Oil layer anti-pollution pipe column and oil layer anti-pollution method

Abstract

The invention discloses an oil layer anti-pollution pipe column and an oil layer anti-pollution method. The tubular column comprises a central tube, an expansion piece, a protector, a packer and a positioner which are sequentially connected from top to bottom, the positioner can expand outwards and be tightly attached to the inner wall of a shaft so that the oil layer anti-pollution pipe column can be positioned at the preset depth of the shaft. The packer is used for blocking a shaft annulus; the protector is used for controlling the flow direction of fluid in the shaft; the expansion piece can be converted into a free expansion state from a locking state so as to partially counteract the force borne by the packer; according to the tubular column, the flow direction of fluid in a shaft is controlled through the protector, different fluid channels are established, well washing fluid directly flows to the shaft annulus, well washing circulation is formed, crude oil is extracted from the center pipe from the well bottom, and therefore the well washing fluid can be prevented from flowing into the well bottom to cause oil layer pollution, and long-term stable production of an oil well is guaranteed; and the operation cost of well washing and production is reduced, and the well repair period is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of oil production, and in particular to an oil layer anti-pollution pipe column and an oil layer anti-pollution method. Background Art

[0002] Well flushing is a routine project in underground operations. It mainly involves injecting a well flushing fluid with certain properties into the wellbore, mixing the wax, dead oil, rust and impurities on the well wall and oil pipe into the well flushing fluid and taking them out of the wellbore, so that the wellbore meets the operation requirements.

[0003] After long-term production in an oil field, the formation pressure gradually decreases. During the well washing and wax removal operation, the well washing fluid will enter the formation. For many water-sensitive formations, the rock pores will become smaller, and the oil well will reduce production or even stop producing oil, which adds a lot of cost to the oil field production. Summary of the invention

[0004] In order to enrich the product categories of oil layer anti-pollution strings and increase the selection space of oil layer anti-pollution methods, an embodiment of the present invention provides an oil layer anti-pollution string and an oil layer anti-pollution method.

[0005] In a first aspect, an embodiment of the present invention provides an oil layer anti-pollution pipe string including a central pipe, a retractor, a protector, a packer and a positioner connected in sequence from top to bottom;

[0006] The positioner can expand outward and adhere to the inner wall of the wellbore to position the oil layer pollution prevention string at a preset wellbore depth;

[0007] The packer is used to seal the wellbore annulus;

[0008] The protector is used to control the flow direction of the fluid in the wellbore;

[0009] The retractor can be converted from a locked state to a freely retractable state to partially offset the force applied to the packer.

[0010] In one or some optional embodiments, the positioner comprises at least two anchoring mechanisms distributed circumferentially;

[0011] The anchoring mechanism includes slips, a first elastic member and a first soluble pin;

[0012] The first elastic member is disposed inside the slip, and the first soluble pin locks the slip so that the first elastic member is in a compressed state.

[0013] In one or some optional embodiments, the packer is a multi-layer leather cup packer;

[0014] The packer can have an interference fit with the wellbore;

[0015] The outer circumference of the packer is provided with chamfers at the top and bottom, so that the packer can be easily lowered into or pulled out of the wellbore.

[0016] In one or some optional embodiments, the protector comprises:

[0017] A cylinder, wherein the inner cavity of the cylinder is connected to the wellbore annulus;

[0018] A ball cover is arranged in the inner cavity of the cylinder, and the ball cover is provided with a limited space, and the limited space is communicated with the inner cavity of the cylinder;

[0019] A sphere, movably arranged in the limited space;

[0020] A core shaft is connected to the ball cover, the interior of the core shaft is connected to the limited space and the wellbore annulus, and the sphere can be sealed at the bottom of the ball cover to cut off the connection between the core shaft and the ball cover;

[0021] A transposition sleeve is connected to the cylinder body and sleeved on the outside of the core shaft. The transposition sleeve can cut off the communication between the inside of the core shaft and the annulus of the wellbore.

[0022] In one or some optional embodiments, the retractor comprises a second elastic member, a second soluble pin, an inner cylinder and an outer cylinder;

[0023] The second elastic member is disposed between the inner tube and the outer tube, and the second soluble pin locks the inner tube to the outer tube, so that the second elastic member is in a compressed state.

