Simple device for cleaning offshore chemical flooding oil pipe

Abstract

The invention discloses a simple device for cleaning an offshore chemical flooding oil pipe, which comprises a flushing inner pipe which is arranged in an injection pipe column through a wellhead suspension device, a closed end is formed at the lower end of the flushing inner pipe, and a plurality of groups of flushing nozzles are arranged on the pipe wall of the flushing inner pipe along the height direction at intervals and are used for flushing the injection pipe column; the outer extraction pipe is coaxially arranged outside the inner flushing pipe in a sleeving mode, a well flushing fluid circulating flow channel is formed between the outer extraction pipe and the inner flushing pipe, a plurality of sets of underground flowback openings are formed in the pipe wall of the outer extraction pipe in the height direction at intervals, and the underground flowback openings and the flushing nozzles are arranged in a staggered mode; the flushing water pump is connected with the inlet end of the flushing inner pipe and used for injecting well flushing fluid into the flushing inner pipe; and the flowback suction pump is connected with the outlet end of the extraction outer pipe and is used for flowback of the blockage dissolved in the extraction outer pipe to the ground. Polymer blockages attached to the injection pipe column and the water nozzle can be effectively removed, the well washing efficiency is improved, the operation cost is reduced, and the device is particularly suitable for the working conditions of limited offshore platform space, narrow operation window and complex environment.

Description

Technical Field

[0001] This invention belongs to the field of petroleum engineering technology, and more specifically, it relates to a simple device for cleaning pipelines used in offshore chemical flooding. Background Technology

[0002] Chemical flooding, an important method for enhancing oil recovery in offshore oilfields, involves injecting chemical agents (such as polymers and surfactants) into the reservoir to improve the oil-water mobility ratio and reduce the oil-water interfacial tension, thereby increasing crude oil recovery. However, during the implementation of chemical flooding, the problem of clogging in the injection system has consistently limited its application effectiveness and economic benefits.

[0003] During chemical flooding, the injected water often contains impurities and high-valence metal ions. These substances react with polymers to form high-viscosity micelles. Simultaneously, during polymer preparation, incomplete dissolution can lead to the formation of "fish-eye" shaped insoluble substances. These micelles and insoluble substances easily accumulate around and at the bottom of the injection string, clogging the tubing and nozzles. Some substances even enter the screen pipe, perforation holes, and near-wellbore area, resulting in reduced injection capacity. According to relevant statistics, in some oilfields that have implemented chemical flooding and profile control operations at sea, polymer-clogging micelles have been found at the bottom of the injection string and at the nozzles during moving the tubing, severely impacting normal oilfield production.

[0004] Currently, the main methods for unclogging the aforementioned injection tubing are water flushing, coiled tubing flushing, and moving tubing flushing. Water flushing is a relatively simple method, but it only flushes the blockage to near-wellbore areas such as sand screens and perforations, failing to address the root cause and potentially causing secondary damage; its unclogging effect is generally limited. While coiled tubing flushing and moving tubing backflushing can establish circulation channels to return the blockage clumps from the injection tubing to the surface, achieving a significant increase in injection volume, these two methods are time-consuming and costly, suitable only for special or critical needs, and difficult to implement on a routine, large-scale basis in offshore oilfields.

[0005] Therefore, developing an efficient, low-cost, and applicable chemical flooding injection string plugging and unblocking technology for offshore oil fields is of great significance for ensuring the smooth implementation of chemical flooding in offshore oil fields and improving recovery rates. Summary of the Invention

