Experimental device and experimental method for dynamic wax precipitation or wax removal

Abstract

The invention discloses an experimental device and an experimental method for dynamic wax precipitation or wax removal, and particularly relates to the technical field of oil and gas field development, the experimental device comprises an experimental chamber, a displacement module, a controller, a pressure adjusting module for adjusting the pressure in the experimental chamber, a temperature control device for adjusting the temperature in the experimental chamber and an oil pumping device; the displacement module comprises a liquid storage device and a driving device used for conveying substances in the liquid storage device into the experiment cavity; during a wax precipitation experiment, a clean shaft or a clean stratum porous medium is placed in the experiment chamber, the liquid storage device stores an oil-water mixture, and the oil pumping device is used for pumping out the oil-water mixture in a central through hole of the clean shaft; during a wax removal experiment, a wax precipitation shaft or a wax precipitation stratum porous medium is placed in the experiment chamber, and a wax removal agent is stored in the liquid storage device. According to the method, the wax precipitation law and influence factors of the shaft and the stratum porous medium can be deeply understood, the wax removal effects of different wax removal agents are evaluated, the oilfield exploitation process is optimized, the recovery efficiency is improved, and the cost is reduced.

Description

Technical Field

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

[0002] Crude oil usually exists in a free state in the pores of the formation underground, filling the pore spaces of these porous media. Since the pores in the formation are interconnected to form channels for the flow of crude oil, during the exploitation process, under the action of the reduced pressure in the wellbore and the formation pressure itself, the crude oil will flow through these pore channels towards the wellbore and then be produced to the ground. When the crude oil is produced to the ground, both the pressure and temperature decrease. Especially in the wellbore and the porous media of the formation, the temperature drops significantly. The solubility of wax in crude oil decreases with the decrease in temperature. When the temperature drops to a certain extent, the wax will precipitate from the crude oil, form crystals and adhere to the surface of the wellbore or porous media.

[0003] When an oil well starts production, under the condition that the bottom-hole pressure is lower than the formation pressure, a pressure difference is formed to drive the crude oil to flow through the porous media. The seepage ability of crude oil in porous media depends on parameters such as porosity and permeability. For formations with high permeability, it is easier for crude oil to flow through the porous media towards the wellbore, and the exploitation efficiency is relatively high; while for formations with low permeability, the seepage resistance of crude oil is large and the exploitation difficulty is relatively high. The wax content in crude oil is inversely proportional to the permeability of the oil reservoir. Therefore, during oil exploitation, due to the wax produced by continuous crystallization and aggregation, the oil-producing formation is blocked, resulting in a continuous reduction in the production of the oil well and a decrease in the quality of crude oil.

[0004] As the crude oil is gradually developed from the bottom of the well to the ground and moves upward along the oil pipe, its temperature gradually decreases, and the wax in the crude oil may gradually precipitate. A large amount of wax components gradually aggregate to form wax crystals adhering to the inner wall of the wellbore, resulting in a reduction in the cross-sectional area of the wellbore, a decrease in the fluid flow channel area, a reduction in the oil and gas production liquid volume, an impact on the production efficiency of the wellbore, and even a phenomenon where the oil well cannot produce. In severe cases, it may block the pipeline and threaten production safety. The surface state of the wellbore has a great influence on wax deposition. The rougher the surface of the wellbore, the easier it is for wax crystals to be hindered and thus deposit and adhere to the wellbore surface, exacerbating wax deposition.

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

[0006] The purpose of the present invention is to provide an experimental device and method for dynamic wax deposition or wax removal to solve the problems existing in the above-mentioned prior art, to be able to deeply understand the wax deposition law and influencing factors in the wellbore and formation porous media, evaluate the wax removal effect of different wax removers, optimize the oilfield exploitation process, improve the recovery rate, and reduce costs.

