Oil production string and oil production system

Abstract

The present invention provides an oil production string and an oil production system. The oil production string includes: an oil pipe and a casing. The casing is sleeved on the outside of the oil pipe. An oil-casing annulus is formed between the casing and the oil pipe. A packer is arranged between the casing and the oil pipe. The packer separates the oil-casing annulus into an upper oil-casing annulus and a lower oil-casing annulus. The upper oil-casing annulus contains a heated heat-insulating liquid. The oil production system includes an oil production string, an oil production tree, a storage device, and a recovery device. The oil production string and the oil production system provided by the embodiments of the present invention can realize the wax prevention of the oil production string, and the heat-insulating liquid can also be recycled, which not only reduces the risk of wax deposition in the oil pipe, but also reduces the risk of mechanical wax removal and the operating cost.

Description

Technical Field

[0001] The invention relates to the technical field of oil production, and in particular to an oil production pipe column and an oil production system. Background Art

[0002] During the production process of oil wells, as the temperature and pressure decrease and the gas precipitates, when certain conditions are reached, the paraffin dissolved in the crude oil will crystallize and precipitate. As the conditions change further, the paraffin continues to precipitate, and its crystals gather and precipitate on equipment and tools such as oil pipes, casings, sucker rods, and oil pumps. This phenomenon is called wax deposition. After the oil well is waxed, the inner diameter of the oil outlet channel gradually decreases, increasing the resistance to the oil flow, reducing the production capacity of the oil well, and even blocking the oil flow channel, causing the oil well to stop production. After the oil well is waxed, it will also cause the oil pump to malfunction, reduce the pumping efficiency, and even jam the deep well pump and damage the equipment.

[0003] In the prior art, the wax removal method commonly used is mainly mechanical wax removal, which is to use a special wax scraping tool (also called wax removal tool) to scrape off the wax attached to the wellbore of the oil well. The mechanical wax removal equipment mainly includes a winch, a steel wire, a pick rod, a pulley, a blowout preventer, a blowout preventer, a steel wire well sealer, a wax scraper and a plumb bob. The staff uses the movable wax scraper installed on the sucker rod to remove the wax on the oil pipe and the sucker rod.

[0004] The mechanical wax removal method in the prior art requires large investment and has a short operation cycle, and needs to be performed every 2-3 days, which affects the oil production efficiency. Summary of the invention

[0005] The present invention provides an oil production pipe string and an oil production system. By adding heated heat-insulating liquid into the oil casing annulus of the oil production pipe string, the temperature of the oil pipe is kept above the wax precipitation temperature, which plays a role in preventing wax and does not require mechanical wax removal.

[0006] On the one hand, the present invention provides an oil production pipe string, comprising: an oil pipe and a casing, wherein the casing is arranged on the outside of the oil pipe, an oil-casing annulus is formed between the casing and the oil pipe, a packer is arranged between the casing and the oil pipe, the packer separates the oil-casing annulus into an upper oil-casing annulus and a lower oil-casing annulus, and the upper oil-casing annulus contains an insulating liquid, and the temperature of the insulating liquid is greater than the safety temperature critical point of crude oil wax precipitation.

[0007] Furthermore, the depth of the packer in the oil well is greater than the depth corresponding to the safety temperature critical point of wax precipitation of crude oil in the oil well.

[0008] Furthermore, the heat-insulating liquid is a liquid containing stearate.

[0009] Furthermore, the casing above the packer is a thermal insulation casing.

[0010] Furthermore, a thermal insulation coating or a thermal insulation film or a vacuum thermal insulation layer is provided in the thermal insulation sleeve.

