaming system is normally enabled.

[0051] In the defoaming system, the defoaming tank 7 is a common liquid tank, and an opening is made at a lower position on the Figure 1 left side to connect the vertical bypass pipe 6, so that when the bubbles float from the variable-diameter pipe 10 into the tank, they can continue to gather at the top of the tank; an opening is made at a higher position on the Figure 1 right side in the middle to lead out the drain pipe 9, and the top is sealed by the installed float level gauge 17.

[0052] In the defoaming system, the float level gauge 17 selects a magnetic float level gauge, which realizes automatic liquid level representation through the up and down movement of the float 19, and then outputs an electric signal of 4 - 20 mA to the electric control valve 8. Among them, when the position of the gas-liquid interface is relatively high, the float 19 rises to the high position as shown in Figure 2 , the electric control valve 8 closes, and the bubbles in the variable-diameter pipe 10 continuously rise and flow through the bypass pipe 6 into the defoaming tank 7 for accumulation. Part of the liquid in the defoaming tank 7 will return to the variable-diameter pipe 10, forming an exchange with the gas phase, and the liquid level continuously drops. As more and more gas phase enters the defoaming tank 7, the liquid level of the defoaming tank 7 continuously drops, and the float 19 drops to the position shown in Figure 3 . The electric signal of the magnetic float level gauge is triggered, the electric control valve 8 opens, and the gas phase in the defoaming tank 7 is continuously discharged from the discharge pipe, and the liquid level in the tank continuously rises. When the liquid level in the tank rises to the position shown in Figure 2 , the float level gauge 17 triggers the defoaming system to work, and the electric control valve 8 closes.

[0053] The drain pipe 9 in the defoaming system is an ordinary metal pipeline, and its outlet is located at Figure 1On the upper right side of the defoaming tank 7, an electric control valve is installed thereon. The pipeline diameter is selected to be a smaller diameter to prevent the flow process from changing too violently during the gas phase discharge process.

[0054] The electric control valve 8 in the defoaming system includes an angular travel electric actuator, and the corresponding valve body can be selected as a butterfly valve, which is opened and closed irregularly under the control of the float level gauge 17.

[0055] The connecting pipeline is a transparent hose with steel rings to meet the low-pressure working conditions. Its orientation can be adjusted flexibly, and the connection with other components is by snap fastening.

[0056] This embodiment provides a proppant transportation experimental device capable of automatically eliminating bubbles, which can automatically eliminate bubbles during the proppant transportation experiment, greatly improving the accuracy of studying the transportation law of proppant in the fracture during the hydraulic fracturing process. At the same time, the defoaming system can be automatically regulated, is convenient to operate and use, and has high applicability.

[0057] Embodiment 3

[0058] As another preferred embodiment of the present invention, a proppant transportation experimental device capable of automatically eliminating bubbles includes a sand mixing tank 4, a connecting pipeline, a reducer 10, a bypass pipe 6, a delivery pump 11, a simulated wellbore 14, a flat fracture 15, and a waste liquid collection tank 16. The sand mixing tank 4 is connected to the simulated wellbore 14 through a connecting pipeline. A reducer 10 with an enlarged diameter is provided on the connecting pipeline. A bypass pipe 6 is provided at the opening at the top of the reducer 10. A delivery pump 11 is installed on the connecting pipeline. The simulated wellbore 14 is connected to the flat fracture 15. The tail outlet of the flat fracture 15 is connected to a waste liquid collection tank 16. The diameter of the reducer 10 , where W is the width of the flow channel in the flat fracture 15, and H is the height of the flow channel in the flat fracture 15. The flat fracture 15 is composed of two pieces of transparent plexiglass, and the top and bottom are supported and separated by long strip plastic sealing strips. The simulated wellbore 14 is a hollow cylinder, and multiple holes are opened in the wellbore in the direction of the fracture.

[0059] This embodiment makes requirements for the diameter of the reducer 10 according to the principle of fluid dynamics, enabling bubbles to float and gather in the reducer 10 and then discharge from the bypass pipe 6, improving the accuracy of studying the transportation law of proppant in the fracture during the hydraulic fracturing process in the proppant transportation experiment, providing strong support for the research on indoor proppant transportation problems, and having important significance in this field.