[0007] To achieve the above object, the present invention provides the following solutions: The present invention provides an experimental device for dynamic wax deposition or wax removal, including an experimental chamber, a displacement module, a controller, a pressure regulation module, a temperature control device, and a pumping device; the experimental chamber includes a liquid inlet and a liquid outlet, and a clean wellbore, a clean formation porous medium, a wax-deposited wellbore, or a wax-deposited formation porous medium is placed in the experimental chamber; the displacement module includes 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 communicated with 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 regulation 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; both the pressure regulation module and the temperature control device are signal-connected to the controller; 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, 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 pump out the oil-water mixture in the central through-hole of the clean wellbore; during the wax removal experiment, a wax-deposited wellbore or a wax-deposited formation porous medium is placed in the experimental chamber, the liquid storage device stores a wax remover, and the driving device is used to transport the wax remover to the central through-hole of the wax-deposited wellbore.

[0008] Preferably, the displacement module further 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 inlet pipe of the peristaltic pump, the 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 a wax remover.

[0009] Preferably, when a clean wellbore is placed in the experimental chamber, the clean wellbore is hermetically connected to the bottom of the experimental chamber, and both the liquid inlet and the liquid outlet are communicated with the central through-hole of the clean wellbore; when a wax-deposited wellbore is placed in the experimental chamber, the wax-deposited wellbore is hermetically connected to the bottom of the experimental chamber, and both the liquid inlet and the liquid outlet are communicated with the central through-hole of the wax-deposited wellbore.

[0010] Preferably, the pumping device includes a submersible pump and a sucker rod, the submersible pump is connected to the sucker rod, and the sucker rod extends into the central through-hole of the clean wellbore.

[0011] Preferably, it further 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.

[0012] Preferably, the pressure regulation 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.

[0013] 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.

[0014] The present invention also provides an experimental method based on the experimental device for dynamic wax deposition or wax removal, including a clean wellbore wax deposition experiment, a clean formation porous media wax deposition experiment, a wax removal experiment for a wax-deposited wellbore, and a wax removal experiment for a wax-deposited formation porous media; The clean wellbore wax deposition experiment includes the following steps: Step A1, injecting an oil-water mixture in a certain proportion 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, adjusting the pressure in the experimental chamber to the simulated formation pressure through the pressure regulation module; Step A4, first turning on the driving device to transport the oil-water mixture in the liquid storage device into the central through-hole of the clean wellbore. When the oil-water mixture in the clean wellbore reaches a certain height, then turning on the pumping device to pump out the oil-water mixture in the clean wellbore, and adjusting the conveying speed of the driving device and the pumping speed of the pumping device to maintain the immersion degree of the clean wellbore; Step A5, after reaching the specified wax deposition duration, turning off the driving device and the pumping device, discharging the remaining oil-water mixture in the experimental chamber from the liquid outlet, taking out the clean wellbore and weighing it, and then calculating the wax mass per unit volume of the wellbore; Step A6, replacing the clean wellbore with different sizes or different roughnesses, and repeating the above steps A2 to A5; The clean formation porous media wax deposition experiment includes the following steps: Step B1, injecting an oil-water mixture in a certain proportion into the liquid storage device; Step B2, weighing the mass of the clean formation porous media, and then placing the clean formation porous media into the experimental chamber; Step B3, adjusting the pressure in the experimental chamber to the simulated formation pressure through the pressure regulation module; Step B4: First, turn on the driving device to transport the oil-water mixture in the liquid storage device to the experimental chamber. When the oil-water mixture in the experimental chamber submerges the clean formation porous medium, open the liquid outlet of the experimental chamber, and adjust the transport speed of the driving device and the outflow speed of the oil-water mixture to maintain that the oil-water mixture in the experimental chamber always submerges the clean formation porous medium. Step B5: After reaching the specified wax deposition duration, turn off the driving device, drain the oil-water mixture in the experimental chamber from the liquid outlet, take out the clean formation porous medium and weigh it, and then calculate the wax retention rate of the clean formation porous medium. Step B6: Replace the clean formation porous medium with different porosities or permeabilities, and repeat the above Steps B2 to B5. The wax removal experiment for the wax-deposited wellbore includes the following steps: Step C1: Inject the wax remover into the liquid storage device. Step C2: Weigh the mass of the wax-deposited wellbore, and then place the wax-deposited wellbore into the experimental chamber. Step C3: Adjust the pressure in the experimental chamber to the simulated formation pressure through the pressure adjustment module, and adjust the temperature in the experimental chamber to the specified temperature through the temperature control device. Step C4: First, turn on the driving device to transport the wax remover in the liquid storage device into 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 turn off the driving device. Step C5: After reaching the specified wax removal duration, drain the wax remover in the experimental chamber from the liquid outlet, take out the wax-deposited wellbore and weigh it, and calculate the wax removal rate of the wax-deposited wellbore. Step C6: Replace different wax removers, and repeat the above Steps C2 to C5 for the wax-deposited wellbores with the same initial conditions. The wax removal experiment for the wax-deposited formation porous medium includes the following steps: Step D1: Inject the wax remover into the liquid storage device. Step D2: Weigh the mass of the wax-deposited formation porous medium, wrap a layer of waterproof material around the side of the wax-deposited formation porous medium, and keep the two ends of the wax-deposited formation porous medium unwrapped and still in an open state to ensure that the wax remover can only freely flow in or out from these two ends, and then place the wax-deposited formation porous medium into the experimental chamber. Step D3: Adjust the pressure in the experimental chamber to the simulated formation pressure through the pressure adjustment module, and adjust the temperature in the experimental chamber to the specified temperature through the temperature control device. Step D4: First, turn on the driving device to deliver the paraffin remover in the liquid storage device to the experimental chamber, ensuring that the porous medium of the paraffin-deposited formation in the experimental chamber is immersed in the paraffin remover, and then turn off the driving device; Step D5: After reaching the specified paraffin removal duration, drain the paraffin remover in the experimental chamber from the liquid outlet, take out the porous medium of the paraffin-deposited formation and weigh it, and calculate the paraffin removal rate of the porous medium of the paraffin-deposited formation; Step D6: Replace the paraffin remover with different ones, and repeat the above steps D2 to D5 for the porous medium of the paraffin-deposited formation under the same initial conditions.

