CN108301827B - System and method for evaluating microcosmic enrichment rule and blockage mechanism of mechanical screen hydrate - Google Patents

Abstract

The invention provides a system and a method for evaluating a microscopic enrichment rule and a blockage mechanism of hydrate in a mechanical screen, which can simulate the influence of differences of gas-liquid flow direction, flow pattern and temperature-pressure conditions on the microscopic enrichment blockage mechanism of the hydrate in the screen at the same time. The system and the method realize the prejudgment of the easy-to-generate position of the natural gas hydrate on the screen mesh sheet in the marine natural gas hydrate exploitation well and the simulation of the hydrate enrichment blocking law, thereby providing a basis for the design of the screen flow guiding groove of the hydrate exploitation well, especially the horizontal well section, and providing a proposal for the blocking removal scheme of the screen pipe in the actual exploitation well after the hydrate enrichment blocking.

Description

Evaluation system and method for microcosmic enrichment law and clogging mechanism of mechanical sieve hydrate

technical field

The invention belongs to the field of natural gas hydrate exploitation, and in particular relates to an evaluation system and method for simulating the microcosmic mechanism of hydrate secondary generation and enrichment blockage in the screen media of sand control screens in marine hydrate exploitation wells.

Background technique

Natural gas hydrate is a clean fossil energy with high energy density. More than 90% of the world's natural gas hydrate occurs in shallow marine sedimentary environments, and a small amount exists in permafrost. Countries around the world are constantly exploring the development and utilization of natural gas hydrates, and have conducted many mining tests. my country first exploited natural gas hydrates in the Shenhu area of the South China Sea in 2017, and achieved two major breakthroughs in gas production duration and cumulative gas production. However, whether it is the trial production of natural gas hydrate in my country or the previous trial production of natural gas hydrate abroad, the problem of sand production always exists and has become the chief culprit restricting the failure of the trial production project in some test productions. Therefore, in order to ensure the long-term safe test production of natural gas hydrate resources, appropriate sand control media must be installed at the bottom of the well for sand control, and the most commonly used sand control media is mesh mechanical screen.

The mesh type machine screen is usually composed of three parts: the outer protective cover, the screen mesh, and the base pipe. Among them, the screen mesh is the main sand control unit and the most "fragile" part of the screen pipe. In actual mine use, the screen mesh may face serious risks of erosion and blockage. Therefore, in the development process of conventional oil and gas fields, a flow guide device with a special structure is usually designed inside the outer protective cover to alleviate the erosion damage of the screen pipe caused by the frontal impact of the mud and sand on the screen mesh; The support layer between the structure and the multi-field mesh can relieve the blockage of the mesh caused by fine particles such as mud. However, for natural gas hydrate production wells, mechanical screens are faced with more complex working conditions. In addition to the erosion damage of the screen mesh by the above-mentioned mud and sand, and the blockage of the mesh by fine particles such as mud, hydrate production The new problem faced in the well is the serious decrease of screen permeability due to the secondary formation of hydrate in the screen (especially in the screen mesh). The superposition of hydrate secondary enrichment blockage and mud blockage in the screen mesh has extremely adverse effects on the actual production of natural gas hydrate. However, the current general-purpose mechanical screen structure design does not consider the influence of microscopic enrichment and clogging of hydrates in the screen mesh, and there is no simulation on the study of the secondary enrichment and clogging of natural gas hydrate in the screen mesh. device.

Therefore, in order to design and develop sand control screens with special structures for natural gas hydrate production wells, it is necessary to have a clear understanding of the preferential generation position and microscopic impact mechanism of hydrates in the screen mesh during the production process, so as to further It is more pertinent to design the special screen structure for hydrate production wells, especially the combination of diversion groove and screen mesh. Therefore, in view of the above problems, it becomes an important subject of the present invention to propose a device for evaluating the microscopic enrichment and clogging mechanism of hydrates in the mechanical screen mesh.

Contents of the invention

The purpose of the present invention is to provide an evaluation system capable of simultaneously simulating the influence of gas-liquid flow direction, flow pattern, and temperature and pressure conditions on the microscopic enrichment and blockage mechanism of hydrates in the screen. Through this system, the prediction of the easy-to-generate location of natural gas hydrate on the screen mesh in marine gas hydrate production wells and the simulation of hydrate enrichment and blockage can be realized, so as to realize the simulation of hydrate production wells, especially the screen diversion grooves in horizontal well sections. The design provides a basis, and provides suggestions for the unblocking scheme of the screen pipe in the actual production well after it is blocked due to hydrate enrichment.

