Experimental device and method for researching wax precipitation rule in porous medium in near wellbore area

Abstract

The invention discloses an experimental device and method for researching a wax precipitation rule in a porous medium in a near wellbore area, and belongs to the technical field of wax precipitation experiments.The experimental device comprises a wax deposition visualization model, a multi-stage temperature control module, a liquid injection and cleaning module, a confining pressure adjusting module, a back pressure control module, a product recovery module and an image acquisition module; a natural rock core slice with a pore throat structure is simulated through a wax deposition visual model, a multi-stage temperature control module is utilized to perform graded local heating to simulate complex temperature conditions of a stratum, confining pressure is provided through a confining pressure adjusting module, and model outlet pressure is adjusted through a back pressure control module to simulate flowing bottomhole pressure. Crude oil and cleaning fluid are injected into the liquid injection and cleaning module, and an oil displacement experiment and cleaning after the oil displacement experiment is completed. The image acquisition module and the visual clamping module are used for visually observing the wax precipitation process in the model, the wax crystal phase change process in the experiment process is analyzed, and the wax step-by-step precipitation law is represented through wax precipitation formulas of different parts of the model.

Description

Technical Field

[0001] The present invention belongs to the technical field of wax deposition experiments, and particularly relates to an experimental device and method for studying the wax deposition law in porous media near the wellbore zone. Background Art

[0002] During the process of crude oil production, if the water injection method is used for development, when the injected water reaches the bottom of the well, the temperature is lower than the reservoir temperature. The injected water will exchange heat with the reservoir, resulting in a decrease in the reservoir temperature in the near-wellbore zone of the injection well. Paraffin dissolved in the crude oil will crystallize out of the crude oil and deposit in the pores, thereby blocking the formation pores, increasing the seepage resistance, and deteriorating the water absorption capacity of the injection well. Therefore, it is urgent to study the wax deposition phenomenon and law in porous media near the wellbore zone.

[0003] At present, the existing wax deposition devices cannot well simulate the formation conditions in porous media near the wellbore zone, cannot characterize the degree of gradual precipitation of wax in crude oil in porous media, and cannot perform hierarchical local heating during experiments. Therefore, it is urgent to develop a wax deposition experimental device and method to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide an experimental device and method for studying the wax deposition law in porous media near the wellbore zone, aiming to solve the technical problems that the existing wax deposition experimental devices cannot simulate the radial seepage characteristics and pressure change characteristics near the wellbore zone, cannot characterize the degree of gradual precipitation of wax in crude oil in porous media, and cannot perform hierarchical local heating.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: An experimental device for studying the wax deposition law in porous media near the wellbore zone, the experimental device includes a wax deposition visualization model, a multi-stage temperature control module, a liquid injection and cleaning module, a confining pressure adjustment module, a backpressure control module, a product recovery module, and an image acquisition module; The multi-stage temperature control module is arranged at the bottom of the wax deposition visualization model for simulating the formation temperature; both the multi-stage temperature control module and the wax deposition visualization model are arranged in a confining pressure chamber, and the confining pressure chamber is arranged in a visualization clamping module; The confining pressure adjustment module is connected to the confining pressure chamber to provide confining pressure for the wax deposition visualization model; The liquid injection and cleaning module is connected to the inlet end of the wax deposition visualization model for injecting crude oil or cleaning liquid into the wax deposition visualization model; The backpressure control module is connected to the outlet end of the wax deposition visualization model to simulate the bottom-hole flowing pressure by controlling the pressure at the outlet end; the product recovery module is connected to the backpressure control module for recovering the products discharged from the wax deposition visualization model; The image acquisition module is arranged above the visualization clamping module and the wax deposition visualization model.

[0006] Preferably, the wax deposition visualization model is used to simulate a natural core thin section with pore-throat structure, and includes a first semi-circular ring lithography visualization model, a second semi-circular ring lithography visualization model, a third semi-circular ring lithography visualization model and a semi-circular lithography visualization model. The first semi-circular ring lithography visualization model, the second semi-circular ring lithography visualization model and the third semi-circular ring lithography visualization model are all semi-circular rings and are arranged on the outer side of the semi-circular lithography visualization model in sequence from outside to inside. The first semi-circular ring lithography visualization model, the second semi-circular ring lithography visualization model and the third semi-circular ring lithography visualization model are all porous medium structures; the semi-circular lithography visualization model is an internal hollow structure for simulating a wellbore. Five equally spaced isobaric liquid injection ports are arranged on the outer edge of the first semi-circular ring lithography visualization model to simulate the radial seepage in the near-wellbore zone; the first semi-circular ring lithography visualization model is connected to the second semi-circular ring lithography visualization model, the second semi-circular ring lithography visualization model is connected to the third semi-circular ring lithography visualization model, and the third semi-circular ring lithography visualization model is connected to the semi-circular lithography visualization model respectively through transmission pipelines with quick connectors. An outlet is arranged at the central position of the semi-circular lithography visualization model; the isobaric liquid injection ports are connected to the injection pipelines, and the inlet end of the injection pipelines penetrates through the confining pressure chamber and extends to the outside of the visualization clamping module to be connected to the liquid injection and cleaning module; the outlet is connected to the production pipeline, and the production pipeline penetrates through the confining pressure chamber and extends to the outside of the visualization clamping module to be connected to the confining pressure adjustment module.