[0015] The present invention has achieved the following technical effects compared with the prior art: An experimental device and experimental method for dynamic paraffin deposition or removal. By replacing the clean wellbore with different cross-sectional areas or roughnesses and conducting paraffin deposition experiments on the clean wellbore, it is possible to understand the paraffin deposition situation of the wellbore under different cross-sectional areas, provide a basis for the selection of the wellbore diameter, understand the paraffin deposition law of the wellbore with different roughnesses, help select the wellbore material and determine the surface treatment method, and provide a basis for improving the paraffin resistance performance of the wellbore; by replacing the clean formation porous medium with different porosities and conducting paraffin deposition experiments on the clean formation porous medium, it is possible to understand the paraffin deposition situation of the clean formation porous medium under different porosities, and deeply understand the paraffin deposition law and influencing factors of the wellbore and the formation porous medium; by replacing different paraffin removers and conducting paraffin removal experiments on the paraffin-deposited wellbore under the same initial conditions and the paraffin-deposited formation porous medium under the same initial conditions, and comparing the paraffin removal effects, it provides a basis for selecting the most suitable paraffin remover. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Figure 1 It is a schematic structural diagram of an experimental device for dynamic paraffin deposition or removal.

[0018] 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 pool. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0020] The object of the present invention is to provide an experimental device and method for dynamic wax deposition or wax removal, so as to solve the problems existing in the above-mentioned prior art, be able to deeply understand the wax deposition law and influencing factors of the wellbore and formation porous media, evaluate the wax removal effect of different wax removers, optimize the oilfield exploitation process, improve the recovery rate and reduce the cost.