[0011] The production pipe string provided by the embodiment of the present invention sets the packer at a calculated depth, the temperature of which is greater than the critical safety temperature point of crude oil wax precipitation. The packer divides the casing annulus into an upper casing annulus and a lower casing annulus, the temperature in the lower casing annulus is greater than the critical safety temperature point of crude oil wax precipitation, and at the same time, a heated insulation liquid is injected into the upper casing annulus, the temperature of the insulation liquid is also greater than the critical safety temperature point of crude oil wax precipitation, so that the temperature of the entire casing annulus is greater than the critical safety temperature point of crude oil wax precipitation. Therefore, the crude oil in the oil pipe will not precipitate wax, which plays a role in preventing wax and no longer needs to perform periodic mechanical wax cleaning, which reduces investment and improves production efficiency.

[0012] Another aspect of the present invention provides an oil production system, comprising: an oil production tree and the oil production string as described above, wherein the top end of the oil production string is connected to the oil production tree.

[0013] Furthermore, the oil production system further comprises a storage device, the storage device is used to store the heat-insulating liquid, the Christmas tree comprises an oil pipe spool, the oil pipe spool comprises a first annulus side outlet, and the storage device is connected to the first annulus side outlet.

[0014] Furthermore, a one-way valve and a booster pump are provided on the connecting channel between the storage device and the first annulus side outlet, the storage device is connected to the input end of the booster pump, the output end of the booster pump is connected to the input end of the one-way valve, and the output end of the one-way valve is connected to the first annulus side outlet.

[0015] Furthermore, the oil production system also includes a recovery device for recovering the insulation liquid in the annulus of the upper oil casing, the oil pipe spool also includes a second annulus side outlet, and the recovery device is connected to the second annulus side outlet.

[0016] Furthermore, the storage device is connected to the recovery device, and a heating device is provided between the storage device and the recovery device, and the heating device is used to heat the insulation liquid in the recovery device. The storage device, the recovery device and the upper oil casing annulus form a circulating connection system so that the insulation liquid circulates in the circulating connection system.

[0017] The oil production column and oil production system provided by the embodiment of the present invention, by setting the packer at a calculated depth, the temperature of the depth is greater than the safety temperature critical point of crude oil wax precipitation, the packer separates the oil casing annulus into an upper oil casing annulus and a lower oil casing annulus, the temperature in the lower oil casing annulus is greater than the safety temperature critical point of crude oil wax precipitation, and at the same time, a heated insulation liquid is injected into the upper oil casing annulus, the temperature of the insulation liquid is also greater than the safety temperature critical point of crude oil wax precipitation, so that the temperature of the entire oil casing annulus is greater than the safety temperature critical point of crude oil wax precipitation, therefore, the crude oil in the oil pipe will not precipitate wax, which plays a role in preventing wax, not only reducing the risk of wax deposition in the oil pipe, but also reducing the risk and operating cost of mechanical wax removal operations, and improving the production efficiency of the oil well. On the other hand, by providing a storage device and a recovery device for the insulation liquid, the insulation liquid can be recycled to save resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 It is a structural schematic diagram of an oil production system in the prior art;

[0020] Figure 2 A front view of an oil production string provided by an embodiment of the present invention;

[0021] Figure 3 A top view of an oil production string provided by an embodiment of the present invention;

[0022] Figure 4 A schematic diagram of the casing structure of an oil production string provided by an embodiment of the present invention;

[0023] Figure 5 A schematic diagram of the structure of an oil production system provided by an embodiment of the present invention;

[0024] Figure 6 A schematic structural diagram of an oil production system provided in another embodiment of the present invention.

[0025] Reference numerals:

[0026] 10-Oil pipe;

[0027] 20- casing;

[0028] 201- casing outer tube;

[0029] 202- casing inner tube;

[0030] 203- thermal insulation layer;

[0031] 30-Packer;

[0032] 40-casing annulus;

[0033] 401- oil casing annulus;

[0034] 402-lower casing annulus;

[0035] 50-perforation;

[0036] 60-heat-keeping liquid;

[0037] 70- Christmas tree;

[0038] 701-Oil pipe spool;

[0039] 80- storage device;

[0040] 801-boosting pump;

[0041] 802- one-way valve;

[0042] 90- Recovery device;

[0043] 110- winch;

