An experimental device and experimental method for simulating and evaluating instability and sand production of an ultra-deep water and ultra-shallow gas reservoir

Abstract

The present application belongs to the field of deep and deepwater oil and gas resource development and exploitation in the oil and gas exploitation industry, and particularly relates to an experimental device and method for simulating and evaluating instability and sand production of an ultra-deepwater ultra-shallow gas reservoir. The present application provides a complete evaluation experimental device, experimental condition setting method, experimental method and quantitative evaluation method for evaluating the whole process of reservoir and interlayer instability and sand production in the process of ultra-deepwater ultra-shallow gas exploitation, and can realize process simulation and quantitative evaluation, thereby providing direct support for the selection and design and implementation of sand control completion methods for ultra-deepwater ultra-shallow gas reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of deep-ground and deep-water oil and gas resource development and exploitation in the oil and gas extraction industry, specifically involving an experimental device and method for simulating and evaluating instability and sand production in ultra-deep-water and ultra-shallow gas reservoirs. Background Technology

[0002] Deep-seated (including deep-earth and deep-water) oil and gas resource development is a major near-wellbore area in oil and gas energy development, with ultra-deepwater and ultra-shallow gas reservoirs being an important type of deep-seated oil and gas resource. Preliminary exploration in a certain sea area has revealed geological reserves of hundreds of billions of cubic meters of natural gas in the Lingshui 36-1 ultra-deepwater and ultra-shallow gas reservoir. However, the ultra-deepwater and ultra-shallow gas reservoir has a water depth of 1500-1700m and a burial depth below the seabed of approximately 150-300m. It is characterized by shallow burial, weak or even uncemented reservoir cementation, thin interlayers and strata (referred to as interlayers and strata), and multiple superimposed layers. In particular, due to the weak or even non-diagenetic formation of the reservoir and the thin interlayers and strata, the extraction process is prone to reservoir structural instability and sand production, as well as serious environmental safety and geological disasters such as natural gas leakage caused by the instability and failure of interlayers and strata.

[0003] Given the characteristics of ultra-deepwater and ultra-shallow gas reservoirs and their potential for damage and safety risks, evaluating instability and sand production during the exploitation process is crucial. This is essential for adopting appropriate sand control completion methods to prevent damage and disasters. Experimental simulation is a vital research tool for instability and sand production evaluation; however, current simulation experiments on instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs still face the following key challenges:

[0004] (1) The world’s first large-scale ultra-deepwater and ultra-shallow gas reservoir was discovered in a certain sea area. There is still a lack of experimental equipment that can simulate the entire process of reservoir and interlayer instability and reservoir sand production during the ultra-deepwater and ultra-shallow gas extraction process.

[0005] (2) The simulation system for sand production simulation experiments of conventional oil and gas reservoirs is mainly based on core holding devices. These devices cannot simulate complex conditions such as overlying deep water conditions, ultra-shallow caprock conditions, thin interlayer conditions, and multiple production layers, and are not suitable for simulating reservoir and interlayer instability and reservoir sand production experiments during ultra-deep water and ultra-shallow gas extraction.

[0006] (3) There is a lack of experimental quantitative evaluation methods for reservoir and interlayer instability and reservoir sand production during the ultra-deep water and ultra-shallow gas extraction process. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides an experimental apparatus and method for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs. Its purpose is to facilitate the simulation of the production process during the exploitation of ultra-deepwater and ultra-shallow gas reservoirs, evaluating whether instability, collapse, and sand production will occur in the interlayers and reservoir. The simulation considers deepwater conditions, ultra-shallow interlayer conditions, and weak-to-uncemented conditions in multi-layered reservoirs. Through experimental simulation and quantitative evaluation, the production safety assessment of ultra-deepwater and ultra-shallow gas reservoirs can be achieved, supporting the selection of sand control completion methods and their engineering implementation.

[0008] The technical problem to be solved by the present invention is achieved by the following technical solution: an experimental device for simulating and evaluating the instability and sand production of ultra-deepwater and ultra-shallow gas reservoirs, comprising a main device for simulating reservoir instability and sand production in a multi-layer production process, a four-column servo hydraulic press, a data acquisition and control system, a sand and liquid collection device, a pressure sensor, a gas flow meter, a liquid flow meter, a control valve, a liquid pipeline, a gas pipeline, an outlet pipeline, a liquid supply system, and a gas supply system;

[0009] The main device for simulating reservoir instability and sand production in the multi-layer production process includes a main tank, an open hydraulic pressure plate, deformable visual partitions, a tank visualization window, a tank inlet, a sand and liquid outlet, a wellbore switch valve, a simulated horizontal wellbore, and a simulated vertical wellbore.

[0010] The main tank has an upward opening, and the open hydraulic pressure plate is slidably installed inside the main tank. The four-column servo hydraulic press is located above the open hydraulic pressure plate and is connected to the open hydraulic pressure plate.

[0011] The main tank body is provided with alternating partition layers and storage layers from top to bottom;

[0012] The deformable and visual partition has a grid-like scale on its surface. The deformable and visual partition is detachably and horizontally installed in the main tank, located between the reservoir and the partition layer. The deformable and visual partition is sealed to the inner wall of the main tank.

[0013] The main tank body has a tank body visualization window provided on its side wall;

[0014] The main tank is provided with a tank inlet and a sand-liquid outlet on the side wall corresponding to the reservoir. The simulated horizontal wellbore is horizontally set in the reservoir, and one end of the simulated horizontal wellbore is connected to the sand-liquid outlet.

[0015] The main tank body and the partition layer are provided with tank inlet ports on their corresponding side walls.

[0016] The open hydraulic pressure plate is provided with a sand and liquid outlet. The simulated vertical well is vertically installed in the main tank. The lower end of the simulated vertical well is located in the lowest layer of the reservoir. The upper end of the simulated vertical well is connected to the sand and liquid outlet.

[0017] The liquid supply system is connected to the tank inlet through a separate liquid pipeline, the gas supply system is connected to the tank inlet through a separate gas pipeline, and the sand liquid outlet is connected to the sand liquid collection device through a separate outlet pipeline.

[0018] Wellbore switch valves are installed at both the inlet and outlet of the tank body;

[0019] Control valves are installed on the liquid pipeline, gas pipeline, and outlet pipeline;

[0020] A liquid flow meter is installed on the liquid pipeline, and a gas flow meter is installed on the gas pipeline.

[0021] Pressure sensors are installed at the tank inlets on both sides of the reservoir, at the sand and liquid outlets, and inside the reservoir.

[0022] The data acquisition and control system is connected to the four-column servo hydraulic press, pressure sensor, gas flow meter, liquid flow meter, control valve, wellbore switch valve, liquid supply system and gas supply system, respectively.

[0023] Preferably, the present invention further includes an internal sliding groove and a slidable buckle;

[0024] The internal sliding groove is vertically arranged on the side wall of the main tank, and multiple slidable buckles are arranged in the internal sliding groove that can slide up and down.

[0025] The two ends of the deformable visual partition are detachably mounted on sliding buckles.

[0026] Preferably, the liquid supply system of the present invention includes a liquid pump and a liquid storage tank, wherein the liquid storage tank is connected to the inlet of the tank body through the liquid pump;

[0027] The gas supply system includes a gas tank and an air compressor. The gas tank is connected to the inlet of the tank body, and the air compressor is used to pressurize the gas tank and supply gas.

