Experimental device and method for simulating sand production of fractured natural gas hydrate reservoir

Abstract

The invention belongs to the technical field of natural gas hydrate reservoir exploitation, and particularly relates to an experimental device and method for simulating sand production of a fractured natural gas hydrate reservoir. The experimental device comprises a constant-temperature control box and a computer system, a hydrate reaction kettle is arranged in the constant-temperature control box, a cross beam is arranged at the top end of the hydrate reaction kettle, the two ends of the cross beam make contact with the side wall of the constant-temperature control box through rails to slide up and down and are controlled through an axial pressure controller, and an axial pressure sensor is arranged at the bottom end of the center of the cross beam; a bracket is arranged at the bottom in the constant-temperature control box for mounting the hydrate reaction kettle; the hydrate reaction kettle barrel is provided with a pressure sensor and a temperature sensor; and each pipeline is provided with an automatic switch valve, and each automatic switch valve is connected with a computer system. The fracture model is generated through the 3D printing technology, the fracture form and distribution in an actual reservoir can be accurately simulated, and the experimental device is simple in structure, easy to operate and capable of being widely applied to laboratory research of natural gas hydrate reservoir exploitation.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas hydrate reservoir exploitation, and in particular relates to a device and method for simulating sand production from a natural gas hydrate reservoir containing fractures. Background Art

[0002] Natural gas hydrates have attracted much attention from all over the world due to their large reserves, wide distribution range and pollution-free characteristics. Whether natural gas hydrates can be commercially exploited is of great strategic significance to ensuring national energy security and high-quality economic development. Due to the limitations of phase equilibrium conditions and geothermal gradients, natural gas hydrates are mainly distributed in deep sea and permafrost areas, and the reservoirs are characterized by shallow burial depth and poor cementation. Judging from the hydrate pilot projects that have been carried out around the world, sand production is an inevitable phenomenon in the hydrate production process and has become one of the bottleneck problems restricting the safe and efficient exploitation of hydrates. Reservoir transformation can increase the strength of hydrate-containing reservoirs, improve the stability of the reservoirs, and provide guarantees for the safe drilling and production of hydrates. However, there is currently little research on the sand production mechanism and sand control methods of reservoirs after reservoir transformation. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide an experimental device and method for simulating sand production from fractured natural gas hydrate reservoirs. By generating a fracture model using 3D printing technology, the experimental device can accurately simulate the fracture morphology and distribution in actual reservoirs. The experimental device has a simple structure and is easy to operate, making it widely applicable to laboratory research on natural gas hydrate reservoir extraction.

[0004] The technical solutions adopted are:

[0005] A device for simulating sand production from a fractured natural gas hydrate reservoir comprises a constant temperature control box and a computer system. A hydrate reactor is disposed within the constant temperature control box, and a crossbeam is disposed at the top of the hydrate reactor. Both ends of the crossbeam contact the side walls of the constant temperature control box via rails to enable up and down sliding. The crossbeam is controlled by an axial pressure controller, and an axial pressure sensor is disposed at the center bottom of the crossbeam. A bracket is disposed at the bottom of the constant temperature control box to mount the hydrate reactor.

[0006] The hydrate reactor comprises a cylinder, which is provided with an upper cover and a lower cover. An inverted T-shaped piston is provided at the top of the cylinder, the vertical end of the piston passes through the center of the upper cover, an air inlet and a water inlet are provided on the piston, a gas booster pump and a constant flow pump are connected to the air inlet and water inlet of the piston respectively through pipelines, and a gas flow controller is also provided on the pipeline of the gas booster pump; the lower cover is provided with air inlet and outlet, and water outlet, and a product collector is connected to the air inlet and outlet, and water outlet through pipelines; a pressure sensor is provided at one end of the side wall of the hydrate reactor cylinder, and a temperature sensor is provided at the other end;

[0007] The axial pressure controller, axial pressure sensor, pressure sensor and temperature sensor are connected to the computer system. Automatic switch valves are arranged on each pipeline, and each automatic switch valve is connected to the computer system.

