Visual proppant migration experiment device used in sand-carrying acid fracturing crack

Abstract

The invention belongs to the technical field of petroleum and natural gas yield increase transformation, and provides a visual proppant migration experiment device used in a sand-carrying acid fracturing fracture, which comprises a plunger pump, a liquid supply tank, a liquid supply tank heater, a sand mixing tank, a gas supply bottle, a visual fracture system, a waste liquid tank, a computer data acquisition system and a high-speed camera. Two micropore plates of the visual crack system are arranged between a front cover plate and a rear cover plate in parallel at intervals, micropores are evenly distributed in the micropore plates, gas in the space between the front cover plate and the rear cover plate and the micropore plates can enter a crack space, and meanwhile the injection direction of the gas is changed into the transverse direction relative to the crack space from the vertical direction. The device can effectively simulate the influence of different sand-carrying fluid viscosities, gas volume proportions, sand ratios, particle sizes, tracing proppant proportions and temperatures on the migration of the proppant in the acid sand-carrying fracturing crack and the distribution form of the sand bank.

Description

Technical Field

[0001] The invention relates to the technical field of oil and natural gas production enhancement and modification, and in particular to a visual proppant migration experimental device for sand-carrying acid fracturing fractures. Technical Background

[0002] In oil and gas field development, acid fracturing with sand significantly improves the fracture conductivity of carbonate reservoirs through the synergistic effect of acid dissolution and proppants, and has become a core technology for deep oil and gas development. However, the migration pattern of proppants within the fracture directly affects the fracturing effect. Unlike conventional hydraulic fracturing, acid-sand fracturing is always accompanied by acid-rock reactions. Acid-rock reactions can produce free CO2 gas, which changes the properties of the acid and directly affects the sedimentation of proppants in the fractures. Therefore, to study the migration and placement of proppants in acid-sand fracturing fractures, the presence of CO2 gas cannot be ignored. Existing proppant migration experimental devices are generally used to simulate the proppant migration process in hydraulic fracturing. There is currently no experimental device that can study proppant migration under gas-liquid-solid three-phase coupling conditions. Summary of the Invention

[0003] To address these issues, the present invention proposes a visual proppant migration experimental device for sand-carrying acid fracturing fractures to simulate the synergistic process of acid-rock reaction and proppant transport. This device allows real-time observation of proppant settling and placement patterns in a coupled gas-liquid-solid three-phase flow, and reveals the intrinsic relationship between fracture morphology, fluid properties, and proppant migration through multi-field coupling analysis. This technology transcends the limitations of traditional hydraulic fracturing simulations, providing a reliable experimental platform for sand-carrying acid fracturing process optimization, fracture conductivity prediction, and complex reservoir reconstruction, significantly enhancing the efficiency of deep oil and gas resource development.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention provides a visual proppant migration experimental device for sand-carrying acid fracturing fractures, comprising: a plunger pump, a liquid supply tank, a liquid supply tank heater, a sand mixing tank, a gas supply bottle, a visual fracture system, a waste liquid tank, a computer data acquisition system and a high-speed camera. The liquid supply tank is connected to the input end of the plunger pump and has a built-in liquid supply tank heater; the sand mixing tank is connected to the liquid supply tank through a pipeline; the electromagnetic flowmeter is respectively connected to the sand mixing tank and the liquid supply tank through pipelines; the visual crack system is connected to the electromagnetic flowmeter, and the visual crack system includes a left cover plate, a right cover plate, an upper cover plate, a lower cover plate, a front cover plate, a rear cover plate and two microporous plates, the front cover plate and the rear cover plate are made of transparent material, the two microporous plates are arranged in parallel and spaced apart between the front and rear cover plates, the left cover plate includes a plurality of liquid inlets, the lower cover plate has two rows of air inlets, which are respectively located between the front cover plate and the microporous plate and between the rear cover plate and the microporous plate. When injecting gas, the gas is filled in the space between the front and rear cover plates and the microporous plates, and the microporous plates are evenly distributed on the microporous plates. The micropores are distributed, which can allow the gas in the space between the front and rear cover plates and the microporous plate to enter the crack space, and at the same time, the gas injection direction is changed from the vertical direction to the horizontal direction relative to the crack space, so as to simulate the situation in which the gas is generated from both sides of the rock crack wall and enters the crack space when the acid reacts with the rock wall, converting the chemical process into a physical process, and being able to quantitatively control the amount of gas in the crack by adjusting the air intake rate; the gas supply bottle is connected to the gas flow meter, the air intake control valve and the two rows of air inlets of the lower cover plate through a pipeline; the computer data acquisition system is connected to the electromagnetic flow meter and the gas flow meter respectively through a data line to accurately record the liquid intake and air intake in the experiment; the high-speed camera is used to record the proppant laying morphology in the crack in real time.