[0060] Embodiment 4

[0061] As another preferred embodiment of the present invention, a proppant transportation experimental device capable of automatically eliminating bubbles includes a sand mixing tank 4, a connecting pipeline, a reducing pipe 10, a bypass pipe 6, a transportation pump 11, a simulated wellbore 14, a flat fracture 15, and a waste liquid collection tank 16. The sand mixing tank 4 is connected to the simulated wellbore 14 through a connecting pipeline. A reducing pipe 10 with an enlarged diameter is provided on the connecting pipeline. A bypass pipe 6 is provided at the opening at the top of the reducing pipe 10. A transportation pump 11 is installed on the connecting pipeline. The simulated wellbore 14 is connected to the flat fracture 15. The tail outlet of the flat fracture 15 is connected to a waste liquid collection tank 16. The diameter of the reducing pipe 10 , where W is the width of the flow channel in the flat fracture 15, and H is the height of the flow channel in the flat fracture 15. The flat fracture 15 consists of two pieces of transparent plexiglass, which are supported and separated by strip-shaped plastic sealing strips at the top and bottom. The simulated wellbore 14 is a hollow cylinder, and multiple holes are opened in the wellbore in the direction of the fracture. The bypass pipe 6 is connected to an anti-foaming system.

[0062] This embodiment makes requirements for the diameter of the reducing pipe 10 according to the principle of fluid dynamics, enabling the bubbles to float and gather in the reducing pipe 10 and then be discharged from the bypass pipe 6, eliminating the influence of bubbles during the proppant transportation experiment, improving the accuracy of the proppant transportation experiment in studying the transportation law of proppants in fractures during the hydraulic fracturing process, providing strong support for the research on indoor proppant transportation problems. At the same time, the bypass pipe 6 is connected to an anti-foaming system, which further collects and treats the discharged bubbles, preventing random discharge and reducing pollution.

[0063] Example 5

[0064] As another preferred embodiment of the present invention, a proppant transportation experimental device capable of automatically eliminating bubbles includes a sand mixing tank 4, a connecting pipeline, a reducing pipe 10, a bypass pipe 6, a transportation pump 11, a simulated wellbore 14, a flat fracture 15, and a waste liquid collection tank 16. The sand mixing tank 4 is connected to the simulated wellbore 14 through a connecting pipeline. A reducing pipe 10 with an enlarged diameter is provided on the connecting pipeline. A bypass pipe 6 is provided at the opening at the top of the reducing pipe 10. A transportation pump 11 is installed on the connecting pipeline. The simulated wellbore 14 is connected to the flat fracture 15. The tail outlet of the flat fracture 15 is connected to a waste liquid collection tank 16. The flat fracture 15 consists of two pieces of transparent plexiglass, which are supported and separated by strip-shaped plastic sealing strips at the top and bottom. The simulated wellbore 14 is a hollow cylinder, and multiple holes are opened in the wellbore in the direction of the fracture. The bypass pipe 6 is connected to an anti-foaming system. A valve 5 is provided on the bypass pipe 6. A vane stirrer, a fracturing fluid inlet pipe 1, and a proppant addition pipe 2 are provided on the sand mixing tank 4. The vane stirrer is installed at the top of the sand tank, and its central axis is aligned with the sand mixing tank 4. A flowmeter 12 and a pressure gauge 13 are provided behind the transportation pump 11.

[0065] In this embodiment, a vane type stirrer, a fracturing fluid inlet pipe 1 and a proppant addition pipe 2 are provided on the sand mixing tank 4. The vane type stirrer is installed at the top of the sand tank, and its central axis is aligned with the sand mixing tank 4, and is used to prepare the sand-carrying fluid required for the experiment. First, the fracturing fluid and the proppant are respectively injected through the fracturing fluid inlet pipe 1 line and the proppant addition pipe 2, and then the proppant and the fracturing fluid are stirred and mixed into a uniform mixture by the stirring mechanism 3. The sand-carrying fluid mixture with the proppant and the fracturing fluid stirred and mixed evenly enters the flat fracture 15 device through the delivery pump 11 via the connecting pipeline, the reducer 10 and the simulated wellbore 14. The entire experimental process is completed in the device. Bubbles contained in the mixture can be collected in the reducer 10 and then discharged through the bypass pipe 6, reducing the influence of bubbles during the proppant transportation experiment and improving the accuracy of the proppant transportation experiment in studying the transportation law of proppant in the fracture during the hydraulic fracturing process.

