A dynamic wax deposition or wax removal experimental device and experimental method

Abstract

The present invention discloses an experimental device and experimental method for dynamic wax deposition or wax removal, which specifically relates to the technical field of oil and gas field development, including an experimental chamber, a displacement module, a controller, a pressure regulating module for regulating the pressure in the experimental chamber, a temperature control device for regulating the temperature in the experimental chamber, and an oil pumping device; the displacement module includes a liquid storage device and a driving device for transporting the substance in the liquid storage device to the experimental chamber; during the wax deposition experiment, a clean wellbore or a clean formation porous medium is placed in the experimental chamber, the liquid storage device stores an oil-water mixture, and the oil pumping device is used to extract the oil-water mixture in the central through hole of the clean wellbore; during the wax removal experiment, a waxed wellbore or a waxed formation porous medium is placed in the experimental chamber, and the liquid storage device stores a wax remover. The present invention can deeply understand the wax deposition rules and influencing factors of wellbores and formation porous media, evaluate the wax removal effects of different wax removers, optimize the oilfield mining process, improve recovery, and reduce costs.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, in particular to an experimental device and an experimental method for dynamic wax deposition or wax removal. Background Art

[0002] Crude oil typically exists in a free state underground within the pores of the formation, filling the interstices of these porous media. Because the pores in the formation are interconnected, they form pathways for the crude oil to flow. During the extraction process, due to the drop in pressure within the wellbore and the pressure of the formation itself, the crude oil flows through these pores toward the wellbore, where it is subsequently extracted to the surface. When crude oil reaches the surface, both pressure and temperature decrease. This temperature drop is particularly pronounced within the wellbore and porous media of the formation. The solubility of wax in crude oil decreases with decreasing temperature. When the temperature drops below a certain level, wax precipitates from the crude oil, forming crystals that adhere to the wellbore or porous media surfaces.

[0003] When an oil well begins production, when the bottomhole pressure is lower than the formation pressure, a pressure differential is created, driving crude oil to seep through the porous medium. The ability of crude oil to seep through porous media depends on parameters such as porosity and permeability. In formations with high permeability, crude oil flows more easily through the porous medium to the wellbore, resulting in relatively high production efficiency. In contrast, formations with low permeability have greater resistance to crude oil seepage, making production more difficult. The wax content in crude oil is inversely proportional to the permeability of the oil layer. Therefore, during oil production, the wax produced by continuous crystallization and aggregation can clog the oil-producing layer, causing a continuous decrease in oil well production and lowering the quality of the crude oil.

[0004] As crude oil is gradually extracted from the bottom of a well and moved upward along the pipeline, its temperature gradually decreases. Wax in the crude oil may gradually precipitate, and large amounts of wax components gradually aggregate to form wax crystals that adhere to the inner wall of the wellbore. This reduces the cross-sectional area of the wellbore, reducing the area of the fluid flow path, reducing oil and gas production, and affecting wellbore production efficiency. It may even cause the well to become inoperable. In severe cases, it may block the pipeline and threaten production safety. The surface condition of the wellbore has a significant impact on wax deposition. The rougher the wellbore surface, the more likely wax crystals are to be blocked, resulting in their deposition and adhesion, exacerbating wax buildup.

[0005] Therefore, it is very necessary to study the wax deposition and dynamic wax removal effects of porous media in wellbore and formation. Summary of the Invention

[0006] The purpose of the present invention is to provide an experimental device and experimental method for dynamic wax deposition or wax removal to solve the problems existing in the above-mentioned prior art, to gain an in-depth understanding of the wax deposition rules and influencing factors of porous media in wellbores and formations, to evaluate the wax removal effects of different wax removers, to optimize the oil field production process, to increase recovery rates, and to reduce costs.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a dynamic wax deposition or wax removal experimental device, comprising an experimental chamber, a displacement module, a controller, a pressure regulating module, a temperature control device and an oil pumping device; the experimental chamber comprises a liquid inlet and a liquid outlet, and the experimental chamber is used to place a clean wellbore, a clean formation porous medium, a waxed wellbore or a waxed formation porous medium; the displacement module comprises a liquid storage device and a driving device, the liquid storage device is used to store an oil-water mixture or a wax removal agent, the liquid storage device is connected to the liquid inlet of the experimental chamber, and the driving device is used to transport the substance in the liquid storage device to the experimental chamber; the pressure regulating module is connected to the experimental chamber, and is used to regulate the pressure in the experimental chamber. pressure; the temperature control device is connected to the experimental chamber for adjusting the temperature in the experimental chamber; the pressure regulating module and the temperature control device are both connected to the controller signal; during the wax deposition experiment, a clean wellbore or a clean formation porous medium is placed in the experimental chamber, the liquid storage device stores the oil-water mixture, the driving device is used to transport the oil-water mixture to the central through hole of the clean wellbore, and the oil pumping device is used to extract the oil-water mixture in the central through hole of the clean wellbore; during the wax removal experiment, a waxed wellbore or a waxed formation porous medium is placed in the experimental chamber, the liquid storage device stores the wax removal agent, and the driving device is used to transport the wax removal agent to the central through hole of the waxed wellbore.