[0021] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Embodiment 1 This embodiment provides an experimental device for dynamic wax deposition or wax removal, as Figure 1As shown in the figure, it includes an experimental chamber 1, a displacement module, a controller 11, a pressure regulation 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 wax-deposited wellbore, or a wax-deposited 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 communicated with the liquid inlet of the experimental chamber 1, and the driving device is used to transport the substances in the liquid storage device 4 into the experimental chamber 1; the pressure regulation module is connected to the experimental chamber 1 and is used to regulate the pressure in the experimental chamber 1; the temperature control device is connected to the experimental chamber 1 and is used to regulate the temperature in the experimental chamber 1; both the pressure regulation module and the temperature control device are signal-connected to the controller 11; 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 into the central through hole of the clean wellbore, and the oil pumping device is used to pump out the oil-water mixture in the central through hole of the clean wellbore to simulate the actual working conditions of the oil-water mixture in the wellbore; during the wax removal experiment, a wax-deposited wellbore or a wax-deposited formation porous medium is placed in the experimental chamber 1, the liquid storage device 4 stores the wax remover, and the driving device is used to transport the wax remover into the central through hole of the wax-deposited wellbore. When a clean wellbore or a wax-deposited wellbore is placed in the experimental chamber 1, the driving device directly transports the substances in the liquid storage device 4 into the central through hole of the clean wellbore or the wax-deposited wellbore, which can more accurately control the experimental parameters and at the same time reduce the usage amount of the oil-water mixture in the experiment; by replacing the clean wellbore with different cross-sectional areas or roughnesses and conducting wax deposition experiments on the clean wellbore, it is possible to understand the wax deposition situation of the wellbore under different cross-sectional areas, provide a basis for the selection of the wellbore diameter, understand the wax deposition law of the wellbore with different roughnesses, help to select the wellbore material and determine the surface treatment method, and provide a basis for improving the anti-wax deposition performance of the wellbore; by replacing the clean formation porous medium with different porosities and conducting wax deposition experiments on the clean formation porous medium, it is possible to understand the wax deposition situation of the clean formation porous medium under different porosities and deeply understand the wax deposition law and influencing factors of the wellbore and the formation porous medium; by replacing different wax removers and conducting wax removal experiments on the wax-deposited wellbore with the same initial conditions and the wax-deposited formation porous medium with the same initial conditions and comparing the wax removal effects, it provides a basis for selecting the most suitable wax remover.

[0023] In a further preferred embodiment of the present embodiment, the displacement module further 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 inlet pipe of the peristaltic pump 5. The outlet pipe of the peristaltic pump 5 is connected and communicated with the inlet of the experimental chamber 1. The intermediate container includes three piston containers 3 connected in parallel, and the three piston containers 3 are respectively filled with oil, water and paraffin remover. When conducting the wax deposition experiment, the outlet valve of the piston container 3 filled with paraffin remover is closed, and the outlet valves of the piston containers 3 filled with oil and water are opened. By adjusting the opening degree of the outlet valve, the ratio of oil to water in the oil-water mixture is adjusted. 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 oil-water mixing. The oil and water are fully mixed in the liquid storage device 4. When conducting the paraffin removal experiment, the outlet valve of the piston container 3 filled with paraffin remover is opened, and the outlet valves of the piston containers 3 filled with oil and water are closed. The displacement pump 2 applies pressure to the paraffin remover, so that it overcomes the pressure in the container and the resistance of the pipeline and flows to the liquid storage device 4. The peristaltic pump 5 can accurately control the flow rate of the fluid, and the flow rate of the fluid output by the peristaltic pump 5 is relatively stable, which can improve the accuracy and reliability of the experiment.

[0024] In a further preferred embodiment of the present embodiment, when a clean wellbore is placed in the experimental chamber 1, the clean wellbore is hermetically connected to the bottom of the experimental chamber 1, and both the inlet and outlet are communicated with the central through hole of the clean wellbore; when a wax-deposited wellbore is placed in the experimental chamber 1, the wax-deposited wellbore is hermetically connected to the bottom of the experimental chamber 1, and both the inlet and outlet are communicated with the central through hole of the wax-deposited wellbore.

[0025] In a further preferred embodiment of the present embodiment, the pumping device includes a submersible pump and a sucker rod 6. The submersible pump is connected to the sucker rod 6, and the sucker rod 6 extends into the central through hole of the clean wellbore.

[0026] In a further preferred embodiment of the present embodiment, a waste liquid pool 12 is further included. The sucker rod 6 is connected and communicated with the waste liquid pool 12, and the outlet of the experimental chamber 1 is connected and communicated with the waste liquid pool 12.

[0027] In a further preferred embodiment of the present embodiment, the pressure regulation module includes a pressure sensor 7 and a high-pressure gas cylinder 8. The pressure sensor 7 is installed inside the experimental chamber 1, and the high-pressure gas cylinder 8 is communicated with the experimental chamber 1. During the 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 inside the experimental chamber 1 in real time, 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, and the gas in the high-pressure gas cylinder 8 flows into the experimental chamber 1 under the action of the pressure difference, so that the pressure inside the experimental chamber 1 gradually increases. When the pressure inside the experimental chamber 1 reaches the set value, the controller 11 closes the valve of the high-pressure gas cylinder 8.