[0024] In a second aspect, an embodiment of the present invention provides an oil layer anti-pollution method, using the oil layer anti-pollution column described in the first aspect, characterized in that it comprises:

[0025] Lowering the oil layer anti-pollution pipe string into the wellbore;

[0026] Positioning the oil layer anti-pollution pipe string at a preset wellbore depth by means of a positioner, and plugging the wellbore annulus by means of a packer;

[0027] The force exerted on the packer is partially offset by converting the expander from a locked state to a free expansion state;

[0028] When washing the well, the washing fluid is injected into the central pipe, the central passage of the oil layer anti-pollution pipe string is blocked through the protector, and the washing fluid flows to the wellbore annulus above the packer to establish a well washing cycle;

[0029] During production, crude oil flows from the bottom of the well to the central pipe, and the central passage of the oil layer anti-pollution pipe string is opened through the protector;

[0030] When the pipe string is pulled out, the oil layer anti-pollution pipe string is lifted up, the oil drain channel is opened to drain the oil, and the oil layer anti-pollution is pulled out.

[0031] In one or some optional embodiments, the oil layer anti-pollution method further comprises:

[0032] When the positioner reaches the preset depth, the first soluble pin is dissolved, and the first elastic member pops outward, so that the slips expand outward and cling tightly to the inner wall of the wellbore to position the oil layer pollution prevention string at the preset wellbore depth.

[0033] In one or some optional embodiments, the oil layer anti-pollution method further comprises:

[0034] During the well washing process, the washing fluid is pumped into the central pipe, pushing the ball to the bottom of the ball cover, cutting off the connection between the core shaft and the ball cover, and blocking the central passage of the oil layer anti-pollution pipe string, so that the washing fluid flows into the inner cavity of the barrel and then enters the wellbore annulus.

[0035] In one or some optional embodiments, the oil layer anti-pollution method further comprises:

[0036] During the production process, crude oil flows from bottom to top, pushing the sphere to the top of the spherical cover and opening the central passage of the oil layer anti-pollution string.

[0037] In one or some optional embodiments, the oil layer anti-pollution method further comprises:

[0038] After the oil layer anti-pollution pipe string is positioned, the second soluble pin is dissolved to convert the expansion joint from a locked state to a free expansion state, so that the inner tube can expand and contract up and down relative to the outer tube to partially offset the force on the packer.

[0039] In one or some optional embodiments, the oil layer anti-pollution method further comprises:

[0040] When killing the well, a killing fluid is injected into the wellbore annulus, so that the killing fluid reaches the top of the packer and then returns upward, and reaches the wellhead through a deep well pump, thus establishing a killing circulation.

[0041] In one or some optional embodiments, the oil layer anti-pollution method further comprises:

[0042] When the tubing string is lifted, the oil layer anti-pollution tubing string is lifted up, the sphere blocks the bottom of the ball cover, the connection between the core shaft and the ball cover is cut off, and the displacement sleeve moves upward relative to the core shaft, so that the inside of the core shaft is connected with the wellbore annulus, and the remaining crude oil in the inner cavity of the barrel flows to the core shaft and then leaks out.

[0043] The beneficial effects of the above technical solution provided in the embodiments of the present invention include at least:

[0044] The oil layer anti-pollution tubing string provided in the embodiment of the present invention is positioned against the inner wall of the wellbore by a positioner, the wellbore annulus is blocked by a sealer, the flow direction of the fluid in the wellbore is controlled by a protector, and different fluid pathways are established, so that the well washing fluid flows directly to the wellbore annulus after passing through the protector, forming a well washing cycle, and the crude oil is produced from the center pipe after flowing through the protector from the bottom of the well, thereby preventing the well washing fluid from flowing into the bottom of the well to cause oil layer pollution, and facilitating the switching between production and well washing operations, thereby ensuring the long-term stable production of the oil well, reducing the operating costs of well washing and production, and extending the well repair cycle; the stability of the sealer is ensured by the positioner and the telescopic device, and the sealer is prevented from being subjected to force and friction due to vibration, thereby ensuring the stability of the oil layer anti-pollution tubing string, increasing the service life of the oil layer anti-pollution tubing string, and improving the oil layer anti-pollution effect of the oil layer anti-pollution tubing string.

[0045] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0046] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0048] Figure 1 This is a schematic diagram of the structure of an oil layer anti-pollution string provided in an embodiment of the present invention;

[0049] Figure 2 A schematic diagram of the use status of the oil layer anti-pollution pipe string provided in an embodiment of the present invention;

[0050] Figure 3 The figure is a schematic flow chart of the oil layer pollution prevention method provided in an embodiment of the present invention.

