Electric submersible screw pump well paraffin removal and viscosity reduction method, device and electric submersible screw pump oil production system

Abstract

The application belongs to the field of oil and gas field development, and specifically discloses an electric submersible screw pump well paraffin removal and viscosity reduction method, device and submersible screw pump oil production system. The method comprises the following steps: identifying an oil well production stage based on oil well production data, wherein the oil well production stage comprises a wellbore liquid discharge stage, a formation liquid discharge start-up stage and a formation stable liquid production stage; and for different oil well production stages, different electric heating control strategies are adopted to control the electric heating device in the oil well to achieve electric submersible screw pump well paraffin removal and viscosity reduction. The scheme of the application identifies the oil well production stage based on the oil well production data, and then intelligently controls the electric heating according to the stage, realizes the linkage control of the electric heating and the electric submersible screw pump well production parameters, achieves the intelligent paraffin removal and viscosity reduction of the electric submersible screw pump well, maximizes the oil well production potential, and maximally reduces the electric heating energy consumption of the wellbore, thereby saving the production cost.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development, specifically relating to a method for dewaxing and reducing viscosity in an electric submersible screw pump well, a device for dewaxing and reducing viscosity in an electric submersible screw pump well, and an oil production system for an electric submersible screw pump. Background Technology

[0002] In recent years, electric submersible screw pump (EMS) oil production technology has been widely used due to its advantages such as stable operation, simple structure, and safety and reliability. Its downhole unit can be directly lowered into the well via tubing connection and uses a rodless lifting method, achieving good results, especially in some low-volume, highly deviated heavy oil wells and wax-laden wells. EMS oil production technology not only effectively solves the problem of rod wear in the application of rod pumps in highly deviated oil wells, but also allows for the configuration of different models (ZLQYDB-114-380-6 / 20, ZLQYDB-114-380-13 / 26, ZLQYDB-114-380-32 / 22) according to the oil well's fluid volume requirements, meeting the needs of oilfield development and possessing high application value.

[0003] During on-site implementation, existing related technologies have at least the following problems: (1) Although the electric submersible screw pump rodless lifting system can effectively avoid the energy loss caused by the sucker rod during transmission and fundamentally eliminate the negative effects caused by sucker rod wear and breakage, it cannot achieve some commonly used wax removal methods for wax-contaminated wells (such as the patent: "Sucker Rod Wax Removal and Straightening Anti-Loosening Device", authorized announcement number: CN202990970 U, which uses the sucker rod to drive the wax remover to remove wax deposits on the pipe wall). The wax removal method can only use manual mechanical wax scraping, which is time-consuming, labor-intensive, ineffective, short-cycle, and has a low degree of wax removal.

[0004] (2) For low-volume heavy oil wells, the rodless lifting system cannot use the existing technology (such as patent: Hollow sucker rod electric heating device and oil production equipment, authorization announcement number: CN 209354100 U) to heat the wellbore by means of a hollow sucker rod electric heating device to solve the problem of easy blockage of crude oil channels in the wellbore because there is no electric heating rod in the wellbore.

[0005] (3) The defects of the traditional electric heating rod heating control system result in high energy consumption during the heating process, which increases the operating cost of the oil field.

[0006] Therefore, in the process of lifting wax-producing wells and low-volume heavy oil wells, the electric submersible screw pump rodless lifting system can easily cause high energy consumption of the downhole unit, poor wax removal and viscosity reduction effect, and even cause the well to shut down and be unable to lift normally. Summary of the Invention

[0007] The purpose of this invention is to provide a method for dewaxing and reducing viscosity in an electric submersible screw pump well, an electric submersible screw pump well dewaxing and viscosity-reducing device, and an electric submersible screw pump oil production system, aiming to solve at least one of the problems existing in the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: According to a first aspect of the present invention, a method for dewaxing and reducing viscosity in an electric submersible screw pump well is provided, comprising the following steps: Based on oil well production data, the oil well production stages are identified, including: wellbore fluid discharge stage, formation initiation fluid production stage, and formation stable fluid production stage. Different electric heating control strategies are adopted for different oil well production stages to control the electric heating device located in the oil well in order to achieve dewaxing and viscosity reduction in electric submersible screw pump wells.

[0009] In one possible implementation, the well production data includes: water cut of the produced fluid, downhole temperature of the electric submersible screw pump, production current of the electric submersible screw pump, and wellhead oil pressure.

[0010] In one possible implementation, the well production stage is identified based on well production data, including: When the water content of the produced fluid is 100%, the downhole temperature of the electric submersible screw pump is stable, the production current of the electric submersible screw pump is stable, and the wellhead oil pressure is stable, the oil well production stage is identified as the wellbore drainage stage. When the water content of the produced fluid is less than 100% but greater than the water content during normal production, the downhole temperature of the electric submersible screw pump gradually increases, the production current of the electric submersible screw pump gradually increases, and the wellhead oil pressure shows an upward trend, the oil well production stage is identified as the formation initiation and fluid production stage. When the water content of the produced fluid is close to that during normal production, the downhole temperature of the electric submersible screw pump rises and stabilizes, the production current of the electric submersible screw pump gradually increases, and the wellhead oil pressure rises, the oil well production stage is identified as the formation stable production stage.

[0011] In one possible implementation, the criterion for determining the downhole temperature stability of the electric submersible screw pump is that the downhole temperature of the electric submersible screw pump varies within the range of 0~3℃. In one possible implementation, the criterion for determining the stability of the production current of the electric submersible screw pump is that the variation range of the production current of the electric submersible screw pump is between 0-3A. In one possible implementation, the criterion for determining the stability of the wellhead oil pressure is that the variation range of the wellhead oil pressure is between 0 and 0.3 MPa.

[0012] In one possible implementation, the criterion for determining that the wellhead oil pressure is increasing is: the wellhead oil pressure increases by more than 0.3 MPa compared to the normal value.

[0013] In one possible implementation, the criterion for determining that the water content of the produced liquid is close to the water content during normal production is that the water content of the produced liquid is within ±2% of the water content during normal production.