[0028] In a preferred embodiment of the present invention, a buffer layer is provided above the uppermost interlayer, and a pad layer is provided at the bottom of the main tank to avoid rigid impact on the sample inside the tank during pressurization.

[0029] Preferably, the deformable and visible partition of the present invention is made of polyurethane elastic composite material with a thickness of 5-20 mm and an elastic modulus of 0.5-2 GPa, which conforms to the mechanical characteristics of the weak bonding of the ultra-shallow partition interlayer.

[0030] Preferably, the deformable visual partition has a sealing ring at its edge, with a sealing gap ≤0.1mm for sliding engagement with the internal sliding groove. The upper surface of the deformable visual partition has an annular sealing groove machined around its perimeter, housing a fluororubber O-ring that fits against the lower surface of the previous sample / partition, achieving interlayer sealing. A polyurethane sealing strip is attached to the outer side of the partition's thickened flange, fitting against the gap between the container's inner wall / guide rail to prevent water vapor media from spreading along the container's inner wall, ensuring precise control of formation pressure stratification.

[0031] This invention also discloses an experimental method for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs. Utilizing the aforementioned experimental apparatus for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs, the method includes the following steps:

[0032] S1. Experimental Conditions Setup

[0033] S1.1 Experimental Sample Preparation and Filling: Prepare reservoir simulation samples and interlayer simulation samples, and fill the main tank in layers;

[0034] S1.2 Synchronous pressurization and water saturation: Simultaneously start the four-column servo hydraulic press and the fluid supply system to achieve complete water saturation;

[0035] S1.3 Synchronous pressure holding and gas saturation: After water saturation and pressure holding are completed, the linkage control mode of the four-column servo hydraulic press is maintained, the liquid supply system is turned off, and the gas supply system is started to achieve complete gas saturation of the reservoir, and the sample in the reservoir is not prematurely damaged or displaced throughout the process.

[0036] S2, Process Experiment Simulation

[0037] S2.1 Production Process Simulation:

[0038] Based on the actual development plan of the target gas reservoir, the opening mode of the wellbore switch valve is preset; the flow rate of gas-liquid production is set according to the actual reservoir development conditions and converted to experimental conditions.

[0039] The wellbore switch valve is opened according to preset parameters by the data acquisition and control system, the gas-liquid flow parameters are set and the gas-liquid delivery system is started, and the gas-liquid production flow is precisely controlled by the gas flow meter and the liquid flow meter to simulate the mining process.

[0040] S2.2 Real-time data acquisition and recording during the experiment;

[0041] During the experiment, the data acquisition and control system collected and stored in real time the pressure at the inlet of the tanks on both sides of the reservoir, the sand liquid outlet, the gas-liquid production flow rate, and the hydraulic press pressurization pressure.

[0042] Using a high-speed camera aimed at the tank's visualization window and deformable visualization partition, the deformation of the reservoir sample, the sand discharge start position, the sand particle migration trajectory, and the displacement and rupture process of the interlayer are captured in real time.

[0043] During the experiment, the overall condition of the device was manually checked every 1-2 hours, and it was recorded whether the reservoir sample had cracks or collapses, whether the interlayer had shifted, and whether the wellbore had sand blockage.

[0044] After the experiment, the sand sample from the sand collection device was subjected to solid-liquid separation, dried and weighed.

[0045] The vertical displacement ΔH, horizontal length displacement ΔL, horizontal width displacement ΔW, and horizontal / vertical displacement of the interlayer are read and recorded using deformable and visualized septum scale lines.

[0046] S3, Quantitative Evaluation

[0047] S3.1 Quantitative Evaluation Indicators and Calculations for Sand Production:

[0048] Based on the experimental data, the critical sand production pressure and critical sand production flow rate were determined, which are the production pressure and gas production flow rate corresponding to when the reservoir begins to show obvious sand production.

[0049] Weigh the total sand output M and the sand output m of each layer. i Based on the actual experimental duration t, calculate the average sand production rate v and the average sand production rate va of each reservoir layer. i ;

[0050] The sand production intensity index I is defined as the sand production rate per unit reservoir volume and per unit pressure drop. The reservoir sand production intensity index I is calculated.

[0051] After the experiment, a laser particle size analyzer was used to analyze the particle size and morphology of the dried sand sample, and to plot the sand particle size distribution curve, as well as the relationship curves between sand output, sand output rate and production pressure and flow rate, thus quantifying the correlation between production parameters and sand output.

[0052] S3.2 Evaluation Indicators and Calculations for Reservoir and Interlayer Instability:

[0053] Evaluation of reservoir and interlayer instability: Based on image data captured by a high-speed camera and the scale lines of a deformable, visualized interlayer, the vertical deformation ε of the reservoir sample is measured. z Horizontal length deformation ε l and horizontal width deformation ε w The volumetric strain ε is calculated by summing the three factors. V ;

[0054] Measure the horizontal displacement d of the interlayer sampleL Vertical displacement d W Calculate the shear strain γ of the interlayer;

[0055] Based on volumetric strain and shear strain, the instability risk of reservoirs and interlayers is classified into three levels:

[0056] Low risk: ε v <2%, γ <5%;

[0057] Medium risk: 2%≤ε v <5%, 5%≤γ<10%;

[0058] High risk: ε v ≥5%, γ≥10%;

[0059] Wellbore perimeter instability evaluation: After the experiment, the collapse radius r of the reservoir around the wellbore was measured, which is the maximum radius of the reservoir collapse area around the wellbore;

[0060] The larger the collapse radius, the more severe the reservoir instability around the wellbore, and the worse the reservoir stability corresponding to the well completion method.

[0061] The preferred embodiment of the present invention further includes step S4, selection and design of well completion method:

[0062] S4.1 Conduct production process simulations under different operating conditions:

[0063] Perforation completion simulation: Using a simulated wellbore assembly with perforation holes, the hole diameter, density, and distribution are set according to the actual perforation parameters. The assembly is then installed in the corresponding position on the main tank and sealed and fixed.

[0064] Simulate the perforation completion and production process, and monitor the deformation and sand production dynamics of the reservoir and interlayer in real time;

[0065] Sand control / no sand control simulation: On the inside of the wellbore of perforated or open hole wells, different types and precision of screen pipes are installed as sand control components according to the actual reservoir sand control measures, which is the sand control condition; removing the sand control components is the no sand control condition. Production simulation is carried out according to preset parameters to compare the sand control effect and monitor the deformation and sand production dynamics of the reservoir and interlayer in real time.

[0066] Open-hole well operation simulation: The perforated section and sand control section of the simulated well are removed, and a solid, perforated well is used as the open-hole well simulation component to simulate the open-hole well mining process and monitor the deformation and sand production dynamics of the reservoir and interlayer in real time.

[0067] Vertical / Horizontal Well, Single / Multi-Layer Production Simulation: Simulating the vertical wellbore separately is the production condition for a vertical well; simulating the horizontal wellbore separately is the production condition for a horizontal well.

[0068] Opening only the wellbore valve corresponding to a single reservoir layer constitutes a single-layer production condition, while opening the wellbore valves corresponding to multiple reservoir layers simultaneously constitutes a multi-layer production condition.

[0069] Production simulations were conducted according to preset parameters, and the reservoir response under different operating conditions was recorded.

[0070] Production process control: During the experiment, the production flow rate was gradually increased according to the experimental design to simulate reservoir conditions under different mining intensities;

[0071] After each parameter adjustment, record the changes in reservoir deformation and sand production;

[0072] When obvious reservoir instability, interlayer rupture, or sudden increase in sand production occur, the experiment can be suspended and critical operating parameters recorded.