The present invention is realized by adopting the following technical solutions:

A mechanical screen hydrate microscopic enrichment and clogging mechanism evaluation system, including: a supply module, used to provide methane and distilled water; a circulation module, used to provide the required flow pattern and gas-liquid ratio, including outlets, inlets and vacuum pumps; constant temperature The module is used to provide a constant temperature; the multi-directional screen fixing module is located in the constant temperature module, including a circular slide rail, a motor located at the center of the slide rail, and four screen fixing devices evenly distributed along the slide rail. The two screen fixing devices are connected in series through right-angled hard tubes. The vertical and horizontal sides of each right-angled tube are fixed with pulleys that are dynamically matched with the slide rails. The two pulleys are connected to the motor through a belt. One of the right-angled tubes is divided into two One section is connected to the inlet of the circulation module through the hose, and the other section is connected to the outlet of the circulation module through the hose; the screen fixing device includes a male head, a female head, and a screen angle between the male head and the female head during installation. An adjustment device, the adjustment device includes two cylinders, the butt surface of the screen is between the two cylinders, and a number of through holes are opened between the butt surface and the bottom surface of each cylinder. The data collection module is used to collect system data.

Further, the right-angle connecting rigid pipe is a transparent high-pressure pipe.

Further, the butt joint surface between the two cylinders is a slope, and the slope angle of the slope is 80°, 70°, 60°, 50°, 40°, 30°, 20° or 10°. Certainly, the butt joint surface between the two cylinders may also be a vertical surface.

Further, the data acquisition module includes: a pressure sensor, a temperature sensor, a differential pressure sensor, an optical camera and a high-speed camera, the differential pressure sensor is located at both ends of each screen in the multi-directional screen fixing module, the pressure sensor and The temperature sensor is used to monitor the temperature and pressure of the system, and the optical camera and high-speed camera are used to observe the flow pattern of the gas-liquid two-phase flow in the pipeline.

Further, the circulation module includes a gas-liquid mixer, a high-pressure coil, and a circulation pump. The inlet of the gas-liquid mixer is connected to the supply module, and the outlet is connected to the high-pressure coil. The high-pressure coil is used to suck in evenly mixed gas. The outlet of the liquid two-phase fluid is connected to a circulation pump, and the circulation pump is directly connected to a multi-directional screen fixed module to control the flow rate of the uniformly mixed two-phase flow.

Further, the supply module includes a high-pressure gas cylinder and a water supply tank. The high-pressure gas cylinder and the water supply tank are directly connected to the gas-liquid mixer of the circulation module. The supply module also includes a replenishment container for replenishing the system with water and methane.

Further, a concave-convex matching structure is provided on the butt joint surface between the two cylinders.

Corresponding to the above-mentioned mechanical screen hydrate microscopic enrichment law and clogging mechanism evaluation system, corresponding to the device, the present invention also proposes a method for evaluating the microscopic formation and enrichment law of hydrate in a mechanical screen and its application method, comprising the steps of:

(1) Select four screen angle adjustment devices: define the angle at which the multi-directional screen fixed module rotates along the circular slide rail under the action of the motor as the revolution angle, and define the gas-liquid mixed fluid adjusted by the screen angle adjustment device The included angle between the flow direction and the screen is the rotation angle. Set the four screen angle adjustment devices, two of which are in the horizontal state, and the revolution angle of the other two in the vertical state is 0°. Select the screen angle adjustment device Combined so that the sum of the rotation angles of two adjacent screen angle adjustment devices is 90°, and the sum of the rotation angles of the other two screen angle adjustment devices is 90°;

(2) Vacuum pumping and gas-liquid supply: vacuumize the system and the multi-directional screen fixed module; inject gas and liquid into the circulation module in a certain proportion to make the system pressure reach the set experimental pressure, and then close the supply module ;

(3) Simulate gas-liquid mixed transmission: start the circulation module to fully mix the gas and liquid, connect the multi-directional screen fixed module and the circulation module, set the circulation pump to circulate at a constant speed, and turn on the temperature control module at the same time to cool down the entire system; After reaching the set temperature, continue to maintain the constant speed cycle of the temperature and record the changes of the absolute pressure value and pressure difference on both sides of the four screen meshes in real time;

