Multifunctional pipe string for oilfield water well and construction method thereof

Abstract

The application discloses a multifunctional pipe column for an oilfield water well, comprising an inner pipe column and an outer pipe column, and discloses a construction method of the multifunctional pipe column for the oilfield water well, comprising the following steps: pre-assembling the outer pipe column and sending the outer pipe column to a designed depth; seat-sealing the outer pipe column; pre-assembling the inner pipe column and sending the inner pipe column to a specified depth; and conducting water injection / acidification / pressure drive / polymer injection construction. The application is suitable for the technical field of oilfield water injection processes, adopts a split type design, the outer pipe is long-term left in the well, the inner pipe is realized to be individually checked and replaced, formation fluid or dirt can be prevented from entering the well shaft, the effect of preventing backflow is achieved, for the well with overflow, the pipe column operation can be realized without waiting and without well killing, micro-deformation sealing is realized, the effect of high pressure bearing and anti-creeploss damage is achieved, and the service life of the pipe column in the well is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of oilfield water injection technology, specifically a multi-functional tubing string for oilfield water wells and its construction method. Background Technology

[0002] Waterflooding remains the primary development method in oilfields. It utilizes injection tubing to continuously inject surface water into the corresponding formation, displacing crude oil from the formation into the production well. Currently, commonly used injection tubing typically consists of a packer and a distributor. The packer isolates the formation, while the distributor accurately distributes the water. However, it has the following drawbacks: 1. The tubing has a single function, only allowing normal water injection and not acidizing, polymer injection, or pressure drive operations. When other operations are needed later, the existing tubing must be pulled out and replaced with the appropriate acidizing, polymer injection, or pressure drive tubing. 2. For wells with formation overflows, tubing replacement operations are usually only performed after the overflow has automatically subsided. This is because pulling up the tubing creates a negative pressure in the formation, increasing the overflow and potentially causing safety accidents during pressurized operations. III. Currently, most injection tubing is a single-layer tubing string. Surface-injected water enters the corresponding formation directly through a distributor. With technological advancements, two-layer tubing strings, such as those with layered sand control and layered water injection, have emerged. This involves inserting an additional sand control tubing string outside the existing tubing string. Surface-injected water passes through a distributor and then through the sand control mesh before entering the corresponding formation. This type of tubing string prevents formation sand from entering the tubing, but it cannot prevent formation overflow from entering the tubing. Subsequent replacement operations still require waiting for the overflow to be released, resulting in a longer well occupancy period. IV. As oilfields age, the casing inside the well will experience varying degrees of damage. Without protection, casing damage will be more severe during high-pressure water injection. However, currently commonly used water injection tubing strings do not have a top-sealing protection function for the casing. V. According to literature review, dual-tube process tubing strings have also emerged, but the seal between the inner and outer tubes relies on a sealing ring, which cannot withstand high-pressure, high-volume water injection. VI. After a certain number of years in the well, the water injection tubing needs to be completely removed for inspection and replacement, which involves a large workload and a long well occupation time. Currently, there is a lack of process tubing that can only be partially inspected and replaced.

[0003] To address the shortcomings of current water injection tubing, we have researched and designed a multi-functional tubing string capable of supporting various construction operations including water injection, acidizing, pressure drive, and polymer injection. During subsequent tubing replacement, it allows for pressurized replacement of overflow wells and separate replacement of the inner tubing section, reducing workload, saving time, and shortening well occupation periods. Simultaneously, this tubing string features anti-backflow functionality, preventing formation backflow or overflow from entering the tubing interior and maintaining cleanliness within the tubing and casing wellbore. The tubing string also incorporates a top packer to protect the casing, extending the service life of older well casings. Furthermore, a special sealing ring structure at the junction of the inner and outer tubing ensures sealing under high pressure and high flow rates. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multi-functional tubing string for oilfield water wells and its construction method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A multi-functional tubing string for oilfield water wells and its construction method, which is installed inside the casing of an oilfield water well, includes:

[0007] The inner tubing string includes a tubing anchor, a positioning plug, and a control cylinder arranged sequentially from top to bottom. The tubing anchor and the positioning plug, as well as the positioning plug and the control cylinder, are connected by small tubing of corresponding lengths. A small tubing of corresponding length is provided at the top of the tubing anchor.

[0008] An outer tubing string is fitted onto the lower end of the inner tubing string. The outer tubing string includes, from top to bottom, a positioning sealing cylinder, a Y-type packer, a check valve, and a plug. The positioning sealing cylinder and the Y-type packer, the Y-type packer and the check valve, and the check valve and the plug are all connected by large oil pipes of corresponding lengths. A positioning insert is located at the top of the positioning sealing cylinder and is engaged with the positioning sealing cylinder. The check valve is located below the control cylinder.

[0009] Preferably, the tubing anchor, the positioning plug, and the control cylinder are all connected to the small tubing via threaded connections.

[0010] Preferably, the positioning sealing cylinder, the Y-type packer, the one-way valve, and the plug are all connected to the main oil pipe via threads.

[0011] A method for constructing a multi-functional tubing string for oilfield water wells includes the following steps:

[0012] The outer tubular column is pre-assembled and delivered to the design depth;

[0013] External tube column seat seal;

[0014] The inner tubing is pre-assembled and delivered to the designated depth;

[0015] Water injection / acidification / pressure drive / polymer injection construction.

[0016] Preferably, it also includes: when the tubing is replaced later, only the inner tubing needs to be removed for replacement. When the control cylinder on the inner tubing is disengaged from the check valve, the piston of the check valve automatically resets under the spring thrust, the outlet of the check valve closes, and the inner tubing is removed for replacement.