[0007] Preferably, the multi-stage temperature control module includes a plurality of temperature control outer shells and heating tapes. The shapes of the plurality of temperature control outer shells are the same as those of the first semi-circular ring lithography visualization model, the second semi-circular ring lithography visualization model, the third semi-circular ring lithography visualization model and the semi-circular lithography visualization model respectively, and the heating tapes are arranged in the arc-shaped cavities of the temperature control outer shells.

[0008] Preferably, the visualization clamping module includes a base and a protective cover on its upper part. A sealing gasket is arranged between the mating surfaces of the protective cover and the multi-stage temperature control module and the base. The four peripheral edges of the protective cover and the base are connected through magnetic attraction components; a light-transmitting component is arranged at the top of the wax deposition visualization model for observing the wax precipitation situation in the wax deposition visualization model.

[0009] Preferably, the liquid injection and cleaning module includes a plunger pump, a liquid storage tank, a petroleum ether storage tank, and a deionized water storage tank. The liquid storage tank is arranged in a constant temperature water bath. The inlet ends of the liquid storage tank, the petroleum ether storage tank, and the deionized water storage tank are respectively connected in parallel to the outlet of the plunger pump. The outlet ends of the liquid storage tank, the petroleum ether storage tank, and the deionized water storage tank are respectively connected in parallel to the injection pipeline of the wax deposition visualization model. A first pressure gauge is arranged on the injection pipeline, and the first pressure gauge is arranged outside the visualization clamping module.

[0010] Preferably, the confining pressure adjustment module includes a tracking confining pressure pump, an intermediate container, and a confining pressure valve. The inlet end of the intermediate container is connected to the outlet of the tracking confining pressure pump. The outlet end of the intermediate container is communicated with the confining pressure chamber through a confining pressure pipeline. The confining pressure valve is arranged on the confining pressure pipeline. A second pressure gauge is also arranged on the confining pressure pipeline. The confining pressure valve and the second pressure gauge are both arranged outside the visualization clamping module.

[0011] Preferably, the back pressure control module includes a back pressure valve and a hand pump. The outlet pipeline of the hand pump is connected to the back pressure valve. A third pressure gauge is arranged on the outlet pipeline of the hand pump. The back pressure valve has three joints: the first joint is connected to the outlet pipeline of the hand pump, the second joint is connected to the production pipeline of the wax deposition visualization model, and the third interface is connected to the product recovery module. A fourth pressure gauge is arranged on the production pipeline.

[0012] Preferably, the product recovery module includes a recovery container and a weighing scale. The outlet of the discharge pipe of the third interface of the back pressure valve extends into the recovery container. The recovery container is arranged on the weighing scale.

[0013] Preferably, the image acquisition module includes a long focal length camera, an infrared thermal imaging camera, a data transmission line, and a computer. The long focal length camera and the infrared thermal imaging camera are arranged in parallel above the wax deposition visualization model. The long focal length camera and the infrared thermal imaging camera are respectively connected to the computer through the data transmission line.

[0014] The present invention also provides an experimental method for studying the wax deposition law in porous media in the near-wellbore area. The above experimental device is used for the experiment, including the following steps: Before the experiment, the wax deposition visualization model is weighed, and then the above experimental device is assembled; The confining pressure adjustment module is started to provide confining pressure for the wax deposition visualization model. After opening the outlet of the wax deposition visualization model to discharge the internal residual gas, the back pressure control module is connected; The wax deposition visualization model is subjected to hierarchical local heating through the multi-stage temperature control module to simulate the formation temperature conditions; Start the liquid injection and cleaning module to first drive the crude oil into the wax deposition visualization model, and apply backpressure to the outlet end of the wax deposition visualization model through the backpressure control module to simulate the bottom-hole flowing pressure; during the experiment, control the displacement pressure in the wax deposition visualization model to be slightly less than the applied confining pressure; Monitor the process of wax precipitation step by step in the wax deposition visualization model through the image acquisition module, and analyze the wax crystal phase change process in the crude oil through the collected images; After the displacement is completed, take out the wax deposition visualization model for secondary weighing, and the mass difference between the previous and subsequent weighings is the wax deposition mass; After putting the wax deposition visualization model back into the confining pressure chamber, drive petroleum ether into the wax deposition visualization model through the liquid injection and cleaning module to clean the residual oil inside it, and then drive deionized water into the wax deposition visualization model for final cleaning; According to the relationships between temperature, pressure and wax deposition mass obtained from the above experiments, the analysis is as follows from the inside to the outside: The relationship for the near-well part in the wax deposition visualization model is as follows: ; The relationship for the middle and far regions in the wax deposition visualization model is as follows: ; The relationship for the far region in the wax deposition visualization model is as follows: ; The relationship for the outer periphery part in the wax deposition visualization model is as follows: ; In the formula: m - Wax deposition mass; T - Experimental temperature; F - Experimental pressure.