[0009] Preferably, the displacement module also includes a displacement pump and an intermediate container, the driving device is a peristaltic pump, the displacement pump is connected to the intermediate container, the outlet of the intermediate container is connected to the liquid storage device, the liquid storage device is connected and communicated with the liquid inlet pipe of the peristaltic pump, the liquid outlet pipe of the peristaltic pump is connected and communicated with the liquid inlet of the experimental chamber, and the intermediate container includes three parallel piston containers, and the three piston containers respectively contain oil, water and dewaxing agent.

[0010] Preferably, when a clean wellbore is placed in the experimental chamber, the clean wellbore is sealed and connected to the bottom of the experimental chamber, and the liquid inlet and the liquid outlet are both connected to the central through hole of the clean wellbore; when a waxed wellbore is placed in the experimental chamber, the waxed wellbore is sealed and connected to the bottom of the experimental chamber, and the liquid inlet and the liquid outlet are both connected to the central through hole of the waxed wellbore.

[0011] Preferably, the oil pumping device includes an oil pump and an oil pumping rod, wherein the oil pump is connected to the oil pumping rod, and the oil pumping rod extends into the central through hole of the clean wellbore.

[0012] Preferably, it further comprises a waste liquid pool, the sucker rod is connected and communicated with the waste liquid pool, and the liquid outlet of the experimental chamber is connected and communicated with the waste liquid pool.

[0013] Preferably, the pressure regulating module includes a pressure sensor and a high-pressure gas cylinder, the pressure sensor is installed in the experimental chamber, and the high-pressure gas cylinder is connected to the experimental chamber.

[0014] Preferably, the temperature control device includes a temperature sensor and a heating device, the temperature sensor is installed in the experimental chamber, and the heating device is connected to the experimental chamber.

[0015] The present invention also provides an experimental method based on the dynamic wax deposition or wax removal experimental device, including a clean wellbore wax deposition experiment, a clean formation porous medium wax deposition experiment, a wax deposition wellbore wax removal experiment, and a wax deposition formation porous medium wax removal experiment;

[0016] The clean wellbore wax deposition experiment includes the following steps:

[0017] Step A1, injecting a certain proportion of oil-water mixture into the liquid storage device;

[0018] Step A2, weighing the mass of the clean wellbore, and then placing the clean wellbore into the experimental chamber;

[0019] Step A3, regulating the pressure in the experimental chamber to the simulated formation pressure through the pressure regulating module;

[0020] Step A4: first, open the driving device to transfer the oil-water mixture in the liquid storage device to the central through hole of the clean wellbore. When the oil-water mixture in the clean wellbore reaches a certain height, open the pumping device to pump out the oil-water mixture in the clean wellbore. Adjust the delivery speed of the driving device and the pumping speed of the pumping device to maintain the submergence of the clean wellbore.

[0021] Step A5: After the specified wax deposition time has elapsed, the driving device and the pumping device are turned off, the residual oil-water mixture in the experimental chamber is discharged from the liquid outlet, the clean wellbore is taken out and weighed, and then the wax mass per unit volume of the wellbore is calculated;

[0022] Step A6, replacing a clean wellbore of different size or roughness, and repeating steps A2 to A5 above;

[0023] The wax deposition experiment of porous media in clean formations includes the following steps:

[0024] Step B1, injecting a certain proportion of oil-water mixture into the liquid storage device;

[0025] Step B2, weighing the mass of the clean formation porous medium, and then placing the clean formation porous medium into the experimental chamber;

[0026] Step B3, regulating the pressure in the experimental chamber to the simulated formation pressure through the pressure regulating module;

[0027] Step B4: First, the driving device is turned on to transfer the oil-water mixture in the liquid storage device into the experimental chamber. When the oil-water mixture in the experimental chamber submerges the clean porous medium in the formation, the liquid outlet of the experimental chamber is opened, and the delivery speed of the driving device and the outflow speed of the oil-water mixture are adjusted to maintain the oil-water mixture in the experimental chamber submerging the clean porous medium in the formation.