[0014] In one possible implementation, the criteria for determining the stability of the downhole temperature rise of the electric submersible screw pump are: the downhole temperature rises by more than 3°C compared to the normal value, the production current drops by more than 3A compared to the normal value, and the wellhead oil pressure drops by more than 0.3 MPa compared to the highest value.

[0015] In one possible implementation, different electric heating control strategies are employed to control the electric heating device located in the well for different oil well production stages, in order to achieve dewaxing and viscosity reduction in electric submersible screw pump wells, including: When the oil well production stage is identified as the wellbore drainage stage, the electric heating device is controlled to stop operating. When the oil well production stage is identified as the formation initiation and fluid production stage, the electric heating device is controlled to operate in preheating mode. When the oil well production stage is identified as the formation's stable fluid production stage, the electric heating device is controlled to operate in an on-demand heating mode. In the preheating operation mode, the electric heating device operates at a frequency and power lower than the normal operating frequency and power. In the on-demand heating operation mode, the electric heating device is controlled according to the current of the electric submersible screw pump downhole unit.

[0016] In one possible implementation, in the on-demand heating operation mode, the electric heating device is controlled according to the current of the electric submersible screw pump downhole unit, including: When the current of the electric submersible screw pump downhole unit reaches the preset upper current limit, the electric heating device is controlled to start and operate at a frequency and power higher than the normal operating frequency and power. As the current of the electric submersible screw pump downhole unit changes, the electric heating frequency of the electric heating device is dynamically adjusted until the current of the electric submersible screw pump downhole unit drops to the preset lower current limit. When the current of the electric submersible screw pump downhole unit reaches the preset lower current limit, the electric heating device is controlled to stop operating.

[0017] In one possible implementation, as the current of the electric submersible screw pump downhole unit changes, the electric heating frequency of the electric heating device is dynamically adjusted until the current of the electric submersible screw pump downhole unit drops to a preset lower current limit, including: As the current of the electric submersible screw pump downhole unit increases, the electric heating frequency is increased until the current of the electric submersible screw pump downhole unit reaches its maximum value; As the current of the electric submersible screw pump downhole unit decreases, the electric heating frequency reduction process is executed until the current of the electric submersible screw pump downhole unit drops to the preset lower current limit.

[0018] In one possible implementation, the process of increasing the electric heating frequency is an alternating process of increasing the electric heating frequency by a first amount and decreasing the electric heating frequency by a second amount, wherein the first amount is greater than the second amount.

[0019] In one possible implementation, the process of decreasing the electric heating frequency is an alternating process of decreasing the electric heating frequency by a third amount and increasing the electric heating frequency by a fourth amount, wherein the third amount is greater than the fourth amount.

[0020] According to a second aspect of the present invention, an electric submersible screw pump well dewaxing and viscosity-reducing device is provided, comprising: Electric heating device located inside the oil well; An electric heating control system connected to and used to control the electric heating device, the electric heating control system being configured to perform the method described in the first aspect of the present invention.

[0021] In one possible implementation, the electric heating device is configured as an electric heating rod inserted into the oil pipe.

[0022] In one possible implementation, the electric heating rod includes a hollow cavity, a first power supply cable extends within the hollow cavity and is connected to the bottom end of the electric heating rod, the first power supply cable forms a current loop with a second power supply cable via the electric heating rod to electrically heat the oil well, one of the first power supply cable and the second power supply cable is connected to the neutral wire of the power supply device, and the other is connected to the live wire of the power supply device.

[0023] In one possible implementation, the electric heating rod is formed by connecting multiple hollow rods in sequence. In one possible implementation, the electric submersible screw pump well dewaxing and viscosity-reducing device further includes: A sealing support structure for supporting the electric heating rod within the oil pipe, the sealing support structure comprising: The main body is used for fixing and sealing with the wellhead device; A hollow rod portion is disposed at the interior center of the main body, and the hollow rod portion is connected to the electric heating rod. The main body and the hollow rod are integrally formed.

[0024] In one possible implementation, the electric submersible screw pump well dewaxing and viscosity-reducing device further includes: An electric heating rod plug is provided to seal the hollow cavity of the electric heating rod, and the second power supply cable is connected to the electric heating rod plug. A hollow electric heating rod tee device includes an upper connecting end, a lower connecting end, and a lateral channel. The upper connecting end is connected to the plug of the electric heating rod, and the lower connecting end is connected to the hollow rod part of the sealed support structure. The first power supply cable enters the hollow cavity of the electric heating rod through the lateral channel.

[0025] In one possible implementation, the electric heating control system is communicatively connected to a water content analyzer used to detect the water content of the wellbore produced fluid, and receives water content data of the produced fluid from it.

[0026] In one possible implementation, the electric heating control system is communicatively connected to a temperature detection device for detecting the downhole temperature of the electric submersible screw pump, and receives downhole temperature data of the electric submersible screw pump from it.

[0027] In one possible implementation, the electric heating control system is communicatively connected to a current detection device for detecting the production current of the electric submersible screw pump, and receives the production current data of the electric submersible screw pump from it.

[0028] In one possible implementation, the electric heating control system is communicatively connected to a wellhead oil pressure detection device for detecting wellhead oil pressure, and receives wellhead oil pressure data from it.

[0029] In one possible implementation, the electric heating control system is communicatively connected to the submersible screw pump control system, receiving downhole temperature data and production current data of the electric submersible screw pump from it.

[0030] According to a third aspect of the present invention, an electric submersible screw pump oil production system is provided, comprising: Oil tubing fixed by wellhead equipment; An electric submersible screw pump downhole unit, wherein the electric submersible screw pump downhole unit is connected to the lower end of the tubing; The electric submersible screw pump well dewaxing and viscosity reducing device of the second aspect of the present invention is wherein the electric heating device of the electric submersible screw pump well dewaxing and viscosity reducing device is inserted into the oil pipe and sealed and fixed with the wellhead device; An electric submersible screw pump control cabinet installed on the ground, the electric submersible screw pump control cabinet being used to control the operation of the electric submersible screw pump; An electric heating control cabinet is installed on the ground, and the electric heating control system of the electric submersible screw pump well dewaxing and viscosity reducing device is installed in the electric heating control cabinet.