[0008] Preferably, the upper cover is connected to the cylinder of the hydrate reactor through a sealing thread, and a sealing ring is installed at the connection. An opening adapted to the piston is provided in the center of the upper cover.

[0009] Preferably, two pipelines are set at the gas booster pump, one connecting to the gas cylinder and the other connecting to the air compressor; an automatic switching valve is installed at the outlet of the gas cylinder, and an automatic switching valve, a pressure gauge and a pressure reducing valve are set on the pipeline connecting to the air compressor.

[0010] Preferably, the gas inlet and outlet pipelines and the water inlet pipelines are also connected to the product collector through a one-way valve, that is, the liquid can flow to the gas inlet and outlet and the water outlet of the lower cover of the reactor through the gas flow controller.

[0011] Preferably, the temperature sensors and pressure sensors are installed at equal intervals from top to bottom, with three of each installed.

[0012] Preferably, a gasket is installed between the bracket and the hydrate reactor, and when the gasket is removed, the hydrate reactor can rotate.

[0013] A method for simulating sand production from a fractured natural gas hydrate reservoir is provided, using a device for simulating sand production from a fractured natural gas hydrate reservoir, and includes the following steps:

[0014] Step 1: Identify the morphology of fractures in the gas hydrate reservoir and generate a 3D model;

[0015] Step 2: Based on the three-dimensional model obtained in step 1, a crack model is generated using 3D printing technology and paraffin as the printing material;

[0016] Step 3: Based on the target gas hydrate reservoir particle size distribution, quartz sand and kaolin of different particle sizes are mixed to match the gas hydrate reservoir particle size distribution;

[0017] Step 4: Clean the interior of the hydrate reactor and install the temperature sensor and pressure sensor;

[0018] Step 5: Mix quartz sand and kaolin to simulate formation sand and lay it on the bottom of the reactor. Then place the printed paraffin fracture model in the formation sand at the bottom of the reactor, ensuring that the position and shape are consistent with the actual characteristics. Finally, fill the remaining mixed particles into the reactor.

[0019] Step 6: Close the hydrate reactor, adjust it to a vertical position, place a pad under the reactor, connect the axial pressure sensor, and apply axial pressure to hold the pressure;

[0020] Step 7: Heat the hydrate reactor and open the gas inlet and water outlet of the reactor bottom cover to collect liquid paraffin;

[0021] Step 8: Cooling the hydrate reactor using a constant temperature control box, calculating the amount of water required based on the hydrate saturation, and charging methane gas and water into the hydrate reactor to generate hydrates;

[0022] Step 9: Exhaust excess methane gas and pump fluid into the hydrate reactor to simulate the production pressure difference during the mining process;

[0023] Step 10: Collect the output from the gas inlet and outlet and the water outlet at the bottom cover of the hydrate reactor, record the liquid production, and place the output in a drying oven to dry. Obtain the particle output quality at different time periods to obtain the sand production pattern of hydrate mining.

[0024] Preferably, the paraffin wax used is refined paraffin wax, and the particle size of the particles after cooling to a solid state is 3-5 mm. The ratio of quartz sand and kaolin is determined according to the sand content and mud content of the target reservoir. The particle sizes of quartz sand and kaolin are selected according to the particle size distribution of the target reservoir. The sorting coefficient and uniformity coefficient of the target reservoir and the prepared formation sand are compared to evaluate whether the formation sand meets the requirements. The sorting coefficient is calculated using the Berg formula:

[0025]

[0026] in:

[0027] φ 90 =-log2d 90 ;

[0028] φ 10 =-log2d 10 ;

[0029] Where F is the sorting coefficient, dimensionless; d 90 is the particle size through which 90% of the particles on the cumulative particle size distribution curve pass, dimensionless; d 10 It is the particle size through which 10% of the particles pass on the cumulative particle size distribution curve, dimensionless;

[0030] The calculation formula of uniformity coefficient is:

[0031]

[0032] Where C is the uniformity coefficient, dimensionless. 40 It is the particle size at which 40% of the particles pass through the cumulative particle size distribution curve, dimensionless.