[0028] Step B5: After the predetermined wax deposition time has elapsed, the driving device is turned off, the oil-water mixture in the experimental chamber is discharged from the liquid outlet, the clean formation porous medium is taken out and weighed, and then the clean formation porous medium wax retention rate is calculated;

[0029] Step B6, replacing the clean formation porous media with different porosity or permeability, and repeating the above steps B2 to B5;

[0030] The wax removal experiment of wax-coated wellbore includes the following steps:

[0031] Step C1, injecting the wax remover into the liquid storage device;

[0032] Step C2, weighing the mass of the wax-coated wellbore, and then placing the wax-coated wellbore into the experimental chamber;

[0033] Step C3, adjusting the pressure in the experimental chamber to the simulated formation pressure by the pressure regulating module, and adjusting the temperature in the experimental chamber to a specified temperature by the temperature control device;

[0034] Step C4, first opening the driving device, delivering the wax remover in the liquid storage device to the central through hole of the wax-congealed wellbore, ensuring that the immersion level of the wax remover in the wax-congealed wellbore is not lower than the previous immersion level of the oil-water mixture, and then closing the driving device;

[0035] Step C5, after the prescribed wax removal time is reached, the wax removal agent in the experimental chamber is discharged from the liquid outlet, the wax-encrusted wellbore is taken out and weighed, and the wax removal rate of the wax-encrusted wellbore is calculated;

[0036] Step C6, replacing a different wax remover and repeating steps C2 to C5 for the wax-deposited wellbore with the same initial conditions;

[0037] The wax removal experiment of porous media in waxy formations includes the following steps:

[0038] Step D1, injecting the wax remover into the liquid storage device;

[0039] Step D2: Weigh the mass of the porous medium in the waxy formation, wrap the sides of the porous medium with a waterproof material, and leave the ends of the porous medium open to ensure that the wax remover can flow freely into or out of the porous medium only from these ends. Then, place the porous medium in the waxy formation into the experimental chamber.

[0040] Step D3, adjusting the pressure in the experimental chamber to the simulated formation pressure by the pressure regulating module, and adjusting the temperature in the experimental chamber to a specified temperature by the temperature control device;

[0041] Step D4, first open the driving device, transport the wax remover in the liquid storage device to the experimental chamber, ensure that the wax remover in the experimental chamber is immersed in the wax-deposited porous medium of the formation, and close the driving device;

[0042] Step D5, after the prescribed wax removal time is reached, the wax removal agent in the experimental chamber is discharged from the liquid outlet, the porous medium in the wax-deposited formation is taken out and weighed, and the wax removal rate of the porous medium in the wax-deposited formation is calculated;

[0043] Step D6: Replace the wax remover with a different one, and repeat the above steps D2 to D5 for the porous medium of the wax formation with the same initial conditions.

[0044] Compared with the prior art, the present invention has achieved the following technical effects:

[0045] A dynamic waxing or wax removal experimental device and experimental method, by replacing clean wellbores of different cross-sectional areas or roughnesses and performing waxing experiments on the clean wellbores, can understand the waxing conditions of wellbores under different cross-sectional areas, provide a basis for selecting wellbores diameters, can understand the waxing laws of wellbores with different roughnesses, help select wellbores materials and determine surface treatment methods, and provide a basis for improving the anti-waxing performance of wellbores; by replacing clean formation porous media of different porosities and performing waxing experiments on the clean formation porous media, can understand the waxing conditions of clean formation porous media under different porosities, and deeply understand the waxing laws and influencing factors of wellbores and formation porous media; by replacing different wax removal agents, performing wax removal experiments on waxed wellbores with the same initial conditions and waxed formation porous media with the same initial conditions, compare the wax removal effects, and provide a basis for selecting the most suitable wax removal agent. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 Schematic diagram of the structure of the experimental device for dynamic wax deposition or wax removal.

[0048] In the figure: 1-experimental chamber; 2-displacement pump; 3-piston container; 4-liquid storage device; 5-peristaltic pump; 6-sucker rod; 7-pressure sensor; 8-high-pressure gas cylinder; 9-temperature sensor; 10-heating device; 11-controller; 12-waste liquid tank. DETAILED DESCRIPTION

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0050] The purpose of the present invention is to provide an experimental device and experimental method for dynamic wax deposition or wax removal to solve the problems existing in the above-mentioned prior art, to gain an in-depth understanding of the wax deposition rules and influencing factors of porous media in wellbores and formations, to evaluate the wax removal effects of different wax removers, to optimize the oil field production process, to increase recovery rates, and to reduce costs.

