Experimental device and method for studying wax deposition law in porous media near wellbore area

Abstract

The present invention discloses an experimental device and method for studying the wax deposition law in porous media in near-wellbore areas, belonging to the technical field of wax deposition 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 adjustment module, a back pressure control module, a product recovery module and an image acquisition module; a natural core slice with a pore throat structure is simulated by a wax deposition visualization model, a multi-stage temperature control module is used to perform graded local heating to simulate complex formation temperature conditions, a confining pressure adjustment module is used to provide confining pressure, a back pressure control module is used to adjust the model outlet pressure to simulate bottom hole flow pressure, a liquid injection and cleaning module is used to inject crude oil and cleaning fluid therein, and an oil displacement experiment and subsequent cleaning are completed; an image acquisition module and a visualization clamping module are used to intuitively observe the wax deposition process in the model, and the wax crystal phase change process during the experiment is analyzed, and the wax deposition formulas of different parts of the model are used to characterize the step-by-step precipitation law of wax.

Description

Technical Field

[0001] The invention belongs to the technical field of wax deposition experiments, and in particular relates to an experimental device and method for studying wax deposition laws in porous media near a wellbore area. Background Art

[0002] During crude oil production, if water injection is used, the injected water reaches the bottom of the well at a temperature lower than the reservoir temperature. This heat exchange between the injected water and the reservoir causes the reservoir temperature to drop near the wellbore. Paraffin wax dissolved in the crude oil crystallizes from the oil and deposits in the pores, blocking the formation pores, increasing seepage resistance, and reducing the water absorption capacity of the injection well. Therefore, research on the phenomenon and characteristics of wax deposition in porous media near the wellbore is urgent.

[0003] Currently, existing wax deposition equipment cannot effectively simulate the formation conditions within porous media near the wellbore, cannot characterize the degree of wax precipitation in crude oil within the porous media, and cannot perform graded localized heating during experiments. Therefore, it is urgent to develop a wax deposition experimental device and method to address these issues. 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 area, aiming to solve the technical problems that the existing wax deposition experimental device cannot simulate the radial seepage characteristics and pressure change characteristics of the near-wellbore area, cannot characterize the degree of step-by-step precipitation of wax in crude oil in porous media, and cannot perform graded local heating.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] An experimental device for studying wax deposition patterns in porous media near wellbore areas, comprising a wax deposition visualization model, a multi-stage temperature control module, a fluid injection and cleaning module, a confining pressure regulation module, a back pressure control module, a product recovery module, and an image acquisition module;

[0007] 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 a confined pressure chamber, and the confined pressure chamber is arranged in the visualization clamping module;

[0008] The confining pressure regulating module is connected to the confining pressure chamber to provide confining pressure for the wax deposition visualization model;

[0009] 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;

[0010] The back pressure control module is connected to the outlet of the wax deposition visualization model and simulates the bottom hole flow pressure by controlling the outlet 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;

[0011] The image acquisition module is arranged above the visualization clamping module and the wax deposition visualization model.

[0012] Preferably, the wax deposition visualization model is used to simulate a natural core slice with a pore-throat structure, and includes a first semicircular ring-shaped photolithography visualization model, a second semicircular ring-shaped photolithography visualization model, a third semicircular ring-shaped photolithography visualization model, and a semicircular photolithography visualization model. The first semicircular ring-shaped photolithography visualization model, the second semicircular ring-shaped photolithography visualization model, and the third semicircular ring-shaped photolithography visualization model are all semicircular in shape and are arranged in sequence from the outside to the inside on the outside of the semicircular photolithography visualization model. The first semicircular ring-shaped photolithography visualization model, the second semicircular ring-shaped photolithography visualization model, and the third semicircular ring-shaped photolithography visualization model are all porous medium structures. The semicircular photolithography visualization model has an internal hollow structure and is used to simulate a wellbore.

[0013] Five equidistant isobaric injection ports are provided on the outer edge of the first semicircular ring lithography visualization model 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 regulation module.

