Screen pipe, well entering method, well washing method and well completion method

Abstract

The invention belongs to the technical field of oil and gas exploitation, and particularly relates to a screen pipe, a well entering method, a well washing method and a well completion method. The screen pipe comprises a center pipe, a filter layer and a protection pipe which are sequentially arranged from inside to outside in a sleeved mode, a plurality of through holes are formed in the center pipe, and plugs made of soluble materials are fixed in the through holes in a sealed mode. The screen pipe provided by the invention can enter a well by adopting a floating casing running process, so that the friction resistance is reduced, and the screen pipe can be smoothly run in place.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas exploitation, and specifically relates to a screen pipe, a method for lowering the screen pipe into a well, a well flushing method, and a well completion method. Background Art

[0002] With the development of oilfields, the application scale of horizontal wells is increasing continuously, and the number of screen pipe sand control completions for new wells and sidetracked horizontal wells is increasing. There are many drawbacks in conventional screen pipe completions.

[0003] For extended reach horizontal wells, especially those with a large vertical-to-horizontal ratio, the friction during the lowering of the completion string is large, and it cannot be smoothly lowered into place. Currently, the floating casing running technology is usually used to solve this problem. However, under the existing technological conditions, due to the structure of the screen pipe itself, sealing cannot be achieved, so the recognized floating casing running technology in the industry cannot be used in screen pipe completions.

[0004] Currently, after the screen pipe completion, the well team cannot carry out well flushing operations, and a special well flushing pipe string needs to be provided by the operation team for well flushing operations. This well flushing method not only increases the construction procedures, prolongs the operation cycle, increases the construction cost, but also increases the number of downhole tools and the operation risk. During the later filling process of the small-diameter sidetrack well screen pipe completion, due to the small inner diameter of the filling pipeline and the large filling pressure, it is very difficult to ensure the filling effect.

[0005] Chinese Patent Document CN201554436U discloses an openable temporary plugging screen pipe, which mainly temporarily plugs the flow channel of the screen pipe to reduce the blockage of the screen pipe flow channel caused by long-term immersion in mud, and can directly carry out well flushing operations without a well flushing pipe string during well flushing. Its technical solution is: the round holes opened in the screen pipe body are temporarily plugged with cylindrical plugs. A blind hole is provided on the end face of the plug facing the outer pipe wall of the central pipe. The outer end face of the cylinder is connected to the through hole by a thread. The depth of the inner blind hole should be greater than the wall thickness of the central pipe. During later release, a downhole tool needs to be lowered to drill out the cylindrical plug, that is, drill out the part of the plug protruding from the inner diameter of the central pipe. In this way, the blind hole at the end of the plug becomes a through hole, and the liquid inside and outside the screen pipe can flow again. This temporary plugging screen pipe has the following problems: since this invention mainly solves the blockage problem of the central pipe body caused by the solid content of the mud, the sealing pressure-bearing capacity of the plug is not enough, and the floating screen pipe technology cannot be realized; later unplugging requires a downhole tool to be lowered for cutting, which increases the construction period and complexity; the drilling effect cannot be judged, and there is a possibility that some plugs are not completely drilled out, affecting later production.

[0006] Therefore, there is an urgent need to develop a screen pipe that can solve the above problems. Summary of the Invention

[0007] Aiming at the above-mentioned technical problems, the present invention aims to provide a screen pipe that can be applicable to the technology of floating casing running.

[0008] The present invention also provides a method for lowering the screen pipe of the present invention into a well, a well flushing method after using the screen pipe of the present invention to lower into the well, and a well completion method.

[0009] According to the present invention, there is provided a screen pipe, which includes a central pipe, a filter layer and a protection pipe sleeved from the inside to the outside in sequence. A plurality of through holes are provided on the central pipe, and a plug made of a soluble material is hermetically fixed in the through holes.

[0010] In a specific embodiment, the plug is hermetically arranged in the through hole by means of threaded connection.

[0011] In a specific embodiment, internal threads are provided in the through hole, external threads adapted to the internal threads are provided on the plug, and sealing grease is provided between the internal threads and the external threads.

[0012] In a specific embodiment, the plug includes a large-diameter part and a small-diameter part arranged coaxially. The external threads are provided on the small-diameter part, and the outer diameter of the large-diameter part is greater than that of the small-diameter part.

[0013] In a specific embodiment, the end face of the large-diameter part contacts the inner wall of the central pipe.

[0014] In a specific embodiment, the plug is arranged in the through hole by means of bonding.

[0015] According to the present invention, there is also provided a method for lowering the screen pipe provided by the present invention into a well, and the screen pipe is lowered into the well by using a floating casing running process.

[0016] In a specific embodiment, a floating collar is arranged at the end of the screen pipe, and then the floating casing running process is implemented.

[0017] According to the present invention, there is also provided a well flushing method. After using the screen pipe provided by the present invention to lower into the well, an injection pipe is lowered into the well for well flushing operation.