[0015] Compared with the prior art, the beneficial effects produced by the present invention are as follows: The present invention simulates a natural core thin section with pore-throat structure through a wax deposition visualization model, locally heats it in stages by using a multi-stage temperature control module to simulate complex formation temperature conditions, provides confining pressure for it through a confining pressure adjustment module, adjusts the outlet pressure of the model through a backpressure control module to simulate bottom-hole flowing pressure, injects crude oil and cleaning fluid into it by using an injection and cleaning module to complete the oil displacement experiment and cleaning after the experiment; uses an image acquisition module and a visualization clamping module to directly observe the wax deposition process in the model and analyze the wax crystal phase change process during the experiment; characterizes the law of wax precipitation step by step through the wax deposition formula of different parts of the model. By adopting the present invention, the radial seepage characteristics near the wellbore area can be simulated, the real seepage situation near the wellbore area can be characterized, the whole experiment process is visible, it is convenient to observe the process of wax precipitation step by step in the porous medium near the wellbore area, and the wax deposition law in the porous medium is analyzed step by step by disassembling the model. The present invention can make the indoor wax deposition experiment closer to the formation conditions, make the experiment more intelligent, further solve the shortcomings of the existing wax deposition experimental devices, and make the indoor wax deposition experiment more perfect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation to the present invention.

[0017] In the drawings: Figure 1 is a schematic structural diagram of an experimental device for studying the wax deposition law in porous media near the wellbore area provided by an embodiment of the present invention; Figure 2 is a schematic structural diagram of a wax deposition visualization model in an embodiment of the present invention; Figure 3 is a schematic structural diagram of a quick connector in an embodiment of the present invention; Figure 4 is a schematic structural diagram of a multi-stage temperature control module in an embodiment of the present invention; Figure 5 is a schematic structural diagram of a visualization clamping module in an embodiment of the present invention; In the figure: 1 - Wax deposition visualization model, 101 - First semi - circular ring lithography visualization model, 102 - Second semi - circular ring lithography visualization model, 103 - Third semi - circular ring lithography visualization model, 104 - Semi - circular lithography visualization model, 105 - Isobaric liquid injection port, 106 - Liquid outlet, 107 - Transmission pipeline, 108 - Connector body, 109 - Plug; 2 - Protective cover, 3 - Base, 4 - Sealing gasket; 5 - Multi - stage temperature control module, 501 - Temperature control housing, 502 - Heating tape; 6 - Injection pipeline, 7 - Production pipeline; 8 - Confining pressure pipeline, 9 - Confining pressure chamber; 10 - Transparent light component; 11 - Magnetic attraction component; 12 - Plunger pump, 13 - Constant temperature water bath, 14 - Liquid storage tank, 15 - Petroleum ether storage tank, 16 - Deionized water storage tank; 17 - Tracking confining pressure pump, 18 - Intermediate container, 19 - Confining pressure valve, 20 - Second pressure gauge; 21 - Fourth pressure gauge, 22 - Back - pressure valve, 23 - Third pressure gauge, 24 - Hand pump; 25 - Long - focal - length camera, 26 - Infrared thermal imaging camera, 27 - Data transmission line, 28 - Computer; 29 - Recovery container, 30 - Weighing scale. Detailed implementation manners

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In the following detailed description of the present invention, some specific details are described in detail. However, for the parts not described in detail, those skilled in the art can also fully understand the present invention.

[0019] In addition, those of ordinary skill in the art should understand that the provided drawings are only for illustrating the purpose, features and advantages of the present invention, and the drawings are not actually drawn to scale.

[0020] At the same time, unless the context clearly requires otherwise, words such as "including", "comprising" and similar words throughout the specification and claims should be interpreted as having an inclusive meaning rather than an exclusive or exhaustive meaning; that is, it is the meaning of "including but not limited to".

[0021] Such as Figure 1As shown in the figure, an experimental device for studying the wax deposition law in porous media near the wellbore. The experimental device includes a wax deposition visualization model 1, a multi-stage temperature control module 5, a liquid injection and cleaning module, a confining pressure adjustment module, a backpressure control module, a product recovery module, and an image acquisition module. The multi-stage temperature control module 5 is arranged at the bottom of the wax deposition visualization model 1 to simulate the formation temperature. The multi-stage temperature control module 5 and the wax deposition visualization model 1 are both arranged in a confining pressure chamber 9, and the confining pressure chamber 9 is arranged in a visualization clamping module. The confining pressure adjustment module is connected to the confining pressure chamber 9 to provide confining pressure for the wax deposition visualization model 1. The liquid injection and cleaning module is connected to the inlet end of the wax deposition visualization model 1 to inject crude oil or cleaning liquid into the wax deposition visualization model 1. The backpressure control module is connected to the outlet end of the wax deposition visualization model 1 to simulate the bottom-hole flowing pressure by controlling the pressure at the outlet end. The product recovery module is connected to the backpressure control module to recover the products discharged from the wax deposition visualization model 1. The image acquisition module is arranged above the visualization clamping module and the wax deposition visualization model 1. Using the above experimental device can characterize the degree of wax precipitation step by step in porous media near the wellbore. The constructed porous media model has a radial seepage characteristic and can characterize the real seepage situation near the wellbore. And the whole experiment is visible, the model can be heated locally in stages, and after the experiment, the model can be disassembled to analyze the wax deposition law in the porous media step by step.