[0051] In the figure:

[0052] 1 is a telescopic device, 11 is an inner cylinder, and 12 is an outer cylinder;

[0053] 2 is a protector, 21 is a cylinder, 22 is a ball cover, 23 is a ball, 24 is a core shaft, 241 is an oil drain hole, 25 is a displacement sleeve, and 26 is a shear pin;

[0054] 3 is a packer;

[0055] 4 is a positioner, 41 is an anchoring mechanism, 411 is a slip, 412 is a first elastic member, and 413 is a first soluble pin;

[0056] 5 is a central pipe, 6 is a rodless pump, and 7 is a wellbore annulus. DETAILED DESCRIPTION

[0057] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0058] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", "far", "near", "front", "back" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0059] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] The inventors found that after long-term production of oil wells, the formation pressure will gradually decrease, and the well washing fluid mixed with various dirty things will enter the underground, causing pollution to the oil layer, causing the oil well to reduce production or even stop producing oil, which greatly increases the cost of oil field production.

[0061] Based on this, an embodiment of the present invention provides an oil layer anti-pollution pipe column and an oil layer anti-pollution method, which are described in detail below through specific embodiments.

[0062] Embodiment 1

[0063] The embodiment of the present invention provides an oil layer anti-pollution column, referring to Figure 1 and Figure 2As shown, it includes a central pipe 5, a telescoping device 1, a protector 2, a packer 3 and a positioner 4 connected in sequence from top to bottom;

[0064] The positioner 4 can expand outward and adhere to the inner wall of the wellbore to position the oil layer pollution prevention string at a preset wellbore depth;

[0065] The packer 3 is used to seal the wellbore annulus 7;

[0066] Protector 2, used to control the flow direction of the fluid in the wellbore;

[0067] The retractor 1 can be converted from a locked state to a freely retractable state to partially offset the force exerted on the packer 3 .

[0068] In the embodiment of the present invention, referring to Figure 1 As shown, the positioner 4 includes at least two circumferentially distributed anchoring mechanisms 41, and the anchoring mechanism 41 includes a slip 411, a first elastic member 412, and a first soluble pin 413; the first elastic member 412 is arranged inside the slip 411, and the first soluble pin 413 locks the slip 411 so that the first elastic member 412 is in a compressed state. After the oil layer anti-pollution string is lowered into the wellbore, the first soluble pin 413 dissolves under the action of the high temperature at the bottom of the well, and the locking of the slip 411 is released, so that the slip 411 expands outward under the elastic force of the first elastic member 412 and is close to the inner wall of the wellbore, thereby realizing the positioning of the oil layer anti-pollution string.

[0069] In the embodiment of the present invention, referring to Figure 1 As shown, the packer 3 can be interference fit with the wellbore, thereby sealing the wellbore annulus 7, so that the well washing fluid cannot enter the oil layer from the wellbore annulus 7; the packer 3 is a multi-layer leather cup packer, which can withstand a larger pressure difference after being lowered into the wellbore with the oil layer anti-pollution pipe string, thereby improving the sealing effect and sealing stability. The outer periphery of the packer 3 is provided with chamfers at the top and bottom, so that the packer 3 is easy to be lowered into or pulled out of the wellbore.

[0070] In the embodiment of the present invention, referring to Figure 1 As shown, the protector 2 comprises a barrel 21, a ball cover 22, a spherical body 23, a core shaft 24 and a displacement sleeve 25. The inner cavity of the barrel 21 is connected to the wellbore annulus 7, the spherical body 22 is arranged in the inner cavity of the barrel 21, and a limited space (not shown in the figure) is arranged on the upper part of the spherical body 22, and the limited space is connected to the inner cavity of the barrel 21; the spherical body 23 is movably arranged in the limited space, the core shaft 24 is connected to the spherical body 22, the inside of the core shaft 24 is connected to the limited space and the wellbore annulus 7, and the spherical body 23 can be blocked at the bottom of the spherical body 22 to cut off the connection between the core shaft 24 and the spherical body 22; the displacement sleeve 25 is connected to the barrel 21 and is sleeved on the outside of the core shaft 24, and the displacement sleeve 25 can cut off the connection between the inside of the core shaft 24 and the wellbore annulus 7.