[0051] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] Example 1

[0053] This embodiment provides a dynamic wax deposition or wax removal experimental device, such as Figure 1As shown, it includes an experimental chamber 1, a displacement module, a controller 11, a pressure regulating module, a temperature control device and an oil pumping device; the experimental chamber 1 includes a liquid inlet and a liquid outlet, and the experimental chamber 1 is used to place a clean wellbore, a clean formation porous medium, a waxed wellbore or a waxed formation porous medium; the displacement module includes a liquid storage device 4 and a driving device, the liquid storage device 4 is used to store an oil-water mixture or a wax remover, the liquid storage device 4 is connected to the liquid inlet of the experimental chamber 1, and the driving device is used to transport the substance in the liquid storage device 4 to the experimental chamber 1; the pressure regulating module is connected to the experimental chamber 1 for adjusting the pressure in the experimental chamber 1; the temperature control device is connected to the experimental chamber The experimental chamber 1 is connected to the experimental chamber 1 for adjusting the temperature therein; the pressure regulating module and the temperature control device are both connected to the controller 11 by signal; during the wax deposition experiment, a clean wellbore or a clean formation porous medium is placed in the experimental chamber 1, the liquid storage device 4 stores the oil-water mixture, the driving device is used to transport the oil-water mixture to the central through hole of the clean wellbore, and the pumping device is used to extract the oil-water mixture in the central through hole of the clean wellbore to simulate the actual working condition of the oil-water mixture in the wellbore; during the wax removal experiment, a waxed wellbore or a waxed formation porous medium is placed in the experimental chamber 1, the liquid storage device 4 stores the wax removal agent, and the driving device is used to transport the wax removal agent to the central through hole of the waxed wellbore. When a clean wellbore or a waxed wellbore is placed in the experimental chamber 1, the driving device transports the substance in the liquid storage device 4 directly to the central through hole of the clean wellbore or the waxed wellbore, which can more accurately control the experimental parameters and reduce the amount of oil-water mixture used in the experiment; by replacing clean wellbores with different cross-sectional areas or roughness and conducting waxing experiments on the clean wellbore, the waxing conditions of wellbores with different cross-sectional areas can be understood, which provides a basis for the selection of wellbore diameters and the waxing laws of wellbores with different roughnesses can be understood, which is helpful for selecting wellbore materials and determining The surface treatment method provides a basis for improving the anti-wax deposition performance of the wellbore; by replacing the clean formation porous media with different porosities and conducting wax deposition experiments on the clean formation porous media, we can understand the wax deposition situation of the clean formation porous media under different porosities, and gain an in-depth understanding of the wax deposition rules and influencing factors of the wellbore and formation porous media; by replacing different wax removal agents, wax removal experiments are conducted on waxed wellbores with the same initial conditions and waxed formation porous media with the same initial conditions, and the wax removal effects are compared, providing a basis for selecting the most suitable wax removal agent.

[0054] It is further preferred in the implementation of this embodiment that the displacement module also includes a displacement pump 2 and an intermediate container, the driving device is a peristaltic pump 5, the displacement pump 2 is connected to the intermediate container, the outlet of the intermediate container is connected to the liquid storage device 4, the liquid storage device 4 is connected and communicated with the liquid inlet of the peristaltic pump 5, the liquid outlet of the peristaltic pump 5 is connected and communicated with the liquid inlet of the experimental chamber 1, and the intermediate container includes three parallel piston containers 3, and the three piston containers 3 are respectively filled with oil, water and dewaxing agent. When doing a wax deposition experiment, the outlet valve of the piston container 3 filled with the dewaxing agent is closed, and the outlet valve of the piston container 3 filled with oil and water is opened. By adjusting the opening of the outlet valve, the ratio of oil and water in the oil-water mixture is adjusted, and the displacement pump 2 applies pressure to the oil and water respectively, so that they overcome the pressure in their respective containers and the resistance of the pipeline, and flow to the liquid storage device 4 for mixing oil and water, and the oil and water are fully mixed in the liquid storage device 4. During the wax removal experiment, the outlet valve of piston container 3 containing the wax remover is opened, while the outlet valves of piston container 3 containing oil and water are closed. Displacement pump 2 applies pressure to the wax remover, causing it to overcome the pressure within the container and the resistance of the pipeline and flow to liquid storage device 4. Peristaltic pump 5 can accurately control the flow rate of the fluid, and the fluid flow output by peristaltic pump 5 is relatively stable, which can improve the accuracy and reliability of the experiment.

[0055] It is further preferred in the implementation manner of this embodiment that when a clean wellbore is placed in the experimental chamber 1, the clean wellbore is sealed and connected to the bottom of the experimental chamber 1, and the liquid inlet and the liquid outlet are both connected to the central through hole of the clean wellbore; when a waxed wellbore is placed in the experimental chamber 1, the waxed wellbore is sealed and connected to the bottom of the experimental chamber 1, and the liquid inlet and the liquid outlet are both connected to the central through hole of the waxed wellbore.

[0056] It is further preferred in the implementation manner of this embodiment that the oil pumping device includes an oil pump and an oil pumping rod 6, the oil pump is connected to the oil pumping rod 6, and the oil pumping rod 6 extends into the central through hole of the clean wellbore.

[0057] In the embodiment of the present invention, it is further preferred that a waste liquid pool 12 is further included, the sucker rod 6 is connected and communicated with the waste liquid pool 12 , and the liquid outlet of the experimental chamber 1 is connected and communicated with the waste liquid pool 12 .