[0031] In one possible implementation, the electric submersible screw pump control cabinet includes an electric submersible screw pump control system and a production parameter display system.

[0032] In one possible implementation, the electric heating control cabinet includes the electric heating control system and the electric heating parameter display system.

[0033] By adopting the above technical solution, the present invention has at least the following beneficial technical effects: The solution of this invention identifies the production stage of an oil well based on oil well production data, and then intelligently controls the electric heating according to the stage. This achieves the linkage control of electric heating and production parameters of the electric submersible screw pump well, realizing the purpose of intelligent wax removal and viscosity reduction in the electric submersible screw pump well. While maximizing the production potential of the oil well, it also minimizes the energy consumption of wellbore electric heating, thereby saving production costs. Attached Figure Description

[0034] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0035] Figure 1 A flowchart of the method for dewaxing and reducing viscosity in an electric submersible screw pump well provided by the present invention; Figure 2 A schematic block diagram of the electric submersible screw pump well dewaxing and viscosity-reducing device provided by the present invention; Figure 3 A schematic diagram of an electric submersible screw pump oil production system provided by the present invention; Figure 4 A schematic diagram showing the sealing and fixing of the electric heating rod to the wellhead device; Figure 5 This is a schematic diagram of a sealing support device used in one embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. These embodiments are provided in this disclosure to make the disclosure thorough and complete, and to fully express the scope of the disclosure to those skilled in the art.

[0037] It should be noted that, in the description of this disclosure, unless otherwise stated, the expressions "multiple," "multiple items," "various types," etc., mean more than or equal to two, two items, or two kinds. In the description of this disclosure, words such as "including" or "containing" mean that the element preceding the word covers the element listed after the word, and do not exclude the possibility of covering other elements as well.

[0038] All terms used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0039] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0040] According to a first aspect of the present invention, a method for dewaxing and reducing viscosity in an electric submersible screw pump well is provided, such as... Figure 1 As shown, the method includes the following steps: S1: Identify the oil well production stage based on oil well production data; S2: For different oil well production stages, adopt different electric heating control strategies to control the electric heating device located in the oil well to electrically heat the oil well to achieve dewaxing and viscosity reduction of the electric submersible screw pump well.

[0041] The solution of this invention identifies the production stage of an oil well based on oil well production data, and then controls the electric heating according to the stage. This achieves the linkage control of electric heating and production parameters of electric submersible screw pump wells, realizing the purpose of intelligent wax removal and viscosity reduction in electric submersible screw pump wells. While maximizing the production potential of oil wells, it also minimizes the energy consumption of wellbore electric heating, thereby saving production costs.

[0042] In one possible implementation, the oil well production stages include: the wellbore drainage stage, the formation initiation and production stage, and the formation stable production stage. The system can intelligently identify which production stage the well is currently in by comparing production parameters. Different intelligent heating control methods are used in different stages to achieve optimized and energy-efficient production operation. The wellbore drainage stage primarily removes fluids lost to the formation or remaining in the wellbore during well workover operations, such as well washing and sand flushing. The formation initiation and production stage mainly involves draining most of the residual fluids lost to the formation or remaining in the wellbore during well workover operations. After this, the formation gradually begins to produce fluids, with the oil-water mixture from the reservoir and the residual fluids entering the tubing for production. The formation stable production stage refers to the stable production stage after the residual fluids have been drained. At this point, the formation fluid production is stable, and the water cut reaches the level before the well workover operation.

[0043] In one possible implementation, oil well production data includes: water cut of produced fluid, downhole temperature of the electric submersible pump, production current of the electric submersible pump, and wellhead oil pressure. Based on this oil well production data, the oil well production stage can be autonomously identified.

[0044] In one possible implementation, step S1 involves identifying the well production stage based on well production data, including: when the produced fluid water cut is 100%, the downhole temperature of the electric submersible pump is stable, the production current of the electric submersible pump is stable, and the wellhead oil pressure is stable, the well production stage is identified as the wellbore drainage stage. The criteria for determining stable downhole temperature of the electric submersible pump are: the downhole temperature variation range is between 0 and 3°C; the criteria for determining stable production current of the electric submersible pump are: the production current variation range is between 0 and 3A; and the criteria for determining stable wellhead oil pressure are: the wellhead oil pressure variation range is between 0 and 0.3 MPa.

[0045] In one possible implementation, in step S1, based on oil well production data, the oil well production stage is identified, including: when the water cut of the produced fluid is less than 100% but greater than the water cut during normal production, the downhole temperature of the electric submersible pump gradually increases, the production current of the electric submersible pump gradually increases, and the wellhead oil pressure shows an upward trend, the oil well production stage is identified as the formation initiation fluid production stage. The criterion for determining an upward trend in wellhead oil pressure is: the wellhead oil pressure continuously increases by more than 0.3 MPa compared to the normal value.

[0046] In one possible implementation, step S1 involves identifying the oil well production stage based on well production data. This stage includes: when the produced fluid water cut is close to the normal production water cut, the downhole temperature of the electric submersible pump stabilizes, the production current of the electric submersible pump gradually increases, and the wellhead oil pressure rises, the oil well production stage is identified as a stable formation fluid production stage. The criteria for determining that the produced fluid water cut is close to the normal production water cut are: the produced fluid water cut is within ±2% of the normal production water cut; the criteria for determining that the downhole temperature of the electric submersible pump stabilizes are: the downhole temperature increases by more than 3°C compared to the normal value, the production current decreases by more than 3A compared to the normal value, and the wellhead oil pressure continuously decreases by more than 0.3 MPa compared to the highest value.