[0073] S4.2 Comparison and Optimization of Different Well Completion Methods:

[0074] A comprehensive comparative analysis was conducted on the critical sand production parameters, critical instability parameters, sand production intensity index, and wellbore perimeter collapse radius indices for different completion methods, including open hole wells, perforated wells, wells with sand control, and wells without sand control, as well as different production methods, including vertical / horizontal wells and single / multi-layer production. The results were compared and optimized for different completion methods and operating conditions.

[0075] Based on the core technical principles of the lowest sand production strength index, the highest critical parameter value, and the smallest collapse radius, and taking into account the economy, construction difficulty, and operability of on-site engineering implementation, the optimal well completion method and production method suitable for the target ultra-deep water and ultra-shallow gas reservoir were selected.

[0076] Well completion parameter optimization: For the selected optimal well completion method, multiple sets of parameter optimization experiments were conducted to further optimize the perforation density, diameter, distribution, and key parameters of the sand control screen, and to determine the optimal selection of well completion parameters.

[0077] The preferred embodiment of the present invention is as follows: S1.2, synchronous pressurization and water saturation specifically involves: simultaneously starting the four-column servo hydraulic press and the liquid supply system; the four-column servo hydraulic press applies axial pressure to the open hydraulic pressurization plate at a preset rate; and the liquid supply system injects water into each reservoir and interlayer chamber at a constant speed, with the water injection rate controlled at 0.1-0.5 L / min.

[0078] During the water injection process, first open the wellbore switch valve to continuously discharge air from the tank through the sand liquid outlet until each sand liquid outlet has a continuous, bubble-free liquid flow, and then close the wellbore switch valve.

[0079] Continue to maintain the synchronous linkage between hydraulic press pressurization and liquid injection. The water injection pressure in the tank increases synchronously with the hydraulic press pressurization pressure until the hydraulic press pressurization pressure reaches 50% of the overburden pressure at the target water depth. The water injection pressure in the reservoir reaches the target reservoir static water pressure. Maintain the pressure for 2 hours. During the pressure holding process, the four-column servo hydraulic press and the liquid supply system remain linked. If there are slight fluctuations in the reservoir pressure, the four-column servo hydraulic press will automatically adjust the pressurization pressure to ensure effective stress stability and achieve complete water saturation.

[0080] The preferred embodiment of this invention, S1.3, involves the following specific steps for synchronous pressure holding and gas saturation: After water saturation and pressure holding are completed, the linkage control mode of the four-column servo hydraulic press is maintained to keep the pressurization pressure stable; the control valve on the liquid pipeline is closed, the control valve on the gas pipeline is opened, the gas supply system is started, and gas is injected into the reservoir chamber. The gas injection adopts a constant pressure mode, and the gas injection pressure increases synchronously with the pressurization pressure of the four-column servo hydraulic press at a preset rate. The gas injection rate is controlled at 0.1-1 m³ / h; during the gas injection process, the data of the pressure sensor inside the tank is monitored in real time.

[0081] Continuous pressure holding and gas injection are carried out simultaneously until the hydraulic press pressure reaches the target water depth overburden pressure of 15.08-17.05 MPa and the reservoir gas injection pressure reaches the original formation pore pressure of the target reservoir. Pressure is held for 2 hours. During the pressure holding process, the data acquisition and control system monitors and adjusts in real time to ensure that the difference between the hydraulic press pressure and the reservoir pore pressure is always equal to the actual effective formation stress, so that the gas can fully enter the pores of the reservoir sample and achieve complete gas saturation of the reservoir.

[0082] Compared with the prior art, the beneficial effects of the present invention are:

[0083] (1) This invention provides a complete evaluation experimental device, experimental condition setting method, experimental method and quantitative evaluation method for evaluating the entire process of reservoir and interlayer instability and reservoir sand production in the ultra-deepwater and ultra-shallow gas extraction process. It can realize process simulation and quantitative evaluation, and provide direct support for the selection and design implementation of sand control completion mode for gas wells in ultra-deepwater and ultra-shallow gas reservoirs.

[0084] (2) The device and method provided by the present invention can simulate multiple complex conditions such as deep water, ultra-shallow cap layer, thin interlayer, multiple production layers, and weak-uncemented reservoir overlying ultra-deep water and ultra-shallow gas storage tanks. It can also flexibly set stress, water depth and production conditions, which can facilitate the simulation of reservoir instability and sand production under various combinations of conditions and achieve quantitative evaluation.

[0085] (3) The device of the present invention can simulate and evaluate the instability and sand production of single-layer production, multi-layer production, vertical well, horizontal well conditions, as well as open hole completion, casing perforation completion conditions, and wellbore sand control and non-sand control conditions. Attached Figure Description

[0086] Figure 1 A schematic diagram of the experimental device for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs;

[0087] Figure 2 A schematic diagram of the main device for simulating reservoir instability and sand production;

[0088] Figure 3 Exploded views of components of the main device for simulating reservoir instability and sand production;

[0089] Figure 4 This is a schematic diagram simulating the structure of a horizontal wellbore (with and without sand control).

[0090] Figure 5 A schematic diagram simulating the structure of a vertical wellbore (with and without sand control);

[0091] Figure 6 A schematic diagram of the deformable visual partition structure;

[0092] In the figure, the main device for simulating reservoir instability and sand production includes: 1. Four-column servo hydraulic press; 2. Data acquisition and control system; 3. Liquid pump; 4. Liquid storage tank; 5. Gas tank; 6. Air compressor; 7. Sand and liquid collection device; 8. Pressure sensor; 9. Gas flow meter; 10. Liquid flow meter; 11. Control valve; 12. Liquid pipeline; 13. Gas pipeline; 14. Outlet pipeline; 15. Electrical wires; 16.

[0093] Main tank 17, open hydraulic pressure plate 18, deformable visual partition 19, tank visualization window 20, internal sliding groove 21, sliding buckle 22, tank inlet 23, sand and liquid outlet 24, well shaft switch valve 25, simulated horizontal well shaft 26 and simulated vertical well shaft 27.

[0094] Reservoir 100, interlayer 200. Detailed Implementation

[0095] The technical solutions in the embodiments of the present invention will now be clearly and completely described in conjunction with the accompanying drawings.

[0096] like Figures 1-5 As shown in the figure, this embodiment provides an experimental device for simulating and evaluating the instability and sand production of ultra-deepwater and ultra-shallow gas reservoirs. It includes a main device 1 for simulating reservoir instability and sand production in a multi-layer production process, a four-column servo hydraulic press 2, a data acquisition and control system 3, a sand and liquid collection device 8, a pressure sensor 9, a gas flow meter 10, a liquid flow meter 11, a control valve 12, a liquid pipeline 13, a gas pipeline 14, an outlet pipeline 15, a liquid supply system, and a gas supply system.

[0097] The main device 1 for simulating reservoir instability and sand production in the multi-layer production process includes a main tank 17, an open hydraulic pressure plate 18, a deformable visual partition 19, a tank visualization window 20, a tank inlet 23, a sand and liquid outlet 24, a wellbore switch valve 25, a simulated horizontal wellbore 26, and a simulated vertical wellbore 27. The simulated horizontal wellbore 26 and the simulated vertical wellbore 27 are simulated wellbore components.

[0098] The main tank 17 has an upward opening, and the open hydraulic pressure plate 18 is slidably installed inside the main tank 17. The four-column servo hydraulic press 2 is located above the open hydraulic pressure plate 18 and is connected to the open hydraulic pressure plate 18.