[0044] 111- steel wire;

[0045] 112- pulley;

[0046] 113-scrape wax sheet;

[0047] 114-Plumb bob. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Before the development of an oil well, wax is completely dissolved in crude oil. During the production process of an oil well, as the temperature and pressure decrease and gas precipitates, when certain conditions are met, the paraffin dissolved in the crude oil will crystallize and precipitate. As conditions change further, paraffin continues to precipitate, and its crystals gather and precipitate on equipment and tools such as oil pipes, casings, sucker rods, and pumps. This phenomenon is called wax deposition. The wax deposition process can be divided into three stages: (1) wax deposition stage, when the temperature drops below the wax deposition point, wax precipitates from the crude oil in the form of crystals; (2) aggregation stage: the temperature continues to drop, and the crystallized wax gathers and grows; (3) deposition stage: the grown wax crystals are deposited on the surface of the pipe wall. After wax deposition in an oil well, the inner diameter of the oil outlet channel gradually decreases, increasing resistance to oil flow and reducing the oil well's production capacity. In some cases, the oil flow channel is blocked, causing the oil well to stop production. After wax deposition in a pump, the pump will also fail, reducing the pumping efficiency. In some cases, the deep well pump will be stuck, damaging the equipment. Therefore, wax prevention and wax removal in oil wells is a very important technical measure to ensure the normal production of waxy crude oil.

[0050] In the prior art, the commonly used oil well wax removal process is mechanical wax removal, that is, a special mechanical wax removal device is used to scrape off the wax attached to the wellbore of the oil well. Figure 1 It is a structural diagram of the oil production system in the prior art, referring to Figure 1 As shown, the oil production system in the prior art includes an oil production pipe column, an oil production tree and a mechanical wax removal device, wherein the mechanical wax removal device includes a winch 110, a steel wire 111, a pulley 112, a wax scraper 113 and a plumb bob 114, wherein the winch 110 is fixed on the ground, the pulley 112 is fixed above the oil production tree, one end of the steel wire 111 is wound around the winch 110, and the other end passes around the pulley 112 and enters the oil pipe in the oil production pipe column through the oil production tree, the steel wire 111 entering the oil pipe is connected with the wax scraper 113 and the plumb bob 114, the wax scraper 113 moves downward to scrape the wax by the gravity of the plumb bob 114, and when lifting up, the winch 110 pulls the steel wire 111 through the pulley 112 to pull the wax scraper 113 upward, and the wax scraping is repeated regularly in this way, and the scraped wax is brought to the ground by the liquid flow, so as to achieve the purpose of removing wax accumulated in the oil pipe. When using wax scrapers to remove wax, it is necessary to master the wax deposition cycle so that the wax deposited in the oil well can be removed in time. The wax deposition is not allowed to be too thick, causing the wax scraper to be blocked and unable to go down.

[0051] The mechanical wax removal method in the prior art requires large investment and has a short operation cycle, and needs to be performed every 2-3 days, which affects the oil production efficiency.

[0052] In order to overcome the above-mentioned defects of the prior art, the present invention provides an oil production tubing string and an oil production system. The oil production tubing string and the oil production system provided by the present invention inject heated insulating liquid into the annulus of the oil casing so that the temperature in the oil pipe is greater than the temperature of the precipitated wax, thereby playing a role in preventing wax. There is no need for subsequent mechanical wax cleaning. The anti-wax process is simple and safe. Oil well production can be carried out while preventing wax, and the oil production efficiency will not be affected.

[0053] The present invention will be described below with reference to the accompanying drawings and in conjunction with specific embodiments.