[0014] Preferably, the multi-stage temperature control module includes multiple temperature control shells and heating belts, and the multiple temperature control shells have the same 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, respectively, and the heating belt is arranged in the arc-shaped cavity of the temperature control shell.

[0015] Preferably, the visualization clamping module includes a base and a protective cover on its upper part, a sealing gasket is provided between the protective cover and the mating surfaces of the multi-stage temperature control module and the base, and 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.

[0016] Preferably, 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, and 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.

[0017] Preferably, 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, 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, and 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 visual clamping module.

[0018] 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, 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.

[0019] Preferably, the product recovery module includes 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, and the recovery container is arranged on the metering scale.

[0020] Preferably, 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 side by side above the wax deposition visualization model, and the telephoto camera and the infrared thermal imaging camera are respectively connected to the computer via a data transmission line.

[0021] The present invention also provides an experimental method for studying the wax deposition law in porous media near the wellbore area. The experiment is carried out using the above-mentioned experimental device, comprising the following steps:

[0022] Before the experiment, the wax deposition visualization model was weighed, and then the above experimental device was assembled;

[0023] 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;

[0024] The wax deposition visualization model is heated locally in stages using a multi-stage temperature control module to simulate formation temperature conditions.

[0025] The injection and cleaning modules were started to drive crude oil into the wax deposition visualization model. Back pressure was then applied to the outlet of the wax deposition visualization model through the back pressure control module to simulate bottomhole flow pressure. During the experiment, the displacement pressure in the wax deposition visualization model was controlled to be slightly lower than the applied confining pressure.

[0026] The image acquisition module monitors the wax precipitation process in the wax deposition visualization model and analyzes the wax crystal phase change process in crude oil through the acquired images.

[0027] After the flooding 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.

[0028] 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;

[0029] Based on the above experiments, the relationship between temperature, pressure and wax deposition mass is obtained, which is analyzed from the inside out as follows:

[0030] The relationship between the near-wellbore portion of the wax deposition visualization model is as follows:

[0031] ;

[0032] The relationship between the mid- and far-field parts of the wax deposition visualization model is as follows:

[0033] ;

[0034] The relationship for the far zone part of the wax deposition visualization model is as follows:

[0035] ;

[0036] The relationship between the peripheral part of the wax deposition visualization model is as follows:

[0037] ;

[0038] Where: m - wax deposition quality; T - Experimental temperature; F -Experimental pressure.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention uses a wax deposition visualization model to simulate a natural core slice with a pore-throat structure. A multi-stage temperature control module is used to perform graded local heating to simulate complex formation temperature conditions. A confining pressure adjustment module provides confining pressure, and a back pressure control module regulates the model outlet pressure to simulate bottomhole flow pressure. A liquid injection and cleaning module is used to inject crude oil and cleaning fluid to complete the oil displacement experiment and post-exposure cleaning. An image acquisition module and a visualization clamping module are used to visually observe the wax deposition process within the model and analyze the wax crystal phase transition during the experiment. Waxing formulas for different parts of the model are used to characterize the step-by-step wax precipitation patterns. The present invention can simulate radial seepage characteristics near the wellbore zone and characterize the actual seepage conditions near the wellbore zone. The entire experiment is visual, facilitating the observation of the step-by-step wax precipitation process within the porous medium near the wellbore zone. The wax deposition patterns within the porous medium can be analyzed step by step by disassembling the model. The present invention can make indoor wax deposition experiments more similar to formation conditions, making the experiments more intelligent, further addressing the shortcomings of existing wax deposition experimental equipment and improving indoor wax deposition experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0042] In the attached figure:

[0043] Figure 1 A schematic diagram of the structure of an experimental device for studying wax deposition patterns in porous media near wellbore areas provided by an embodiment of the present invention;

[0044] Figure 2 Schematic diagram of the structure of the wax deposition visualization model in an embodiment of the present invention;