[0071] In the embodiment of the present invention, referring to Figure 1 As shown, the telescope 1 includes a second elastic member (not shown in the figure), a second soluble pin (not shown in the figure), an inner tube 11 and an outer tube 12; the second elastic member is arranged between the inner tube 11 and the outer tube 12, and the second soluble pin locks the inner tube 11 to the outer tube 12, so that the second elastic member is in a compressed state, thereby locking the telescope 1 in a contracted state. The dissolution time of the second soluble pin is longer than the dissolution time of the first soluble pin 413. Therefore, when the oil layer pollution prevention string is lowered into the wellbore and the positioning is completed, the second soluble pin dissolves, the inner tube 11 extends under the elastic force of the second elastic member, and the telescope 1 is converted into a free telescopic state. The telescope 1 can partially offset the force on the packer 3 in the free telescopic state, which helps the packer 3 to maintain stability, prevent the packer 3 from sliding relative to the wellbore under the action of factors such as mechanical vibration, thereby avoiding wear of the packer 3 and extending the service life of the packer 3.

[0072] The oil layer anti-pollution string provided in the embodiment of the present invention is positioned by the positioner 4 against the inner wall of the wellbore, the wellbore annulus 7 is blocked by the packer 3, and the flow direction of the fluid in the wellbore is controlled by the protector 2, so that the well washing fluid flows directly to the wellbore annulus 7 after passing through the protector 2, forming a well washing cycle, and the crude oil is produced from the central pipe 5 after flowing through the protector 2 from the bottom of the well, thereby preventing the well washing fluid from flowing into the bottom of the well to cause oil layer pollution, and facilitating the switching between production and well washing operations; continuous mechanical vibration is generated during operation, and the positioning is performed by the lower positioner 4, and the upper telescopic device 1 is freely retracted to prevent the packer 3 from being subjected to force and friction due to vibration, thereby ensuring the stability of the oil layer anti-pollution string, increasing the service life of the oil layer anti-pollution string, and improving the oil layer anti-pollution effect of the oil layer anti-pollution string.

[0073] Embodiment 2

[0074] Based on the same inventive concept, the embodiment of the present invention also provides an oil layer anti-pollution method, using the oil layer anti-pollution column of embodiment 1, referring to Figure 3 As shown, including:

[0075] S101: lowering the oil layer pollution prevention string into the wellbore;

[0076] S102: positioning the oil layer anti-pollution pipe string at a preset wellbore depth by means of the positioner 4, and sealing the wellbore annulus 7 by means of the packer 3;

[0077] S103: converting the telescopic device 1 from a locked state to a free telescopic state to partially offset the force exerted on the packer 3;

[0078] S104: When washing the well, the washing fluid is injected into the central pipe 5, the central passage of the oil layer anti-pollution string is blocked through the protector 2, and the washing fluid flows to the wellbore annulus 7 above the packer 3 to establish a well washing cycle;

[0079] S105: During production, crude oil flows from the bottom of the well to the central pipe 5, and the central passage of the oil layer anti-pollution pipe string is opened through the protector 2;

[0080] S106: When lifting the pipe string, the oil layer anti-pollution pipe string is lifted up, the oil drainage channel is opened to drain the oil, and the oil layer anti-pollution pipe string is lifted out.

[0081] In an embodiment of the present invention, the positioner 4 is in a retracted state during the process of going down the well. When the oil layer anti-pollution tubing reaches a preset depth range in the wellbore and stays there for a period of time, the anchoring mechanism 41 of the positioner 4 expands outward and adheres closely to the inner wall of the wellbore, thereby positioning the oil layer anti-pollution tubing at the preset depth in the wellbore. Specifically, the process of the anchoring mechanism 41 expanding outward may include: the first soluble pin 413 dissolves under the action of the high temperature at the bottom of the well, and after the first soluble pin 413 dissolves, the lock on the cava 411 is released, so that the cava 411 pops outward and adheres closely to the inner wall of the wellbore under the elastic force of the first elastic member 412, thereby realizing the positioning of the oil layer anti-pollution tubing.