[0033] Preferably, in step 6, an axial pressure of 10 MPa to 20 MPa is applied and the pressure is held for 1 to 2 hours; the axial pressure during the pressure holding is set to be the same as the pressure of the overlying rock formation of the reservoir; when the axial pressure is applied, the axial pressure sensor contacts the piston.

[0034] Preferably, in step 8, the hydrate formation temperature is set according to the hydrate reservoir characteristics of the target area, and methane is pumped in by adopting a two-end air intake method to avoid "gas driving water".

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention uses 3D printing technology (paraffin material) to accurately reproduce the three-dimensional morphology of reservoir fractures, solving the problem that traditional physical models are difficult to depict complex fracture networks. The melting point of the paraffin model matches the phase transition temperature of natural gas hydrates, and real fracture gaps can be formed by melting the wax by heating, avoiding the mechanical damage and interference of artificial prefabricated fractures. The data is closer to the real response of the reservoir, improving the reliability of the experiment.

[0037] This method simulates formation sand by mixing quartz sand and kaolin, combined with temperature and pressure control (low-temperature axial compression + methane injection), to simultaneously simulate reservoir particle distribution, temperature and pressure conditions, and the hydrate formation process, enabling a multi-factor coupled experiment involving "fractures-particles-fluids-temperature-pressure." Using an in-situ generation method of "quantified water + excess gas," this method covers the entire lifecycle of "hydrate formation → pressure holding → temperature-increased production → sand collection." In particular, the collection of melted paraffin through the drainage port simulates spatial changes in fractures, more closely resembling actual production dynamics. This approach offers low cost, excellent repeatability, and manageable safety risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the experimental device for simulating sand production from fractured natural gas hydrate reservoirs according to the present invention;

[0039] Figure 2 This is a flow chart of the experimental method for simulating sand production from fractured natural gas hydrate reservoirs according to the present invention;

[0040] Figure 3 This is a side view of the hydrate reactor of the present invention;

[0041] Figure 4 This is a front view of the hydrate reactor of the present invention;

[0042] Figure 5 Schematic diagram of artificial fractured hydrate sample.

[0043] Among them, 1. Constant temperature control box; 2. Axial pressure controller; 3. Crossbeam; 4. Axial pressure sensor; 5. Hydrate reactor; 6. Piston; 7. Temperature sensor; 8. Pressure sensor; 9. Gasket; 10. Constant flow pump; 11. Gas booster pump; 12. Air compressor; 13. Gas flow controller; 14. Product collector; 15. Gas cylinder; 16. Computer system; 17. Bracket; 18. Upper cover; 19. Lower cover; 20. Cylinder; 21. Air inlet and water inlet; 22. Air inlet and outlet, water outlet; 23. Pressure reducing valve; 24. Pressure gauge; 25. One-way valve. DETAILED DESCRIPTION

[0044] The accompanying drawings are for illustrative purposes only. The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0045] Example 1

[0046] like Figure 1 As shown, a device for simulating sand production from a fractured natural gas hydrate reservoir is provided, comprising a constant temperature control box 1 and a computer system 16. A hydrate reactor 5 is disposed within the constant temperature control box 1, and a crossbeam 3 is disposed at the top of the hydrate reactor 5. Both ends of the crossbeam 3 contact the side walls of the constant temperature control box 1 via rails to enable up and down sliding. The crossbeam 3 is controlled by an axial pressure controller 2, and an axial pressure sensor 4 is disposed at the center bottom of the crossbeam 3. A bracket 17 is disposed at the bottom of the constant temperature control box 1 to mount the hydrate reactor 5.