[0054] Embodiment 1

[0055] Figure 2 A front view of an oil production string provided by an embodiment of the present invention, Figure 3 The top view of the oil production string provided by the embodiment of the present invention is shown in FIG. Figure 2 and Figure 3 As shown, the production tubing string provided by the embodiment of the present invention includes: an oil pipe 10 and a casing 20. The casing 20 is sleeved on the outside of the oil pipe. An oil-casing annulus 40 is formed between the oil pipe 10 and the casing 20. A packer 30 is also arranged between the oil pipe 10 and the casing 20. The packer 30 separates the oil-casing annulus 40 into an upper oil-casing annulus 401 and a lower oil-casing annulus 402. The upper oil-casing annulus 401 contains a heated heat-insulating liquid 60. The casing 20 is also provided with perforations 50.

[0056] Specifically, due to different geothermal gradients, the formation temperature at a depth of 6,000 meters can reach 140 degrees Celsius. The closer to the surface, the lower the temperature, and even not much different from the ambient temperature. In the process of crude oil from the bottom through the oil pipe 10 to the ground, at a certain depth, when the temperature of the crude oil drops to the wax precipitation point of the crude oil, the wax in the crude oil will precipitate from the crude oil and condense in the oil pipe. Therefore, in order to prevent the wax in the crude oil from precipitating, a depth is calculated, the temperature of this depth is greater than the safety temperature critical point of the crude oil wax precipitation, and the packer 30 is set at this depth. The packer 30 separates the oil casing annulus 40 into an upper oil casing annulus 401 and a lower oil casing annulus 402. Since the depth of the packer 30 is greater than the depth of the safety temperature critical point of the crude oil wax precipitation, the temperature in the lower oil casing annulus 402 is greater than the safety temperature critical point of the crude oil wax precipitation, and the wax in the crude oil will not precipitate. Similarly, since the depth above the packer 30 is less than the depth of the safe temperature critical point of crude oil wax precipitation, the temperature in the upper casing annulus 401 will be lower than the safe temperature critical point of crude oil wax precipitation. Under normal circumstances, wax in the crude oil will precipitate.

[0057] In order to prevent wax from precipitating out of crude oil, the production pipe string provided in the embodiment of the present invention injects heated insulating liquid 60 into the upper casing annulus 401. The temperature of the insulating liquid 60 is heated to above the safe temperature critical point for wax precipitation of crude oil. In this way, the temperature in the upper casing annulus 401 is also greater than the safe temperature critical point for wax precipitation of crude oil. Wax in the crude oil in the oil pipe 10 will not be precipitated, thereby achieving an anti-wax effect.

[0058] Furthermore, the heat-insulating liquid 60 is a liquid with the characteristics of thermochemical stability and non-oxidation, and can be a liquid containing stearate, etc. The specific material of the heat-insulating liquid 60 is not limited here.

[0059] Figure 4 The schematic diagram of the casing structure of the oil production pipe string provided in the embodiment of the present invention is shown in FIG. Figure 4 As shown, further, in order to improve the anti-wax effect, in the oil production string provided by the embodiment of the present invention, the casing 20 above the packer 30 is an insulating casing, which can be an inner coating, an inner coating film or a vacuum insulating casing. Specifically, the casing 20 above the packer 30 includes a casing outer tube 201, a casing inner tube 202 and an insulating layer 203, and the insulating layer 203 can be made of insulating materials such as titanium alloys and nanomaterials, and the material of the insulating layer 203 is not limited here.

[0060] Furthermore, in order to ensure that the temperature of the insulating liquid 60 is always higher than the safety temperature critical point of wax precipitation in crude oil, a temperature detection device can be set to monitor the temperature of the insulating liquid 60 in real time. When the temperature of the insulating liquid is lower than the safety temperature critical point of wax precipitation in crude oil, new heated insulating liquid is injected to ensure that the temperature in the upper casing annulus 401 is always above the safety temperature critical point to prevent wax precipitation in the crude oil.

[0061] Furthermore, the production tubing string provided in the embodiment of the present invention further includes perforations 50 located on the casing 20 , the perforations 50 correspond to the positions of the crude oil reservoirs, and the crude oil in the crude oil reservoirs enters the lower casing annulus 402 through the perforations 50 .