[0058] It is further preferred in the implementation of this embodiment that the pressure regulating module includes a pressure sensor 7 and a high-pressure gas cylinder 8, the pressure sensor 7 is installed in the experimental chamber 1, and the high-pressure gas cylinder 8 is connected to the experimental chamber 1. When doing an experiment, the valve of the high-pressure gas cylinder 8 is opened to allow the gas in the high-pressure gas cylinder 8 to enter the experimental chamber 1. The pressure sensor 7 monitors the pressure value in the experimental chamber 1 in real time, and converts the pressure signal into an electrical signal and outputs it to the controller 11. The controller 11 adjusts the valve of the high-pressure gas cylinder 8. The gas in the high-pressure gas cylinder 8 flows into the experimental chamber 1 under the action of the pressure difference, thereby gradually increasing the pressure in the experimental chamber 1. When the pressure in the experimental chamber 1 reaches the set value, the controller 11 closes the valve of the high-pressure gas cylinder 8.

[0059] In the embodiment of this invention, the temperature control device preferably includes a temperature sensor 9 and a heating device 10. The temperature sensor 9 is installed in the experimental chamber 1, and the heating device 10 is connected to the experimental chamber 1. The temperature sensor 9 monitors the temperature value in the experimental chamber 1 in real time, converts the temperature signal into an electrical signal, and outputs it to the controller 11. The controller 11 controls the heating device 10 to heat the experimental chamber 1, thereby gradually increasing the temperature in the experimental chamber 1 to reach the set value.

[0060] Example 2

[0061] This embodiment provides an experimental method for the dynamic wax deposition or wax removal experimental device based on the embodiment 1, including a clean wellbore wax deposition experiment, a clean formation porous medium wax deposition experiment, a wax deposition wellbore wax removal experiment, and a wax deposition formation porous medium wax removal experiment;

[0062] The clean wellbore wax deposition experiment includes the following steps:

[0063] Step A1, injecting a certain proportion of oil-water mixture into the liquid storage device 4;

[0064] Step A2, weighing the mass of the clean wellbore, and then placing the clean wellbore into the experimental chamber 1;

[0065] Step A3, adjusting the pressure in the experimental chamber 1 to the simulated formation pressure through the pressure regulating module;

[0066] In step A4, the driving device is first activated to deliver the oil-water mixture in the liquid storage device 4 to the central through-hole of the clean wellbore. When the oil-water mixture in the clean wellbore reaches a certain height, the pumping device is activated to pump out the oil-water mixture in the clean wellbore. The delivery speed of the driving device and the pumping speed of the pumping device are adjusted to maintain the submergence of the clean wellbore (i.e., maintain the depth of the oil-water mixture in the clean wellbore).

[0067] Step A5: After the specified wax deposition time has elapsed, the drive unit and the pumping unit are turned off, the residual oil-water mixture in the experimental chamber 1 is discharged from the liquid outlet, the clean wellbore is taken out and weighed, and then the wax mass per unit volume of the wellbore is calculated;

[0068] Based on the wellbore inner wall roughness Ra, the wellbore inner diameter D, and the mass of wax deposited on the wellbore inner wall m1, the wax deposited mass m1 is related to the wax volume V and the wax density ρ (i.e., m1 = ρV). The wax volume V can be approximately considered the product of the tubing inner wall area and the wax thickness d (ignoring the complexity of the wax deposit shape). The tubing inner wall area A can be approximately equal to πDH. Furthermore, it is assumed that the wax deposit is uniformly distributed on the wellbore inner wall and the direct effect of wellbore roughness on the wax volume calculation is ignored (i.e., the wax deposit is assumed to fill the smooth surface of the wellbore inner wall, and roughness is only a factor affecting the initial attachment and growth rate of the wax deposit). Under this assumption, the wax volume V can be more simply expressed as πDHL, where L is the length of the wellbore submerged in the oil-water mixture.

[0069] Combining the above assumptions, the following formula is obtained to approximate the relationship between the wax thickness d, the inner diameter D of the oil pipe, the wax mass m1, and the length L of the wellbore immersed in the oil-water mixture:

[0070]

[0071] In practice, wellbore roughness may affect the initial adhesion and growth of wax deposits, but the extent of this influence usually requires experimental determination. Therefore, a roughness-related coefficient, k(Ra), can be introduced to represent the increase or decrease in the wax deposition rate due to roughness. In this way, a function can be approximated to obtain the functional relationship between the wellbore inner wall roughness Ra, the wellbore inner diameter D, the wax deposition thickness d, the length L of the wellbore immersed in the oil-water mixture, and the wax deposition mass m1 on the wellbore inner wall:

[0072]

[0073] Where,

[0074] d: Wax deposition thickness on the inner wall of the oil pipe, mm;

[0075] k (Ra): Adhesion coefficient related to the pipe wall roughness Ra;

[0076] D: inner diameter of the oil pipe, mm;

[0077] L: length of the oil pipe immersed in the oil-water mixture, mm;

[0078] m1: wax mass on the inner wall of the oil pipe, g;

[0079] ρ: wax density in the oil pipe, g / cm 3 ;