[0047] like Figure 3 、 4 As shown, the hydrate reactor 5 is provided with an upper cover 18 and a lower cover 19, an inverted T-shaped piston 6 is provided on the top of the hydrate reactor 5, the vertical end of the piston 6 passes through the center of the upper cover 18, and an air inlet and a water inlet 21 are provided on the piston 6. The gas booster pump 11 and the constant flow pump 10 are respectively connected to the air inlet and the water inlet 21 of the piston 6 through pipelines, and a gas flow controller 13 is also provided on the pipeline of the gas booster pump 11; the lower cover 19 is provided with air inlet and outlet, and water outlet 22, and the product collector 14 is connected to the air inlet and outlet, and water outlet 22 through pipelines; a pressure sensor 8 is provided at one end of the side wall of the hydrate reactor 5, and a temperature sensor 7 is provided at the other end;

[0048] Axial pressure controller 2, axial pressure sensor 4, pressure sensor 8, and temperature sensor 7 are connected to computer system 16. Automatic on / off valves are installed on each pipeline, and each automatic on / off valve is connected to computer system 16. Three temperature sensors 7 and pressure sensors 8 are installed at equal intervals from top to bottom.

[0049] As a further preference, the upper cover 18 is connected to the cylinder of the hydrate reactor 5 through a sealing thread, and a sealing ring is installed at the connection. An opening adapted to the piston 6 is provided in the center of the upper cover 18, and the interfaces are all sealed.

[0050] Two pipelines are set at the gas booster pump 11, one connected to the gas cylinder 15 (two gas cylinders can be set, and each has an automatic switch valve at the outlet for backup), and the other connected to the air compressor 12; an automatic switch valve is installed at the outlet of the gas cylinder 15, and an automatic switch valve, a pressure gauge 24 and a pressure reducing valve 23 are set on the pipeline connecting the air compressor 12.

[0051] The pipelines of the air inlet and water inlet 21 are also connected to the product collector through a one-way valve, that is, the liquid can flow to the air inlet and water outlet 22 of the lower cover of the reactor through the gas flow controller.

[0052] A gasket 9 is installed between the bracket 17 and the hydrate reactor 5. When the gasket 9 is removed, the hydrate reactor 5 can rotate 360 ​​degrees.

[0053] like Figure 2 As shown, a method for simulating sand production from fractured natural gas hydrate reservoirs uses a device for simulating sand production from fractured natural gas hydrate reservoirs. A computer system can control the opening and closing of each automatic switch valve, and data from each sensor is transmitted to the computer system. The method specifically includes the following steps:

[0054] Step 1: Identify the morphology of fractures in the gas hydrate reservoir and generate a 3D model;

[0055] Step 2: Based on the three-dimensional model obtained in step 1, a crack model is generated using 3D printing technology and paraffin as the printing material;

[0056] Step 3: Determine the ratio of quartz sand and kaolin according to the target reservoir sand content and mud content, select the quartz sand and kaolin particle sizes according to the reservoir particle size distribution, and mix the different particle ratios to match the natural gas hydrate reservoir particle size distribution;

[0057] Step 4: Clean the interior of the hydrate reactor and install the temperature sensor and pressure sensor;

[0058] Step 5: Mix quartz sand and kaolin to simulate formation sand, lay it on the bottom of the reactor, then place the printed paraffin crack model, ensuring that the position and shape are consistent with the actual characteristics, and finally fill the remaining mixed particles into the reactor.

[0059] Step 6: Close the hydrate reactor and adjust it to a vertical position. Place a spacer under the reactor, connect the axial pressure sensor, and apply axial pressure to maintain pressure. The axial pressure applied is 10 MPa and maintained for 2 hours. The axial pressure during the maintenance period is set to be the same as the pressure of the overburden in the reservoir. When applying axial pressure, the axial pressure sensor contacts the piston.

[0060] Step 7: Heat the hydrate reactor and open the gas inlet and water outlet of the reactor bottom cover to collect liquid paraffin;

[0061] Step 8: Cooling the hydrate reactor using a constant temperature control box, calculating the amount of water required based on the hydrate saturation, and charging methane gas and water into the hydrate reactor to generate hydrates;

[0062] Step 9: Exhaust excess methane gas and pump fluid into the hydrate reactor to simulate the production pressure difference during the mining process;

[0063] Step 10: Collect the output from the gas inlet and outlet and the water outlet at the bottom cover of the hydrate reactor, record the liquid production, and place the output in a drying oven to dry. Obtain the particle output quality at different time periods to obtain the sand production pattern of hydrate mining.