[0022] In a specific embodiment of the present invention, the wax deposition visualization model 1 for simulating a natural core thin slice with a pore-throat structure is a lithography model. Referring to the digital image processing results of the natural core thin slice, a special glass material is selected and made by laser etching technology. The model is close to the pore-throat characteristics of the natural core, has a porous media structure, and the pore-throat characteristics are constructed based on the structural characteristics of representative microscopic pores and throats in reservoir rocks. As Figure 2 shown, the wax deposition visualization model 1 includes a first semi-circular ring lithography visualization model 101, a second semi-circular ring lithography visualization model 102, a third semi-circular ring lithography visualization model 103, and a semi-circular lithography visualization model 104. The first semi-circular ring lithography visualization model 101, the second semi-circular ring lithography visualization model 102, and the third semi-circular ring lithography visualization model 103 are all semi-circular rings and are arranged outside the semi-circular lithography visualization model 104 in sequence from outside to inside. The first semi-circular ring lithography visualization model 101, the second semi-circular ring lithography visualization model 102, and the third semi-circular ring lithography visualization model 103 are all porous media structures. The semi-circular lithography visualization model 104 is an internal hollow structure for simulating a wellbore.

[0023] On the outer edge of the first semi-circular lithographic visualization model 101, there are five equally spaced isobaric liquid injection ports 105 for simulating the radial seepage in the near-wellbore zone; the first semi-circular lithographic visualization model 101 is connected to the second semi-circular lithographic visualization model 102, the second semi-circular lithographic visualization model 102 is connected to the third semi-circular lithographic visualization model 103, and the third semi-circular lithographic visualization model 103 is connected to the semi-circular lithographic visualization model 104 respectively through transmission pipelines 107 with quick connectors. At the central position of the semi-circular lithographic visualization model 104, there is a liquid outlet 106; the isobaric liquid injection ports 105 are connected to the injection pipeline 6, and the inlet end of the injection pipeline 6 penetrates through the confining pressure chamber 9 and extends to the outside of the visualization clamping module to be connected to the liquid injection and cleaning module; the liquid outlet 106 is connected to the production pipeline 7, and the production pipeline 7 penetrates through the confining pressure chamber 9 and extends to the outside of the visualization clamping module to be connected to the confining pressure adjustment module. The five equally spaced isobaric liquid injection ports 105 on the outermost ring of the first semi-circular lithographic visualization model 101 form a constant pressure injection boundary for simulating the radial seepage characteristics in the near-wellbore zone; a circular groove is set at the center position of the semi-circular lithographic visualization model 104 in the innermost ring as the liquid outlet 106 for simulating the wellbore. At the beginning of the experiment, the transmission pipeline 107 can be connected for the experiment. After the experiment is over, the transmission pipeline 107 is disassembled, and each part of the model is removed separately to facilitate the subsequent measurement of the step-by-step precipitation of wax.

[0024] During the specific production, the surface of the wax deposition visualization model is polished by the ultra-precision lapping method to facilitate the subsequent visual observation of the step-by-step precipitation process of wax; the injection pipeline 6, the production pipeline 7 and the transmission pipeline 107 all have compressive resistance characteristics, and the pressure resistance limit is 30 MPa. At the same time, a plurality of temperature measurement points and pressure measurement points are evenly distributed along the pore channels of the wax deposition visualization model. At the same time, the data changes of each temperature measurement point and pressure measurement point can be recorded in real time by a computer, and the change curves of the temperature and pressure of each test point with time are generated synchronously to facilitate subsequent analysis.

[0025] As a preferred structure, as Figure 3 shown, the quick connector includes a connector body 108 and a plug 109. The connector body 108 is embedded in the first semi-circular lithographic visualization model 101, the second semi-circular lithographic visualization model 102, the third semi-circular lithographic visualization model 103 and the semi-circular lithographic visualization model 104. One end of the plug 109 is communicated with the connector body 108, and the other end is connected to the transmission pipeline 107. During the experiment, the connector body is embedded in the model, and the plug is connected to the transmission pipeline to ensure the overall sealing of the model. The connector body and the plug are connected by threads. After the experiment is over, only the plug needs to be pulled out to cut off the passage and disassemble the connected transmission pipeline.

[0026] In the specific embodiment of the present invention, as Figure 4As shown, the multi-stage temperature control module 5 includes a plurality of temperature control housings 501 and heating tapes 502. The shapes of the plurality of temperature control housings 501 are the same as those of the first semi-circular lithographic visualization model 101, the second semi-circular lithographic visualization model 102, the third semi-circular lithographic visualization model 103, and the semi-circular lithographic visualization model 104 respectively. The heating tape 502 is disposed in the arc-shaped cavity of the temperature control housing 501. During assembly, each part of the wax deposition visualization model is adhesively fixed on the plurality of temperature control housings, and the two are closely adhered to ensure tightness.