[0047] In one possible implementation, in step S2, different electric heating control strategies are employed to control the electric heating device located in the oil well for different oil well production stages to achieve wax removal and viscosity reduction in the electric submersible screw pump well. This includes: when the oil well production stage is identified as the wellbore drainage stage, the electric heating device is controlled to stop operating. Since the wellbore during the drainage stage is filled with 100% water-containing wastewater, wax deposition will not occur in the wellbore during this stage, and it will also not cause excessive current in the downhole unit of the electric submersible screw pump, leading to well shutdown. Therefore, the electric heating control at this stage is: stop operation.

[0048] In one possible implementation, in step S2, different electric heating control strategies are used to control the electric heating device located in the well for different oil well production stages to achieve dewaxing and viscosity reduction in the electric submersible pump well. This includes: when the oil well production stage is identified as the formation initiation and fluid production stage, the electric heating device is controlled to operate in a preheating mode. In the preheating mode, the electric heating device operates at a frequency and power lower than the normal operating frequency and power. During the formation initiation and fluid production stage, because the formation has begun producing fluid but has not yet reached normal production levels, the water cut is still relatively high, the oil production is still relatively low, wax deposition in the wellbore is just beginning and not abundant, and the viscosity of the produced fluid is not high, so it will not cause excessive current in the electric submersible pump downhole unit, leading to well shutdown. However, preheating preparation is needed at this stage to gradually establish a temperature field for the wellbore fluid, laying the foundation for the subsequent stable formation fluid production stage. Therefore, the electric heating control at this stage is a low-frequency, low-power preheating operation mode.

[0049] In one possible implementation, in step S2, different electric heating control strategies are employed to control the electric heating device located in the well for different well production stages to achieve wax removal and viscosity reduction in the electric submersible pump well. This includes: when the well production stage is identified as a stable formation fluid production stage, the electric heating device is controlled to operate in an on-demand heating mode. In the on-demand heating mode, the electric heating device is controlled based on the current of the electric submersible pump downhole unit. During the stable formation fluid production stage, due to normal well production, wax begins to form in the wellbore, and the viscosity of the produced fluid also increases. This stage is the main stage of the intelligent heating control method. Entering this normal production stage, the intelligent heating control method mainly relies on the current of the electric submersible pump downhole unit for control.

[0050] In one possible implementation, in step S2, under the on-demand heating operation mode, the electric heating device is controlled according to the current of the electric submersible screw pump downhole unit, including: presetting an upper limit and a lower limit for the current of the electric submersible screw pump downhole unit, which is used to control the start and stop of the electric heating to achieve the purpose of on-demand heating.

[0051] In one possible implementation, when the current of the electric submersible screw pump downhole unit reaches a preset upper current limit, the electric heating device is started and controlled to operate at a frequency and power higher than the normal operating frequency and power. As the current of the electric submersible screw pump downhole unit changes, the electric heating frequency of the electric heating device is dynamically adjusted until the current of the electric submersible screw pump downhole unit drops to a preset lower current limit. When the current of the electric submersible screw pump downhole unit reaches the preset lower current limit, the electric heating device is stopped.

[0052] In one possible implementation, as the current of the electric submersible screw pump downhole unit changes, the electric heating frequency of the electric heating device is dynamically adjusted until the current of the electric submersible screw pump downhole unit drops to a preset lower current limit. This includes: as the current of the electric submersible screw pump downhole unit increases, the electric heating frequency is increased until the current of the electric submersible screw pump downhole unit rises to its maximum value; as the current of the electric submersible screw pump downhole unit decreases, the electric heating frequency is decreased until the current of the electric submersible screw pump downhole unit drops to the preset lower current limit. This setting helps to achieve stepless automatic adjustment of the electric heating and on-demand heating.

[0053] Specifically, when the current of the electric submersible screw pump downhole unit reaches the preset upper current limit, the electric heating is activated, operating at high frequency and high power. During this process, as the electric heating just starts, the wellbore temperature gradually rises, the wax deposits inside the wellbore gradually dissolve, and the crude oil viscosity gradually decreases. However, the current of the electric submersible screw pump downhole unit will still slowly increase. Although the electric heating power is operating at high frequency and high power, as the current slowly increases, the electric heating is controlled to increase its frequency until it reaches a maximum value. As the wax deposits inside the wellbore gradually dissolve and the crude oil viscosity gradually decreases, the current of the electric submersible screw pump downhole unit will gradually decrease after reaching its maximum value. When the current of the electric submersible screw pump downhole unit is detected to be decreasing during operation, most of the wax deposits in the wellbore have dissolved, and the crude oil viscosity can still ensure normal oil well production. At this time, the electric heating is controlled to decrease its frequency. Since the electric heating is still running, the current of the submersible screw pump downhole unit will continue to decrease. When the current of the electric submersible screw pump downhole unit drops to the preset lower current limit, the system detects during operation that the current value of the electric submersible screw pump downhole unit is lower than the preset lower current limit and controls the electric heating to stop operating.

[0054] In one possible implementation, the process of increasing the electric heating frequency is an alternating process of increasing the electric heating frequency by a first amount and decreasing it by a second amount, where the first amount is greater than the second amount. Specifically, as the current of the electric submersible screw pump downhole unit increases, the electric heating operating frequency also gradually increases. However, this increase is not continuous; instead, it increases by a certain value and then decreases by a certain value, with the increase being greater than the decrease, and this process repeats. This alternating process of increasing the electric heating frequency, rather than continuously increasing the frequency, aims to avoid overheating the wellbore and wasting energy due to a continuous increase in the electric heating frequency. In another possible implementation, the process of decreasing the electric heating frequency is an alternating process of decreasing the electric heating frequency by a third amount and increasing it by a fourth amount, where the third amount is greater than the fourth amount. Specifically, as the current of the electric submersible screw pump downhole unit decreases, the electric heating operating frequency also gradually decreases. However, this decrease is not continuous; instead, it decreases by a certain amount and then increases by a certain value, with the decrease being greater than the increase, and this process repeats. The electric heating frequency is gradually reduced, rather than continuously, to avoid insufficient heating at the bottom of the well, which could prevent normal production. In summary, this invention utilizes intelligent wellbore heating to reduce the flow resistance during heavy oil lifting while maintaining wellbore temperature. This prevents wax crystal precipitation of formation fluid during lifting, achieving the most economical lifting process while ensuring normal oil well production. This invention solves the problems of establishing a temperature field for the wellbore fluid in rodless lifting technologies and the short pump inspection cycle caused by rod wear in rod-type lifting technologies. It provides a tubing heating technology for wax-contaminated heavy oil wells using electric submersible screw pumps, addressing the issue of uniform heating of formation fluids throughout the entire process, thus preventing wax formation in the produced fluid due to wellbore temperature field loss and subsequent well shutdown. The present invention addresses the problem of wax buildup in wax-producing wells during the lifting process, which suffers from limited solutions, time-consuming and labor-intensive manual wax removal, short-term effects, and low wax removal efficiency. By applying an electric submersible screw pump with electric heating technology, manual mechanical wax removal is no longer required, reducing labor intensity, increasing well production rate and single-well productivity, and reducing the frequency and cost of well workover operations.