[0064] The paraffin wax used is refined paraffin wax, and the particle size after cooling to a solid state is 3 mm. The ratio of quartz sand and kaolin is determined according to the sand content and mud content of the target reservoir. The particle sizes of quartz sand and kaolin are selected according to the particle size distribution of the target reservoir. The sorting coefficient and uniformity coefficient of the target reservoir and the prepared formation sand are compared to evaluate whether the formation sand meets the requirements. The sorting coefficient is calculated using the Berg formula:

[0065]

[0066] in:

[0067] φ 90 =-log2d 90 ;

[0068] φ 10 =-log2d 10 ;

[0069] Where F is the sorting coefficient, dimensionless; d 90 is the particle size through which 90% of the particles on the cumulative particle size distribution curve pass, dimensionless; d 10 It is the particle size through which 10% of the particles pass on the cumulative particle size distribution curve, dimensionless;

[0070] The calculation formula of uniformity coefficient is:

[0071]

[0072] Where C is the uniformity coefficient, dimensionless. 40 It is the particle size at which 40% of the particles pass through the cumulative particle size distribution curve, dimensionless.

[0073] In step 8, the hydrate formation temperature is set according to the hydrate reservoir characteristics of the target area, and methane is pumped in by adopting the method of air intake at both ends to avoid "gas driving water".

[0074] like Figure 5 Shown is a schematic diagram of an artificial hydrate specimen with generated fractures.

[0075] Example 2

[0076] The paraffin wax used is refined paraffin wax, and the particle size of the particles after cooling to a solid state is 5 mm; an axial pressure of 20 MPa is applied and the pressure is held for 1 hour; the axial pressure during the holding pressure is set to be the same as the pressure of the overlying rock formation of the reservoir; when the axial pressure is applied, the axial pressure sensor contacts the piston.

[0077] Other unmentioned places are the same as those in Example 1.

[0078] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A device for simulating sand production from fractured natural gas hydrate reservoirs, comprising a constant temperature control box and a computer system, characterized in that: A hydrate reactor is arranged in the constant temperature control box, a crossbeam is arranged on the top of the hydrate reactor, both ends of the crossbeam are in contact with the side wall of the constant temperature control box through rails to achieve up and down sliding, and is controlled by an axial pressure controller, and an axial pressure sensor is arranged at the center bottom of the crossbeam; A bracket is provided at the bottom of the constant temperature control box to install the hydrate reactor; The hydrate reactor comprises a cylinder, which is provided with an upper cover and a lower cover. An inverted T-shaped piston is provided at the top of the cylinder, the vertical end of the piston passes through the center of the upper cover, an air inlet and a water inlet are provided on the piston, a gas booster pump and a constant flow pump are connected to the air inlet and water inlet of the piston respectively through pipelines, and a gas flow controller is also provided on the pipeline of the gas booster pump; the lower cover is provided with air inlet and outlet, and water outlet, and a product collector is connected to the air inlet and outlet, and water outlet through pipelines; a pressure sensor is provided at one end of the side wall of the hydrate reactor cylinder, and a temperature sensor is provided at the other end; The axial pressure controller, axial pressure sensor, pressure sensor and temperature sensor are connected to the computer system. Automatic switch valves are arranged on each pipeline, and each automatic switch valve is connected to the computer system.

2. The device for simulating sand production from fractured natural gas hydrate reservoirs according to claim 1, characterized in that: The upper cover is connected to the cylinder of the hydrate reactor through a sealing thread, and a sealing ring is installed at the connection. An opening adapted to the piston is provided at the center of the upper cover.

3. The device for simulating sand production from fractured natural gas hydrate reservoirs according to claim 1, characterized in that: Two pipelines are set at the gas booster pump, one connecting to the gas cylinder and the other connecting to the air compressor; an automatic switching valve is installed at the outlet of the gas cylinder, and an automatic switching valve, a pressure gauge and a pressure reducing valve are set on the pipeline connecting to the air compressor.