[0082] In the embodiment of the present invention, the packer 3 has an interference fit with the wellbore casing. After the oil layer anti-pollution string is lowered into the wellbore, the packer 3 can tightly seal the wellbore annulus 7 and separate the wellbore annulus 7 up and down, so that the well washing fluid will not enter the bottom of the well from the wellbore annulus 7, thereby preventing the oil layer from being polluted. Since the outer periphery of the packer 3 is provided with chamfers at the top and bottom, and the outer layer of the packer 3 is a material with strong flexibility, such as rubber, the packer 3 can be smoothly lowered into the wellbore without affecting the lowering of the oil layer anti-pollution string as a whole. The packer 3 is configured as a multi-layer leather cup packer 3, which can achieve multi-stage plugging, thereby being able to withstand a larger pressure difference, improve the plugging effect and the sealing stability, and thus ensure the anti-pollution effect of the oil layer anti-pollution string.

[0083] In a specific embodiment, the oil layer anti-pollution pipe string is positioned at a preset wellbore depth by the positioner 4, and the wellbore annulus 7 is blocked by the packer 3, which may specifically include: when the positioner 4 reaches the preset depth, wait for a period of time to ensure that the first soluble pin 413 is dissolved, the anchoring mechanism 41 expands outward to complete the positioning, and the packer 3 performs long-term isolation of the wellbore annulus 7. Since the positioner 4 is arranged below the packer 3, the positioner 4 plays a certain supporting role on the oil layer anti-pollution pipe string after positioning, so that the packer 3 is more stable during production or well washing operations, and to a certain extent, the wear of the packer 3 due to mechanical vibration and other factors is avoided.

[0084] In the embodiment of the present invention, since the dissolution time of the second soluble pin is longer than that of the first soluble pin 413, after the positioning is completed, the telescopic device 1 is still in a compressed closed state. After waiting for a period of time, the second soluble pin dissolves, and the telescopic device 1 changes from the original compressed closed state to a free telescopic state. In the subsequent production and well washing operations, the telescopic device 1 stretches up and down, partially offsetting the force exerted on the packer 3, making the packer 3 more stable during the production or well washing operations, and to a certain extent avoiding the wear of the packer 3 due to friction with the inner wall of the wellbore due to mechanical vibration and other factors. The telescopic device 1 is a double-layer long cylindrical structure, and is made of high temperature and high pressure resistant materials, which can adapt to oil wells of various depths and viscosities.

[0085] In the embodiment of the present invention, the force applied to the packer 3 is partially offset by converting the expander 1 from a locked state to a freely expandable state. Specifically, the method may include: after the positioner 4 completes positioning, waiting for the second soluble pin to dissolve, thereby releasing the lock on the inner tube 11, so that the inner tube 11 can freely expand and contract under the elastic force of the second elastic member, thereby partially offsetting the force applied to the packer 3.

[0086] In the embodiment of the present invention, when the oil layer anti-pollution pipe string is positioned and the telescopic device 1 is converted into a free telescopic state, production operations and well washing operations can be started. A rodless pump 6 can also be arranged in the oil layer anti-pollution pipe for oil production.

[0087] In the embodiment of the present invention, the protector 2 is a multi-channel assembly, which can establish different passages by controlling the flow direction of the fluid in the wellbore, so that well washing and production use different passages respectively, and cooperate with the packer 3 to prevent the well washing fluid from entering the oil layer, thereby achieving the effect of preventing oil layer pollution.

[0088] When washing the well, the washing fluid is injected from the top of the central pipe 5. The washing fluid flows from top to bottom in the oil layer anti-pollution pipe column. After entering the protector 2, the sphere 23 is pushed to the bottom of the ball cover 22. The sphere 23 and the bottom of the ball cover 22 are tightly matched under the pressure of the washing fluid, thereby blocking the passage below the bottom of the ball cover 22, so that the washing fluid cannot continue to flow down to the bottom of the well in the oil layer anti-pollution pipe column, thereby preventing the oil layer from being contaminated by the washing fluid. The protector 2 is arranged above the packer 3, and the inner cavity of the cylinder 21 is connected to the wellbore annulus 7. After the passage below the bottom of the ball cover 22 is blocked, the washing fluid flows from the protector 2 to the wellbore annulus 7. The blocking of the packer 3 prevents the washing fluid from falling from the wellbore annulus 7 into the bottom oil layer of the well, but returns from the wellbore annulus 7. At this point, the establishment of the well washing circulation passage is completed.