[0006] Furthermore, the crack visualization system further includes an upper heating block and a lower heating block, wherein the upper heating block contacts the upper cover plate, and the lower heating block contacts the lower cover plate.

[0007] Furthermore, the microporous plate is connected to the upper cover plate and the lower cover plate through the upper clamping plate groove and the lower clamping plate groove respectively.

[0008] Furthermore, the microporous plate is a smooth-surface microporous plate or a rough-surface microporous plate.

[0009] Furthermore, the top end of the liquid supply tank is connected to the steam safety valve, and the bottom end is connected to the vent valve A.

[0010] Furthermore, a valve A is provided between the sand mixing tank and the liquid supply tank.

[0011] Furthermore, a valve C is provided between the sand mixing tank and the electromagnetic flowmeter.

[0012] Furthermore, a valve B is provided between the liquid supply tank and the electromagnetic flowmeter.

[0013] Furthermore, liquid inlet control valve A, liquid inlet control valve B, and liquid inlet control valve C are respectively provided between the visual crack system and the electromagnetic flowmeter, and the left cover plate includes liquid inlet A, liquid inlet B, and liquid inlet C, which are respectively connected to liquid inlet control valve A, liquid inlet control valve B, and liquid inlet control valve C through pipelines.

[0014] Furthermore, the top end of the right cover plate is connected to the exhaust safety valve through a pipeline, and the bottom end of the right cover plate is connected to the vent valve B through a pipeline.

[0015] The advantages and positive effects of the present invention are:

[0016] The visual proppant migration experimental device for sand-carrying acid fracturing fractures of the present invention can effectively simulate the effects of different sand-carrying fluid viscosities, gas volume ratios, sand ratios, particle sizes, tracer proppant ratios, and temperatures on proppant migration and sand bank distribution morphology in acid sand fracturing fractures. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic structural diagram of a device for visualizing proppant migration in sand-carrying acid fracturing fractures according to the present invention.

[0018] Figure 2 for Figure 1 Stereoscopic image of the fracture visualization system.

[0019] Figure 3 for Figure 2 3D exploded view of .

[0020] 1-Computer data acquisition system; 2-High-speed camera; 3-Plunger pump; 4-Liquid supply tank; 5-Vent valve A; 6-Steam safety valve; 7-Liquid supply tank heater; 8-Valve B; 9-Valve A; 10-Sand mixing tank; 11-Valve C; 12-Electromagnetic flowmeter; 13-Liquid inlet control valve A; 14-Liquid inlet control valve B; 15-Liquid inlet control valve C; 16-Liquid inlet A; 17-Liquid inlet B; 18-Liquid inlet C; 19-Left Cover; 20-upper heating block; 21-upper cover; 22-upper clamping plate groove; 23-rear cover; 24-microplate; 25-front cover; 26-lower cover; 27-lower clamping plate groove; 28-air inlet; 29-lower heating block; 30-right cover; 31-drain port; 32-vent valve B; 33-exhaust safety valve; 34-exhaust port; 35-waste liquid tank; 36-gas flow meter; 37-inlet control valve; 38-gas supply bottle. DETAILED DESCRIPTION

[0021] The present invention will be further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the scope of protection of the present invention cannot be limited thereto.