4. The device for simulating sand production from fractured natural gas hydrate reservoirs according to claim 1, characterized in that: The pipelines of the air inlet and water inlet are also connected to the product collector through a one-way valve, that is, the liquid can flow to the air inlet and water outlet of the lower cover of the reactor through the gas flow controller.

5. The device for simulating sand production from fractured natural gas hydrate reservoirs according to claim 1, characterized in that: The temperature sensors and pressure sensors are installed at equal intervals from top to bottom, with three of each installed.

6. The device for simulating sand production from fractured natural gas hydrate reservoirs according to claim 1, characterized in that: A gasket is installed between the bracket and the hydrate reactor. When the gasket is removed, the hydrate reactor can rotate.

7. A method for simulating sand production from a fractured natural gas hydrate reservoir, using the device for simulating sand production from a fractured natural gas hydrate reservoir according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: Identify the morphology of fractures in the gas hydrate reservoir and generate a 3D model; Step 2: Based on the three-dimensional model obtained in step 1, a crack model is generated using 3D printing technology and paraffin as the printing material; Step 3: Based on the target gas hydrate reservoir particle size distribution, quartz sand and kaolin of different particle sizes are mixed to match the gas hydrate reservoir particle size distribution; Step 4: Clean the interior of the hydrate reactor and install the temperature sensor and pressure sensor; Step 5: Mix quartz sand and kaolin to simulate formation sand and lay it on the bottom of the reactor. Then place the printed paraffin fracture model in the formation sand at the bottom of the reactor, ensuring that the position and shape are consistent with the actual characteristics. Finally, fill the remaining mixed particles into the reactor. Step 6: Close the hydrate reactor, adjust it to a vertical position, place a pad under the reactor, connect the axial pressure sensor, and apply axial pressure to hold the pressure; Step 7: Heat the hydrate reactor and open the gas inlet and water outlet of the reactor bottom cover to collect liquid paraffin; Step 8: Cooling the hydrate reactor using a constant temperature control box, calculating the amount of water required based on the hydrate saturation, and charging methane gas and water into the hydrate reactor to generate hydrates; Step 9: Exhaust excess methane gas and pump fluid into the hydrate reactor to simulate the production pressure difference during the mining process; Step 10: Collect the output from the gas inlet and outlet and the water outlet at the bottom cover of the hydrate reactor, record the liquid production, and place the output in a drying oven to dry. Obtain the particle output quality at different time periods to obtain the sand production pattern of hydrate mining.

8. The method for simulating sand production from a fractured natural gas hydrate reservoir according to claim 7, wherein: The paraffin wax used is refined paraffin wax, and the particle size after cooling to a solid state is 3-5mm. The ratio of quartz sand and kaolin is determined according to the sand content and mud content of the target reservoir. The particle sizes of quartz sand and kaolin are selected according to the particle size distribution of the target reservoir. The sorting coefficient and uniformity coefficient of the target reservoir and the prepared formation sand are compared to evaluate whether the formation sand meets the requirements. The sorting coefficient is calculated using the Berg formula: in: φ 90 =-log2d 90 ; φ 10 =-log2d 10 ; Where F is the sorting coefficient, dimensionless; d 90 is the particle size through which 90% of the particles on the cumulative particle size distribution curve pass, dimensionless; d 10 It is the particle size through which 10% of the particles pass on the cumulative particle size distribution curve, dimensionless; The calculation formula of uniformity coefficient is: Where C is the uniformity coefficient, dimensionless; d 40 It is the particle size at which 40% of the particles pass through the cumulative particle size distribution curve, dimensionless.

9. The method for simulating sand production from a fractured natural gas hydrate reservoir according to claim 7, wherein: In step 6, an axial pressure of 10 MPa to 20 MPa is applied for 1 to 2 hours; the axial pressure during the pressure holding is set to be the same as the pressure of the overlying rock formation of the reservoir; when the axial pressure is applied, the axial pressure sensor contacts the piston.

10. The method for simulating sand production from a fractured natural gas hydrate reservoir according to claim 7, wherein: In step 8, the hydrate formation temperature is set according to the hydrate reservoir characteristics of the target area, and methane is pumped in by adopting a two-end air intake method to avoid "gas driving water".

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