[0045] Figure 3 This is a schematic structural diagram of a quick connector according to an embodiment of the present invention;

[0046] Figure 4 This is a schematic structural diagram of a multi-stage temperature control module in an embodiment of the present invention;

[0047] Figure 5 This is a schematic structural diagram of a visual clamping module in an embodiment of the present invention;

[0048] In the picture:

[0049] 1-wax deposition visualization model, 101-first semicircular ring lithography visualization model, 102-second semicircular ring lithography visualization model, 103-third semicircular ring lithography visualization model, 104-semicircular lithography visualization model, 105-isobaric 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 shell, 502-heating belt; 6-injection pipeline, 7-production pipeline; 8-confining pressure Pipeline, 9-confining pressure chamber; 10-light-transmitting component; 11-magnetic 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-telephoto camera, 26-infrared thermal imaging camera, 27-data transmission line, 28-computer; 29-recovery container, 30-weighing scale. DETAILED DESCRIPTION

[0050] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and Examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In the following detailed description of the present invention, some specific details are described in detail. However, for parts not described in detail, those skilled in the art can also fully understand the present invention.

[0051] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present invention, and are not actually drawn to scale.

[0052] At the same time, unless the context clearly requires otherwise, words such as "include", "comprising" and the like throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, as "including but not limited to".

[0053] like Figure 1As shown, an experimental device for studying the wax deposition law in porous media near the wellbore area, 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 back pressure 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 for simulating 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 for injecting crude oil or cleaning fluid into the wax deposition visualization model 1; the back pressure control module is connected to the outlet end of the wax deposition visualization model 1 for simulating the bottom hole flow pressure by controlling the outlet pressure; the product recovery module is connected to the back pressure control module for recovering the product 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. The above-mentioned experimental device can characterize the degree of wax precipitation in the porous media near the wellbore area. The constructed porous medium model has radial seepage characteristics and can characterize the actual seepage conditions near the wellbore area. The entire experiment is visual, and the model can be locally heated in stages. After the experiment, the model can be disassembled to analyze the wax deposition pattern in the porous medium step by step.

[0054] In a specific embodiment of the present invention, the wax deposition visualization model 1 for simulating a natural core slice with a pore-throat structure is a photolithographic model. Referring to the digital image processing results of a natural core slice, a special glass material is selected and made using laser etching technology. The model is close to the pore-throat characteristics of the natural core and has a porous medium structure. The pore-throat characteristics are constructed based on the structural characteristics of the representative microscopic pores and throats of the reservoir rock. Figure 2 As shown, the wax deposition visualization model 1 includes a first semicircular ring lithography visualization model 101, a second semicircular ring lithography visualization model 102, a third semicircular ring lithography visualization model 103 and a semicircular lithography visualization model 104. The first semicircular ring lithography visualization model 101, the second semicircular ring lithography visualization model 102 and the third semicircular ring lithography visualization model 103 are all semicircular ring-shaped and are arranged on the outside of the semicircular lithography visualization model 104 from the outside to the inside. The first semicircular ring lithography visualization model 101, the second semicircular ring lithography visualization model 102 and the third semicircular ring lithography visualization model 103 are all porous medium structures; the semicircular lithography visualization model 104 is an internal hollow structure for simulating a wellbore.