[0080] According to the wax mass formula,

[0081]

[0082] Combined with the definition of unit volume,

[0083]

[0084] The formula for the mass of wax deposited per unit volume in the wellbore is derived as follows:

[0085]

[0086] m vol : wax mass per unit volume of tubing (g / cm³);

[0087] Step A6: Replace the clean wellbore with one of different sizes or roughness, and repeat steps A2 to A5 above. By replacing the clean wellbore with one of different cross-sectional areas or roughness, wax deposition experiments are conducted on multiple types of clean wellbores. This can quantitatively reveal the regulatory mechanism of the wellbore structural parameters on the wax deposition dynamics, and can optimize anti-wax measures in a targeted manner, providing a basis for improving the anti-wax performance of the wellbore, thereby improving the production efficiency and stability of the oil well.

[0088] The wax deposition experiment of porous media in clean formations includes the following steps:

[0089] Step B1, injecting a certain proportion of oil-water mixture into the liquid storage device 4;

[0090] Step B2, weighing the mass of the clean formation porous medium, and then placing the clean formation porous medium into the experimental chamber 1;

[0091] Step B3, adjusting the pressure in the experimental chamber 1 to the simulated formation pressure through the pressure regulating module;

[0092] Step B4: First, open the drive device to transfer the oil-water mixture in the liquid storage device 4 to the experimental chamber 1. When the oil-water mixture in the experimental chamber 1 submerges the porous medium in the formation, open the liquid outlet of the experimental chamber 1 and adjust the delivery speed of the drive device and the outflow speed of the oil-water mixture to maintain the oil-water mixture in the experimental chamber 1 submerging the porous medium in the formation.

[0093] Step B5: After the prescribed wax deposition time is reached, the driving device is turned off, the oil-water mixture in the experimental chamber 1 is discharged from the liquid outlet, the clean formation porous medium is taken out and weighed, and then the clean formation porous medium wax retention rate is calculated;

[0094] For porous media, greater porosity means more space within the medium for wax deposition. Therefore, other things being equal, greater porosity may lead to increased wax deposition. Permeability is a physical quantity that measures the ease with which a fluid can pass through a porous medium. The higher the permeability, the smoother the fluid flows through the porous medium. While permeability may not directly affect wax deposition, it can influence the flow rate and path of the fluid within the porous medium, thereby impacting wax deposition and distribution. For example, areas of lower permeability may result in slower fluid velocity, increasing the chance of wax deposition.

[0095] After determining the porosity and permeability of the porous medium in the net formation, the wax retention in the porous medium is observed by adjusting the injection rate of the oil-water mixture to obtain the formula for the wax retention rate in the porous medium:

[0096]

[0097] Where,

[0098] R w : wax retention rate (mass of wax deposited per unit volume of porous medium per unit time, g / (m³·s));

[0099] D: experimental fitting constant (related to oil composition, temperature, and pressure);

[0100] φ: porosity of porous media (dimensionless);

[0101] S w : wax saturation in oil-water mixture (mass fraction);

[0102] k: porous media permeability, md;

[0103] v: fluid velocity (m / s);

[0104] v c : Critical scour velocity (when v≥v c When , the shear stress is sufficient to inhibit wax deposition);

[0105] n: velocity decay exponent;

[0106] Step B6, replacing the clean formation porous media with different porosity or permeability, and repeating the above steps B2 to B5;

[0107] The wax removal experiment of wax-coated wellbore includes the following steps:

[0108] Step C1, injecting the wax remover into the liquid storage device 4;

[0109] Step C2, weighing the mass of the wax-coated wellbore, and then placing the wax-coated wellbore into the experimental chamber 1;

[0110] Step C3, adjusting the pressure in the experimental chamber 1 to the simulated formation pressure through the pressure regulating module, and adjusting the temperature in the experimental chamber 1 to a specified temperature through the temperature control device;

[0111] Step C4: first open the driving device, transfer the wax remover in the liquid storage device 4 to the central through hole of the wax-deposited wellbore, ensure that the immersion position of the wax remover in the wax-deposited wellbore is not lower than the previous immersion position of the oil-water mixture, and then close the driving device;

[0112] Step C5: After the prescribed wax removal time is reached, the wax removal agent in the experimental chamber 1 is discharged from the liquid outlet, the wax-encrusted wellbore is taken out and weighed, and the wax removal rate of the wax-encrusted wellbore is calculated;

[0113] Step C6, replacing a different wax remover and repeating steps C2 to C5 for the wax-deposited wellbore with the same initial conditions;

[0114] The wax removal experiment of porous media in waxy formations includes the following steps:

[0115] Step D1, injecting the wax remover into the liquid storage device 4;

[0116] Step D2: Weigh the mass of the porous medium in the waxy formation, wrap the sides of the porous medium in the waxy formation with a layer of waterproof material to prevent the wax remover from entering or seeping out from the sides of the porous medium in the waxy formation. The ends of the porous medium in the waxy formation are not wrapped and remain open to ensure that the wax remover can freely flow into or out of the porous medium in the waxy formation only from these ends. Then, place the porous medium in the waxy formation in the experimental chamber 1.