[0089] During production, crude oil flows from the bottom of the well into the oil layer anti-pollution string, and the crude oil flows from bottom to top in the oil layer anti-pollution string. After entering the protector 2, the sphere 23 is pushed away from the bottom of the ball cover 22, so that the sphere 23 is against the top of the ball cover 22. Since the side of the limiting space on the upper part of the ball cover 22 is hollow, the crude oil can smoothly ascend to the central pipe 5 in the oil layer anti-pollution string until it is produced to the ground. At this point, the establishment of the production path is completed.

[0090] In the embodiment of the present invention, the wellbore annulus 7 is isolated by the packer 3, and the fluid flow direction is controlled by the protector 2 to establish different passages, which can not only prevent the well washing fluid from contaminating the oil layer and avoid oil layer damage and production reduction, but also realize the convenient switching between production operations and well washing operations, and the two operations can be switched at any time without setting up special procedures; further, through the supporting effect of the positioner 4 and the buffering effect of the expansion joint 1, the isolation stability of the packer 3 is guaranteed, and the service life of the packer 3 is extended.

[0091] In the embodiment of the present invention, referring to Figure 1 As shown, the protector 2 is also provided with a shear pin 26, which is inserted into the transposition sleeve 25 and the core shaft 24 to fix the transposition sleeve 25 to the outside of the core shaft 24 to ensure that the transposition sleeve 25 does not slide down; an oil drain hole 241 is provided on the side of the core shaft 24, and if the shear pin 26 breaks, the transposition sleeve 25 slides down to open the oil drain hole 241, so that the remaining crude oil in the inner cavity of the cylinder 21 flows into the core shaft 24 and then leaks out from the oil drain hole 241; lifting the oil layer anti-pollution pipe string can cause the shear pin 26 to break.

[0092] In a specific embodiment, when the above-mentioned tubing is lifted, the oil layer anti-pollution tubing is lifted, the oil drain channel is opened to drain the oil, and the oil layer anti-pollution tubing is lifted out. Specifically, it may include: lifting the oil layer anti-pollution tubing, cutting the shear pin 26, so that the displacement sleeve 25 slides down to open the oil drain hole 241, and the remaining crude oil in the oil layer anti-pollution tubing flows into the core shaft 24 through the inner cavity of the cylinder 21 and then leaks out, and the oil layer anti-pollution tubing continues to be lifted out.

[0093] In a specific embodiment, the oil layer pollution prevention method may also include: when killing the well, injecting killing fluid into the wellbore annulus 7, so that the killing fluid reaches the top of the packer 3 and then returns upward, and reaches the wellhead through a deep well pump, establishing a killing circulation, thereby completing the well killing.

[0094] In the embodiment of the present invention, both the well washing operation and the well killing operation can use a deep well pump to pump the well washing fluid or the well killing fluid into the wellbore. The deep well pump can be a tubular pump or an electric pump, which is suitable for deep well washing and killing.

[0095] The oil layer pollution prevention method provided in the embodiment of the present invention isolates the wellbore annulus 7 through the packer 3, improves the stability of the packer 3 through the positioner 4 and the expander 1, and establishes different fluid pathways through the protector 2. Without affecting normal production, the well washing fluid mixed with dirt is prevented from entering the oil layer, thereby ensuring the long-term stable production of the oil well. The oil leakage channel established by the protector 2 prevents the crude oil from splashing onto the ground when the tubing is lifted, thereby reducing the operating costs of well washing and production, extending the well repair cycle, and protecting the oil layer and the ground environment from being damaged, while greatly improving the economic benefits.

[0096] Obviously, various changes and modifications may be made to the present invention by those skilled in the art without departing from the spirit and scope of the present invention. The present disclosure is not limited to the precise structure described above and shown in the accompanying drawings, and various changes and modifications may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims. Thus, if these changes and modifications of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these changes and modifications.

Claims

1. An oil layer anti-pollution column, characterized in that: It includes a central pipe, a retractor, a protector, a packer and a positioner connected in sequence from top to bottom; The positioner can expand outward and adhere to the inner wall of the wellbore to position the oil layer pollution prevention string at a preset wellbore depth; The packer is used to seal the wellbore annulus; The protector is used to control the flow direction of the fluid in the wellbore; The retractor can be converted from a locked state to a freely retractable state to partially offset the force applied to the packer.

2. The oil layer anti-pollution pipe string according to claim 1, characterized in that: The positioner comprises at least two anchoring mechanisms distributed circumferentially; The anchoring mechanism includes slips, a first elastic member and a first soluble pin; The first elastic member is disposed inside the slip, and the first soluble pin locks the slip so that the first elastic member is in a compressed state.