[0055] Five equidistant isobaric injection ports 105 are provided on the outer edge of the first semicircular ring lithography visualization model 101 to simulate radial seepage in the near-wellbore area; the first semicircular ring lithography visualization model 101 and the second semicircular ring lithography visualization model 102, the second semicircular ring lithography visualization model 102 and the third semicircular ring lithography visualization model 103, and the third semicircular ring lithography visualization model 103 and the semicircular lithography visualization model 104 are respectively connected through transmission pipelines 107 with quick connectors, and a liquid outlet 106 is provided at the center of the semicircular lithography visualization model 104; the isobaric injection port 105 is connected to the injection pipeline 6, the inlet end of the injection pipeline 6 passes through the confining pressure chamber 9 and extends to the outside of the visualization clamping module and is connected to the injection and cleaning module; the liquid outlet 106 is connected to the production pipeline 7, the production pipeline 7 passes through the confining pressure chamber 9 and extends to the outside of the visualization clamping module and is connected to the confining pressure regulation module. Five equally spaced isobaric injection ports 105 on the outermost semicircular ring of the photolithographic visualization model 101 form a constant-pressure injection boundary to simulate radial flow characteristics near the wellbore. A circular groove is provided at the center of the innermost semicircular photolithographic visualization model 104, serving as a liquid outlet 106 to simulate the wellbore. At the beginning of the experiment, the transmission line 107 can be connected for testing. After the experiment is complete, the transmission line 107 can be disassembled, facilitating subsequent measurements of wax precipitation.

[0056] During production, the wax deposition visualization model was polished using ultra-fine grinding and polishing to facilitate subsequent visualization of the wax's gradual precipitation process. The injection pipeline 6, the production pipeline 7, and the transmission pipeline 107 are all compressive-resistant, with a maximum pressure resistance of 30 MPa. Furthermore, the wax deposition visualization model features multiple temperature and pressure measurement points evenly distributed throughout the pore channels. Data changes at each of these points can be recorded in real time using a computer, and a simultaneous curve of temperature and pressure changes over time at each measurement point is generated, facilitating subsequent analysis.

[0057] As a preferred structure, Figure 3 As shown, the quick connector includes a connector body 108 and a plug 109. The connector body 108 is embedded in the first semicircular lithography visualization model 101, the second semicircular lithography visualization model 102, the third semicircular lithography visualization model 103, and the semicircular lithography visualization model 104. One end of the plug 109 is connected to 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 plug are connected using a threaded connection. After the experiment, simply pull out the plug to cut off the passage and disconnect the connected transmission pipeline.

[0058] In a specific embodiment of the present invention, Figure 4As shown, the multi-stage temperature control module 5 includes multiple temperature control housings 501 and heating belts 502. The multiple temperature control housings 501 are shaped identically to the first semi-circular photolithography visualization model 101, the second semi-circular photolithography visualization model 102, the third semi-circular photolithography visualization model 103, and the semi-circular photolithography visualization model 104. The heating belts 502 are disposed within the arc-shaped cavities of the temperature control housings 501. During assembly, each component of the wax deposition visualization model is bonded and fixed to the multiple temperature control housings, ensuring a tight seal.

[0059] The temperature control housing is constructed of insulating materials to prevent heat loss from affecting the heating effect on the wax deposition visualization model. A heating tape is placed within the cavity of the housing to heat the fluid within the wax deposition visualization model above. Furthermore, a multi-stage temperature control module is connected to a computer, allowing the temperature of different heating tapes to be controlled independently. This allows the four local models above to be heated at different temperatures simultaneously, creating a complex temperature gradient system near the wellbore.

[0060] In a specific embodiment of the present invention, Figure 5 As shown, the visualization clamping module includes a base 3 and a protective cover 2 on its upper portion, 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, and the edges of the protective cover 2 and the base 3 are connected via a magnetic component 11; a light-transmitting component 10 is provided on the top of the wax deposition visualization model 1 for observing the wax precipitation in the wax deposition visualization model 1. The magnetic component adopts an electromagnetic suction cup, which realizes the connection between the protective cover and the base by turning the power on and off. The protective cover is made of transparent material, and the light-transmitting component is made of sapphire material, which has the characteristics of high temperature resistance, pressure resistance and high transparency, with a temperature resistance limit of 110°C and a pressure resistance limit of 40MPa.

[0061] The electromagnetic assembly 11 forms a magnetic connection with the base, and the electromagnetic assembly 11 adjusts the magnetic force through the controller. During the experiment, the magnetic force is increased to connect and seal the visual clamping module. After the experiment, the power is turned off and the magnet is demagnetized to facilitate the removal of the visual clamping module.