[0027] During specific design, the temperature control housing is made of heat-insulating material to prevent heat loss from affecting the heating effect on the wax deposition visualization model. The heating tape is placed in the internal cavity of the temperature control housing to heat the fluid in the wax deposition visualization model above. At the same time, the multi-stage temperature control module is connected to a computer, and the heating tapes of different parts can be separately controlled in temperature by the computer. Different temperatures can be used to heat the four local models above simultaneously to construct a complex temperature gradient system in the near-wellbore area.

[0028] In a specific embodiment of the present invention, as Figure 5 shown, the visualization clamping module includes a base 3 and a protective cover 2 on its upper part. A sealing gasket 4 is provided between the mating surfaces of the protective cover 2 and the multi-stage temperature control module 5 and the base 3. The four peripheral edges of the protective cover 2 and the base 3 are connected by a magnetic attraction assembly 11. A light-transmitting assembly 10 is provided at the top of the wax deposition visualization model 1 for observing the wax precipitation in the wax deposition visualization model 1. Among them, the magnetic attraction assembly uses an electromagnetic chuck, and the connection between the protective cover and the base is realized by energizing and de-energizing. The protective cover is made of a transparent material, and the light-transmitting assembly is made of sapphire material, which has the characteristics of high temperature resistance, high pressure resistance, and high transparency. The temperature resistance limit is 110 °C, and the pressure resistance limit is 40 MPa.

[0029] Among them, the electromagnetic assembly 11 forms a magnetic attraction connection with the base, and the magnetic force of the electromagnetic assembly 11 is adjusted by a controller. During the experiment, the magnetic force is increased to connect and seal the visualization clamping module. After the experiment, the power is cut off to demagnetize, which is convenient for disassembling the visualization clamping module.

[0030] In a specific embodiment of the present invention, as Figure 1As shown, the liquid injection and cleaning module includes a plunger pump 12, a liquid storage tank 14, a petroleum ether storage tank 15, and a deionized water storage tank 16. The liquid storage tank 14 is arranged in a constant temperature water bath 13 to prevent crude oil from waxing in the liquid storage tank and pipelines in advance. The inlet ends of the liquid storage tank 14, the petroleum ether storage tank 15, and the deionized water storage tank 16 are respectively connected in parallel to the outlet of the plunger pump 12. The outlet ends of the liquid storage tank 14, the petroleum ether storage tank 15, and the deionized water storage tank 16 are respectively connected in parallel to the injection pipeline 6 of the wax deposition visualization model 1. A first pressure gauge is provided on the injection pipeline 6, and the first pressure gauge is arranged outside the visualization clamping module. Among them, the plunger pump uses an ISCO pump to provide injection pressure for the model. At the same time, a magnetic stirrer is also provided in the liquid storage tank to prevent the crude oil from solidifying in the storage tank due to too high a freezing point.

[0031] As Figure 1 shown, the confining pressure adjustment module includes a tracking confining pressure pump 17, an intermediate container 18, and a confining pressure valve 19. The inlet end of the intermediate container 18 is connected to the outlet of the tracking confining pressure pump 17. The outlet end of the intermediate container 18 is communicated with the confining pressure chamber 9 through a confining pressure pipeline. The confining pressure valve 19 is arranged on the confining pressure pipeline. A second pressure gauge 20 is also provided on the confining pressure pipeline. Both the confining pressure valve 19 and the second pressure gauge 20 are arranged outside the visualization clamping module. The tracking confining pressure pump injects the confining pressure medium in the intermediate container into the confining pressure chamber in the visualization clamping module through the confining pressure pipeline by means of liquid pressurization to pressurize the protective cover, thereby applying a confining pressure to the wax deposition visualization model. Specifically, during implementation, both the plunger pump and the tracking confining pressure pump are connected to a computer. The displacement pressure is controlled by the computer to be slightly less than the confining pressure to ensure that the crude oil can be smoothly driven into the wax deposition visualization model without damaging the wax deposition visualization model due to too large a pressure difference.

[0032] In Figure 1 the shown embodiment, the back pressure control module includes a back pressure valve 22 and a hand pump 24. The outlet pipeline of the hand pump 24 is connected to the back pressure valve 22. A third pressure gauge 23 is provided on the outlet pipeline of the hand pump 24. The back pressure valve 22 has three connectors: the first connector is connected to the outlet pipeline of the hand pump 24, the second connector is connected to the production pipeline 7 of the wax deposition visualization model 1, and the third interface is connected to the product recovery module. A fourth pressure gauge 21 is provided on the production pipeline 7. At the same time, the product recovery module includes a recovery container 29 and a weighing scale 30. The discharge pipe outlet of the third interface of the back pressure valve 22 extends into the recovery container 29. The recovery container 29 is arranged on the weighing scale 30. Among them, the recovery container is selected as a test tube, and the weighing scale is selected as an electronic balance. The electronic balance is placed under the beaker to facilitate measuring the liquid output.