[0099] The main tank 17 has alternating partition layers 200 and storage layers 100 arranged from top to bottom, with at least two storage layers 100 and three partition layers 200.

[0100] like Figure 6 As shown, the deformable visual partition 19 has a grid-like scale on its surface. The deformable visual partition 19 is detachably and horizontally positioned within the main tank 17, between the reservoir 100 and the interlayer 200. The deformable visual partition 19 is sealed to the inner wall of the main tank 17. In this embodiment, a 1cm × 1cm coordinate grid is printed on the surface of the deformable visual partition. During the experiment, the deformation amplitude, collapse range, and fracture extension direction of the reservoir instability can be visually quantified through coordinate offset.

[0101] The main tank 17 is provided with a tank visualization window 20 on its side wall. In this embodiment, the main tank 17 of the main device 1 is made of 316L stainless steel and high borosilicate glass composite. The tank pressure rating is ≥20MPa, which is suitable for the pressure simulation requirements of 1500-1700m deep water. The tank is 800mm long, 500mm wide, and 1000-1500mm high. The tank visualization window 20 is an embedded pressure-resistant glass structure with a window size of ≥100×400mm and a light transmittance of ≥90%, which facilitates real-time observation of the deformation and sand production dynamics of the reservoir and interlayer.

[0102] The open hydraulic pressure plate 18 is a solid stainless steel plate with an area that perfectly matches the upper surface of the main tank 17. The top of the open hydraulic pressure plate 18 is rigidly connected to the power output end of the four-column servo hydraulic press 2. The maximum loading force of the four-column servo hydraulic press 2 is ≥500kN, the loading accuracy is ±0.1kN, and the loading rate can be steplessly adjusted within the range of 0.01-1kN / s, accurately simulating the static and dynamic changes of deep water pressure.

[0103] The main tank 17 is provided with a tank inlet 23 and a sand and liquid outlet 24 on the side wall corresponding to the reservoir 100. The simulated horizontal wellbore 26 is horizontally arranged in the reservoir 100, and one end of the simulated horizontal wellbore 26 is connected to the sand and liquid outlet 24.

[0104] The main tank 17 and the partition layer 200 are provided with tank inlet 23 on their corresponding side walls.

[0105] The open hydraulic pressure plate 18 is provided with a sand and fluid outlet 24. The simulated vertical wellbore 27 is vertically arranged inside the main tank 17. The lower end of the simulated vertical wellbore 27 is located in the lowest reservoir 100, and the upper end of the simulated vertical wellbore 27 is connected to the sand and fluid outlet 24. In this embodiment, the simulated wellbore system includes a simulated horizontal wellbore 26 and a simulated vertical wellbore 27, both of which are detachable stainless steel pipe structures. The simulated horizontal wellbore 26 runs horizontally through the reservoir chambers along the main tank 17, and the simulated vertical wellbore 27 extends vertically from the top of the tank into each reservoir chamber. The wellbore sidewalls can be opened with perforation holes of 1-5 mm in diameter according to experimental requirements, and different types and precision sand control screens can also be installed to adapt to perforated well completion and sand control well simulation respectively. Wellbore switch valves 25 are installed at the ends of both the simulated horizontal wellbore 26 and the simulated vertical wellbore 27.

[0106] The liquid supply system is connected to the tank inlet 23 via a separate liquid pipeline 13, the gas supply system is connected to the tank inlet 23 via a separate gas pipeline 14, and the sand liquid outlet 24 is connected to the sand liquid collection device 8 via a separate outlet pipeline 15.

[0107] Wellbore switch valves 25 are installed at both the tank inlet 23 and the sand slurry outlet 24. The wellbore switch valves 25 are commercially available.

[0108] Control valves 12 are installed on the liquid pipeline 13, gas pipeline 14, and outlet pipeline 15.

[0109] A liquid flow meter 11 is installed on the liquid pipeline 13, and a gas flow meter 10 is installed on the gas pipeline 14.

[0110] Pressure sensors 9 are installed at the tank inlet 23 on both sides of the reservoir 100, at the sand liquid outlet 24, and inside the reservoir 100.

[0111] The data acquisition and control system 3 is connected to the four-column servo hydraulic press 2, pressure sensor 9, gas flow meter 10, liquid flow meter 11, control valve 12, wellbore switch valve 25, liquid supply system and gas supply system via circuit wires 16.

[0112] The experimental device for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs also includes an internal sliding groove 21 and a sliding buckle 22. The internal sliding groove 21 and the sliding buckle 22 are commercially available products.

[0113] The internal sliding groove 21 is vertically arranged on the side wall of the main tank 17, and the multiple sliding buckles 22 are arranged vertically within the internal sliding groove 21.

[0114] The deformable and visualized partition 19 is detachably mounted on the sliding buckles 22 at both ends. The main tank 17 has 3-5 sets of parallel internal sliding grooves 21 pre-reserved inside, with an adjustable groove spacing of 50-300mm to match the thickness simulation of ultra-shallow thin interlayers. The deformable and visualized partition 19 has millimeter-level graduations on its surface for easy quantification of deformation displacement. The sliding buckles 22 are made of stainless steel, with 2-6 buckles configured in each sliding groove, allowing the partition to be fixed at any position, meeting the simulation requirements of multi-layer superposition of reservoir and interlayer.

[0115] In this embodiment, four dovetail sliding guide rails are vertically fixed along the front, back, left, and right sides of the inner wall of the cubic pressure vessel, forming a symmetrical distribution. Each guide rail can be slidably fitted with 2-4 sets of micro-clamping components. The clamps on the four guide rails are horizontally aligned and directly clamp the four edges of the deformable visual partition / sample to achieve load-bearing and positioning functions. The edge of the deformable visual partition integrates annular sealing flanges, forming a sealing structure with the gap between the inner wall of the container / guide rails to achieve interlayer sealing and pressure transmission. All metal structural components are made of 316L stainless steel, and the seals are made of fluororubber + polyurethane, suitable for high pressure ≥25MPa and humid environments with water or gas injection.

[0116] The liquid supply system includes a liquid pump 4 and a liquid storage tank 5, wherein the liquid storage tank 5 is connected to the tank inlet 23 via the liquid pump 4.

[0117] The gas supply system includes a gas tank 6 and an air compressor 7. The gas tank 6 is connected to the inlet 23 of the tank body, and the air compressor 7 is used to pressurize and supply gas to the gas tank 6.

[0118] In this embodiment, the maximum outlet pressure of the liquid pump 4 is ≥30MPa, and the flow rate adjustment range is 0.1-10L / min; the volume of the gas tank 6 is ≥100L, the rated pressure is ≥25MPa, and the exhaust pressure of the air compressor 7 is ≥20MPa; the pressure sensor 9 is a high-precision sensor with a measurement range of 0-25MPa and an accuracy of ±0.02MPa; the gas flow meter 10 has a measurement range of 0.01-100m³ / h and an accuracy of ±0.1%; and the liquid flow meter 11 has a measurement range of 0.01-20L / min and an accuracy of ±0.2%.

[0119] A buffer layer is provided above the uppermost interlayer 200, that is, a flexible buffer pad (not shown in the figure) is provided at the bottom of the open hydraulic pressure plate 18, which is generally unbonded interlayer stratum sand. A pad layer made of quartz sand is provided at the bottom of the main tank 17.

[0120] The deformable and visible partition 19 is made of polyurethane elastic composite material with a thickness of 5-20 mm and an elastic modulus of 0.5-2 GPa.