[0062] The production tubing string provided in the embodiment of the present invention sets the packer 30 at a calculated depth, the temperature of which is greater than the critical safety temperature point of crude oil wax precipitation. The packer 30 separates the casing annulus 40 into an upper casing annulus 401 and a lower casing annulus 402. The temperature in the lower casing annulus 402 is greater than the critical safety temperature point of crude oil wax precipitation. At the same time, a heated high-temperature insulating liquid 60 is injected into the upper casing annulus 401. The temperature of the insulating liquid 60 is also greater than the critical safety temperature point of crude oil wax precipitation. In this way, the temperature in the entire casing annulus is greater than the critical safety temperature point of crude oil wax precipitation. Therefore, the crude oil in the oil pipe will not precipitate wax, which plays a role in preventing wax. There is no need to perform periodic mechanical wax cleaning, which reduces investment and improves production efficiency.

[0063] Embodiment 2

[0064] Figure 5 The structural diagram of the oil production system provided by the embodiment of the present invention is shown in FIG. Figure 5 As shown, the oil production system provided by the embodiment of the present invention includes an oil production tree 70 and the oil production string described in the first embodiment, and the oil production tree 70 is connected to the top of the oil production string. The oil production string includes: an oil pipe 10 and a casing 20, the casing 20 is sleeved on the outside of the oil pipe, and an oil casing annulus 40 is formed between the oil pipe 10 and the casing 20, and a packer 30 is also arranged between the oil pipe 10 and the casing 20, and the packer 30 separates the oil casing annulus 40 into an upper oil casing annulus 401 and a lower oil casing annulus 402, and the upper oil casing annulus 401 has a heated heat-insulating liquid 60, and the casing 20 is also provided with perforations 50, and the packer 30 is located at a certain depth between the wellhead and the bottom of the well, and the temperature at this depth is greater than the safety temperature critical point of crude oil wax precipitation, which is obtained by calculation. The Christmas tree 70 includes a tubing head and a Christmas tree body. The tubing head is composed of a tubing hanger and its body, and is used to hang the tubing string and seal the annular space between the tubing 10 and the casing 20. The tubing head is usually a short section connected by upper and lower flanges, and has two annular side outlets, forming a four-way, so it is also called a tubing four-way. The Christmas tree body is the main equipment for controlling and regulating oil and gas production at the top of the oil well. It is composed of valves, reducers, nozzles and pipeline accessories. It is a device used to control production and provide conditions for well repair operations such as steel wire, cable, and continuous tubing.

[0065] Furthermore, the oil production system provided by the embodiment of the present invention also includes a storage device 80, which is used to store heated insulating liquid. The storage device 80 is connected to the first annulus side outlet of the oil pipe spool 701, so that the insulating liquid 60 in the storage device 80 can be injected into the upper casing annulus 401 through the annulus side outlet on the oil pipe spool 701.

[0066] Specifically, a one-way valve 802 and a booster pump 801 are also provided on the connection channel between the storage device and the annular side outlet of the tubing spool 701, wherein the storage device 80 is connected to the input end of the booster pump 801, the output end of the booster pump 801 is connected to the input end of the one-way valve 802, and the output end of the one-way valve 802 is connected to the annular side outlet of the tubing spool 701. Due to the one-way valve 802, the insulation liquid 60 can only flow in one direction, that is, the insulation liquid 60 can only flow from the storage device 80 into the upper casing annular space 401, but cannot flow from the upper casing annular space 401 into the storage device 80. The function of the booster pump 801 is to pressurize the insulation liquid 60, so that the insulation liquid 60 is pumped from the storage device 80 into the upper casing annular space 401 in the production pipe string.

[0067] Specifically, the storage device 80 can be a storage tank fixed on the ground, or it can be a mobile storage equipment, such as a tank truck. The storage device 80 is made of thermal insulation material and can play a thermal insulation role. The storage device 80 can have its own heating function, or it can only have a storage function. The thermal insulation liquid 60 is injected into the storage device 90 after being heated. The specific form of the storage device is not limited here.