[0028] In a further preferred embodiment of the present embodiment, the temperature control device includes a temperature sensor 9 and a heating device 10. The temperature sensor 9 is installed inside the experimental chamber 1, and the heating device 10 is connected to the experimental chamber 1. The temperature sensor 9 monitors the temperature value inside the experimental chamber 1 in real time, converts the text 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, so that the temperature inside the experimental chamber 1 gradually increases to reach the set value.

[0029] Embodiment 2 The present embodiment provides an experimental method for an experimental device for dynamic wax deposition or wax removal based on 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; 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 4; Step A2, weighing the mass of the clean wellbore, and then placing the clean wellbore into the experimental chamber 1; Step A3, adjusting the pressure inside the experimental chamber 1 to the simulated formation pressure through the pressure regulation module; Step A4, first turning on the driving device to transport the oil-water mixture in the liquid storage device 4 into the central through-hole of the clean wellbore. When the oil-water mixture in the clean wellbore reaches a certain height, then turn on the pumping device to pump out the oil-water mixture in the clean wellbore, and adjust the transport speed of the driving device and the pumping speed of the pumping device to maintain the submergence degree of the clean wellbore (that is, maintain the depth of the oil-water mixture in the clean wellbore); Step A5, after reaching the specified wax deposition duration, turn off the driving device and the pumping device, discharge the remaining oil-water mixture in the experimental chamber 1 from the liquid outlet, take out the clean wellbore and weigh it, and then calculate the wax mass per unit volume of the wellbore; Based on the inner wall roughness Ra of the wellbore, the inner diameter D of the wellbore, and the wax deposition mass m1 on the inner wall of the wellbore. Since the wax deposition mass m1 is related to the wax deposition volume V and the wax density ρ (i.e., m1 = ρV), and the wax deposition volume V can be approximately regarded as the product of the inner wall area of the tubing and the wax deposition thickness d (ignoring the complexity of the wax deposition shape). The inner wall area A of the tubing can be approximately equal to πDH. Further assume that the wax deposition is evenly distributed on the inner wall of the wellbore, and the direct influence of the wellbore roughness on the calculation of the wax deposition volume is ignored (i.e., assume that the wax deposition fills the smooth surface of the inner wall of the wellbore, and the roughness is only a factor affecting the initial attachment and growth rate of the wax deposition). Under this assumption, the wax deposition volume V can be more simply expressed as πDHL, where L is the length of the wellbore immersed in the oil-water mixture.

[0030] Combining the above assumptions, the following formula is obtained to approximately represent the relationship between the wax deposition thickness d, the inner diameter D of the tubing, the wax deposition mass m1, and the length L of the wellbore immersed in the oil-water mixture:

[0031] In practice, the wellbore roughness may affect the initial attachment and growth process of the wax deposition, but this usually needs to be determined through experiments to find out the degree of its influence. Therefore, a roughness-related coefficient k(Ra) can be introduced, which represents the increase or decrease in the wax deposition rate due to the roughness. In this way, a function can be approximately fitted to obtain the functional relationship among the inner wall roughness Ra of the wellbore, the inner diameter D of the wellbore, 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 inner wall of the wellbore:

[0032] In the formula, d: The wax deposition thickness on the inner wall of the tubing, mm; k(Ra): The attachment coefficient related to the wall roughness Ra; D: The inner diameter of the tubing, mm; L: The length of the tubing immersed in the oil-water mixture, mm; m1: The wax deposition mass on the inner wall of the tubing, g; ρ: The wax deposition density in the tubing, g / cm 3 ; From the wax deposition mass formula,

[0033] Combined with the definition of unit volume,

[0034] The formula for the mass of wax deposition per unit volume in the wellbore is derived as:

[0035] m vol : wax mass per unit volume of tubing (g / cm³); Step A6, replace the clean wellbore with different sizes or roughnesses and repeat the above Steps A2 to A5; by replacing the clean wellbore with different cross-sectional areas or roughnesses, conducting wax deposition experiments on multiple types of clean wellbores can quantitatively reveal the regulation mechanism of wellbore structure parameters on wax deposition dynamics, can optimize wax prevention measures targeted, provide a basis for improving the wax resistance performance of the wellbore, and thus improve the production efficiency and stability of the oil well.