[0018] According to the present invention, there is also provided a well completion method, which includes the following steps:

[0019] Lower the screen pipe provided by the present invention into the well;

[0020] Inject a solution into the pipe section where the screen pipe is provided to dissolve the plug of the screen pipe.

[0021] Compared with the prior art, the advantages of the present application are as follows.

[0022] The plug of the present invention is hermetically fixed in the through hole of the central pipe, thereby sealing the through hole of the central pipe and temporarily sealing the radial direction of the screen pipe. At this time, the screen pipe can be used as an ordinary casing, so that various construction processes corresponding to the casing can be applied. For example, a floating collar is arranged at the end of the screen pipe to implement the floating screen pipe running process; the well flushing operation can be directly carried out without the cooperation of a well flushing string; filling can be directly carried out in a small-diameter wellbore. Later, to release the plugging of the through hole of the central pipe, only a specific salt solution needs to be injected into the screen pipe. After the salt solution contacts the plug for a period of time, the plug is dissolved, thereby opening the through hole, and this operation is simple and reliable.

[0023] The screen pipe with a temporary plugging function provided by the present invention can realize the floating screen pipe running process in a long displacement wellbore, reducing the running friction of the pipe string. During well flushing, it is not necessary to use a special well flushing string for pickling, and the drilling team can directly carry out the well flushing operation after completion, reducing the number of pipe strings entering the well and saving the construction period. The plug removal process is simple and only requires injecting a specific salt solution to dissolve it, and the operation is simple and reliable. Brief Description of the Drawings

[0024] The present invention will be described below with reference to the accompanying drawings.

[0025] Figure 1 A schematic diagram showing an embodiment of the screen pipe according to the present invention is shown.

[0026] In the figure: 1, protection pipe; 2, filter layer; 3, central pipe; 4, plug; 41, large-diameter part; 42, small-diameter part; 5, through hole; 100, screen pipe.

[0027] In the present application, all the drawings are schematic drawings, only used to illustrate the principle of the present invention and not drawn to actual scale. Detailed Embodiments

[0028] The present invention will be introduced below with reference to the accompanying drawings.

[0029] It should be noted that the directional term or qualifier "inside" used in the present application refers to the direction close to the central axis of the screen pipe, that is, Figure 1 the right side of. The directional term or qualifier "outside" used in the present application refers to the direction away from the central axis of the screen pipe, that is, Figure 1 the left side of. They do not limit the absolute positions of the components involved, but can vary according to specific situations.

[0030] Figure 1 The structure of the screen pipe 100 according to the present invention is shown. Specifically, Figure 1 A schematic cross-sectional structure diagram of the screen pipe 100 is shown. The screen pipe 100 includes a central pipe 3, a filter layer 2, and a protection pipe 1 sleeved from the inside to the outside in sequence.

[0031] In this embodiment, the protection tube 1 is arranged on the outermost side of the screen tube 100, mainly playing a protective role for the internal filter layer 2. It is easy to understand that a plurality of channels (not shown) are provided on the protection tube 1, and the fluid outside the screen tube 100 can enter through the channels of the protection tube 1 and then pass through the filter layer 2.

[0032] The filter layer 2 is arranged inside the protection tube 1. After the fluid outside the screen tube 100 passes through the channels of the protection tube 1, it can pass through the filter layer 2, and the filter layer 2 filters the passing fluid.

[0033] It should be noted that the specific structures of the protection tube 1 and the filter layer 2 are not the technical key points of the present invention. The protection scope of the present invention is not limited to the protection tube 1 and the filter layer 2 shown in this embodiment, and the protection tube 1 and the filter layer 2 can adopt the existing technologies.

[0034] According to the present invention, the central tube 3 has a certain thickness, a plurality of through holes 5 are provided on the central tube 3, and a plug 4 is hermetically fixed in the through holes 5.

[0035] The plug 4 is made of a soluble material. The plug 4 made of the soluble material can be dissolved after contacting with the dissolving liquid, thereby opening the through hole 5.

[0036] It is easy to understand that both the soluble material and the dissolving liquid are existing technologies in the field of downhole tools. The soluble material has a certain strength before contacting with the dissolving liquid. After the soluble material contacts with the dissolving liquid, it can be dissolved within a certain period of time. The specific components, manufacturing methods, etc. of the soluble material and the dissolving liquid are not the technical key points of the present invention and will not be elaborated here.

[0037] When the plug 4 does not contact with the dissolving liquid, the plug 4 has sufficient strength to ensure the sealing performance of the through hole 5 within a certain pressure range and prevent the fluid on both sides of the central tube 3 from flowing through the through hole 5. At this time, the whole screen tube 100 is similar to an ordinary casing. By setting a floating collar at the end of the screen tube 100, the screen tube 100 can be lowered into the well according to the existing floating casing technology, reducing the frictional torque of the pipe string during lowering. During the later well flushing process, since the screen tube 100 of the present invention has a temporary plugging function, that is, the through hole 5 is closed by the plug 4, at this time, there is no need to lower a special well flushing pipe string into the well, and the well flushing operation can be directly carried out by lowering an insertion pipe, thereby simplifying the operation process, shortening the production cycle, and greatly improving the construction safety.