[0068] The oil production system provided by the embodiment of the present invention sets the packer 30 at a calculated depth, the temperature of which is greater than the safety temperature critical point of crude oil wax precipitation. The packer 30 separates the casing annulus 40 into an upper casing annulus 401 and a lower casing annulus 402. The temperature in the lower casing annulus 402 is greater than the safety temperature critical point of crude oil wax precipitation. At the same time, a heated insulating liquid 60 is injected into the upper casing annulus 401, and the temperature of the insulating liquid 60 is also greater than the safety temperature critical point of crude oil wax precipitation. In this way, the temperature in the entire casing annulus is greater than the safety temperature critical point of crude oil wax precipitation. Therefore, the crude oil in the oil pipe will not precipitate wax, which plays a wax prevention role, not only reducing the risk of wax deposition in the oil pipe, but also reducing the risk and operating costs of mechanical wax removal operations, thereby improving the production efficiency of the oil well.

[0069] Embodiment 3

[0070] Figure 6 A schematic diagram of the structure of an oil production system according to another embodiment of the present invention is shown in FIG. Figure 6 As shown, this embodiment is obtained by further improving the embodiment 2. On the basis of the embodiment 2, the oil production system provided in this embodiment further includes a recovery device 90, which is connected to another annular side outlet of the tubing head spool 701, so as to be connected to the upper casing annular space 401 of the production pipe string. The recovery device 90 is used to recover the insulation liquid 60 in the upper casing annular space 401. When the insulation liquid 60 in the upper casing annular space 401 is lower than the safety temperature critical point of crude oil wax precipitation, the insulation liquid 60 in the upper casing annular space 401 is recovered to the recovery device 90. Specifically, a pump can be set between the recovery device 90 and the second annular side outlet of the tubing spool 701, and the insulation liquid 60 can be pumped into the recovery device 90 by the pump. The liquid in the recovery device 90 can be reheated and placed in the storage device 80 for continued use.

[0071] Furthermore, the recovery device 90 and the storage device 80 can be connected, and a heating device is provided between the storage device 80 and the recovery device 90. The heating device is used to heat the insulation liquid in the recovery device 90, so that the storage device 80, the upper casing annulus 401 and the recovery device 90 form a circulating connection system, and the insulation liquid 60 can circulate in the circulating connection system to achieve the reuse of the insulation liquid 60.

[0072] Specifically, the recovery device 90 can be a recovery tank fixed on the ground, or it can be a mobile recovery equipment, such as a tank truck. The recovery device 90 is made of insulation material and can play an insulation role. The recovery device 90 can have its own heating function, so that the insulation liquid 60 in the recovery device 90 is directly injected into the storage device 80 after heating, and then injected into the upper casing annulus 401 of the oil production pipe column through the storage device 80. The operation is faster and more convenient, and the production efficiency is improved.

[0073] Specifically, the temperature of the insulating liquid 60 in the upper casing annulus 401 can be monitored in real time by a temperature detection device. When the temperature is lower than the critical safety temperature point for wax precipitation of crude oil, the insulating liquid 60 in the upper casing annulus 401 is recovered and recycled into the recovery device 90. At the same time, the heated insulating liquid 60 in the storage device 80 is injected into the upper casing annulus 401 through a booster pump to ensure that the temperature of the insulating liquid 60 in the upper casing annulus 401 is always higher than the critical safety temperature point for wax precipitation of crude oil. After being heated, the liquid in the recovery device 90 is continuously injected into the storage device 80 to wait for the next cycle.