[0036] The wax deposition experiment on the clean formation porous medium includes the following steps: Step B1, inject a certain proportion of oil-water mixture into the liquid storage device 4; Step B2, weigh the mass of the clean formation porous medium, and then place the clean formation porous medium into the experimental chamber 1; Step B3, adjust the pressure in the experimental chamber 1 to the simulated formation pressure through the pressure regulation module; Step B4, first turn on the driving device to transport the oil-water mixture in the liquid storage device 4 into the experimental chamber 1. When the oil-water mixture in the experimental chamber 1 submerges the clean formation porous medium, open the liquid outlet of the experimental chamber 1, and adjust the transport speed of the driving device and the outflow speed of the oil-water mixture to maintain the oil-water mixture in the experimental chamber 1 always submerging the clean formation porous medium; Step B5, after reaching the specified wax deposition duration, turn off the driving device, drain the oil-water mixture in the experimental chamber 1 from the liquid outlet, take out the clean formation porous medium and weigh it, and then calculate the wax retention rate of the clean formation porous medium; For porous media, the larger the porosity, it means there is more space in the porous medium to accommodate wax deposition. Therefore, under other unchanged conditions, the larger the porosity may lead to an increase in the wax deposition mass. Permeability is a physical quantity that measures the ease of fluid flow through a porous medium. The higher the permeability, the smoother the fluid flow in the porous medium. The influence of permeability on the wax deposition mass may not be direct, but it may affect the flow rate and path of the fluid in the porous medium, thereby affecting the deposition and distribution of wax. For example, areas with lower permeability may cause the fluid velocity to slow down, thus increasing the chance of wax deposition.

[0037] After determining the porosity and permeability of the clean formation porous medium, by adjusting different injection speeds of the oil-water mixture, observing the wax retention situation in the porous medium, the wax retention rate formula of the porous medium is obtained:

[0038] In the formula, R w:Wax retention rate (mass of wax deposited in a unit volume of porous medium per unit time, g / (m³·s)); D: Experimentally fitted constant (related to the composition, temperature, and pressure of the oil); φ: Porosity of the porous medium (dimensionless); S w : Wax saturation in the oil-water mixture (mass fraction); k: Permeability of the porous medium, md; v: Fluid flow velocity (m / s); v c : Critical erosion velocity (when v ≥ v c , the shear stress is sufficient to inhibit wax deposition); n: Velocity decay exponent; Step B6, Replace the clean formation porous medium with different porosities or permeabilities, and repeat the above Steps B2 to B5; The wax removal experiment for the waxed wellbore includes the following steps: Step C1, Inject the wax remover into the liquid storage device 4; Step C2, Weigh the waxed wellbore, and then place the waxed wellbore into the experimental chamber 1; Step C3, Adjust the pressure in the experimental chamber 1 to the simulated formation pressure through the pressure regulation module, and adjust the temperature in the experimental chamber 1 to the specified temperature through the temperature control device; Step C4, First, turn on the driving device to transport the wax remover in the liquid storage device 4 into the central through-hole of the waxed wellbore, ensure that the immersion position of the wax remover in the waxed wellbore is not lower than the previous immersion position of the oil-water mixture, and then turn off the driving device; Step C5, After reaching the specified wax removal duration, drain the wax remover in the experimental chamber 1 from the liquid outlet, take out the waxed wellbore and weigh it, and calculate the wax removal rate of the waxed wellbore; Step C6, Replace the different wax removers, and repeat the above Steps C2 to C5 for the waxed wellbore under the same initial conditions; The wax removal experiment for the waxed formation porous medium includes the following steps: Step D1, Inject the wax remover into the liquid storage device 4; Step D2, Weigh the waxed formation porous medium, wrap a layer of waterproof material on the side of the waxed formation porous medium to prevent the wax remover from entering or leaking out from the side of the waxed formation porous medium, while the two ends of the waxed formation porous medium are not wrapped and remain open, ensuring that the wax remover can only freely flow in or out from these two ends, and then place the waxed formation porous medium into the experimental chamber 1; Step D3: Adjust the pressure in the experimental chamber 1 to the simulated formation pressure through the pressure regulation module, and adjust the temperature in the experimental chamber 1 to the specified temperature through the temperature control device; Step D4: First, turn on the driving device to deliver the paraffin remover in the liquid storage device 4 to the experimental chamber 1, ensuring that the paraffin wax - formed formation porous medium is submerged in the paraffin remover in the experimental chamber 1, and then turn off the driving device; Step D5: After reaching the specified paraffin - removing duration, discharge the paraffin remover in the experimental chamber 1 from the liquid outlet, take out the paraffin wax - formed formation porous medium and weigh it, and calculate the paraffin - removing rate of the paraffin wax - formed formation porous medium; Step D6: Replace the different paraffin removers, and repeat the above steps D2 to D5 for the paraffin wax - formed formation porous media with the same initial conditions.