[0033] In the specific design, the image acquisition module includes a long - focal - length camera 25, an infrared thermal imaging camera 26, a data transmission line 27, and a computer 28. The long - focal - length camera 25 and the infrared thermal imaging camera 26 are arranged in parallel above the wax deposition visualization model 1. The long - focal - length camera 25 and the infrared thermal imaging camera 26 are respectively connected to the computer 28 through the data transmission line 27. Among them, the long - focal - length camera is a high - definition high - speed long - focal - length camera. By arranging the high - definition high - speed long - focal - length camera and the infrared thermal imaging camera above the light - transmitting component 10, the process of wax precipitation step by step can be visually photographed and characterized by infrared thermal imaging according to the experimental requirements, and the photographed images and videos can be imported into the computer in real time through the data transmission line and named for storage.

[0034] During the experiment, the high - definition high - speed long - focal - length camera and the infrared thermal imaging camera can change their positions on the horizontal plane according to the requirements of the observation area.

[0035] The present invention also provides an experimental method for studying the wax deposition law in porous media near the wellbore. The above experimental device is used for the experiment, including the following steps: Before the experiment, each part of the wax deposition visualization model 1 is weighed to facilitate subsequent analysis of the wax precipitation situation; Assemble the above experimental device: Place the wax deposition visualization model 1 into the confining pressure chamber 9. There is a sealing gasket 4 under the wax deposition visualization model 1. Then place the protective cover 2 on the base 3, and use the electromagnetic component 11 to connect and seal the protective cover 2 and the base 3 to form a visualization clamping module; Place the high - definition high - speed long - focal - length camera and the infrared thermal imaging camera above the wax deposition visualization model 1 and start real - time recording.

[0036] Use the tracking confining pressure pump 17 to inject the confining pressure medium in the intermediate container 18 into the confining pressure chamber 9 through the confining pressure pipeline to provide confining pressure for the wax deposition visualization model 1; Open the outlet of the wax deposition visualization model 1, and under the action of the confining pressure, discharge the internal residual gas until no gas is discharged, and then connect the outlet of the wax deposition visualization model 1 to the fourth pressure gauge 21, the back - pressure valve 22, and the hand pump 24 in sequence through the production pipeline 7.

[0037] Add the experimental crude oil into the liquid storage tank, and turn on the magnetic stirrer and the constant - temperature water bath 13 to heat and stir the experimental crude oil to prevent wax crystals from precipitating prematurely in the liquid storage tank 14.

[0038] Open the multi - stage temperature control module 5, and adjust the temperature of each heating belt through the computer to accurately perform hierarchical local heating on each part of the wax deposition visualization model 1 to simulate the complex formation temperature conditions; Connect the ISCO pump to the liquid storage tank 14 through a pipeline. The other end of the liquid storage tank 14 is connected to the inlet end of the wax deposition visualization model 1 through an injection pipeline.

[0039] Turn on the ISCO pump and adjust the displacement mode to provide displacement pressure for the liquid storage tank 14. The crude oil in the liquid storage tank 14 is driven into the wax deposition visualization model 1 through the injection pipeline under the action of the pressure difference.

[0040] Manually adjust the hand pump 24 to apply the back pressure required for the experiment to the outlet end of the wax deposition visualization model 1 to simulate the bottom hole flowing pressure.

[0041] During the experiment, maintain the displacement pressure slightly less than the applied confining pressure to ensure that the crude oil can be smoothly driven into the model without damaging the model due to excessive pressure difference.

[0042] During the experiment, use a high-definition high-speed long-focus camera to take real-time pictures and monitor the process of wax precipitation step by step, and use the infrared imaging pictures taken by the infrared thermal imaging camera to analyze the wax crystal phase change process in the crude oil.

[0043] After the displacement is completed, analyze the experimental parameters, and use special computer software to analyze and process the collected pictures and videos.

[0044] Take out the wax deposition visualization model 1 and weigh the model after the experiment for the second time. The mass difference between the two weighings is the wax deposition mass.

[0045] After putting the wax deposition visualization model 1 back into the confining pressure chamber 9, drive petroleum ether into the wax deposition visualization model 1 through the injection pipeline to clean the residual oil in the wax deposition visualization model 1. Finally, drive deionized water into the wax deposition visualization model 1 for the final cleaning.

[0046] After cleaning, unload the confining pressure, back pressure and the pressure inside the wax deposition visualization model 1, cut off the power of the electromagnetic component 11 for degaussing treatment, and then separate the visualization clamping module to take out the wax deposition visualization model 1, dry it and place it properly for the next use.

[0047] According to the temperature, pressure data and wax deposition mass data of each group, obtain the relationship formula between temperature, pressure and wax deposition mass, and the analysis is as follows from the inside to the outside: Analyze the semi-circular lithographic visualization model 104 part, and the relationship formula for the near-well part in the wax deposition visualization model 1 can be obtained as follows: ; Analyze the third semi-circular annular lithographic visualization model 103, and the relationship formula for the middle and far regions in the wax deposition visualization model 1 can be obtained as follows: ; Analyzing the second semi-circular ring lithography visualization model 102, the relational expressions for the far region part in the wax deposition visualization model are as follows: ; Analyzing the first semi-circular ring lithography visualization model 101, the relational expressions for the peripheral part in the wax deposition visualization model 1 are as follows: ; In the formulas: m - Wax deposition mass; T - Experimental temperature; F - Experimental pressure.