[0022] like Figure 1 The device shown is a visualization proppant migration experimental device for sand-carrying acid fracturing fractures, comprising a plunger pump 3, a liquid supply tank 4, a liquid supply tank heater 7, a sand mixing tank 10, a gas supply bottle 38, a visualization fracture system, a waste liquid tank 35, a computer data acquisition system 1, and a high-speed camera 2.

[0023] The plunger pump 3 is connected to the liquid supply tank 4. The reciprocating motion of the plunger in the cylinder changes the volume of the sealed working chamber to transport the liquid. It has the advantages of high working pressure, high transmission power, and long service life. In addition, the flow rate can be changed by changing the stroke of the plunger, and it is easy to make various variable types.

[0024] The liquid supply tank 4 is connected to the input end of the plunger pump 3; a built-in liquid supply tank heater 7 is capable of constant temperature control of the temperature of the supplied liquid; the top end is connected to the steam safety valve 6, which can discharge excess steam in time to prevent abnormal pressure increase in the liquid supply tank 4 from causing damage to personnel, equipment and pipelines; the bottom end is connected to the vent valve A5, which can discharge the remaining liquid in the experiment; it is connected to the sand mixing tank 10 through a pipeline, and a valve A9 is provided between the liquid supply tank 4 and the sand mixing tank 10; it is connected to the electromagnetic flowmeter 12 through a pipeline, and a valve B8 is provided between the liquid supply tank 4 and the electromagnetic flowmeter 12.

[0025] The sand mixing tank 10 is connected to the liquid supply tank 4 through a pipeline, and a valve A9 is provided between the sand mixing tank 10 and the liquid supply tank 4; it is connected to the electromagnetic flowmeter 12 through a pipeline, and a valve C11 is provided between the sand mixing tank 10 and the electromagnetic flowmeter 12.

[0026] Electromagnetic flowmeter 12 is connected to the visual crack system. Liquid inlet control valves A13, B14, and C15 are respectively installed between the electromagnetic flowmeter 12 and the visual crack system. Electromagnetic flowmeter 12 is a volumetric flowmeter based on the Faraday principle of electromagnetic induction. Its sensor consists of a coil, electrodes, and an insulating lining. It features a simple structure with no moving parts or throttling components that would impede fluid flow. This eliminates any additional pressure loss when fluid passes through it, resulting in low operating energy consumption. During measurement, electromagnetic flowmeter 12 does not come into contact with the fluid and is therefore unaffected by the temperature, viscosity, density, and conductivity (within a certain range) of the measured medium. This makes it suitable for measuring corrosive or abrasive fluids, offering high sensitivity and a wide measuring range.

[0027] like Figure 2 , Figure 3As shown, the visualization crack system includes a left cover plate 19, a right cover plate 30, an upper cover plate 21, a lower cover plate 26, a front cover plate 25, a rear cover plate 23, a microplate 24, an upper heating block 20, and a lower heating block 29. The left cover plate 19, right cover plate 30, upper cover plate 21, and lower cover plate 26 are made of stainless steel; the front cover plate 25 and rear cover plate 23 are made of transparent tempered glass. The left cover plate includes liquid inlet A16, liquid inlet B17, and liquid inlet C18, which are connected to liquid inlet control valves A13, B14, and C15 via pipelines, respectively, allowing independent control of the liquid inlet position. The top of the right cover plate 30 is connected to an exhaust safety valve 33 via a pipeline, which can promptly discharge excess gas and prevent abnormal pressure increases in the crack from damaging personnel, equipment, and pipelines. The bottom of the right cover plate 30 is connected to a vent valve B32 via a pipeline to discharge experimental waste liquid. The lower cover plate 26 is connected to a gas flow meter 36, an air inlet control valve 37, and a gas supply bottle 38 via pipelines. The upper and lower heating blocks 20 and 29 are in contact with the upper and lower cover plates 21 and 26, respectively, to maintain the temperature of the fracture system. The microporous plates 24 are connected to the upper and lower cover plates 21 and 26, respectively, via upper and lower clamping plate grooves 22 and 27. The microporous plates 24 are available in smooth and rough surface styles to study proppant migration under different acid fracturing fracture morphologies.