[0117] Step D3, adjusting the pressure in the experimental chamber 1 to the simulated formation pressure through the pressure regulating module, and adjusting the temperature in the experimental chamber 1 to a specified temperature through the temperature control device;

[0118] Step D4: first open the driving device to transport the wax remover in the liquid storage device 4 to the experimental chamber 1, ensure that the wax remover in the experimental chamber 1 is immersed in the wax-deposited porous medium, and then close the driving device;

[0119] Step D5: After the prescribed wax removal time is reached, the wax removal agent in the experimental chamber 1 is discharged from the liquid outlet, the porous medium in the waxy formation is taken out and weighed, and the wax removal rate of the porous medium in the waxy formation is calculated;

[0120] Step D6: Replace the wax remover with a different one, and repeat the above steps D2 to D5 for the porous medium of the wax formation with the same initial conditions.

[0121] The wax removal rate of the wax remover can be observed based on the change in the mass of the waxed sample. In addition, multiple rounds of wax removal experiments can be performed to observe the relationship between the wax removal rate and the number of wax removal rounds.

[0122]

[0123] Where,

[0124] Z: wax removal rate;

[0125] m2: wax mass, g;

[0126] m3: mass after wax removal, g.

[0127] By evaluating the wax removal effects and performance of different wax removers, a basis is provided for selecting the most suitable wax remover in practical applications.

[0128] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. An experimental device for dynamic wax deposition or wax removal, characterized by: The invention comprises an experimental chamber, a displacement module, a controller, a pressure regulating module, a temperature control device and an oil pumping device; the experimental chamber comprises a liquid inlet and a liquid outlet, and the experimental chamber is used to place a clean wellbore, a clean formation porous medium, a waxed wellbore or a waxed formation porous medium; the displacement module comprises a liquid storage device and a driving device, the liquid storage device is used to store an oil-water mixture or a wax remover, the liquid storage device is connected to the liquid inlet of the experimental chamber, and the driving device is used to transport the substance in the liquid storage device to the experimental chamber; the pressure regulating module is connected to the experimental chamber for regulating the pressure in the experimental chamber; the temperature control device is connected to the experimental chamber for regulating the temperature in the experimental chamber; the pressure regulating module and the temperature control device are both connected to the controller signal; wax deposition experiment During the test, a clean wellbore or a clean formation porous medium is placed in the experimental chamber, the liquid storage device stores the oil-water mixture, the driving device is used to transport the oil-water mixture to the central through hole of the clean wellbore, and the oil pumping device is used to extract the oil-water mixture in the central through hole of the clean wellbore; during the wax removal test, a waxed wellbore or a waxed formation porous medium is placed in the experimental chamber, the liquid storage device stores the wax remover, and the driving device is used to transport the wax remover to the central through hole of the waxed wellbore. When a clean wellbore is placed in the experimental chamber, the clean wellbore is sealed and connected to the bottom of the experimental chamber, and the liquid inlet and the liquid outlet are both connected to the central through hole of the clean wellbore; when a waxed wellbore is placed in the experimental chamber, the waxed wellbore is sealed and connected to the bottom of the experimental chamber, and the liquid inlet and the liquid outlet are both connected to the central through hole of the waxed wellbore.

2. The dynamic wax deposition or wax removal experimental device according to claim 1, characterized in that: The displacement module also includes a displacement pump and an intermediate container. The driving device is a peristaltic pump. The displacement pump is connected to the intermediate container. The outlet of the intermediate container is connected to the liquid storage device. The liquid storage device is connected and communicated with the liquid inlet pipe of the peristaltic pump. The liquid outlet pipe of the peristaltic pump is connected and communicated with the liquid inlet of the experimental chamber. The intermediate container includes three parallel piston containers, and the three piston containers are respectively filled with oil, water and wax remover.

3. The dynamic wax deposition or wax removal experimental device according to claim 1, characterized in that: The oil pumping device comprises an oil pump and an oil pumping rod, wherein the oil pump is connected to the oil pumping rod, and the oil pumping rod extends into the central through hole of the clean wellbore.

4. The dynamic wax deposition or wax removal experimental device according to claim 3, characterized in that: It also includes a waste liquid pool, the sucker rod is connected and communicated with the waste liquid pool, and the liquid outlet of the experimental chamber is connected and communicated with the waste liquid pool.

5. The dynamic wax deposition or wax removal experimental device according to claim 1, characterized in that: The pressure regulating module includes a pressure sensor and a high-pressure gas cylinder. The pressure sensor is installed in the experimental chamber, and the high-pressure gas cylinder is communicated with the experimental chamber.