[0121] The deformable, visible partition 19 has a sealing ring at its edge, and the sealing gap between the sealing ring and the internal sliding groove 21 is ≤0.1mm. The sealing ring can withstand high temperature and high pressure environments and can be purchased as needed.

[0122] An experimental method for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs, utilizing the experimental apparatus for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs described in this embodiment, includes the following steps:

[0123] S1. Experimental Conditions Setup

[0124] S1.1 Experimental Sample Preparation and Filling: Prepare reservoir simulation samples and interlayer simulation samples, and fill the main tank 17 in layers.

[0125] Specifically: Based on the core experimental data and formation sand grain size and composition data of the target ultra-deep water and ultra-shallow gas reservoir, reservoir simulation samples are prepared for weakly cemented / uncemented reservoir characteristics; and interlayer simulation samples are prepared based on the lithology and mechanical characteristics of the actual interlayers.

[0126] First, a 5-10mm layer of quartz sand is laid at the bottom of the tank. Then, according to the number and thickness of the reservoir layers designed for the experiment, simulated samples of the interlayer and reservoir are laid layer by layer. During the filling process, the layers are compacted according to the degree of bonding between the actual reservoir and the interlayer. Deformable and visible spacers 19 are embedded into the corresponding internal sliding grooves 21 at the upper and lower ends of the simulated reservoir and fixed with sliding buckles 22. After filling, a 5-10mm buffer layer is laid on the surface of the uppermost reservoir sample. The buffer layer is generally made of unbonded formation sand from the simulated interlayer. Its function is to prevent the interlayer from rigidly cracking / fractured or deforming under pressure. The open hydraulic pressure plate 18 is then placed on top to complete the sample filling.

[0127] S1.2 Synchronous pressurization and water saturation: Simultaneously start the four-column servo hydraulic press 2 and the liquid supply system to achieve complete water saturation.

[0128] S1.3 Synchronous pressure holding and gas saturation: After water saturation and pressure holding are completed, the linkage control mode of the four-column servo hydraulic press 2 is maintained, the liquid supply system is turned off, and the gas supply system is started to achieve complete gas saturation of the reservoir, and the samples within the reservoir 100 throughout the process are not prematurely damaged or displaced.

[0129] S2, Process Experiment Simulation

[0130] S2.1 Production Process Simulation: Based on the actual exploitation plan of the target gas reservoir, preset the opening mode of the wellbore switch valve 25 (single well / multiple wells, single layer / layer opening); set the gas-liquid production flow rate according to the actual reservoir exploitation conditions converted to experimental conditions. After all production parameters are preset, maintain the entire device under the final pressure state of synchronous pressurization and saturation for 30 minutes. Verify the working status of all sensors, flow meters, valves, and hydraulic presses through the data acquisition and control system 3 to confirm that there are no fluctuations in parameters and that the equipment is operating normally; at the same time, observe the initial state of the reservoir and interlayer samples through the tank visualization window 20 to confirm that there is no deformation, no sand production, and no displacement. Complete all condition settings before production simulation and enter the experimental ready-to-start state.

[0131] The data acquisition and control system 3 opens the wellbore switch valve 25 according to preset parameters, sets the gas-liquid flow parameters and starts the gas-liquid delivery system, and accurately controls the gas-liquid production flow through the gas flow meter 10 and the liquid flow meter 11 to simulate the mining process.

[0132] S2.2 Real-time data acquisition and recording during the experiment:

[0133] Routine parameter acquisition: During the experiment, the data acquisition and control system 3 collects and stores in real time the pressure, gas-liquid production flow rate, and hydraulic press pressure of the inlet 23 and outlet 24 of the tanks on both sides of the reservoir 100. The acquisition frequency is 1-5Hz, and real-time data curves are generated for subsequent analysis.

[0134] Visual image acquisition: A high-speed camera is used to capture real-time images of the deformation of the reservoir sample, the sand discharge start position, the sand particle migration trajectory, and the displacement and rupture process of the interlayer. The image data is synchronized with the conventional parameters and timestamps to achieve data synchronization.

[0135] Sample status record: During the experiment, the overall status of the device was manually checked every 1-2 hours, and the reservoir sample was recorded for cracks or collapses, interlayer displacement, and sand blockage in the wellbore.

[0136] After the experiment, the sand sample from the sand collection device 8 was subjected to solid-liquid separation, dried and weighed.

[0137] After the deformable visualization spacer 19 is removed, the vertical displacement ΔH, horizontal length displacement ΔL, horizontal width displacement ΔW, and horizontal / vertical displacement of the interlayer 200 of each reservoir sample are read and recorded through the scale lines after the deformable visualization spacer 19 is deformed.

[0138] S3, Quantitative Evaluation

[0139] During the experiment, parameters such as inlet and outlet pressure, gas-liquid flow rate, sand output, and liquid output were collected in real time through the data acquisition and control system 3. The vertical displacement ΔH, horizontal length displacement ΔL, and horizontal width displacement ΔW of each reservoir sample, as well as the horizontal / vertical displacement of the interlayer, were read and recorded through the deformable visual partition scale lines and the tank visualization window. The sand output starting position and sand particle migration characteristics were recorded. After the experiment, the sand output samples in the sand-liquid collection device 8 were subjected to solid-liquid separation, dried and weighed, and the sand particle size distribution characteristics were analyzed using a laser particle size analyzer.

[0140] S3.1 Quantitative Evaluation Indicators and Calculations for Sand Production:

[0141] Based on the experimental data, the critical sand production pressure and critical sand production flow rate were determined, which are the production pressure and gas production flow rate corresponding to when the reservoir begins to produce significant sand.

[0142] Weigh the total sand output M and the sand output m of each layer. i Based on the actual experimental duration t, calculate the average sand production rate v and the average sand production rate va of each reservoir layer. i .

[0143] The sand production intensity index I is defined as the amount of sand produced per unit reservoir volume and per unit pressure drop. The sand production intensity index I is then calculated.

[0144] Specifically:

[0145] After the experiment, the solid sand in the sand-liquid collection device 8 was first subjected to solid-liquid separation. The sand was then dried in an oven at 60-80℃ until constant weight. The total sand output M and the sand output m of each layer were weighed. i Based on the actual experimental duration t, calculate the average sand output rate v and the average sand output rate va of each layer. i :

[0146]

[0147] Define the sand production intensity index I as the sand production rate per unit reservoir volume and per unit pressure drop. Calculate the reservoir sand production intensity index I:

[0148]

[0149] In the formula, V is the reservoir sample volume (cm³), and ΔP is the pressure drop during the experiment (MPa). The larger the Isand value, the greater the sand production per unit volume and per unit pressure drop, and the higher the risk of sand production from the reservoir.

[0150] After the experiment, a laser particle size analyzer was used to analyze the particle size and morphology of the dried sand sample, and to plot the sand particle size distribution curve, as well as the relationship curves between sand output, sand output rate and production pressure and flow rate, thus quantifying the correlation between production parameters and sand output.

[0151] S3.2 Evaluation Indicators and Calculations for Reservoir and Interlayer Instability:

[0152] Evaluation of reservoir and interlayer instability: Based on image data captured by a high-speed camera and the scale lines of the deformable visual interlayer 19, the vertical deformation ε of the reservoir sample was measured. z Horizontal length deformation ε l and horizontal width deformation ε w The volumetric strain ε is calculated by summing the three factors. V .