[0006] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention provides a simple device for cleaning offshore chemical flooding pipelines, designed to solve the problem of difficulty in timely and preventative flushing of existing injection tubing and nozzles after blockage in an economical, efficient, and convenient manner, thus ensuring the maintenance of chemical flooding injection capacity and its large-scale application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a simple device for cleaning offshore chemical flooding tubing, comprising: a flushing inner tube, which is installed in the injection string via a wellhead suspension device, the lower end of the flushing inner tube forming a closed end, and several sets of flushing nozzles spaced along the height direction on the tube wall of the flushing inner tube for flushing the injection string; a production outer tube, coaxially sleeved outside the flushing inner tube, forming a well-washing fluid circulation channel between the production outer tube and the flushing inner tube, and several sets of downhole return ports spaced along the height direction on the tube wall of the production outer tube, with the downhole return ports and the flushing nozzles arranged alternately; a flushing water pump connected to the inlet end of the flushing inner tube for injecting well-washing fluid into the flushing inner tube; and a return suction pump connected to the outlet end of the production outer tube for returning dissolved blockages in the production outer tube to the surface.

[0008] Preferably, a water nozzle protective screen is provided outside the water nozzle of the injection tube.

[0009] Preferably, the mesh size of the water tap protective screen is 40-200 mesh.

[0010] Preferably, the flushing nozzle is positioned to correspond to the position of the water nozzle on the injection column.

[0011] Preferably, the flushing nozzle has a 360° flushing angle range.

[0012] Preferably, the flushing water pump and the return suction pump are metering pumps, controlled by a control system, which can adjust the flushing volume of the flushing water pump and the flow rate of the return suction pump at any time.

[0013] Preferably, the flushing flow rate of the flushing water pump is in the range of 50-200 cubic meters per day.

[0014] Preferably, the inner diameter of the flushing inner tube is 1-2 cm, and the inner diameter of the extraction outer tube is 3-4 cm.

[0015] Preferably, the well-washing fluid is water or a polymer floc oxidation and unblocking fluid.

[0016] Preferably, the number of flushing nozzles is designed according to the actual number of polymer injection layers, so as to flush the blockages in each layer simultaneously.

[0017] The present invention has the following advantages due to the adoption of the above technical solutions: 1. Long-term stable deployment, enabling immediate well washing response. This invention uses a wellhead suspension device to stably fix the circulating casing (consisting of an inner flushing pipe and an outer production pipe) inside the injection string, achieving long-term reliable internal installation of the well washing pipeline. This overcomes the limitation of traditional well washing devices requiring temporary installation, allowing well washing operations to be started at any time, significantly shortening operation preparation time, and meeting the needs of offshore oil fields and other scenarios for rapid response and high-frequency well washing.

[0018] 2. Construct a closed-loop circulation channel to improve the efficiency of blockage removal. The innovative design of the circulating casing in this invention forms an independent well-washing fluid circulation loop. The well-washing fluid can directionally flush the inner wall of the tubing string, and the dislodged blockages are efficiently returned to the surface treatment system through the produced outer pipe. Compared with conventional open-loop well-washing methods, this closed-loop system reduces well-washing fluid waste and avoids secondary deposition of blockages, significantly improving the well-washing effect.

[0019] 3. Multi-level protection design ensures the safety of the formation and equipment. The water nozzle protective screen of this invention adopts a high-precision filtration structure, which can intercept blockages such as colloids and polymer residues. The intercepted blockages can be returned to the surface through the well washing circulation casing. This design has a dual protection function: on the one hand, it avoids the decrease in injection efficiency caused by water nozzle blockage; on the other hand, it prevents blockages from entering the reservoir pores and causing permanent damage, effectively protecting the reservoir permeability.

[0020] 4. Layered synchronous flushing achieves thorough cleaning of the entire well section without any blind spots. The multi-stage flushing nozzle in this invention employs a differentiated spray angle design, enabling simultaneous directional flushing targeting the blockage characteristics of different sections of the injection tubing. Compared to traditional single-stage flushing methods, this significantly improves well cleaning coverage, making it particularly suitable for complex tubing structures with long well sections and multiple layers, thereby greatly enhancing the space utilization of well cleaning operations.