[0048] In summary, the porous medium model constructed by the present invention has five isobaric liquid injection ports and one liquid outlet, can simulate the radial seepage characteristics, and characterize the real seepage situation near the near-wellbore zone; the pressure at the outlet end of the model is adjusted by the backpressure control module to simulate the bottom-hole flowing pressure, and more realistically reflect the geological characteristics of the near-wellbore zone; the experimental model is designed with a detachable structure in blocks, which is convenient for subsequent step-by-step analysis of the wax deposition situation; during the experiment, the whole device is visible, and the process of wax precipitation step by step can be directly observed; through the multi-stage temperature control module, the rapidity and controllability of heating are ensured, and four local models can be rapidly heated at multi-gradient temperatures to construct a complex temperature gradient system in the near-wellbore zone; the confining pressure can be applied to the model by using the tracking confining pressure pump, and at the same time, the size of the confining pressure can be intelligently adjusted according to the change of the displacement pressure to avoid damaging the model; the infrared thermal imaging camera can more intuitively display the process of wax precipitation step by step, analyze the wax crystal phase change process during the experiment, reduce the error of manual observation, and is more intuitive and accurate compared with an ordinary camera. The present invention can solve the problem that the current indoor wax deposition experiment cannot characterize the wax precipitation situation in the porous medium near the near-wellbore zone, and at the same time can obtain the law of wax precipitation step by step. At the same time, the heating process, displacement pressure, outlet pressure, and confining pressure of the model can be intelligently controlled and adjusted, making the indoor wax deposition experiment closer to the formation conditions, making the experiment more intelligent, further solving the shortcomings of the existing wax deposition experimental devices, and making the indoor wax deposition experiment more perfect.

[0049] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. An experimental device for studying the wax deposition law in porous media near the wellbore, characterized by: The experimental device includes a wax deposition visualization model, a multi-stage temperature control module, a liquid injection and cleaning module, a confining pressure adjustment module, a back pressure control module, a product recovery module and an image acquisition module; The multi-stage temperature control module is arranged at the bottom of the wax deposition visualization model to simulate the formation temperature; the multi-stage temperature control module and the wax deposition visualization model are both arranged in the confining pressure chamber, and the confining pressure chamber is arranged in the visualization clamping module; The confining pressure regulating module is connected to the confining pressure chamber to provide confining pressure for the wax deposition visualization model; The injection and cleaning module is connected to the inlet end of the wax deposition visualization model and is used to inject crude oil or cleaning liquid into the wax deposition visualization model; The back pressure control module is connected to the outlet end of the wax deposition visualization model, and simulates the bottom hole flow pressure by controlling the outlet end pressure; the product recovery module is connected to the back pressure control module, and is used to recover the product discharged by the wax deposition visualization model; The image acquisition module is arranged above the visualization clamping module and the wax deposition visualization model.

2. The experimental device for studying the wax deposition law in porous media near the wellbore according to claim 1, characterized in that: The wax deposition visualization model is used to simulate a natural core slice with a pore throat structure, and includes a first semicircular ring lithography visualization model, a second semicircular ring lithography visualization model, a third semicircular ring lithography visualization model and a semicircular lithography visualization model, wherein the first semicircular ring lithography visualization model, the second semicircular ring lithography visualization model and the third semicircular ring lithography visualization model are all semicircular ring-shaped and are arranged in sequence from the outside to the inside on the outside of the semicircular lithography visualization model, and the first semicircular ring lithography visualization model, the second semicircular ring lithography visualization model and the third semicircular ring lithography visualization model are all porous medium structures; the semicircular lithography visualization model is an internal hollow structure and is used to simulate a wellbore; The outer edge of the first semicircular ring lithography visualization model is provided with five equidistant isobaric injection ports to simulate radial seepage in the near-wellbore area; the first semicircular ring lithography visualization model and the second semicircular ring lithography visualization model, the second semicircular ring lithography visualization model and the third semicircular ring lithography visualization model, and the third semicircular ring lithography visualization model and the semicircular lithography visualization model are respectively connected through transmission pipelines with quick connectors, and a liquid outlet is provided at the center of the semicircular lithography visualization model; the isobaric injection port is connected to the injection pipeline, the inlet end of the injection pipeline passes through the confining pressure chamber and extends to the outside of the visualization clamping module and is connected to the injection and cleaning module; the liquid outlet is connected to the production pipeline, the production pipeline passes through the confining pressure chamber and extends to the outside of the visualization clamping module and is connected to the confining pressure adjustment module.