(4) Recognition of the flow direction of the diversion groove of the optimal screen outer protective cover under the condition of fixed rotation angle: adjust the preset temperature and gas-liquid ratio, and repeat steps (2)-(3) to obtain the flow direction of the screen under a certain revolution angle. Three-dimensional critical state distribution map of hydrate microscopic formation;

(5) Adjust the rotation angle combination, repeat steps (2)-(4), and obtain the four-dimensional critical state diagram of the critical condition for the secondary enrichment of hydrate in the screen mesh sheet under a certain revolution angle;

(6) Stop the experiment.

Further, stop the experiment when any of the following conditions are met in step (6): A, when the pressure difference on both sides of the screen in the multi-directional screen fixed module increases to 5 times or more than the initial pressure difference; B, the whole system When the pressure value reaches 14MPa.

Compared with prior art, advantage and positive effect of the present invention are:

The invention innovatively proposes a simulation experiment system for hydrate micro-enrichment and clogging mechanism evaluation in the screen mesh, and answers the location and clogging law of mechanical screen pipe clogging in the process of hydrate mining from a quantitative perspective. The demand for energy development provides certain support for the design of mechanical screen mechanisms suitable for natural gas hydrate production wells and the formulation of production parameters and depressurization rates for depressurization production.

By simulating the hydrate enrichment and clogging of the screen under a certain gas-liquid ratio and flow form, the present invention can compare the secondary generation and clogging of hydrate in all directions of the screen in the horizontal well section, and then in the construction process In the process, the methane hydrate suppression device can be used in a targeted manner at the screen position where hydrates are easily generated secondary to improve production efficiency and output.

The invention adjusts the supply module and the circulation module to realize the regularity and critical conditions of the secondary generation and blockage of screen hydrate under different gas-liquid ratios and different flow rates, and the obtained data can be used for the production of daily output and depressurization rate of on-site production. Conditions, etc. to provide certain guidance.

The present invention obtains the relationship between the flow direction of the gas-liquid two-phase flow and the angle between the screen and the degree of hydrate enrichment and blockage on the screen through experiments, which has certain guiding significance for the optimization design of the diversion groove of the protective cover outside the screen pipe. In addition, in the evaluation When selecting a screen tube, experiments can be carried out on its screen mesh, and the property of secondary generation and blockage of hydrate on the mesh can also be used as a certain evaluation index.

Description of drawings

Fig. 1 is a block diagram of the mechanical screen hydrate microscopic enrichment and clogging mechanism evaluation system of the present invention;

Fig. 2 is a schematic structural view of the screen fixing device of the present invention;

Fig. 3 is a structural schematic diagram of the screen angle adjusting device of the present invention;

In the above figures: 1. Constant temperature module; 2. Circulation module; 3. Supply module; 4. Data acquisition module; 5. Pressure difference sensor; 6. Screen fixing device; 9. Transparent high-pressure resistant pipeline; Hose; 11. male head; 12. female head; 13. high pressure resistant sealing gasket; 14. screen; 15. screen angle adjustment device; 17-2, second pressure measuring hole; 18, pulley; 19, slide rail; 20, motor; 15-1, through hole; 15-2, docking surface; 15-3, bottom surface; 6-1, 6 in the figure -2, 6-3 and 6-4 are the screen fixing device numbers.

Detailed ways

Proposal process of the present invention: the mechanical screen is the first station through which the gas and liquid flow after being produced from the formation, and faces a relatively high risk of secondary formation of hydrates. Specific to the screen mesh wrapped around the periphery of the base pipe in a cylindrical shape, if the influence of the screen diversion groove is not considered, for vertical wells, since the angle between the screen mesh and the gas-liquid flow direction is fixed Therefore, it can be considered that the gas-liquid flow direction impacting the surface of the screen mesh is uniform and horizontal, so the screen tube is also uniformly blocked by hydrate enrichment. However, for horizontal wells or other well types, it is foreseeable that the enrichment and plugging of hydrate in the screen will occur unevenly. Therefore, studying the influence of the gas-liquid flow direction, the angle between the gas-liquid flow direction and the screen mesh on the secondary formation and enrichment of hydrate in the screen will be the key to revealing the clogged position of the screen tube in hydrate mining from the mechanism and optimizing the screen tube. The premise of the diversion tank is also to provide "eyes" for "blockage removal" measures for the hydrate blockage in the screen.