[0074] The oil production system provided in this embodiment is provided with a packer 30 at a calculated depth, the temperature of which is greater than the critical point of safe temperature for wax precipitation of crude oil. The packer 30 separates the casing annulus 40 into an upper casing annulus 401 and a lower casing annulus 402, the temperature in the lower casing annulus 402 is greater than the critical point of safe temperature for wax precipitation of crude oil, and at the same time, a heated insulating liquid 60 is injected into the upper casing annulus 401, the temperature of the insulating liquid 60 is also greater than the critical point of safe temperature for wax precipitation of crude oil, so that the temperature in the entire casing annulus is greater than the critical point of safe temperature for wax precipitation of crude oil, and therefore, the crude oil in the oil pipe will not precipitate wax, which plays a role in preventing wax, not only reducing the risk of wax formation in the oil pipe, but also reducing the risk and operating cost of mechanical wax removal operations, and improving the production efficiency of the oil well. On the other hand, by providing a storage device 80 and a recovery device 90 for the insulating liquid 60, the insulating liquid 60 can be recycled to save resources.

[0075] In the description of the present invention, it is necessary to understand that the terms used such as “center”, “length”, “width”, “thickness”, “top”, “bottom”, “up”, “down”, “left”, “right”, “front”, “back”, “vertical”, “horizontal”, “inside”, “outside”, “axial”, “circumferential”, etc. to indicate directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred position or component must have a specific direction, a specific structure and operation, and therefore cannot be understood as limiting the present invention.

[0076] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0077] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, they can be fixedly connected, detachably connected, or integrated; they can be mechanically connected, electrically connected, or can communicate with each other; they can be directly connected, or indirectly connected through an intermediate medium, so that the internal communication of two elements or the interaction relationship between two elements can be achieved. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0078] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An oil production pipe string, characterized in that: It comprises an oil pipe and a casing, wherein the casing is sleeved on the outside of the oil pipe, an oil-casing annulus is formed between the casing and the oil pipe, a packer is arranged between the casing and the oil pipe, the packer separates the oil-casing annulus into an upper oil-casing annulus and a lower oil-casing annulus, and the upper oil-casing annulus contains a heat-insulating liquid, and the temperature of the heat-insulating liquid is greater than the safety temperature critical point of crude oil wax precipitation; The depth of the packer in the oil well is greater than the depth corresponding to the safe temperature critical point of wax precipitation of crude oil in the oil well; The heat-insulating liquid is a liquid containing stearate; The casing above the packer is a heat-insulating casing; wherein the casing above the packer comprises a casing outer tube, a heat-insulating layer and a casing inner tube; the heat-insulating layer is a heat-insulating coating or a heat-insulating film or a vacuum heat-insulating layer; the heat-insulating layer is made of titanium alloy or nano-material heat-insulating material; The oil production pipe string also includes: a temperature detection device, which is used to monitor the temperature of the insulation liquid in real time, so as to inject new heated insulation liquid when the temperature of the insulation liquid is lower than the safe temperature critical point of crude oil wax precipitation.

2. An oil production system, characterized in that: include: A Christmas tree and a production pipe string as claimed in claim 1, wherein the top end of the production pipe string is connected to the Christmas tree.

3. The oil production system according to claim 2, characterized in that: The oil production system further comprises a storage device, the storage device is used to store the heat-insulating liquid, the Christmas tree comprises an oil pipe spool, the oil pipe spool comprises a first annulus side outlet, and the storage device is connected to the first annulus side outlet.

4. The oil production system according to claim 3, characterized in that: A one-way valve and a booster pump are also provided on the connecting passage between the storage device and the first annulus side outlet; the storage device is connected to the input end of the booster pump, the output end of the booster pump is connected to the input end of the one-way valve, and the output end of the one-way valve is connected to the first annulus side outlet.

5. The oil production system according to claim 4, characterized in that: The oil production system further comprises a recovery device for recovering the heat-insulating liquid in the annulus of the upper oil casing, the oil pipe spool further comprises a second annulus side outlet, and the recovery device is connected to the second annulus side outlet.

6. The oil production system according to claim 5, characterized in that: The storage device is connected to the recovery device, and a heating device is arranged between the storage device and the recovery device. The heating device is used to heat the insulation liquid in the recovery device. The storage device, the recovery device and the upper oil casing annulus form a circulating connection system so that the insulation liquid circulates in the circulating connection system.

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