[0055] According to a second aspect of the present invention, an electric submersible screw pump well dewaxing and viscosity-reducing device is provided, such as... Figure 2 As shown, the device includes: an electric heating device 10 located within an oil well; and an electric heating control system 20 connected to and used for controlling the electric heating device 10, the electric heating control system 20 being configured to perform the method described in the first aspect of the present invention. The method described in the first aspect of the present invention can be implemented as a computer program executed by a processor, which, when executed by the processor, performs the functions defined in the method described in the first aspect of the present invention.

[0056] In one possible implementation, such as Figures 3-4 As shown, the electric heating device 10 is configured as an electric heating rod inserted into the oil pipe 2. The electric heating rod includes a hollow cavity, and a first power supply cable 17 extends within the hollow cavity and is connected to the bottom end of the electric heating rod. The first power supply cable 17 and a second power supply cable 16 form a current loop via the electric heating rod to electrically heat the oil well. For example, the first power supply cable 17, the second power supply cable 16, and the electric heating rod form a current loop, constituting a skin effect heating element to electrically heat the oil well. The ferromagnetic material of the electric heating rod determines that current flows only on its inner surface; there is no voltage or current on the outer surface, only leakage current and leakage voltage. The leakage voltage is only tens of millivolts, and the leakage current is only tens of milliamperes, which is very safe for production. One of the first power supply cable 17 and the second power supply cable 16 is connected to the neutral wire of the power supply device, and the other is connected to the live wire of the power supply device. For example, in the illustrated embodiment, the first power supply cable 17 is connected to the live wire of the power supply device, and the second power supply cable 16 is connected to the neutral wire of the power supply device.

[0057] In one possible implementation, such as Figures 3-4 As shown, the electric heating rod is formed by connecting multiple hollow rods sequentially. This helps to improve the overall strength of the electric heating rod. In the illustrated embodiment, the electric heating rod includes a main rod portion 4 and a rod portion 3 with a return loop connected below the main rod portion 4. The rod portion 3 with the return loop contacts the exposed connecting wire at the end of the first power supply cable 17. The first power supply cable 17 passes through the interior of the main rod portion 4 to reach the rod portion 3 with the return loop, and then forms a current loop with the second power supply cable 16 through the main rod portion 4, realizing the conversion of electrical energy into heat energy to heat the formation fluid produced in the wellbore. The main rod portion 4 serves both a connecting function and the function of converting electrical energy into heat energy.

[0058] In one possible implementation, such as Figures 3-5As shown, the electric submersible screw pump well dewaxing and viscosity-reducing device also includes a sealing support structure 8 for supporting the electric heating rod within the tubing 2. The sealing support structure 8 includes a main body 81 and a hollow rod portion 82 located at the internal center of the main body 81. The main body 81 is used for fixed sealing with the wellhead device 5. For example, the main body 81 has the same function and role as a commonly used slip coupling, and can be fixed and sealed with the small four-way connector at the top of the wellhead device 5 through matching slips, thereby achieving a seal with the wellhead device 5. The hollow rod portion 82 is connected and fixed to the electric heating rod (specifically, the main rod portion 4). For example, the hollow rod portion 82 is configured as a hollow cylindrical rod adapted to the main rod portion 4, and the two are threaded together. Preferably, the main body 81 and the hollow rod portion 82 are integrally formed, that is, they are machined as a single unit. The sealing support structure 8 provided in this application has two functions: sealing and bearing pressure. The sealing between the main body 81 and the wellhead device 5 is the first sealing. Since the sealing support structure 8 is machined as a whole, the hollow rod part 82 is fixed to the electric heating rod (specifically the main rod part 4) to achieve a second sealing between the electric heating rod (specifically the main rod part 4) and the wellhead device 5. Because the sealing support structure 8 is machined as a whole, the lower part is connected to the electric heating rod inside the wellbore and fixed to the top of the wellhead device 5, thereby being able to bear the weight of the electric heating rod inside the wellbore and transfer it to the wellhead device 5.

[0059] In one possible implementation, such as Figures 3-4 As shown, the electric submersible screw pump well dewaxing and viscosity-reducing device also includes an electric heating rod plug 14 and a hollow electric heating rod tee device 13. The electric heating rod plug 14 is used to seal the top of the hollow electric heating rod tee device 13 to prevent rainwater from entering the interior of the hollow electric heating rod in the field. A second power supply cable 16 is connected to the electric heating rod plug 14. For example, the second power supply cable 16 is fixed to the electric heating rod plug 14 by a connecting screw 15. The hollow electric heating rod tee device 13 includes an upper connecting end, a lower connecting end, and a lateral channel. The upper connecting end is connected to the electric heating rod plug 14, and the lower connecting end is connected to the hollow rod portion 82 of the sealing support structure 8. The first power supply cable 17 enters the hollow cavity of the electric heating rod through the lateral channel. This arrangement prevents rainwater from entering the hollow cavity of the electric heating rod in the field. In the illustrated embodiment, a prefabricated electric heating rod 12 is also provided between the hollow electric heating rod tee device 13 and the sealed support structure 8. The prefabricated electric heating rod 12 is a short section of hollow electric heating rod, used to assist in connecting the sealed support structure 8 and the hollow electric heating rod tee device 13. In the illustrated embodiment, a current loop is formed via the first power supply cable 17, the loop rod portion 3, the main rod portion 4, the hollow rod portion 82 of the sealed support structure 8, the prefabricated electric heating rod 12, the hollow electric heating rod tee device 13, the electric heating rod plug 14, and the second power supply cable 16.