In order to understand the purpose, features and advantages of the present invention more clearly, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Embodiment 1, this embodiment proposes a mechanical screen hydrate microscopic enrichment law and clogging mechanism evaluation system, as shown in Figure 1, including: circulation module 2, supply module 3, constant temperature module 1, multi-directional screen fixing Module and data acquisition module4.

The circulation module 2 is used to evacuate the pipeline of the experimental system, inject the two-phase fluid of methane and distilled water into the experimental pipeline and the multi-directional screen fixed module, and provide the flow pattern and gas-liquid ratio required for the simulation experiment. It mainly includes gas-liquid mixer, high-pressure coil, circulation pump, vacuum pump and related valve pipelines. The gas-liquid mixer is connected to the supply module, and the supply module provides distilled water and methane gas, which are fully mixed in the gas-liquid mixer to form a two-phase fluid with a specified gas-liquid ratio. The high-pressure coil sucks the evenly mixed gas-liquid two-phase fluid in the gas-liquid mixer, and the outlet end of the high-pressure plate is connected with the circulation pump. The circulation pump is directly connected to the pipeline of the multi-directional screen fixed module to control the flow rate of the evenly mixed two-phase flow to ensure the progress of the experiment. The vacuum pump is used to empty the gas in the pipeline before the experiment starts.

The supply module includes a high-pressure gas cylinder and a water supply tank, and the high-pressure gas cylinder and the water supply tank are directly connected with the gas-liquid mixer of the circulation module to provide the required methane gas and distilled water. In addition, it also includes a rehydration container. When the hydrate is generated in the experiment, the pressure of the system is reduced, and the system is replenished with water and gas through the rehydration container.

The data acquisition module includes pressure sensors, temperature sensors, differential pressure sensors, optical cameras, high-speed cameras and corresponding acquisition software. The two ends of each screen in the multi-directional screen fixing module are equipped with differential pressure sensors, and the clogging caused by the secondary generation of methane hydrate on the screen is reflected by measuring the change in pressure difference between the two ends. Pressure sensors and temperature sensors are used to monitor the temperature and pressure of the system, and to explore the critical temperature and pressure conditions required for the secondary formation of hydrates, etc. Optical cameras and high-speed cameras can be used to observe the flow pattern of gas-liquid two-phase flow in the pipeline, and explore the influence of flow parameters such as flow shape and gas-liquid ratio on the secondary generation of hydrate on the screen, so as to provide production parameters. provide a basis for its formulation.

The constant temperature module is a low-temperature constant temperature box, and the multi-directional screen fixing module is located inside the constant temperature module. Referring to Figure 1, the multi-directional screen fixing module includes a slide rail 19, a motor 20 located at the center of the slide rail, and four motors evenly distributed along the slide rail. Screen fixing device 6, the four screen fixing devices 6 are connected in series by right-angled hard pipes 16, and the vertical and horizontal sides of each right-angled connected hard pipe 16 are respectively fixed with pulleys 18 that are dynamically matched with slide rails. The pulley 18 is connected with the motor 20 through a belt, and one of the right-angle pipes is divided into two sections, one section is connected to the inlet of the circulation module through the hose, and the other section is connected to the outlet of the circulation module through the hose. The screen fixing devices 6 connected in series are respectively in the horizontal state and the vertical state under the connection of the transparent high-pressure-resistant pipe, and the flow rate under the conditions of three different flow directions from top to bottom, horizontal penetration and bottom to top can be studied respectively. Microcosmic enrichment and blockage of hydrate in the screen. The motor drives the pulley to drive the rotation of the multi-directional screen fixed module, which can further study the microscopic enrichment and blockage of hydrate in the screen under the condition of multi-angle flow direction. The main effect of the transparent high-pressure-resistant pipe used in the right-angled connecting hard pipe 16 is to observe the flow pattern when passing through the screen and play the role of fixing and connecting the screens in series.