[0039] Observe the paraffin - removing rate of the paraffin remover based on the mass change of the paraffin - waxed sample. In addition, multiple rounds of paraffin - removing experiments can be carried out to observe the relationship between the paraffin - removing rate and the number of paraffin - removing rounds.

[0040]

[0041] In the formula, Z: Paraffin - removing rate; m2: Mass of paraffin wax, g; m3: Mass after paraffin removal, g.

[0042] By evaluating the paraffin - removing effects and performances of different paraffin removers, it provides a basis for selecting the most suitable paraffin remover in practical applications.

[0043] In the present invention, specific examples are used to elaborate on the principle and implementation mode of the present invention. The description of the above - mentioned embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An experimental device for dynamic wax deposition or wax removal, characterized in that: It includes an experimental chamber, a displacement module, a controller, a pressure regulation module, a temperature control device, and an oil pumping device; the experimental chamber includes a liquid inlet and a liquid outlet, and a clean wellbore, clean formation porous medium, wax-deposited wellbore, or wax-deposited formation porous medium is placed in the experimental chamber; the displacement module includes a liquid storage device and a driving device, the liquid storage device is used to store the oil-water mixture or the wax remover, the liquid storage device is communicated with 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 regulation module is connected to the experimental chamber and is used to regulate the pressure in the experimental chamber; the temperature control device is connected to the experimental chamber and is used to regulate the temperature in the experimental chamber; both the pressure regulation module and the temperature control device are signal-connected to the controller; 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 into the central through-hole of the clean wellbore, and the oil pumping device is used to pump out the oil-water mixture in the central through-hole of the clean wellbore; during the wax removal experiment, a wax-deposited wellbore or a wax-deposited 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 into the central through-hole of the wax-deposited wellbore.

2. The experimental device for dynamic wax deposition or wax removal according to claim 1, characterized in that: The displacement module further 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 inlet pipe of the peristaltic pump, the 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 experimental device for dynamic wax deposition or wax removal according to claim 1, characterized in that: When a clean wellbore is placed in the experimental chamber, the clean wellbore is hermetically connected to the bottom of the experimental chamber, and both the liquid inlet and the liquid outlet are communicated with the central through-hole of the clean wellbore; when a wax-deposited wellbore is placed in the experimental chamber, the wax-deposited wellbore is hermetically connected to the bottom of the experimental chamber, and both the liquid inlet and the liquid outlet are communicated with the central through-hole of the wax-deposited wellbore.

4. The experimental device for dynamic wax deposition or wax removal according to claim 1, characterized in that: The oil pumping device includes an oil pump and a sucker rod, the oil pump is connected to the sucker rod, and the sucker rod extends into the central through-hole of the clean wellbore.

5. The experimental device for dynamic wax deposition or wax removal according to claim 4, characterized in that: It further 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.

6. The experimental device for dynamic wax deposition or wax removal according to claim 1, characterized in that: The pressure regulation 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.

7. The experimental device for dynamic wax deposition or wax removal 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.