[0060] In one possible implementation, the hollow rod portion 82 of the sealing support structure 8 is configured as a hollow cylindrical rod, with the upper end of the hollow cylindrical rod having an internal thread that is connected and fixed to the prefabricated electric heating rod 12, and the lower end of the hollow cylindrical rod having an external thread that is connected and fixed to the main rod portion 4 in the well shaft.

[0061] In one possible implementation, the electric heating control system 20 is communicatively connected to a water cut analyzer used to detect the water cut of the wellbore produced fluid, and receives the water cut data of the produced fluid from it.

[0062] In one possible implementation, the electric heating control system 20 is communicatively connected to a temperature detection device for detecting the downhole temperature of the electric submersible screw pump, and receives downhole temperature data of the electric submersible screw pump from it.

[0063] In one possible implementation, the electric heating control system 20 is communicatively connected to a current detection device for detecting the production current of the electric submersible screw pump, and receives the production current data of the electric submersible screw pump from it.

[0064] In one possible implementation, the electric heating control system 20 is communicatively connected to a wellhead oil pressure detection device for detecting wellhead oil pressure, and receives wellhead oil pressure data from it.

[0065] In one possible implementation, the electric heating control system 20 is communicatively connected to the submersible screw pump control system, receiving downhole temperature data and production current data of the electric submersible screw pump from it.

[0066] The device provided by this invention, by implementing the method provided in the first aspect of this invention, can achieve the same technical effects as the aforementioned method, and will not be described in detail here. In addition, the device provided by this invention also realizes rod heating of the wellbore in the rodless lifting process by designing an electric heating rod structure and a sealing support structure. By inserting an electric heating rod inside the tubing of an electric submersible screw pump well, a uniform heat source is provided to the liquid in the wellbore, avoiding waxing of the produced fluid caused by temperature field loss in the wellbore, and well shutdown problems caused by increased crude oil viscosity. This solves the problem in the rodless lifting technology of electric submersible screw pumps that cannot establish a temperature field for the wellbore fluid, and that heavy oil and wax-producing wells are prone to high energy consumption or even failure to lift normally during the wellbore lifting process.

[0067] According to a third aspect of the present invention, an electric submersible screw pump oil production system is provided, such as... Figure 3As shown, the oil production system includes: an oil pipe 2 fixed by a wellhead device 5; an electric submersible screw pump downhole unit 1 connected to the lower end of the oil pipe 2; an electric submersible screw pump well dewaxing and viscosity reducing device as described in the second aspect of the present invention, wherein the electric heating device of the electric submersible screw pump well dewaxing and viscosity reducing device is inserted into the oil pipe 2 and sealed and fixed to the wellhead device 5; an electric submersible screw pump control cabinet 18 installed on the ground, which is used to control the operation of the electric submersible screw pump; and an electric heating control cabinet 11 installed on the ground, wherein the electric heating control system of the electric submersible screw pump well dewaxing and viscosity reducing device is installed in the electric heating control cabinet 11.

[0068] The electric submersible screw pump downhole unit 1 is the power source for this oil production system. The submersible motor is located at the bottom of the wellbore via tubing 2. During normal operation, it lifts the formation fluid through tubing 2 to the surface gathering and transportation process. At the bottom of the electric submersible screw pump downhole unit 1, there is a downhole temperature and pressure measuring device with high-precision, digital data acquisition and processing capabilities. This device can measure parameters such as downhole temperature and pressure in the electric submersible screw pump well. Simultaneously, it can collect and transmit data to the electric submersible screw pump control cabinet 18 via the submersible pump monitoring system for real-time monitoring of the well's dynamic changes.

[0069] The tubing 2 is a connecting device. Its lower part is connected to the electric submersible screw pump downhole unit 1 and other downhole tools via threads, and its upper part is connected to the wellhead device 5.

[0070] The wellhead assembly 5 is configured as a Christmas tree, which connects to various instruments to ensure normal well production. On one side of the Christmas tree are a casing pressure gauge 6 and an oil pressure gauge 7, both equipped with digital displays and data acquisition and transmission functions. The casing pressure gauge 6 measures casing pressure, and the oil pressure gauge 7 measures tubing pressure, i.e., pipeline back pressure. The casing and oil pressure values ​​can be transmitted to the electric submersible screw pump control cabinet 18 and to the data acquisition system for remote viewing. A water cut analyzer 9 is also connected to the Christmas tree outlet pipeline. The water cut analyzer 9 measures and displays the water cut of the produced fluid in the wellbore. The water cut value can be transmitted to the electric submersible screw pump control cabinet 18 and to the data acquisition system for remote viewing.

[0071] In one possible implementation, the electric submersible screw pump control cabinet 18 includes an electric submersible screw pump control system and a production parameter display system. The electric submersible screw pump control system is used to control the operation of the electric submersible screw pump. The production parameter display system is used to display the production parameters of the electric submersible screw pump.

[0072] In one possible implementation, the electric heating control cabinet 11 includes an electric heating control system and an electric heating parameter display system. The electric heating parameter display system is used to display the electric heating parameters.