Referring to Fig. 2 and Fig. 3, the screen fixing device 6 of the present embodiment includes a male head 11, a female head 12 and a screen angle adjusting device 15 positioned between the male head and the female head during installation. The adjusting device includes two cylinders, Between the two cylinders is the butt joint surface 15-2 of the screen, and several through holes 15-1 are opened between the butt joint surface 15-2 and the bottom surface 15-3 of each cylinder. Use planer hoop to clamp between male head 11 and female head 12 to ensure the sealing of both of them. The screen angle adjusting device 15 can press the screen 14 placed in the screen fixing device 6 to prevent it from moving and being greatly deformed under the impact of the gas-liquid two-phase flow. The first pressure measuring hole 17-1 and the second pressure measuring hole 17-2 are respectively provided on the male head 11 and the female head 12 of the screen fixing device, which are used to measure the differential pressure at both ends of the screen in real time during the experiment.

The screen angle adjusting device 15 can set the butt surface 15-2 between the two cylinders as an inclined plane according to requirements, and the inclination angle α of the inclined plane can be 80°, 70°, 60°, 40°, 30°, 20° or 10°. °. Of course, the butt surface 15-2 between the two cylinders can also be set as a vertical surface. During the experiment, by replacing different screen angle adjustment devices 15, the gas-liquid two-phase flow flowing through the screen and the screen surface have a certain angle, so as to realize the angle between the fluid flow direction and the screen mesh medium. Simulation, so as to provide support for the design of special screen diversion grooves for gas hydrate test production wells.

In this embodiment, the bottom surfaces 15-3 of the two cylinders of the screen angle adjusting device 15 are respectively docked with the male head 11 and the female head 12 of the fixing device. In order to make the screen mesh more firmly fixed, a concave-convex matching structure is provided on the butt joint surface between the two cylinders, and the screen mesh 14 can be reliably compressed by the concave-convex structure.

In this system, the motor 20 drives the pulley 18 to slide along the slide rail 19 so that the multi-directional screen fixed module can rotate as a whole to realize the control of the angle between the flow direction of the gas-liquid two-phase flow and the direction of gravity, so as to simulate the flow direction of the fluid. The influence of the microscopic enrichment and blockage of hydrate in the screen mesh medium; by controlling the gas-liquid ratio, fluid flow rate, temperature and pressure in the experimental pipeline and other experimental conditions, the microscopic mechanism and the secondary formation of hydrate on the screen in various directions can be observed. Critical conditions, and related sensitivity analysis. In addition, through the cooperation of transparent high-pressure resistant pipes, high-pressure resistant hoses and screen fixing devices, the purpose of simultaneously observing the flow pattern and the differential pressure of screen clogging is realized, and the evolution law of the degree of hydrate enrichment and clogging in the screen is obtained through simulation experiments. Establish laws with flow patterns, and further describe the mechanism of hydrate enrichment and blockage in screens under different conditions.

This system can more realistically simulate the requirements of the actual bottom-hole working conditions of natural gas hydrate production wells, and the simulation results have guiding significance for on-site construction.

Embodiment 2. This embodiment proposes a method for evaluating the microscopic formation and enrichment of hydrates in a mechanical screen, which mainly includes the following steps:

(1) Select the screen angle adjustment device:

Define the angle at which the multi-directional screen fixing module rotates along the circular slide rail under the action of the motor as the revolution angle. Referring to Figure 1, define the screen fixing device as 6-1, 6-2, and 6 from the inlet of the device in sequence. -3, 6-4, define that 6-2, 6-4 are in the horizontal state, 6-1, 6-3 are in the vertical state when the revolution angle is 0°, and the motor rotates clockwise to form the revolution angle;

The angle between the flow direction of the gas-liquid mixed fluid adjusted by the screen angle adjustment device and the screen is defined as the rotation angle. The coordination of the rotation angle realizes the influence of the fluid flow direction and the diversion groove of the outer protective cover on the secondary microscopic enrichment and generation conditions of hydrate in the screen, and provides a basis for the direction design of the diversion groove of the screen under different well type conditions.

Set the revolution angle to 0°, select the screen angle adjustment device combination, make the sum of the rotation angles of the screen angle adjustment devices in 6-1 and 6-3 be 90° (or directly select the vertical plane), make 6-2 The sum of the rotation angles of the screen angle adjustment device in 6-4 is 90° (or directly select the vertical plane);

(2) Vacuum pumping and gas-liquid supply: close the valve between the supply module and the mixed transport module, connect the multi-directional screen fixing module and the circulation module, turn on the vacuum pump in the circulation module, and fix the circulation system and the multi-directional screen. The module is vacuumized; then open the valve between the supply module and the circulation module, close the valve between the multi-directional screen fixed module and the circulation module, and inject gas and liquid into the circulation module in a certain proportion to make the system pressure reach the set value. Set the experimental pressure, and then close the supply module.