[0038] According to the present invention, in a specific embodiment, the plug 4 is hermetically arranged in the through hole 5 by means of threaded connection. An internal thread is provided in the through hole 5, an external thread adapted to the internal thread is provided on the plug 4, and a sealing grease is provided between the internal thread and the external thread. The sealing grease is applied to the external thread of the plug 4 and the internal thread of the through hole 5, and then the plug 4 is screwed into the through hole 5 by means of threaded connection to complete the closing of the through hole 5 by the plug 4. By providing the sealing grease, the sealing of the plug 4 to the through hole 5 can be strengthened, and the fastening strength between the plug 4 and the through hole 5 can be increased.

[0039] In a specific embodiment, as Figure 1 shown, the plug 4 includes a large-diameter portion 41 and a small-diameter portion 42 arranged coaxially, the external thread is provided on the small-diameter portion 42, and the outer diameter of the large-diameter portion 41 is greater than that of the small-diameter portion 42. After the plug 4 is fixed in the through hole 5, the end face of the large-diameter portion 41 contacts the inner wall of the central tube 3.

[0040] In an embodiment, the plug 4 is arranged in the through hole 5 by means of bonding.

[0041] In an embodiment of the present invention, a method for lowering a screen pipe 100 into a well is provided, and the floating casing running process is adopted to lower the screen pipe into the well. A floating collar is arranged at the end of the screen pipe, and then the floating casing running process is implemented, which can reduce the running friction of the screen pipe.

[0042] It should be noted that the structure of the floating collar is a prior art and is not a technical key point of the present invention, so it will not be elaborated here.

[0043] It should be noted that the floating casing running process is a prior art and will not be elaborated here.

[0044] In an embodiment of the present invention, a well flushing method is provided. The screen pipe 100 provided according to the present invention is used to enter the well, and then a downhole pipe is lowered for well flushing operations.

[0045] In an embodiment of the present invention, a well completion method is provided, which is characterized by including the following steps: lowering the screen pipe 100 provided according to the present invention into the well; injecting a dissolving solution into the pipe section where the screen pipe 100 is arranged to dissolve the plug 4 of the screen pipe 100.

[0046] In one embodiment of the present invention, the process of constructing with the screen pipe 100 is as follows. A floating collar is arranged at the end of the screen pipe 100, and the screen pipe 100 is lowered into the well by using the floating casing string technology. After that, a well flushing process is implemented. Without using a dedicated well flushing pipe string, the well flushing operation can be directly carried out by lowering an inserted pipe. Before production, only a dissolving liquid needs to be injected into the pipe section where the screen pipe 100 is located, and the plug 4 on the screen pipe 100 can be completely dissolved within a certain period, thereby opening the through hole 5. Fluids on both the inner and outer sides of the central pipe 3 can flow through the through hole 5, and the filtering function of the screen pipe 100 is restored.

[0047] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0048] In the present invention, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected to", "fixed" and other terms should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0049] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0050] Finally, it should be noted that the above are only the preferred implementation schemes of the present invention and do not constitute any limitation to the present invention. Although the present invention has been described in detail with reference to the foregoing implementation schemes, for those skilled in the art, it is still possible to modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A screen tube, It is characterized in that The invention comprises a central tube (3), a filter layer (2) and a protective tube (1) which are sequentially sleeved from the inside to the outside, a plurality of through holes (5) are arranged on the central tube (3), and plugs (4) made of a soluble material are sealed and fixed in the through holes (5).

2. The screen tube according to claim 1, It is characterized in that The plug (4) is sealed and arranged in the through hole (5) by means of a threaded connection.

3. The screen tube according to claim 2, It is characterized in that An internal thread is arranged in the through hole (5), an external thread matching the internal thread is arranged on the plug (4), and sealing grease is arranged between the internal thread and the external thread.

4. The screen tube according to claim 3, It is characterized in that The plug (4) comprises a coaxially arranged large diameter portion (41) and a small diameter portion (42), the external thread is arranged on the small diameter portion (42), and the outer diameter of the large diameter portion (41) is greater than that of the small diameter portion (42).

5. The screen tube according to claim 4, It is characterized in that The end surface of the large diameter portion (41) contacts the inner wall of the central tube (3).

6. The screen tube according to claim 1, It is characterized in that The plug (4) is arranged in the through hole (5) by bonding.

7. A method for placing a screen pipe into a well according to any one of claims 1 to 6, It is characterized in that The screen pipe is lowered into the well by adopting the floating casing technology.

8. The method for entering a well according to claim 7, It is characterized in that A floating collar is arranged at the end of the screen pipe, and then a floating casing process is implemented.

9. A well washing method, It is characterized in that The screen pipe according to any one of claims 1 to 6 is used to enter the well, and then the pipe is inserted to perform well washing operations.

10. A well completion method, It is characterized in that The steps include: Lowering the screen according to any one of claims 1 to 6 into the well; A solution is injected into the pipe section where the screen tube is provided to dissolve the plug of the screen tube.

Images