[0073] The on-site working process of the oil production system provided by this invention is as follows: (1) Complete the wellbore string operation: During well workover operations, the electric submersible screw pump downhole unit 1 and related accessories are connected and fixed to the tubing 2 and lowered into the well to the designated depth. Simultaneously, the rod section 3 with a return loop is connected to the main rod section 4 and lowered into the tubing. After reaching the designated depth, a sealing support structure 8 is connected to the uppermost end of the main rod section 4. The sealing support structure 8 is then placed on the small four-way connector at the top of the wellhead device 5 and fixed to the small four-way connector using slips, providing both pressure and load-bearing capacity as well as sealing and fixation. A prefabricated electric heating rod 12, a hollow electric heating rod tee device 13, and an electric heating rod plug 14 are connected to the upper end of the sealing support structure 8. The first power supply cable 17 is lowered into the main rod section 4 through the hollow electric heating rod tee device 13, with its exposed end reaching into the rod section 3 with a return loop. The second power supply cable 16 is fixed to the electric heating rod plug 14 using connecting screws 15.

[0074] (2) Connect the wellhead device and turn on the power: Install and fix the casing pressure gauge 6, oil pressure gauge 7, and water cut analyzer 9 in the designated positions. Connect the data transmission acquisition line of the water cut analyzer 9 to the transmission RTU control cabinet. Connect the second power supply cable 16 and the first power supply cable 17 to the electric heating control cabinet 11 and turn on the power. Connect the power line of the electric submersible screw pump downhole unit 1 to the electric submersible screw pump control cabinet 18 and turn on the power.

[0075] (3) Start the electric submersible screw pump and electric heating rod: Start the electric submersible screw pump and electric heating rod according to production needs, and adjust the production frequency of the electric submersible screw pump and the operating mode of the electric heating rod.

[0076] (4) Classification of electric heating intelligent heating for wax removal and viscosity reduction: The electric heating wax removal and viscosity reduction process is available in two modes: manual and automatic. Automatic mode: The PLC intelligently analyzes the wellbore operating status and instructs the electric heating control cabinet 11 to optimize the control of electric heating time and power.

[0077] Manual mode: The heating time and operating power of the electric heating can be controlled by manually adjusting the relevant operating parameters of the electric heating control cabinet 11.

[0078] The intelligent start / stop, running time, and power of the electric heating system are primarily based on the production current of the electric submersible screw pump; secondary criteria include changes in the downhole temperature, wellhead oil pressure, and water content of the produced fluid. The electric heating power is automatically and steplessly adjusted via PLC intelligent control, providing heat as needed.

[0079] The oil production system provided by the present invention includes the device described in the second aspect of the present invention, so it can achieve the same technical effect as the aforementioned device, and will not be described again here.

[0080] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. The sequence numbers of the disclosed embodiments of this invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0081] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for dewaxing and reducing viscosity in an electric submersible screw pump well, characterized in that, Includes the following steps: Based on oil well production data, the oil well production stages are identified, including: wellbore fluid discharge stage, formation initiation fluid production stage, and formation stable fluid production stage. Different electric heating control strategies are adopted for different oil well production stages to control the electric heating device located in the oil well in order to achieve dewaxing and viscosity reduction in electric submersible screw pump wells.

2. The method for dewaxing and reducing viscosity in electric submersible screw pump wells according to claim 1, characterized in that, The oil well production data includes: water content of produced fluid, downhole temperature of electric submersible screw pump, production current of electric submersible screw pump, and wellhead oil pressure.

3. The method for dewaxing and reducing viscosity in electric submersible screw pump wells according to claim 2, characterized in that, Based on oil well production data, identify the oil well production stages, including: When the water content of the produced fluid is 100%, the downhole temperature of the electric submersible screw pump is stable, the production current of the electric submersible screw pump is stable, and the wellhead oil pressure is stable, the oil well production stage is identified as the wellbore drainage stage. When the water content of the produced fluid is less than 100% but greater than the water content during normal production, the downhole temperature of the electric submersible screw pump gradually increases, the production current of the electric submersible screw pump gradually increases, and the wellhead oil pressure shows an upward trend, the oil well production stage is identified as the formation initiation and fluid production stage. When the water content of the produced fluid is close to that during normal production, the downhole temperature of the electric submersible screw pump rises and stabilizes, the production current of the electric submersible screw pump gradually increases, and the wellhead oil pressure rises, the oil well production stage is identified as the formation stable production stage.

4. The method for dewaxing and reducing viscosity in electric submersible screw pump wells according to claim 3, characterized in that: The criterion for determining the downhole temperature stability of the electric submersible screw pump is that the downhole temperature of the electric submersible screw pump varies within the range of 0~3℃. The criterion for determining the stability of the production current of the electric submersible screw pump is that the variation range of the production current of the electric submersible screw pump is between 0-3A. The criterion for determining the stability of the wellhead oil pressure is that the variation range of the wellhead oil pressure is between 0 and 0.3 MPa. The criteria for determining that the wellhead oil pressure is increasing is: the wellhead oil pressure increases by more than 0.3 MPa compared to the normal value. The criterion for determining that the water content of the produced liquid is close to that of normal production is: the water content of the produced liquid is within ±2% of the water content of normal production. The criteria for determining the stability of downhole temperature rise in the electric submersible screw pump are as follows: the downhole temperature rises by more than 3°C compared to the normal value, the production current drops by more than 3A compared to the normal value, and the wellhead oil pressure drops by more than 0.3 MPa compared to the highest value.

5. The method for dewaxing and reducing viscosity in an electric submersible screw pump well according to claim 2, characterized in that, Different electric heating control strategies are employed to control the electric heating devices located in the wells at different stages of oil well production in order to achieve dewaxing and viscosity reduction in electric submersible screw pump wells, including: When the oil well production stage is identified as the wellbore drainage stage, the electric heating device is controlled to stop operating. When the oil well production stage is identified as the formation initiation and fluid production stage, the electric heating device is controlled to operate in preheating mode. When the oil well production stage is identified as the formation's stable fluid production stage, the electric heating device is controlled to operate in an on-demand heating mode. In the preheating operation mode, the electric heating device operates at a frequency and power lower than the normal operating frequency and power. In the on-demand heating operation mode, the electric heating device is controlled according to the current of the electric submersible screw pump downhole unit.