[0062] In a specific embodiment of the present invention, Figure 1As shown, the 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 located in a constant temperature water bath 13 to prevent premature wax formation in the liquid storage tank and pipelines. The inlet ends of the liquid storage tank 14, petroleum ether storage tank 15, and 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, petroleum ether storage tank 15, and deionized water storage tank 16 are respectively connected in parallel to the injection pipeline 6 of the wax deposition visualization model 1. The injection pipeline 6 is equipped with a first pressure gauge, which is located outside the visualization clamping module. The plunger pump uses an ISCO pump to provide injection pressure for the model. The liquid storage tank is also equipped with a magnetic stirrer to prevent the crude oil from condensing in the tank due to its high freezing point.

[0063] like Figure 1 As shown, the confining pressure regulating 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, and the outlet end of the intermediate container 18 is connected to 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. The confining pressure valve 19 and the second pressure gauge 20 are both 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 liquid pressurization, pressurizes the protective cover, and thus applies confining pressure to the wax deposition visualization model. In specific implementation, the plunger pump and the tracking confining pressure pump are both connected to a computer, and the computer controls the displacement pressure to be slightly lower than the confining pressure, ensuring that the crude oil can be smoothly driven into the wax deposition visualization model without damaging the wax deposition visualization model due to excessive pressure difference.

[0064] exist Figure 1 In the illustrated 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, and a third pressure gauge 23 is provided on the outlet pipeline of the hand pump 24. The back-pressure valve 22 has three connectors: a first connector connected to the outlet pipeline of the hand pump 24, a second connector connected to the production pipeline 7 of the wax deposition visualization model 1, and a third connector connected to the product recovery module, on which a fourth pressure gauge 21 is provided. Furthermore, the product recovery module includes a recovery container 29 and a weighing scale 30. The discharge pipe outlet of the third connector of the back-pressure valve 22 extends into the recovery container 29, which is mounted on the weighing scale 30. The recovery container is a test tube, and the weighing scale is an electronic balance. The electronic balance is placed below the beaker to facilitate measurement of the liquid output.

[0065] In a specific design, the image acquisition module includes a telephoto camera 25, an infrared thermal imaging camera 26, a data transmission line 27, and a computer 28. The telephoto camera 25 and the infrared thermal imaging camera 26 are positioned side by side above the wax deposition visualization model 1 and are connected to the computer 28 via the data transmission line 27. The telephoto camera is a high-definition, high-speed telephoto camera. Positioning the high-definition, high-speed telephoto camera and the infrared thermal imaging camera above the light-transmitting component 10 allows visualization and infrared thermal imaging of the wax precipitation process according to experimental requirements. The captured images and videos are then imported into the computer in real time via the data transmission line for naming and storage.

[0066] During the experiment, the high-definition, high-speed, telephoto camera and infrared thermal imaging camera can be repositioned on the horizontal plane according to the needs of the observation area.

[0067] The present invention also provides an experimental method for studying the wax deposition law in porous media near the wellbore area. The experiment is carried out using the above-mentioned experimental device, comprising the following steps:

[0068] Before the experiment, each part of the wax deposition visualization model 1 was weighed to facilitate the subsequent analysis of wax precipitation;

[0069] Assemble the experimental device: Place the wax deposition visualization model 1 into the confining pressure chamber 9 with a sealing gasket 4 underneath. Then place the protective cover 2 on the base 3. Use the electromagnetic assembly 11 to connect and seal the protective cover 2 and the base 3 to form a visualization clamping module.

[0070] Place a high-definition, high-speed, telephoto camera and an infrared thermal imaging camera above the wax deposition visualization model 1 and start real-time recording.

[0071] Use the tracking confining pressure pump 17 to inject the confining pressure medium in the intermediate container 18 into the confining pressure cavity 9 through the confining pressure pipeline to provide confining pressure for the wax deposition visualization model 1;

[0072] Open the outlet of the wax deposition visualization model 1 and discharge the residual gas inside under the action of the confining pressure until no gas is discharged. 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.