[0028] The gas supply bottle 38 is connected to the gas flow meter 36, the air intake control valve 37 and the lower cover plate 26 through a pipeline. The air inlets 28 on both sides of the lower cover plate 26 are respectively located between the front and rear cover plates 23 and the microporous plate 24. When gas is injected, the gas is filled in the space between the front and rear cover plates 23 and the microporous plate 24.

[0029] The microporous plate 24 is connected to the upper cover plate 21 and the lower cover plate 26 through the upper clamping plate groove 22 and the lower clamping plate groove 27 respectively to form a gas-liquid-solid three-phase flow fracture space. The microporous plate 24 is evenly distributed with micropores, which can allow the gas in the space between the front and rear cover plates 23 and the microporous plate 24 to enter the fracture space, and at the same time change the injection direction of the gas from the vertical direction to the horizontal direction relative to the fracture space, so as to simulate the situation when the acid reacts with the rock wall, and the gas is generated from both sides of the rock fracture wall and enters the fracture space, thereby converting the chemical process into a physical process and being able to quantitatively control the amount of gas in the fracture by adjusting the gas intake rate. The microporous plate 24 styles include smooth surface microporous plates and rough surface microporous plates as well as microporous plates 24 with different pore sizes to simulate the migration of proppant in acid-sand-carrying fractures under different working conditions.

[0030] The computer data acquisition system 1 is connected to the electromagnetic flowmeter 12 and the gas flowmeter 36 via data lines, respectively, to accurately record the liquid intake and gas intake during the experiment.

[0031] The high-speed camera 2 is used to record the proppant placement morphology in the fracture in real time.

[0032] The method of using this device is:

[0033] 1. Preparation before the experiment

[0034] (1) Equipment inspection and installation

[0035] Component connection confirmation: Check whether the pipeline connections of components such as the plunger pump 3, liquid supply tank 4, sand mixing tank 10, electromagnetic flowmeter 12, visual crack system, and gas supply bottle 38 are firm and whether the valves are in the closed state.

[0036] Installation of the visual crack system: Select a smooth or rough microporous plate 24 according to experimental requirements, and fix it between the upper cover plate 21 and the lower cover plate 26 through the upper clamping plate groove 22 and the lower clamping plate groove 27, ensuring that the front cover plate 25 and the rear cover plate 23 (transparent material) are well sealed to form a crack space.

[0037] Heating system settings: Start the liquid supply tank heater 7, the upper heating block 20 and the lower heating block 29, adjust the liquid temperature in the liquid supply tank 4 and the fracture system temperature to the temperature required for the experiment (such as simulated formation temperature), and monitor in real time through the temperature sensor.

[0038] (2) Fluid and proppant configuration

[0039] Preparation of sand-carrying fluid: Sand-carrying fluids of varying viscosities (e.g., base fluid + thickener) are prepared in the fluid supply tank 4 and thermostatically controlled by the fluid supply tank heater 7. Proppant (including tracer proppant) and a portion of the sand-carrying fluid are mixed in the sand mixing tank 10 according to the designed sand ratio (proppant volume ratio) and stirred evenly.

[0040] Gas preparation: The gas supply cylinder 38 is filled with CO2 or other simulated gas, and the initial gas intake rate (simulating the gas production rate of the acid-rock reaction) is set through the gas flow meter 36 and the gas intake control valve 37.

[0041] (3) Initialization of detection and recording system

[0042] Data acquisition system: Connect the computer data acquisition system 1 with the electromagnetic flowmeter 12 and the gas flowmeter 36, and debug the software to ensure real-time recording of the liquid intake, gas intake and time parameters.

[0043] High-speed camera: Aim the high-speed camera 2 at the front cover plate 25 and the rear cover plate 23, adjust the focus until the fracture space is clearly imaged, and start the video function to prepare to record the proppant migration pattern in real time.