6. The dynamic wax deposition or wax removal experimental device according to claim 1, characterized in that: The temperature control device includes a temperature sensor and a heating device. The temperature sensor is installed in the experimental chamber, and the heating device is connected to the experimental chamber.

7. An experimental method based on the dynamic wax deposition or wax removal experimental device according to any one of claims 1 to 6, characterized in that: Including clean wellbore wax deposition test, clean formation porous media wax deposition test, wax deposition wellbore wax removal test and wax deposition porous media wax removal test; The clean wellbore wax deposition experiment includes the following steps: Step A1, injecting a certain proportion of oil-water mixture into the liquid storage device; Step A2, weighing the mass of the clean wellbore, and then placing the clean wellbore into the experimental chamber; Step A3, regulating the pressure in the experimental chamber to the simulated formation pressure through the pressure regulating module; Step A4: first, open the driving device to transfer the oil-water mixture in the liquid storage device to the central through hole of the clean wellbore. When the oil-water mixture in the clean wellbore reaches a certain height, open the pumping device to pump out the oil-water mixture in the clean wellbore. Adjust the delivery speed of the driving device and the pumping speed of the pumping device to maintain the submergence of the clean wellbore. Step A5: After the specified wax deposition time has elapsed, the driving device and the pumping device are turned off, the residual oil-water mixture in the experimental chamber is discharged from the liquid outlet, the clean wellbore is taken out and weighed, and then the wax mass per unit volume of the wellbore is calculated; Step A6, replacing a clean wellbore of different size or roughness, and repeating steps A2 to A5 above; The wax deposition experiment of porous media in clean formations includes the following steps: Step B1, injecting a certain proportion of oil-water mixture into the liquid storage device; Step B2, weighing the mass of the clean formation porous medium, and then placing the clean formation porous medium into the experimental chamber; Step B3, regulating the pressure in the experimental chamber to the simulated formation pressure through the pressure regulating module; Step B4: First, the driving device is turned on to transfer the oil-water mixture in the liquid storage device into the experimental chamber. When the oil-water mixture in the experimental chamber submerges the clean porous medium in the formation, the liquid outlet of the experimental chamber is opened, and the delivery speed of the driving device and the outflow speed of the oil-water mixture are adjusted to maintain the oil-water mixture in the experimental chamber submerging the clean porous medium in the formation. Step B5: After the predetermined wax deposition time has elapsed, the driving device is turned off, the oil-water mixture in the experimental chamber is discharged from the liquid outlet, the clean formation porous medium is taken out and weighed, and then the clean formation porous medium wax retention rate is calculated; Step B6, replacing the clean formation porous media with different porosity or permeability, and repeating the above steps B2 to B5; The wax removal experiment of wax-coated wellbore includes the following steps: Step C1, injecting the wax remover into the liquid storage device; Step C2, weighing the mass of the wax-coated wellbore, and then placing the wax-coated wellbore into the experimental chamber; Step C3, adjusting the pressure in the experimental chamber to the simulated formation pressure by the pressure regulating module, and adjusting the temperature in the experimental chamber to a specified temperature by the temperature control device; Step C4, first opening the driving device, delivering the wax remover in the liquid storage device to the central through hole of the wax-congealed wellbore, ensuring that the immersion level of the wax remover in the wax-congealed wellbore is not lower than the previous immersion level of the oil-water mixture, and then closing the driving device; Step C5, after the prescribed wax removal time is reached, the wax removal agent in the experimental chamber is discharged from the liquid outlet, the wax-encrusted wellbore is taken out and weighed, and the wax removal rate of the wax-encrusted wellbore is calculated; Step C6, replacing a different wax remover and repeating steps C2 to C5 for the wax-deposited wellbore with the same initial conditions; The wax removal experiment of porous media in waxy formations includes the following steps: Step D1, injecting the wax remover into the liquid storage device; Step D2: Weigh the mass of the porous medium in the waxy formation, wrap the sides of the porous medium with a waterproof material, and leave the ends of the porous medium open to ensure that the wax remover can flow freely into or out of the porous medium only from these ends. Then, place the porous medium in the waxy formation into the experimental chamber. Step D3, adjusting the pressure in the experimental chamber to the simulated formation pressure by the pressure regulating module, and adjusting the temperature in the experimental chamber to a specified temperature by the temperature control device; Step D4, first open the driving device, transport the wax remover in the liquid storage device to the experimental chamber, ensure that the wax remover in the experimental chamber is immersed in the wax-deposited porous medium of the formation, and close the driving device; Step D5, after the prescribed wax removal time is reached, the wax removal agent in the experimental chamber is discharged from the liquid outlet, the porous medium in the wax-deposited formation is taken out and weighed, and the wax removal rate of the porous medium in the wax-deposited formation is calculated; Step D6: Replace the wax remover with a different one, and repeat the above steps D2 to D5 for the porous medium of the wax formation with the same initial conditions.

Images