[0073] The experimental crude oil is added into the liquid storage tank, and the magnetic stirrer and the constant temperature water bath 13 are turned on to heat and stir the experimental crude oil to prevent the crude oil from prematurely precipitating wax crystals in the liquid storage tank 14.

[0074] The multi-stage temperature control module 5 is turned on, and the temperature of each heating zone is adjusted by a computer so that each part of the wax deposition visualization model 1 is accurately heated in stages to simulate the complex temperature conditions of the formation.

[0075] The ISCO pump is connected to the liquid storage tank 14 through a pipeline, and 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.

[0076] The ISCO pump is turned on and the displacement mode is adjusted to provide displacement pressure to 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.

[0077] The hand pump 24 is manually adjusted to apply the back pressure required for the experiment to the outlet of the wax deposition visualization model 1 to simulate the bottom hole flow pressure.

[0078] During the experiment, the displacement pressure was maintained slightly lower than the applied confining pressure to ensure that the crude oil could be smoothly driven into the model without damaging the model due to excessive pressure difference.

[0079] In the experiment, a high-definition, high-speed, telephoto camera was used to capture and monitor the wax precipitation process in real time, and infrared imaging images taken by an infrared thermal imaging camera were used to analyze the phase change process of wax crystals in crude oil.

[0080] After the displacement is completed, the experimental parameters are analyzed and the collected pictures and videos are analyzed and processed using computer-specific software.

[0081] The wax deposition visualization model 1 was taken out and the model after the experiment was weighed twice. The difference in mass before and after weighing was the mass of the wax deposition.

[0082] After the wax deposition visualization model 1 is placed back into the confined pressure chamber 9, petroleum ether is driven into the wax deposition visualization model 1 through the liquid injection pipeline to clean the residual oil in the wax deposition visualization model 1. Finally, deionized water is driven into the wax deposition visualization model 1 for final cleaning.

[0083] After cleaning, unload the confining pressure, back pressure and pressure inside the wax deposition visualization model 1, turn off the power to the electromagnetic component 11 for demagnetization, and then separate the visualization clamping module to take out the wax deposition visualization model 1, dry it and place it properly for next use.

[0084] Based on the temperature, pressure and wax deposition mass data of each group, the relationship between temperature, pressure and wax deposition mass is obtained, which is analyzed from the inside out as follows:

[0085] By analyzing the semicircular lithography visualization model 104, the relationship between the near-wellbore portion of the wax deposition visualization model 1 is as follows:

[0086] ;

[0087] By analyzing the third semicircular ring lithography visualization model 103, the relationship between the mid- and far-field regions in the wax deposition visualization model 1 is as follows:

[0088] ;

[0089] By analyzing the second semicircular ring lithography visualization model 102, the relationship of the far region portion in the wax deposition visualization model can be obtained as follows:

[0090] ;

[0091] By analyzing the first semicircular ring lithography visualization model 101, the relationship between the peripheral portion of the wax deposition visualization model 1 is as follows:

[0092] ;

[0093] Where: m - wax deposition quality; T - Experimental temperature; F -Experimental pressure.