[0066] Example 6

[0067] A proppant transportation experimental device capable of automatically eliminating bubbles, including a sand mixing tank 4, a connecting pipeline, a reducer 10, a bypass pipe 6, a delivery pump 11, a simulated wellbore 14, a flat fracture 15 and a waste liquid collection tank 16. The sand mixing tank 4 is connected to the simulated wellbore 14 through a connecting pipeline. A reducer 10 with an enlarged diameter is provided on the connecting pipeline. A bypass pipe 6 is provided at the opening at the top of the reducer 10. A delivery pump 11 is installed on the connecting pipeline. The simulated wellbore 14 is connected to the flat fracture 15. A waste liquid collection tank 16 is connected to the tail outlet of the flat fracture 15. The flat fracture 15 is composed of two pieces of transparent plexiglass, and is supported and separated by long strip PC board strips at the top and bottom. The simulated wellbore 14 is a hollow cylinder, and multiple holes are opened in the wellbore in the direction of the fracture. A valve 5 is provided on the bypass pipe 6. A vane type stirrer, a fracturing fluid inlet pipe 1 and a proppant addition pipe 2 are provided on the sand mixing tank 4. The vane type stirrer is installed at the top of the sand tank. A flow meter 12 and a pressure gauge 13 are provided at the rear side of the delivery pump 11. The bypass pipe 6 is connected to an anti-foaming system. The anti-foaming system includes an anti-foaming tank 7, a float level gauge 17 provided at the top of the anti-foaming tank 7 and an emptying pipe 9 led out from the upper opening of the anti-foaming tank 7. An electric control valve 8 is installed on the emptying pipe 9.

[0068] In this embodiment, the sand mixing tank 4 stirs and mixes the proppant and the fracturing fluid to form a uniform sand-carrying fluid mixture, which enters the flat fracture 15 device through the transfer pump 11 via the connecting pipeline, the reducer 10 and the simulated wellbore 14. The entire experimental process is completed in the device. Bubbles contained in the mixture can be collected in the reducer 10 and then discharged through the bypass pipe 6 to the defoaming system. The defoaming system collects the bubbles floating up from the reducer 10. When the bubbles accumulate to a certain height, they are automatically discharged through the electric control valve 8. Then, the valve 5 is closed, and the bubbles in the subsequent reducer 10 are continuously collected. This embodiment can automatically collect the bubbles during the proppant transportation experiment, greatly improving the accuracy of the proppant transportation experiment in studying the transportation law of the proppant in the fracture during the hydraulic fracturing process. At the same time, the defoaming system can be automatically regulated, and the operation and use are convenient.

[0069] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. An experimental device for transporting proppants that can automatically eliminate air bubbles, characterized in that, It includes a sand mixing tank (4), a connecting pipeline, a reducing pipe (10), a bypass pipe (6), a delivery pump (11), a simulated wellbore (14), a flat fracture (15) and a waste liquid collection tank (16). The sand mixing tank (4) is connected to the simulated wellbore (14) through a connecting pipeline. A reducing pipe (10) with an enlarged diameter is arranged on the connecting pipeline. A bypass pipe (6) is arranged at the opening at the top of the reducing pipe (10). A delivery pump (11) is installed on the connecting pipeline. The simulated wellbore (14) is connected to the flat fracture (15), and the tail outlet of the flat fracture (15) is connected to a waste liquid collection tank (16); the pipe diameter of the reducing pipe (10) , where W is the width of the flow channel in the flat fracture (15), and H is the height of the flow channel in the flat fracture (15).

2. The experimental device for transporting proppants capable of automatically eliminating air bubbles according to claim 1, wherein: The flat crack (15) consists of two transparent plates, which are supported and separated by strip-shaped objects at the top and bottom.

3. The experimental device for transporting proppant capable of automatically eliminating air bubbles according to claim 1, wherein: The simulated wellbore (14) is a hollow cylinder, and multiple holes are drilled in the wellbore in the direction of the crack.

4. The experimental device for transporting proppant capable of automatically eliminating air bubbles according to claim 1, characterized in that: A valve (5) is provided on the bypass pipe (6).

5. The experimental device for transporting proppant capable of automatically eliminating air bubbles according to claim 1, wherein: A vane agitator, a fracturing fluid inlet pipe (1) and a proppant addition pipe (2) are provided on the sand mixing tank (4). The vane agitator is installed at the top of the sand tank, and its central axis is aligned with the sand mixing tank (4).

6. The experimental device for transporting proppant capable of automatically eliminating air bubbles according to claim 1, characterized in that: A flowmeter (12) and a pressure gauge (13) are provided at the rear of the transfer pump (11).

7. An experimental device for transporting proppant capable of automatically eliminating air bubbles according to claim 1, wherein: The bypass pipe (6) is connected to an anti-foaming system.

8. An experimental device for transporting proppant capable of automatically eliminating air bubbles, according to claim 7, characterized in that: The anti-foaming system includes an anti-foaming tank (7), a float level gauge (17) provided at the top of the anti-foaming tank (7), and an emptying pipe (9) led out from an opening in the upper part of the anti-foaming tank (7). An electric control valve (8) is installed on the emptying pipe (9).

9. The experimental device for transporting proppant capable of automatically eliminating air bubbles according to claim 8, wherein: The float level gauge (17) is a magnetic float level gauge.

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