[0044] 2. Experimental Procedure

[0045] (1) Fluid injection and fracture filling

[0046] Pre-injection of base fluid: Open valve B8 between the fluid supply tank 4 and the electromagnetic flowmeter 12, start the plunger pump 3, and inject pure base fluid (without proppant) into the visualized fracture system at a low flow rate to remove air from the fracture space until stable liquid is discharged from the waste liquid tank 35, and then close valve B8.

[0047] Sand-carrying fluid injection:

[0048] Open the valve C11 between the sand mixing tank 10 and the electromagnetic flowmeter 12, and the valve A9 between the sand mixing tank and the liquid supply tank, start the plunger pump 3, and inject the sand-carrying liquid in the sand mixing tank 10 into the crack system through the liquid inlet A / B / C of the left cover plate 19 and the corresponding liquid inlet control valve A / B / C (a single liquid inlet or multiple liquid inlets can be selected for injection at the same time to simulate different crack entrance shapes).

[0049] The flow rate is monitored in real time by the electromagnetic flowmeter 12, and the plunger pump speed is adjusted to the target flow rate (corresponding to the sand-carrying liquid flow rate of the experimental design).

[0050] Gas injection: Synchronously open the air intake control valve 37, and adjust the air intake rate through the gas flow meter 36 according to the gas volume ratio of the experimental design. The gas is filled into the space between the front / rear cover plate and the microporous plate 24 through the two rows of air inlets 28 of the lower cover plate 26, and then enters the fracture space in the transverse direction (simulating the gas production direction of the acid-rock reaction) through the micropores of the microporous plate, forming a gas-liquid-solid three-phase flow with the sand-carrying fluid.

[0051] (2) Dynamic observation and parameter adjustment

[0052] Real-time recording: The high-speed camera 2 continuously records the migration trajectory of the proppant in the fracture, the settlement process and the distribution morphology of the sand bank (such as suspension, rolling, and accumulation). The computer data acquisition system 1 simultaneously records parameters such as flow rate, air intake, and temperature.

[0053] Parameter adjustment:

[0054] If the sand ratio or particle size needs to be changed, the plunger pump 3 is stopped, the sand mixing tank 10 is emptied and the proppant is reconfigured, and the sand-carrying fluid injection step is repeated.

[0055] If the gas volume ratio needs to be adjusted, the air intake rate is adjusted in real time through the air intake control valve 37; if different crack wall roughness needs to be simulated, the machine is stopped and the smooth / rough surface microporous plate 24 is replaced.

[0056] Multi-condition simulation: By changing the viscosity of the liquid in the liquid supply tank 4 (changing the base liquid formula), adjusting the temperature of the heating block (simulating formation temperature changes), or adjusting the liquid inlet combination (simulating fracture branching morphology), multiple groups of comparative experiments are carried out.

[0057] (3) End of experiment and data collection

[0058] Stop injection: first close the air inlet control valve 37 and the air supply bottle 38, then stop the plunger pump 3, close all liquid inlet control valves (13 / 14 / 15), valves A / B / C (9 / 8 / 11) to prevent fluid backflow.

[0059] Pressure release and drainage: Open the exhaust safety valve 33 at the top of the right cover plate 30 to release the residual gas in the fracture. After the pressure returns to zero, open the bottom vent valve B32 to drain the waste liquid into the waste liquid tank 35. If necessary, flush the residual proppant in the fracture system with clean water.

[0060] Data preservation: Export the flow rate, air intake volume, temperature and other data from the computer data acquisition system 1, and classify and store the videos and images taken by the high-speed camera 2 and annotate the experimental parameters, such as time, sand ratio, gas ratio, etc.

[0061] 3. Equipment maintenance and cleaning

[0062] Component cleaning: disassemble the sand mixing tank 10 , electromagnetic flowmeter 12 and detachable components of the fracture system, and clean the remaining proppant and sand-carrying fluid with clean water or solvent to avoid clogging the micropores of the microporous plate 24 .