[0094] In summary, the porous medium model constructed by the present invention has five isobaric injection ports and one outlet, which can simulate radial seepage characteristics and characterize the actual seepage conditions near the wellbore area; the pressure at the outlet of the model is adjusted by the back pressure control module to simulate the bottom hole flow pressure, which more realistically reflects the geological characteristics of the wellbore area; the experimental model is designed with a disassembled structure that can be divided into blocks, which is convenient for subsequent step-by-step analysis of wax deposition; during the experiment, the entire device is visible, and the step-by-step precipitation process of wax can be observed intuitively; the rapidity and controllability of heating are guaranteed by the multi-stage temperature control module, and the four local models can be quickly heated with multi-gradient temperatures to construct a complex temperature gradient system near the wellbore area; the tracking confining pressure pump can be used to apply confining pressure to the model, and the confining pressure can be intelligently adjusted according to the change of displacement pressure to avoid damage to the model; the infrared thermal imaging camera can more intuitively display the step-by-step precipitation process of wax and analyze the wax crystal phase change process during the experiment, reducing the error of human observation, and is more intuitive and accurate than ordinary cameras. This invention addresses the problem that current indoor wax deposition experiments are unable to characterize wax precipitation within porous media near the wellbore, while also enabling the identification of the wax precipitation pattern. Furthermore, the model's heating process, displacement pressure, outlet pressure, and confining pressure can all be intelligently controlled and adjusted, making indoor wax deposition experiments more closely aligned with formation conditions and more intelligent. This further addresses the shortcomings of existing wax deposition experimental devices and improves indoor wax deposition experiments.

[0095] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles 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 regulation module, a back pressure control module, a product recovery module and an image acquisition module; The wax deposition visualization model is used to simulate a natural core slice with a pore-throat structure, and includes a first semicircular ring-shaped photolithography visualization model, a second semicircular ring-shaped photolithography visualization model, a third semicircular ring-shaped photolithography visualization model, and a semicircular photolithography visualization model. The first semicircular ring-shaped photolithography visualization model, the second semicircular ring-shaped photolithography visualization model, and the third semicircular ring-shaped photolithography visualization model are all semicircular in shape and are arranged in sequence from the outside to the inside on the outside of the semicircular photolithography visualization model. The first semicircular ring-shaped photolithography visualization model, the second semicircular ring-shaped photolithography visualization model, and the third semicircular ring-shaped photolithography visualization model are all porous medium structures. The semicircular photolithography visualization model is an internal hollow structure and is used to simulate a wellbore. Five equidistant isobaric injection ports are provided on the outer edge of the first semicircular ring lithography visualization model 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 regulation 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 a confined pressure chamber, and the confined 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 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, and 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; 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 of the wax deposition visualization model and simulates the bottom hole flow pressure by controlling the outlet 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 wax deposition in porous media near the wellbore according to claim 1, characterized in that: The multi-stage temperature control module includes multiple temperature control shells and heating belts. The multiple temperature control shells have the same 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, respectively. The heating belt is arranged in the arc-shaped cavity of the temperature control shell.

3. The experimental device for studying wax deposition in porous media near the wellbore according to claim 2, 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 protective cover and the mating surface of 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.

4. The experimental device for studying wax deposition 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.

5. The experimental device for studying wax deposition 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.

6. The experimental device for studying wax deposition in porous media near the wellbore according to claim 5, characterized in that: The product recovery module includes 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, and the recovery container is arranged on the metering scale.

7. The experimental device for studying wax deposition 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 side by side above the wax deposition visualization model, and the telephoto camera and the infrared thermal imaging camera are respectively connected to the computer through the data transmission line.

8. An experimental method for studying the wax deposition law in porous media near the wellbore, characterized in that: An experiment is carried out using the experimental device according to any one of claims 1 to 7, comprising the following steps: Before the experiment, the wax deposition visualization model was weighed and then the experimental apparatus 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 using a multi-stage temperature control module to simulate formation temperature conditions. The injection and cleaning modules are started to drive crude oil into the wax deposition visualization model. Back pressure is then applied to the outlet of the wax deposition visualization model through the back pressure control module to simulate the bottom hole flow pressure. The image acquisition module monitors the wax precipitation process in the wax deposition visualization model and analyzes the wax crystal phase change process in crude oil through the acquired images. After the flooding 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; Based on the above experiments, the relationship between temperature, pressure and wax deposition mass is obtained, which is analyzed from the inside out as follows: The relationship between the near-wellbore portion of the wax deposition visualization model is as follows: ; The relationship between the mid- and far-field parts of 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 between 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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