(3) Simulate gas-liquid mixed transport: start the circulation module to fully mix the gas and liquid, connect the multi-directional screen fixed module and the circulation module, set the pump speed of the circulation pump, start the pump to circulate at a constant speed, and at the same time, turn on the temperature Control module, set the temperature value (such as 2°C) to cool down the entire system; after falling to the set temperature, continue to maintain the temperature at a constant speed cycle and record the absolute pressure on both sides of the 4 screen meshes in real time during this process Variations in value and differential pressure. A decrease in absolute pressure indicates that hydrates have been generated at a certain position in the system, and an increase in the differential pressure on both sides of the screen indicates that hydrates have begun to be generated in the screen. Record the absolute pressure at this time as the hydrate generated in the screen mesh. Critical pressure (4 pressure values can be obtained here, as critical pressure conditions under four kinds of rotation angle conditions);

(4) Recognition of the flow direction of the flow direction of the diversion groove of the optimal screen outer protective cover under the condition of fixed rotation angle: adjust the preset temperature (such as 4°C), gas-liquid ratio conditions, and repeat steps (2)-(3), so that is enough The three-dimensional critical state distribution map (temperature, pressure, gas-liquid ratio) of the microscopic formation of hydrate in the screen under a certain revolution angle is obtained.

(5) Adjust the rotation angle combination and repeat steps (2)-(4) to obtain the four-dimensional critical state diagram (rotation angle) of the critical condition for the secondary enrichment of hydrate in the screen mesh under a certain revolution angle

(6) Stop the experiment.

The sign of judging the end of the simulation experiment involved in the present invention is: ① When the pressure difference on both sides of the screen in the multi-directional screen fixed module increases to 5 times or more than the initial pressure difference, it indicates that the hydrate is on the screen. ② When the displacement pressure of the circulation pump increases due to the formation of hydrate on the screen, and the pressure value of the entire system reaches 14MPa, the test is close to the safe pressure of the system, so the experiment is stopped.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention to other forms. Any skilled person who is familiar with this profession may use the technical content disclosed above to change or modify the equivalent of equivalent changes. The embodiments are applied to other fields, but any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the technical solutions of the present invention without departing from the content of the technical solutions of the present invention.

Claims (8)

1. A mechanical screen hydrate microscopic enrichment law and blockage mechanism evaluation system, comprising:

a supply module for providing methane and distilled water;

the circulation module is used for providing a required flow pattern and a gas-liquid ratio and comprises an outlet, an inlet and a vacuum pump;

a constant temperature module for providing a constant temperature;

the multi-azimuth screen fixing module is positioned in the constant temperature module and comprises a round sliding rail, a motor positioned at the center of the sliding rail, four screen fixing devices uniformly distributed along the sliding rail, wherein the four screen fixing devices are connected in series through right-angle connecting hard pipes, the right-angle connecting hard pipes are transparent high-pressure resistant pipes, pulleys in movable fit with the sliding rail are respectively fixed on the vertical side and the horizontal side of each right-angle connecting hard pipe, the two pulleys are connected with the motor through belts, one right-angle connecting hard pipe is divided into two sections, one section is connected with an inlet of the circulating module through a high-pressure resistant hose, and the other section is connected with an outlet of the circulating module through the high-pressure resistant hose;

the screen fixing device comprises a male head, a female head and a screen angle adjusting device arranged between the male head and the female head during installation, wherein the adjusting device comprises two cylinders, a screen butt joint surface is arranged between the two cylinders, and a plurality of through holes are formed between the butt joint surface and the bottom surface of each cylinder;

the data acquisition module is used for acquiring system data and comprises: pressure sensor, temperature sensor, differential pressure sensor and optical pick-up head and high-speed camera, differential pressure sensor is arranged in the fixed module of diversified screen cloth at the both ends of every screen cloth, and pressure sensor and temperature sensor are used for monitoring the temperature and pressure of system, and optical pick-up head and high-speed camera are used for observing the flow pattern of the gas-liquid two-phase flow in the pipeline.