[0063] Inspection and reset: Check whether the valves, sealing rings and other wearing parts are intact, and replace the aging parts; reset the parts of the equipment to prepare for the next experiment.

[0064] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention.

Claims

1. A visual proppant migration experimental device for sand-carrying acid fracturing fractures, characterized in that: include: Plunger pump (3); A liquid supply tank (4) is connected to the input end of the plunger pump (3) and has a built-in liquid supply tank heater (7); A sand mixing tank (10), the sand mixing tank (10) is connected to the liquid supply tank (4) via a pipeline; an electromagnetic flowmeter (12), the electromagnetic flowmeter (12) being connected to the sand mixing tank (10) and the liquid supply tank (4) through pipelines; A visual crack system is connected to the electromagnetic flowmeter (12), and the visual crack system includes a left cover plate (19), a right cover plate (30), an upper cover plate (21), a lower cover plate (26), a front cover plate (25), a rear cover plate (23) and two microporous plates (24), wherein the front cover plate (25) and the rear cover plate (23) are made of transparent material, and the two microporous plates (24) are arranged in parallel and spaced apart between the front and rear cover plates, the left cover plate includes a plurality of liquid inlets, and the lower cover plate (26) has two rows of air inlets (28), which are respectively located between the front cover plate (25) and the microporous plates (24) and the rear cover plate. The gas is injected into the space between the front and rear cover plates and the microporous plate (24). The microporous plate (24) is evenly distributed with micropores, which can allow the gas in the space between the front and rear cover plates and the microporous plate (24) to enter the crack space. At the same time, the injection direction of the gas is changed from the vertical direction to the horizontal direction relative to the crack space, so as to simulate the situation in which the gas is generated from both sides of the rock crack wall and enters the crack space when the acid reacts with the rock wall, thereby converting the chemical process into a physical process and being able to quantitatively control the amount of gas in the crack by adjusting the gas intake rate. A gas supply bottle (38), wherein the gas supply bottle (38) is connected to a gas flow meter (36), an air intake control valve (37) and two rows of air intake ports (28) of a lower cover plate (26) through pipelines; Computer data acquisition system (1): The computer data acquisition system (1) is connected to the electromagnetic flow meter (12) and the gas flow meter (36) through data lines, and accurately records the liquid intake and gas intake in the experiment; A high-speed camera (2) is used to record the proppant placement morphology in the fracture in real time.

2. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: The crack visualization system further comprises an upper heating block (20) and a lower heating block (29), wherein the upper heating block (20) contacts the upper cover plate (21), and the lower heating block (29) contacts the lower cover plate (26).

3. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: The microporous plate (24) is connected to the upper cover plate (21) and the lower cover plate (26) via the upper clamping plate groove (22) and the lower clamping plate groove (27), respectively.

4. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: The microporous plate (24) is a smooth-surface microporous plate or a rough-surface microporous plate.

5. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: The top end of the liquid supply tank (4) is connected to the steam safety valve (6), and the bottom end is connected to the vent valve A (5).

6. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: A valve A (9) is provided between the sand mixing tank (10) and the liquid supply tank (4).

7. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: A valve C (11) is provided between the sand mixing tank (10) and the electromagnetic flowmeter (12).

8. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: A valve B (8) is provided between the liquid supply tank (4) and the electromagnetic flowmeter (12).

9. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: A liquid inlet control valve A (13), a liquid inlet control valve B (14), and a liquid inlet control valve C (15) are respectively provided between the visual crack system and the electromagnetic flowmeter (12); the left cover plate (19) comprises a liquid inlet A (16), a liquid inlet B (17), and a liquid inlet C (18), which are respectively connected to the liquid inlet control valve A (13), the liquid inlet control valve B (14), and the liquid inlet control valve C (15) through pipelines.

10. The visual proppant migration experimental device for sand-carrying acid fracturing fractures according to claim 1, characterized in that: The top end of the right cover plate (30) is connected to the exhaust safety valve (33) through a pipeline, and the bottom end of the right cover plate (30) is connected to the vent valve B (32) through a pipeline.

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