[0021] 5. Intelligent dynamic control to adapt to complex well conditions. The flushing water pump and the return suction pump of this invention both adopt high-precision metering pumps, and together with the control system, the flushing intensity and return flow rate can be adjusted in real time to achieve flushing of the injection tubing under different discharge rates and meet the well washing requirements under different well conditions.

[0022] In summary, the present invention has a simple structure and is easy to operate. It can effectively remove polymer blockages attached to the injection tubing and nozzle, improve well washing efficiency, and reduce operating costs. It is especially suitable for offshore platforms with limited space and complex environments. Attached Figure Description

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings: Figure 1 This is a schematic diagram of a simple device for cleaning offshore chemical flooding pipelines according to an embodiment of the present invention.

[0024] The labels for the attached figures are as follows: 1-Wellhead suspension device; 2-Flush inner pipe; 3-Production outer pipe; 4-Flush water pump; 5-Return suction pump; 6-Flush nozzle; 7-Downhole return outlet; 8-Water nozzle; 9-Water nozzle protective screen; 10-Injection tubing; 11-Polymer injection packer; 12-Sand control screen. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments of the present invention will be further described below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0026] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0028] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0030] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0031] This invention provides a simple device for cleaning offshore chemical flooding tubing, comprising: an inner flushing pipe, which is installed within the injection string via a wellhead suspension device, with its lower end forming a closed end. Several sets of flushing nozzles are spaced along the height of the inner flushing pipe for flushing the injection string; an outer production pipe, coaxially sleeved outside the inner flushing pipe, forming a well-washing fluid circulation channel between them. Several sets of downhole return ports are spaced along the height of the outer production pipe and are staggered with the flushing nozzles; a flushing water pump, connected to the inlet end of the inner flushing pipe, for injecting well-washing fluid into the inner flushing pipe; and a return suction pump, connected to the outlet end of the outer production pipe, for returning dissolved blockages in the outer production pipe to the surface. This invention can effectively remove polymer blockages adhering to the injection string and nozzles, improving well-washing efficiency and reducing operating costs. It is particularly suitable for offshore platforms with limited space, narrow operating windows, and complex environments.

[0032] The following is a detailed description of the simplified apparatus for cleaning offshore chemical flooding pipelines provided by embodiments of the present invention, with reference to the accompanying drawings.

[0033] Please see Figure 1 This invention provides a simple device for cleaning offshore chemical flooding tubing, comprising: an inner flushing pipe 2, which is installed within an injection string 10 via a downhole suspension device 1; the lower end of the inner flushing pipe 2 forms a closed end; and several sets of flushing nozzles 6 are spaced along the height direction on the pipe wall of the inner flushing pipe 2 for flushing the injection string 10. A flushing water pump 4 is connected to the inlet end of the inner flushing pipe 2 for injecting washing fluid into the inner flushing pipe 2. An outer production pipe 3 is coaxially sleeved outside the inner flushing pipe 2, forming a washing fluid circulation channel between the outer production pipe 3 and the inner flushing pipe 2; and several sets of downhole return ports 7 are spaced along the height direction on the pipe wall of the outer production pipe 3, with the downhole return ports 7 and flushing nozzles 6 arranged alternately. A return suction pump 5 is connected to the outlet end of the outer production pipe 3 for returning dissolved blockages in the outer production pipe 3 to the surface.

[0034] In the above embodiments, preferably, a water nozzle protective screen 9 is provided outside the water nozzle 8 of the injection tube 10 to intercept blockages on the surface of the water nozzle protective screen 9 and prevent the water nozzle 8 from becoming clogged. More preferably, the mesh size of the water nozzle protective screen 9 is 40-200 mesh.

[0035] In the above embodiments, preferably, the flushing nozzle 6 is positioned corresponding to the position of the water nozzle 8 on the injection column 10, so that the flushing nozzle 6 can be used to flush and unblock the water nozzle protective screen 9 after it becomes clogged. More preferably, the flushing nozzle 6 has a 360° flushing angle range, thereby enabling all-round flushing and cleaning of the injection column 10 and the water nozzle protective screen 9.