3. The oil layer anti-pollution pipe string according to claim 1, characterized in that: The packer is a multi-layer leather cup packer; The packer can have an interference fit with the wellbore; The outer circumference of the packer is provided with chamfers at the top and bottom, so that the packer can be easily lowered into or pulled out of the wellbore.

4. The oil layer anti-pollution pipe string according to claim 1, characterized in that: The protector comprises: A cylinder, wherein the inner cavity of the cylinder is connected to the wellbore annulus; A ball cover is arranged in the inner cavity of the cylinder, and the ball cover is provided with a limited space, and the limited space is communicated with the inner cavity of the cylinder; A sphere, movably arranged in the limited space; A core shaft is connected to the ball cover, the interior of the core shaft is connected to the limited space and the wellbore annulus, and the sphere can be sealed at the bottom of the ball cover to cut off the connection between the core shaft and the ball cover; A transposition sleeve is connected to the cylinder body and sleeved on the outside of the core shaft. The transposition sleeve can cut off the communication between the inside of the core shaft and the annulus of the wellbore.

5. The oil layer anti-pollution pipe string according to claim 1, characterized in that: The telescoping device comprises a second elastic member, a second soluble pin, an inner cylinder and an outer cylinder; The second elastic member is disposed between the inner tube and the outer tube, and the second soluble pin locks the inner tube to the outer tube, so that the second elastic member is in a compressed state.

6. A method for preventing oil layer pollution, characterized in that: The oil layer anti-pollution pipe string according to any one of claims 1 to 5 is characterized by comprising: Lowering the oil layer anti-pollution pipe string into the wellbore; Positioning the oil layer anti-pollution pipe string at a preset wellbore depth by means of a positioner, and plugging the wellbore annulus by means of a packer; The force exerted on the packer is partially offset by converting the expander from a locked state to a free expansion state; When washing the well, the washing fluid is injected into the central pipe, the central passage of the oil layer anti-pollution pipe string is blocked through the protector, and the washing fluid flows to the wellbore annulus above the packer to establish a well washing cycle; During production, crude oil flows from the bottom of the well to the central pipe, and the central passage of the oil layer anti-pollution pipe string is opened through the protector; When the pipe string is pulled out, the oil layer anti-pollution pipe string is lifted up, the oil drain channel is opened to drain the oil, and the oil layer anti-pollution pipe string is pulled out.

7. The oil layer anti-pollution method according to claim 6, characterized in that: Also includes: When the positioner reaches the preset depth, the first soluble pin is dissolved, and the first elastic member pops outward, so that the slips expand outward and cling tightly to the inner wall of the wellbore to position the oil layer pollution prevention string at the preset wellbore depth.

8. The oil layer anti-pollution method according to claim 6, characterized in that: Also includes: During the well washing process, the washing fluid is pumped into the central pipe, pushing the ball to the bottom of the ball cover, cutting off the connection between the core shaft and the ball cover, and blocking the central passage of the oil layer anti-pollution pipe string, so that the washing fluid flows into the inner cavity of the barrel and then enters the wellbore annulus.

9. The oil layer anti-pollution method according to claim 6, characterized in that: Also includes: During the production process, crude oil flows from bottom to top, pushing the sphere to the top of the spherical cover and opening the central passage of the oil layer anti-pollution string.

10. The oil layer anti-pollution method according to claim 6, characterized in that: Also includes: After the oil layer anti-pollution pipe string is positioned, the second soluble pin is dissolved to convert the expansion joint from a locked state to a free expansion state, so that the inner tube can expand and contract up and down relative to the outer tube to partially offset the force on the packer.

11. The oil layer anti-pollution method according to claim 6, characterized in that: Also includes: When killing the well, a killing fluid is injected into the wellbore annulus, so that the killing fluid reaches the top of the packer and then returns upward, and reaches the wellhead through a deep well pump, thus establishing a killing circulation.

12. The oil layer anti-pollution method according to claim 6, characterized in that: Also includes: When the tubing string is lifted, the oil layer anti-pollution tubing string is lifted up, the sphere blocks the bottom of the ball cover, the connection between the core shaft and the ball cover is cut off, and the displacement sleeve moves upward relative to the core shaft, so that the inside of the core shaft is connected with the wellbore annulus, and the remaining crude oil in the inner cavity of the barrel flows to the core shaft and then leaks out.

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