3. The experimental device for studying the wax deposition law in porous media near the wellbore according to claim 2, characterized in that: The multi-stage temperature control module includes multiple temperature control shells and heating belts. The multiple temperature control shells are respectively the same in shape as the first semicircular ring lithography visualization model, the second semicircular ring lithography visualization model, the third semicircular ring lithography visualization model and the semicircular lithography visualization model. The heating belt is arranged in the arc-shaped cavity of the temperature control shell.

4. The experimental device for studying the wax deposition law in porous media near the wellbore according to claim 3, characterized in that: The visualization clamping module includes a base and a protective cover on its upper part. A sealing gasket is provided between the matching surfaces of the protective cover and the multi-stage temperature control module and the base. The protective cover and the surrounding edges of the base are connected by a magnetic suction component. A light-transmitting component is provided on the top of the wax deposition visualization model for observing the wax precipitation in the wax deposition visualization model.

5. The experimental device for studying the wax deposition law in porous media near the wellbore according to claim 1, characterized in that: The injection and cleaning module includes a plunger pump, a liquid storage tank, a petroleum ether storage tank and a deionized water storage tank. The liquid storage tank is arranged in a constant temperature water bath. The inlet ends of the liquid storage tank, the petroleum ether storage tank and the deionized water storage tank are respectively connected in parallel with the outlet of the plunger pump. The outlet ends of the liquid storage tank, the petroleum ether storage tank and the deionized water storage tank are respectively connected in parallel with the injection pipeline of the wax deposition visualization model. A first pressure gauge is provided on the injection pipeline, and the first pressure gauge is arranged outside the visualization clamping module.

6. The experimental device for studying the wax deposition law in porous media near the wellbore according to claim 1, characterized in that: The confining pressure regulating module includes a tracking confining pressure pump, an intermediate container and a confining pressure valve. The inlet end of the intermediate container is connected to the outlet of the tracking confining pressure pump, and the outlet end of the intermediate container is connected to the confining pressure chamber through a confining pressure pipeline. The confining pressure valve is arranged on the confining pressure pipeline. A second pressure gauge is also provided on the confining pressure pipeline. The confining pressure valve and the second pressure gauge are both arranged outside the visualization clamping module.

7. The experimental device for studying the wax deposition law in porous media near the wellbore according to claim 1, characterized in that: The back pressure control module includes a back pressure valve and a hand pump, the outlet pipeline of the hand pump is connected to the back pressure valve, and a third pressure gauge is provided on the outlet pipeline of the hand pump; the back pressure valve is provided with three connectors: the first connector is connected to the outlet pipeline of the hand pump, the second connector is connected to the production pipeline of the wax deposition visualization model, and the third interface is connected to the product recovery module, and a fourth pressure gauge is provided on the production pipeline.

8. The experimental device for studying the wax deposition law in porous media near the wellbore according to claim 7, characterized in that: The product recovery module comprises a recovery container and a metering scale. The discharge pipe outlet of the third interface of the back pressure valve extends into the recovery container. The recovery container is arranged on the metering scale.

9. The experimental device for studying the wax deposition law in porous media near the wellbore according to claim 1, characterized in that: The image acquisition module includes a telephoto camera, an infrared thermal imaging camera, a data transmission line and a computer. The telephoto camera and the infrared thermal imaging camera are arranged in parallel above the wax deposition visualization model. The telephoto camera and the infrared thermal imaging camera are respectively connected to the computer through the data transmission line.

10. An experimental method for studying the wax deposition law in porous media near the wellbore, characterized in that: The experiment is carried out using the experimental device as described in any one of claims 1 to 9, comprising the following steps: Before the experiment, the wax deposition visualization model was weighed and then the experimental device was assembled; Start the confining pressure regulating module to provide confining pressure for the wax deposition visualization model, open the outlet of the wax deposition visualization model to discharge the internal residual gas, and then connect the back pressure control module; The wax deposition visualization model is heated locally in stages through a multi-stage temperature control module to simulate formation temperature conditions; The injection and cleaning module is started to drive crude oil into the wax deposition visualization model, and the back pressure control module is used to apply back pressure to the outlet of the wax deposition visualization model to simulate the bottom hole flow pressure. The image acquisition module is used to monitor the wax precipitation process in the wax deposition visualization model, and the wax crystal phase change process in crude oil is analyzed through the acquired images; After the displacement is completed, the wax deposition visualization model is taken out and weighed twice. The difference in mass before and after weighing is the wax deposition mass. After the wax deposition visualization model is placed back into the confining pressure chamber, petroleum ether is driven into the wax deposition visualization model through the injection and cleaning module to clean the residual oil inside it, and then deionized water is driven into the wax deposition visualization model for final cleaning; According to the above experiment, the relationship between temperature, pressure and wax deposition mass is obtained, which is analyzed from the inside to the outside as follows: The relationship of the near-wellbore part of the wax deposition visualization model is as follows: ； The relationship for the mid-to-distal region in the wax deposition visualization model is as follows: ； The relationship for the far zone part of the wax deposition visualization model is as follows: ； The relationship for the peripheral part of the wax deposition visualization model is as follows: ； Where: m - wax deposition quality; T - Experimental temperature; F - Experimental pressure.

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