2. The mechanical screen hydrate microscopic enrichment rule and blockage mechanism evaluation system of claim 1, wherein: the butt joint surface between the two cylinders is an inclined surface, and the inclined angle of the inclined surface is 80 degrees, 70 degrees, 60 degrees, 50 degrees, 40 degrees, 30 degrees, 20 degrees or 10 degrees.

3. The mechanical screen hydrate microscopic enrichment rule and blockage mechanism evaluation system of claim 1, wherein: the circulating module comprises a gas-liquid mixer, a high-pressure coil pipe and a circulating pump, wherein an inlet of the gas-liquid mixer is communicated with the supply module, an outlet of the gas-liquid mixer is communicated with the high-pressure coil pipe, the high-pressure coil pipe is used for sucking uniformly mixed gas-liquid two-phase fluid in the gas-liquid mixer, an outlet end of the high-pressure coil pipe is connected with the circulating pump, and the circulating pump is directly connected into the multi-directional screen fixing module and used for controlling the flow speed of the uniformly mixed two-phase fluid.

4. The mechanical screen hydrate microscopic enrichment rule and blockage mechanism evaluation system of claim 3, wherein: the supply module comprises a high-pressure gas cylinder and a water supply tank, and the high-pressure gas cylinder and the water supply tank are directly connected with the gas-liquid mixer of the circulation module.

5. The mechanical screen hydrate microscopic enrichment rule and blockage mechanism evaluation system of claim 4, wherein: the feed module also includes a make-up vessel to make-up water and methane to the system.

6. The mechanical screen hydrate microscopic enrichment rule and blockage mechanism evaluation system of claim 2, wherein: and a concave-convex matching structure is arranged on the butt joint surface between the two cylinders.

7. The method for evaluating the microcosmic enrichment rule and the blockage mechanism of the mechanical screen hydrate is characterized by comprising the following steps of:

(1) Four screen angle adjusting devices are selected: defining the angle of the multi-azimuth screen fixing module which integrally rotates along the circular sliding rail under the action of a motor as a revolution angle, defining the included angle between the flow direction of the gas-liquid mixed fluid regulated by the screen angle regulating device and the screen as a self-rotation angle, setting two of the four screen angle regulating devices to be in a horizontal state, setting the revolution angle of the other two to be 0 DEG when the other two are in a vertical state, and selecting the combination of the screen angle regulating devices to ensure that the sum of the self-rotation angles of the two adjacent screen angle regulating devices is 90 DEG and the sum of the self-rotation angles of the other two screen angle regulating devices is 90 DEG;

(2) Vacuumizing and gas-liquid replenishing: vacuumizing the system and the multidirectional screen fixing module; injecting gas and liquid into the circulation module according to a certain proportion to enable the system pressure to reach a set experimental pressure, and then closing the supply module;

(3) Simulating gas-liquid mixing transportation: starting a circulation module to fully mix gas and liquid, connecting a multi-azimuth screen fixing module and the circulation module, setting a circulation pump to circulate at a constant speed, and starting a temperature control module to cool the whole system; continuously maintaining the constant-speed circulation of the temperature after the temperature is reduced to the set temperature, and respectively recording the absolute pressure values and the change conditions of the pressure differences at two sides of the four screen meshes in real time in the process;

(4) And (3) identifying the flow direction of the diversion trench of the outer protective cover of the optimal screen pipe under the condition of fixed self-rotation angle: adjusting a preset temperature and a gas-liquid ratio, and repeating the steps (2) - (3) to obtain a three-dimensional critical state distribution map generated by microcosmic generation of hydrate in the screen under the condition of a certain public rotation angle;

(5) Adjusting rotation angle combination, repeating the steps (2) - (4), and obtaining a four-dimensional critical state diagram of a critical condition generated by secondary enrichment of hydrate in the screen mesh under a certain revolution angle condition;

(6) The experiment was stopped.

8. The method for evaluating the microscopic enrichment rule and the blockage mechanism of the hydrate of the mechanical screen according to claim 7, which is characterized in that: stopping the experiment in step (6) when any of the following conditions are met: A. when the pressure difference of two sides of the screen in the multi-directional screen fixing module is increased to 5 times or more of the initial pressure difference; B. when the pressure value of the whole system reaches 14 MPa.

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