[0153] Specifically:

[0154] Based on image data captured by a high-speed camera and the scale lines on the deformable visualization spacer 19, the vertical deformation ε of the reservoir sample was measured. z Horizontal length deformation ε l and horizontal width deformation ε w (Vertical displacement ΔH of the reservoir: The difference between the initial and real-time values ​​of the vertical scale of the deformable visual partition, which represents the vertical deformation displacement of the corresponding reservoir sample along the height of the tank; Horizontal displacement ΔL of the reservoir: The difference between the initial and real-time values ​​of the horizontal scale of the partition, which represents the deformation displacement of the reservoir sample along the length of the tank; Horizontal displacement ΔW of the reservoir: The difference between the initial and real-time values ​​of the longitudinal scale of the partition, which represents the deformation displacement of the reservoir sample along the width of the tank), calculate the volumetric strain ε. V :

[0155]

[0156]

[0157] In the formula, ΔH, ΔL, and ΔW represent the vertical and horizontal length and width displacements of the reservoir, respectively, in mm; H0, L0, and W0 represent the original thickness, length, and width of the reservoir, respectively, in mm.

[0158] Measure the horizontal length displacement d of the interlayer sample L / Horizontal width displacement d W Calculate the shear strain γ of the interlayer.

[0159] Specifically:

[0160] Measure the horizontal length displacement d of the interlayer sample L / Horizontal width displacement dW The vertical displacement (the difference between the initial and real-time values ​​of the horizontal and vertical scales of the deformable visual partition 19, respectively, represents the horizontal displacement of the partition layer along the length and width of the tank body; the vertical displacement of the partition layer is the vertical offset value of the deformable visual partition 19, which is only used as an observation item and is not included in the shear strain calculation), is used to calculate the shear strain γ of the partition layer:

[0161]

[0162] In the formula, h0 is the original thickness of the interlayer, in mm.

[0163] Based on volumetric strain and shear strain, the instability risk of reservoirs and interlayers is classified into three levels:

[0164] Low risk: ε v <2%, γ <5%;

[0165] Medium risk: 2%≤ε v <5%, 5%≤γ<10%;

[0166] High risk: ε v ≥5%, γ≥10%.

[0167] Wellbore perimeter instability assessment: After the experiment, the collapse radius r of the reservoir around the wellbore is measured, which is the maximum radius of the reservoir collapse area around the wellbore.

[0168] The larger the collapse radius, the more severe the reservoir instability around the wellbore, and the worse the reservoir stability corresponding to the well completion method.

[0169] The experimental method for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs also includes step S4, well completion method selection and design:

[0170] S4.1 Conduct production process simulations under different operating conditions:

[0171] Perforation completion simulation: Using a simulated wellbore assembly with perforation holes, the hole diameter, density, and distribution are set according to the actual perforation parameters. The assembly is then installed at the corresponding position on the main tank 17 and sealed and fixed.

[0172] Simulate the perforation completion and production process, and monitor the deformation and sand production dynamics of the reservoir and interlayers in real time.

[0173] Sand control / no sand control working condition simulation: On the inside of the wellbore of perforated completion or open hole well, screens of different types and precision are installed as sand control components according to the actual reservoir sand control measures, which is the sand control working condition; removing the sand control components is the no sand control working condition. Production simulation is carried out according to preset parameters to compare the sand control effect and monitor the deformation and sand production dynamics of the reservoir and interlayer in real time.

[0174] Open-hole well operation simulation: The perforated section and sand control section of the simulated well are removed, and a solid, perforated well is used as the open-hole well simulation component to simulate the open-hole well mining process and monitor the deformation and sand production dynamics of the reservoir and interlayer in real time.

[0175] Vertical / Horizontal Well, Single / Multi-Layer Production Simulation: Simulate vertical wellbore 27 separately for vertical well production conditions, and simulate horizontal wellbore 26 separately for horizontal well production conditions.

[0176] Opening only the wellbore switch valve 25 corresponding to a single reservoir layer constitutes a single-layer production condition, while opening the wellbore switch valve 25 corresponding to multiple reservoir layers constitutes a multi-layer production condition.

[0177] Production simulations were conducted according to preset parameters, and the reservoir response under different operating conditions was recorded.

[0178] Production process control: During the experiment, the production flow rate was gradually increased according to the experimental design to simulate reservoir conditions under different mining intensities.

[0179] After each parameter adjustment, record the changes in reservoir deformation and sand production.

[0180] When obvious reservoir instability, interlayer rupture, or sudden increase in sand production occur, the experiment should be suspended and the critical operating parameters recorded.

[0181] S4.2 Comparison and Optimization of Different Well Completion Methods:

[0182] A comprehensive comparative analysis was conducted on the critical sand production parameters, critical instability parameters, sand production intensity index, and wellbore perimeter collapse radius indices for different completion methods, including open hole wells, perforated wells, wells with sand control, and wells without sand control, as well as different production methods, including vertical / horizontal wells and single / multi-layer production. The results were used to compare and optimize different completion methods and operating conditions.

[0183] Based on the core technical principles of minimizing sand production intensity index, maximizing critical parameter value, and minimizing collapse radius, and taking into account the economic efficiency, construction difficulty, and operability of on-site engineering implementation, the optimal well completion and production methods suitable for the target ultra-deep water and ultra-shallow gas reservoirs were selected.

[0184] Well completion parameter optimization: For the selected optimal well completion method, multiple sets of parameter optimization experiments were conducted to further optimize the perforation density, diameter, distribution, and key parameters of the sand control screen, and to determine the optimal selection of well completion parameters.

[0185] S1.2, Synchronous pressurization and water saturation are specifically as follows: The four-column servo hydraulic press 2 and the liquid supply system are started simultaneously. The four-column servo hydraulic press 2 applies axial pressure to the open hydraulic press plate 18 at a preset rate. The liquid supply system injects water into each reservoir 100 and interlayer 200 chamber at a constant speed, and the water injection rate is controlled at 0.1-0.5L / min.

[0186] During the water injection process, first open the wellbore switch valve 25, and continuously discharge the air in the tank through the sand liquid outlet 24 until each sand liquid outlet 24 has a continuous, bubble-free liquid flowing out, and then close the wellbore switch valve 25.

[0187] Continue to maintain the synchronous linkage between hydraulic press pressurization and liquid injection. The water injection pressure in the tank increases synchronously with the hydraulic press pressurization pressure until the hydraulic press pressurization pressure reaches 50% of the overburden pressure of the target water depth. The water injection pressure of reservoir 100 reaches the target reservoir static water pressure. Maintain pressure for 2 hours. During the pressure holding process, the four-column servo hydraulic press 2 and the liquid supply system remain linked. If there are slight fluctuations in the reservoir pressure, the four-column servo hydraulic press 2 will automatically adjust the pressurization pressure to ensure effective stress stability and achieve complete water saturation.

[0188] S1.3 The specific steps for synchronous pressure holding and gas saturation are as follows: After water saturation and pressure holding are completed, the linkage control mode of the four-column servo hydraulic press 2 is maintained to keep the pressurization pressure stable; the control valve 12 on the liquid pipeline 13 is closed, the control valve 12 on the gas pipeline 14 is opened, the gas supply system is started, and gas is injected into the reservoir 100 chamber. The gas injection adopts a constant pressure mode, and the gas injection pressure increases synchronously with the pressurization pressure of the four-column servo hydraulic press 2 at a preset rate. The gas injection rate is controlled at 0.1-1m³ / h; during the gas injection process, the data of the pressure sensor 9 in the tank is monitored in real time.