6. The method for dewaxing and reducing viscosity in electric submersible screw pump wells according to claim 5, characterized in that, In the on-demand heating operation mode, the electric heating device is controlled according to the current of the electric submersible screw pump downhole unit, including: When the current of the electric submersible screw pump downhole unit reaches the preset upper current limit, the electric heating device is controlled to start and operate at a frequency and power higher than the normal operating frequency and power. As the current of the electric submersible screw pump downhole unit changes, the electric heating frequency of the electric heating device is dynamically adjusted until the current of the electric submersible screw pump downhole unit drops to the preset lower current limit. When the current of the electric submersible screw pump downhole unit reaches the preset lower current limit, the electric heating device is controlled to stop operating.

7. The method for dewaxing and reducing viscosity in an electric submersible screw pump well according to claim 6, characterized in that, As the current of the electric submersible screw pump downhole unit changes, the electric heating frequency of the electric heating device is dynamically adjusted until the current of the electric submersible screw pump downhole unit drops to a preset lower current limit, including: As the current of the electric submersible screw pump downhole unit increases, the electric heating frequency is increased until the current of the electric submersible screw pump downhole unit reaches its maximum value; As the current of the electric submersible screw pump downhole unit decreases, the electric heating frequency reduction process is executed until the current of the electric submersible screw pump downhole unit drops to the preset lower current limit.

8. The method for dewaxing and reducing viscosity in electric submersible screw pump wells according to claim 7, characterized in that: The process of increasing the electric heating frequency is an alternating process of increasing the electric heating frequency by a first amount and decreasing the electric heating frequency by a second amount, wherein the first amount is greater than the second amount; The process of decreasing the electric heating frequency is an alternating process of decreasing the electric heating frequency by a third amount and increasing the electric heating frequency by a fourth amount, wherein the third amount is greater than the fourth amount.

9. An electric submersible screw pump well dewaxing and viscosity-reducing device, characterized in that, include: Electric heating device located inside the oil well; An electric heating control system connected to and used to control the electric heating device, the electric heating control system being configured to perform the method of any one of claims 1-8.

10. The electric submersible screw pump well dewaxing and viscosity-reducing device according to claim 9, characterized in that, The electric heating device is configured as an electric heating rod inserted into the oil pipe.

11. The electric submersible screw pump well dewaxing and viscosity-reducing device according to claim 10, characterized in that, The electric heating rod includes a hollow cavity. A first power supply cable extends into the hollow cavity and is connected to the bottom end of the electric heating rod. The first power supply cable forms a current loop with a second power supply cable via the electric heating rod to electrically heat the oil well. One of the first power supply cable and the second power supply cable is connected to the neutral wire of the power supply device, and the other is connected to the live wire of the power supply device.

12. The electric submersible screw pump well dewaxing and viscosity-reducing device according to claim 11, characterized in that, The electric heating rod is formed by connecting multiple hollow rods in sequence.

13. The electric submersible screw pump well dewaxing and viscosity-reducing device according to claim 11, characterized in that, The electric submersible screw pump well dewaxing and viscosity-reducing device also includes: A sealing support structure for supporting the electric heating rod within the oil pipe, the sealing support structure comprising: The main body is used for fixing and sealing with the wellhead device; A hollow rod portion is disposed at the interior center of the main body, and the hollow rod portion is connected to the electric heating rod. The main body and the hollow rod are integrally formed.

14. The electric submersible screw pump well dewaxing and viscosity-reducing device according to claim 13, characterized in that, The electric submersible screw pump well dewaxing and viscosity-reducing device also includes: An electric heating rod plug is provided to seal the hollow cavity of the electric heating rod, and the second power supply cable is connected to the electric heating rod plug. A hollow electric heating rod tee device includes an upper connecting end, a lower connecting end, and a lateral channel. The upper connecting end is connected to the plug of the electric heating rod, and the lower connecting end is connected to the hollow rod part of the sealed support structure. The first power supply cable enters the hollow cavity of the electric heating rod through the lateral channel.

15. The electric submersible screw pump well dewaxing and viscosity-reducing device according to claim 9, characterized in that: The electric heating control system is communicatively connected to a water content analyzer used to detect the water content of the wellbore produced fluid, and receives the water content data of the produced fluid from it. The electric heating control system is communicatively connected to a temperature detection device for detecting the downhole temperature of the electric submersible screw pump, and receives downhole temperature data of the electric submersible screw pump from it. The electric heating control system is communicatively connected to a current detection device for detecting the production current of the electric submersible screw pump, and receives the production current data of the electric submersible screw pump from it. The electric heating control system is communicatively connected to the wellhead oil pressure detection device used to detect wellhead oil pressure, and receives wellhead oil pressure data from it.

16. The electric submersible screw pump well dewaxing and viscosity-reducing device according to claim 9, characterized in that, The electric heating control system is communicatively connected to the submersible screw pump control system, and receives downhole temperature data and production current data of the electric submersible screw pump from it.

17. An electric submersible screw pump oil production system, characterized in that, include: Oil tubing fixed by wellhead equipment; An electric submersible screw pump downhole unit, wherein the electric submersible screw pump downhole unit is connected to the lower end of the tubing; The electric submersible screw pump well dewaxing and viscosity reducing device according to any one of claims 9-16, wherein the electric heating device of the electric submersible screw pump well dewaxing and viscosity reducing device is inserted into the tubing and sealed and fixed to the wellhead device; An electric submersible screw pump control cabinet installed on the ground, the electric submersible screw pump control cabinet being used to control the operation of the electric submersible screw pump; An electric heating control cabinet is installed on the ground, and the electric heating control system of the electric submersible screw pump well dewaxing and viscosity reducing device is installed in the electric heating control cabinet.

18. The electric submersible screw pump oil production system according to claim 17, characterized in that: The electric submersible screw pump control cabinet includes an electric submersible screw pump control system and a production parameter display system; The electric heating control cabinet includes the electric heating control system and the electric heating parameter display system.

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