8. An experimental method based on the experimental device for dynamic wax deposition or wax removal according to any one of claims 1-7, characterized in that: It includes a clean wellbore wax deposition experiment, a clean formation porous medium wax deposition experiment, a wax-deposited wellbore wax removal experiment, and a wax-deposited formation porous medium wax removal experiment; The clean wellbore wax deposition experiment includes the following steps: Step A1, injecting an oil-water mixture in a certain proportion into the liquid storage device; Step A2, weigh the quality of the clean wellbore, and then place the clean wellbore into the experimental chamber; Step A3, adjust the pressure in the experimental chamber to the simulated formation pressure through the pressure adjustment module; Step A4, first turn on the driving device to transport the oil-water mixture in the liquid storage device into the central through-hole of the clean wellbore. When the oil-water mixture in the clean wellbore reaches a certain height, then turn on the pumping device to pump out the oil-water mixture in the clean wellbore, and adjust the conveying speed of the driving device and the pumping speed of the pumping device to maintain the immersion depth of the clean wellbore; Step A5, after reaching the specified wax deposition duration, turn off the driving device and the pumping device, discharge the remaining oil-water mixture in the experimental chamber from the liquid outlet, take out the clean wellbore and weigh it, and then calculate the wax mass per unit volume of the wellbore; Step A6, replace the clean wellbore with different sizes or different roughnesses, and repeat the above steps A2 to A5; The wax deposition experiment on the clean formation porous medium includes the following steps: Step B1, inject a certain proportion of oil-water mixture into the liquid storage device; Step B2, weigh the quality of the clean formation porous medium, and then place the clean formation porous medium into the experimental chamber; Step B3, adjust the pressure in the experimental chamber to the simulated formation pressure through the pressure adjustment module; Step B4, first turn on the driving device to transport 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 formation porous medium, open the liquid outlet of the experimental chamber, and adjust the conveying speed of the driving device and the outflow speed of the oil-water mixture to maintain that the oil-water mixture in the experimental chamber always submerges the clean formation porous medium; Step B5, after reaching the specified wax deposition duration, turn off the driving device, discharge the oil-water mixture in the experimental chamber from the liquid outlet, take out the clean formation porous medium and weigh it, and then calculate the wax retention rate of the clean formation porous medium; Step B6, replace the clean formation porous medium with different porosities or different permeabilities, and repeat the above steps B2 to B5; The wax removal experiment on the wax-deposited wellbore includes the following steps: Step C1, inject the wax remover into the liquid storage device; Step C2, weigh the quality of the wax-deposited wellbore, and then place the wax-deposited wellbore into the experimental chamber; Step C3, adjust the pressure in the experimental chamber to the simulated formation pressure through the pressure adjustment module, and adjust the temperature in the experimental chamber to the specified temperature through the temperature control device; Step C4, first turn on the driving device to transport the wax remover in the liquid storage device into 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 turn off the driving device; Step C5, after reaching the specified wax removal duration, discharge the wax remover in the experimental chamber from the liquid outlet, take out the wax-deposited wellbore and weigh it, and calculate the wax removal rate of the wax-deposited wellbore; Step C6, replace different wax removers, and repeat the above steps C2 to C5 for the wax-deposited wellbore with the same initial conditions; The wax removal experiment on the wax-deposited formation porous medium includes the following steps: Step D1: Inject the paraffin remover into the liquid storage device; Step D2: Weigh the mass of the porous medium of the paraffin - waxed formation. Wrap a waterproof material around the sides of the porous medium of the paraffin - waxed formation, while leaving the two ends of the porous medium of the paraffin - waxed formation unwrapped and still in an open state, ensuring that the paraffin remover can only freely flow in or out from these two ends. Then place the porous medium of the paraffin - waxed formation into the experimental chamber; Step D3: Adjust the pressure in the experimental chamber to the simulated formation pressure through the pressure - regulating module, and adjust the temperature in the experimental chamber to the specified temperature through the temperature - control device; Step D4: First, turn on the driving device to transport the paraffin remover in the liquid storage device to the experimental chamber, ensuring that the paraffin remover in the experimental chamber submerges the porous medium of the paraffin - waxed formation, and then turn off the driving device; Step D5: After reaching the specified paraffin - removal duration, drain the paraffin remover in the experimental chamber from the liquid outlet, take out the porous medium of the paraffin - waxed formation and weigh it, and calculate the paraffin - removal rate of the porous medium of the paraffin - waxed formation; Step D6: Replace the paraffin remover with a different one, and repeat steps D2 to D5 for the porous medium of the paraffin - waxed formation under the same initial conditions.

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