[0189] Continuous pressure holding and gas injection are carried out simultaneously until the hydraulic press pressure reaches the target water depth overburden pressure of 15.08-17.05 MPa and the reservoir gas injection pressure reaches the original formation pore pressure of the target reservoir. Pressure is held for 2 hours. During the pressure holding process, the data acquisition and control system 3 monitors and adjusts in real time to ensure that the difference between the hydraulic press pressure and the reservoir pore pressure is always equal to the actual effective formation stress, so that the gas can fully enter the pores of the reservoir sample and achieve complete gas saturation of the reservoir.

Claims

1. An experimental device for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs, characterized in that: The system includes a reservoir instability and sand production simulation main device (1), a four-column servo hydraulic press (2), a data acquisition and control system (3), a sand and liquid collection device (8), a pressure sensor (9), a gas flow meter (10), a liquid flow meter (11), a control valve (12), a liquid pipeline (13), a gas pipeline (14), an outlet pipeline (15), a liquid supply system, and a gas supply system. The main device (1) for simulating reservoir instability and sand production in the multi-layer production process includes a main tank (17), an open hydraulic pressure plate (18), a deformable visual partition (19), a tank visualization window (20), a tank inlet (23), a sand and liquid outlet (24), a wellbore switch valve (25), a simulated horizontal wellbore (26), and a simulated vertical wellbore (27). The main tank (17) has an opening facing upwards, and the open hydraulic pressure plate (18) is slidably installed inside the main tank (17). The four-column servo hydraulic press (2) is located above the open hydraulic pressure plate (18) and connected to the open hydraulic pressure plate (18). The main tank (17) is provided with alternating partitions (200) and reservoirs (100) from top to bottom. The deformable visual partition (19) has a grid-like scale on its surface. The deformable visual partition (19) is detachably and horizontally arranged inside the main tank (17), located between the reservoir (100) and the interlayer (200). The deformable visual partition (19) is sealed to the inner wall of the main tank (17). The main tank (17) has a tank visualization window (20) on its side wall. The main tank (17) is provided with a tank inlet (23) and a sand and liquid outlet (24) on the side wall corresponding to the reservoir (100). The simulated horizontal wellbore (26) is horizontally arranged in the reservoir (100), and one end of the simulated horizontal wellbore (26) is connected to the sand and liquid outlet (24). The main tank (17) and the partition layer (200) are provided with tank inlet (23) on their corresponding side walls. The open hydraulic pressure plate (18) is provided with a sand and liquid outlet (24), the simulated vertical wellbore (27) is vertically arranged in the main tank (17), the lower end of the simulated vertical wellbore (27) is located in the lowest reservoir (100), and the upper end of the simulated vertical wellbore (27) is connected to the sand and liquid outlet (24). The liquid supply system is connected to the tank inlet (23) via a separate liquid pipeline (13), the gas supply system is connected to the tank inlet (23) via a separate gas pipeline (14), and the sand liquid outlet (24) is connected to the sand liquid collection device (8) via a separate outlet pipeline (15). Wellbore switch valves (25) are installed at both the tank inlet (23) and the sand liquid outlet (24). Control valves (12) are installed on the liquid pipeline (13), gas pipeline (14), and outlet pipeline (15). A liquid flow meter (11) is installed on the liquid pipeline (13), and a gas flow meter (10) is installed on the gas pipeline (14). Pressure sensors (9) are installed at the tank inlet (23) on both sides of the reservoir (100), at the sand liquid outlet (24), and inside the reservoir (100). The data acquisition and control system (3) is connected to the four-column servo hydraulic press (2), pressure sensor (9), gas flow meter (10), liquid flow meter (11), control valve (12), well shaft switch valve (25), liquid supply system and gas supply system respectively.

2. The experimental apparatus for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs according to claim 1, characterized in that: It also includes an internal sliding groove (21) and a sliding buckle (22); The internal sliding groove (21) is vertically arranged on the side wall of the main tank (17), and multiple sliding buckles (22) are arranged in the internal sliding groove (21) in a way that allows them to slide up and down. The two ends of the deformable visual partition (19) are detachably mounted on the sliding buckle (22).

3. The experimental apparatus for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs according to claim 1, characterized in that: The liquid supply system includes a liquid pump (4) and a liquid storage tank (5), wherein the liquid storage tank (5) is connected to the tank inlet (23) through the liquid pump (4); The gas supply system includes a gas tank (6) and an air compressor (7). The gas tank (6) is connected to the inlet (23) of the tank body, and the air compressor (7) is used to pressurize the gas tank (6) to supply gas.

4. The experimental apparatus for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs according to claim 1, characterized in that: A buffer layer is provided above the uppermost interlayer (200), and a pad layer is provided at the bottom of the main tank (17).

5. The experimental apparatus for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs according to claim 1, characterized in that: The deformable visual partition (19) is made of polyurethane elastic composite material with a thickness of 5-20 mm and an elastic modulus of 0.5-2 GPa.

6. The experimental apparatus for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs according to claim 2, characterized in that: The deformable visual partition (19) has a sealing ring at its edge.

7. A simulation and evaluation experimental method for instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs, utilizing the simulation and evaluation experimental apparatus for instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Experimental Conditions Setup S1.1 Experimental Sample Preparation and Filling: Prepare reservoir simulation samples and interlayer simulation samples, and fill the main tank (17) in layers; S1.2, Synchronous pressurization and water saturation: Simultaneously start the four-column servo hydraulic press (2) and the liquid supply system to achieve complete water saturation; S1.3, Synchronous pressure holding and gas saturation: After the water saturation pressure holding is completed, the linkage control mode of the four-column servo hydraulic press (2) is maintained, the liquid supply system is closed, the gas supply system is started, and the reservoir is fully saturated with gas. The sample in the reservoir (100) is not damaged or displaced in advance throughout the entire process. S2, Process Experiment Simulation S2.1 Production Process Simulation: Based on the actual exploitation plan of the target gas reservoir, the opening mode of the wellbore switch valve (25) is preset; the flow rate of gas-liquid production is set according to the actual reservoir exploitation conditions converted to experimental conditions. The wellbore switch valve (25) is opened according to preset parameters by the data acquisition and control system (3), the gas-liquid flow parameters are set and the gas-liquid delivery system is started. The gas-liquid production flow is precisely controlled by the gas flow meter (10) and the liquid flow meter (11) to simulate the mining process. S2.2 Real-time data acquisition and recording during the experiment; During the experiment, the pressure, gas-liquid production flow rate, and hydraulic press press pressure of the inlet (23) and outlet (24) of the tanks on both sides of the reservoir (100) were collected and stored in real time through the data acquisition and control system (3); Using a high-speed camera aimed at the tank's visualization window (20) and deformable visualization partition (19), the deformation of the reservoir sample, the sand discharge start position, the sand particle migration trajectory, and the displacement and rupture process of the interlayer were captured in real time. During the experiment, the overall condition of the device was manually checked every 1-2 hours, and it was recorded whether the reservoir sample had cracks or collapses, whether the interlayer had shifted, and whether the wellbore had sand blockage. After the experiment, the sand sample from the sand collection device (8) was subjected to solid-liquid separation, dried and weighed. The vertical displacement ΔH, horizontal length displacement ΔL, horizontal width displacement ΔW, and horizontal / vertical displacement of the interlayer (200) of each reservoir sample are read and recorded by the scale lines of the deformable visualization spacer (19). S3, Quantitative Evaluation S3.1 Quantitative Evaluation Indicators and Calculations for Sand Production: Based on the experimental data, the critical sand production pressure and critical sand production flow rate were determined, which are the production pressure and gas production flow rate corresponding to when the reservoir begins to show obvious sand production. Weigh the total sand output M and the sand output m of each layer. i ; Based on the actual experimental duration t, calculate the average sand production rate v and the average sand production rate va of each reservoir layer. i ; The sand production intensity index I is defined as the sand production rate per unit reservoir volume and per unit pressure drop. The reservoir sand production intensity index I is calculated. After the experiment, a laser particle size analyzer was used to analyze the particle size and morphology of the dried sand sample, and to plot the sand particle size distribution curve, as well as the relationship curves between sand output, sand output rate and production pressure and flow rate, thus quantifying the correlation between production parameters and sand output. S3.2 Evaluation Indicators and Calculations for Reservoir and Interlayer Instability: Evaluation of reservoir and interlayer instability: Based on image data captured by a high-speed camera and the scale lines of a deformable visual interlayer (19), the vertical deformation ε of the reservoir sample was measured. z Horizontal length deformation ε l and horizontal width deformation ε w The volumetric strain ε is calculated by summing the three factors. V ; Measure the horizontal displacement d of the interlayer sample L Vertical displacement d W Calculate the shear strain γ of the interlayer; Based on volumetric strain and shear strain, the instability risk of reservoirs and interlayers is classified into three levels: Low risk: ε v <2%, γ <5%; Medium risk: 2%≤ε v <5%, 5%≤γ<10%; High risk: ε v ≥5%, γ≥10%; Wellbore perimeter instability evaluation: After the experiment, the collapse radius r of the reservoir around the wellbore was measured, which is the maximum radius of the reservoir collapse area around the wellbore; The larger the collapse radius, the more severe the reservoir instability around the wellbore, and the worse the reservoir stability corresponding to the well completion method.