[0036] In the above embodiments, preferably, the flushing water pump 4 and the return suction pump 5 are metering pumps, controlled by a control system. The flushing volume of the flushing water pump 4 and the flow rate of the return suction pump 5 can be adjusted at any time to achieve flushing of the injection tubing 10 under different discharge rates, meeting the well washing requirements under different well conditions. More preferably, the flushing flow rate of the flushing water pump 4 is in the range of 50-200 cubic meters / day.

[0037] In the above embodiments, preferably, the inner diameter of the flushing inner tube 2 is 1-2 cm, and the inner diameter of the extraction outer tube 3 is 3-4 cm.

[0038] In the above embodiments, preferably, the well-washing fluid is water or a polymer floc oxidation unblocking fluid.

[0039] In the above embodiments, preferably, the number of flushing nozzles 6 can be designed according to the actual number of injection layers, so as to flush the blockages in each layer simultaneously.

[0040] The present invention provides a simple device for cleaning offshore chemical flooding pipelines. During well cleaning, the flushing fluid is injected from the flushing inner pipe 2 into the flushing nozzle 6 through the flushing water pump 4 on the ground. The flushing nozzle 6 can flush the injection string 10 and the water nozzle protective screen 9 in all directions. The flushed and dissolved blockages are returned to the ground through the well cleaning fluid circulation channel between the production outer pipe 3 and the flushing inner pipe 2 by the return suction pump 5. This realizes the function of discharging the blockages from inside the injection string 10 and improves the well cleaning efficiency.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A simple device for cleaning pipelines used in offshore chemical flooding, characterized in that, include: The flushing inner tube is installed inside the injection tubing via a wellhead suspension device. The lower end of the flushing inner tube forms a closed end. Several sets of flushing nozzles are spaced along the height direction on the tube wall of the flushing inner tube for flushing the injection tubing. The outer tube is coaxially sleeved outside the inner flushing tube, and a well-washing fluid circulation channel is formed between the outer tube and the inner flushing tube. Several sets of downhole return outlets are spaced along the height direction on the wall of the outer tube, and the downhole return outlets are staggered with the flushing nozzles. A flushing water pump, connected to the inlet end of the flushing inner pipe, is used to inject well-washing fluid into the flushing inner pipe; A backflow suction pump, connected to the outlet end of the extraction pipe, is used to backflow the dissolved blockage in the extraction pipe to the ground.

2. The simplified device according to claim 1, characterized in that, A water nozzle protective screen is installed outside the water nozzle of the injection tube.

3. The simplified device according to claim 2, characterized in that, The mesh size of the water faucet protective screen is 40-200 mesh.

4. The simplified device according to claim 2, characterized in that, The flushing nozzles are positioned in a manner corresponding to the water nozzles on the injection tubing.

5. The simplified device according to claim 4, characterized in that, The flushing nozzle has a 360° flushing angle range.

6. The simplified device according to claim 1, characterized in that, The flushing water pump and the return suction pump are metering pumps, controlled by a control system, which can adjust the flushing volume of the flushing water pump and the flow rate of the return suction pump at any time.

7. The simplified device according to claim 6, characterized in that, The flushing flow rate of the flushing water pump ranges from 50 to 200 cubic meters per day.

8. The simplified device according to any one of claims 1 to 7, characterized in that, The inner diameter of the flushing inner tube is 1-2 cm, and the inner diameter of the extraction outer tube is 3-4 cm.

9. The simplified device according to any one of claims 1 to 7, characterized in that, The well-washing fluid is either water or a polymer floc oxidation and unblocking fluid.

10. The simplified device according to any one of claims 1 to 7, characterized in that, The number of flushing nozzles is designed according to the actual number of polymer injection layers, so as to flush the blockages in each layer simultaneously.

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