8. The experimental method for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs according to claim 7, characterized in that, It also includes step S4, well completion method selection and design: S4.1 Conduct production process simulations under different operating conditions: Simulation of perforation completion conditions: Using a simulated wellbore assembly with perforation holes, the diameter, density and distribution of the holes are set according to the actual perforation parameters. The assembly is then installed in the corresponding position of the main tank (17) and sealed and fixed. Simulate the perforation completion and production process, and monitor the deformation and sand production dynamics of the reservoir and interlayer in real time; Sand control / no sand control simulation: On the inside of the wellbore of perforated or open hole wells, different types and precision of screen pipes are installed as sand control components according to the actual reservoir sand control measures, which is the sand control condition; removing the sand control components is the no sand control condition. Production simulation is carried out according to preset parameters to compare the sand control effect and monitor the deformation and sand production dynamics of the reservoir and interlayer in real time. Open-hole well operation simulation: The perforated section and sand control section of the simulated well are removed, and a solid, perforated well is used as the open-hole well simulation component to simulate the open-hole well mining process and monitor the deformation and sand production dynamics of the reservoir and interlayer in real time. Vertical well / horizontal well, single-layer / multi-layer production simulation: The vertical wellbore simulation (27) is activated separately for vertical well production conditions, and the horizontal wellbore simulation (26) is activated separately for horizontal well production conditions; Opening only the wellbore switch valve (25) corresponding to a single reservoir layer is a single-layer production condition, while opening the wellbore switch valve (25) corresponding to multiple reservoir layers is a multi-layer production condition. Production simulations were conducted according to preset parameters, and the reservoir response under different operating conditions was recorded. Production process Control: During the experiment, the production flow rate was gradually increased according to the experimental design to simulate reservoir conditions under different mining intensities; After each parameter adjustment, record the changes in reservoir deformation and sand production; When obvious reservoir instability, interlayer rupture, or a sudden increase in sand production occur, the experiment should be suspended and the critical operating parameters recorded. S4.2 Comparison and Optimization of Different Well Completion Methods: A comprehensive comparative analysis was conducted on the critical sand production parameters, critical instability parameters, sand production intensity index, and wellbore perimeter collapse radius indices for different completion methods, including open hole wells, perforated wells, wells with sand control, and wells without sand control, as well as different production methods, including vertical / horizontal wells and single / multi-layer production. The results were compared and optimized for different completion methods and operating conditions. Based on the core technical principles of the lowest sand production strength index, the highest critical parameter value, and the smallest collapse radius, and taking into account the economy, construction difficulty, and operability of on-site engineering implementation, the optimal well completion method and production method suitable for the target ultra-deep water and ultra-shallow gas reservoir were selected. Well completion parameter optimization: For the selected optimal well completion method, optimize the perforation density, diameter, and distribution, as well as the key parameters of the sand control screen. Conduct multiple sets of parameter optimization experiments to determine the optimal selection of well completion parameters.

9. The experimental method for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs according to claim 7, characterized in that, S1.2, Synchronous pressurization and water saturation are as follows: The four-column servo hydraulic press (2) and the liquid supply system are started at the same time. The four-column servo hydraulic press (2) applies axial pressure to the open hydraulic press plate (18) at a preset rate. The liquid supply system injects water into each reservoir (100) and interlayer (200) chamber at a constant speed. The water injection rate is controlled at 0.1-0.5L / min. During the water injection process, first open the wellbore switch valve (25) and continuously discharge the air in the tank through the sand liquid outlet (24) until each sand liquid outlet (24) has a continuous, bubble-free liquid flow out, and then close the wellbore switch valve (25). Continue to maintain the synchronous linkage between hydraulic press pressurization and liquid injection. The water injection pressure in the tank increases synchronously with the hydraulic press pressurization pressure until the hydraulic press pressurization pressure reaches 50% of the overburden pressure of the target water depth. The water injection pressure of the reservoir (100) reaches the target reservoir static water pressure. Hold the pressure for 2 hours. During the pressure holding process, the four-column servo hydraulic press (2) and the liquid supply system remain linked. If the reservoir pressure fluctuates slightly, the four-column servo hydraulic press (2) automatically adjusts the pressurization pressure to ensure effective stress stability and achieve complete water saturation.

10. The experimental method for simulating and evaluating instability and sand production in ultra-deepwater and ultra-shallow gas reservoirs according to claim 7, characterized in that, S1.3, The specific steps of synchronous pressure holding and gas saturation are as follows: After the water saturation pressure holding is completed, the linkage control mode of the four-column servo hydraulic press (2) is maintained to keep the pressurization pressure stable; the control valve (12) on the liquid pipeline (13) is closed, the control valve (12) on the gas pipeline (14) is opened, the gas supply system is started, and gas is injected into the reservoir (100) chamber. The gas injection adopts the constant pressure mode, and the gas injection pressure increases synchronously with the pressurization pressure of the four-column servo hydraulic press (2) at the preset rate. The gas injection rate is controlled at 0.1-1m³ / h; during the gas injection process, the data of the pressure sensor (9) in the tank is monitored in real time. Continuously maintain pressure and inject gas until the hydraulic press press reaches the target water depth overburden pressure of 15.08-17.05 MPa and the reservoir gas injection pressure reaches the target reservoir original formation pore pressure. Maintain pressure for 2 hours. During the pressure maintenance process, the data acquisition and control system (3) monitors and adjusts in real time to ensure that the difference between the hydraulic press press pressure and the reservoir pore pressure is always equal to the actual formation effective stress, so that the gas can fully enter the pores of the reservoir sample and achieve complete gas saturation of the reservoir.

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