[0017] Preferably, the pre-assembly of the outer tubing and its delivery to the designed depth includes:

[0018] Based on the design depth, the plugs, check valves, Y-type packers, and positioning sealing cylinders of the outer tubing are connected by large oil pipes of appropriate length. The upper part of the positioning sealing cylinder is connected to the delivery oil pipe, and the outer tubing is delivered to the design depth using the delivery oil pipe.

[0019] Preferably, the outer tube seat includes:

[0020] After the outer tubing reaches the designed depth, steel balls are dropped into the wellhead. Then, hydraulic pressure is applied at the wellhead using a pressurizing device to set the Y-type packer, causing the Y-type packer rubber sleeve to adhere to the casing. At the same time as pressurizing and setting the packer, the packer is released, allowing the outer tubing to detach from the delivery tubing at the positioning sealing cylinder. The part below the positioning sealing cylinder remains downhole, while the delivery tubing above the positioning sealing cylinder is pulled out of the well.

[0021] Preferably, the pre-assembly of the inner tubing and its delivery to a designated depth includes:

[0022] Based on the designed construction depth, the control cylinder, positioning insert, and tubing anchor of the inner tubing string are connected to the small tubing. The inner tubing string is then lowered to the designed depth, allowing the positioning insert of the inner tubing string to enter the positioning sealing cylinder of the outer tubing string. This causes the control mechanism of the control cylinder to contact the piston of the check valve. The control mechanism pushes the piston open, putting the check valve in the open state for the next construction step.

[0023] Preferably, the water injection / acidification / pressure displacement / polymer injection construction includes:

[0024] Water / acid / pressure drive fluid / polymer is injected from the wellhead into the water injection layer through a one-way valve for water injection / acidification / pressure drive / polymer injection operations.

[0025] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0026] 1. In this invention, the multi-functional tubing string consists of two layers, an inner and an outer layer, and is designed as a separate unit. The outer tubing remains in the well for a long period of time, while the inner tubing can be inspected and replaced separately.

[0027] 2. In this invention, after the tubing is lowered into place, the positioning insert and the positioning sealing cylinder work together to achieve the function of the top packer of the tubing, and together with the Y-type packer, they also serve as the top seal to protect the sleeve above the top seal.

[0028] 3. In this invention, the outer tubing string is equipped with a check valve. When the inner and outer tubing lose contact, the check valve piston automatically resets and closes, preventing formation fluids or contaminants from entering the wellbore and thus preventing backflow. For wells with overflow, tubing string tripping can be performed without waiting or well pressure.

[0029] 4. In this invention, the seal between the inner and outer tubes adopts an insertion design. The inner tube positioning seal uses multiple sets of V-shaped seals to achieve micro-deformation sealing, which provides high pressure resistance and resistance to creep damage, thus extending the service life of the tubing string in the well. Attached Figure Description

[0030] Figure 1 This is a diagram of the overall structure of the tubular column in this invention;

[0031] Figure 2 This is a structural diagram of the anti-backflow outer tube in this invention;

[0032] Figure 3 This is a structural diagram of the insertable inner tube in this invention.

[0033] Reference numerals: 1. Inner tubing string; 11. Small tubing; 12. Tubing anchor; 13. Positioning plug; 14. Control tube; 2. Outer tubing string; 21. Positioning sealing tube; 22. Y-type packer; 23. Large tubing; 24. Check valve; 25. Plug; 3. Casing; 4. Artificial bottom hole. Detailed Implementation

[0034] The following is in conjunction with the appendix Figure 1 This invention further illustrates the specific implementation of a multifunctional tubing string for oilfield water wells and its construction method. The multifunctional tubing string for oilfield water wells and its construction method are not limited to the descriptions in the following embodiments.

[0035] Example 1:

[0036] This embodiment provides a specific structure of a multi-functional tubing string for oilfield water wells and its construction method, such as... Figure 1 As shown, it is installed inside the casing 3 of an oilfield water well and includes:

[0037] The inner tubing string 1 includes a tubing anchor 12, a positioning plug 13, and a control cylinder 14 arranged sequentially from top to bottom. The tubing anchor 12 and the positioning plug 13, and the positioning plug 13 and the control cylinder 14 are respectively connected by small tubing 11 of corresponding length. The top of the tubing anchor 12 is provided with a small tubing 11 of corresponding length.

[0038] The outer tubing 2 is sleeved at the lower end of the inner tubing 1. The outer tubing 2 includes a positioning sealing cylinder 21, a Y-type packer 22, a check valve 24, and a plug 25 arranged sequentially from top to bottom. The positioning sealing cylinder 21 and the Y-type packer 22, the Y-type packer 22 and the check valve 24, and the check valve 24 and the plug 25 are all connected by large oil pipes 23 of corresponding lengths. The positioning insert 13 is set at the top of the positioning sealing cylinder 21 and is engaged with the positioning sealing cylinder 21. The check valve 24 is set below the control cylinder 14.

[0039] The tubing anchor 12, the positioning plug 13, and the control cylinder 14 are all connected to the small tubing 11 via threaded connections.

[0040] The positioning sealing cylinder 21, the Y-type packer 22, the check valve 24, and the plug 25 are all connected to the main oil pipe 23 by thread.

[0041] Among them, the one-way valve 24 in the outer tube column 2 has an automatic reset function, which is mainly achieved by the spring mechanism and the piston mechanism; the Y-type packer 22 has a release function, which is mainly achieved by throwing a ball to press; the control cylinder 14 in the inner tube column 1 has a control mechanism, which can achieve the purpose of opening the one-way valve 24 on the outer tube column 2; the outer wall of the positioning insert 13 is equipped with an array of V-shaped seals, which cooperate with the positioning sealing cylinder 21 on the outer tube column 2 to achieve the sealing between the inner and outer tubes.

[0042] Example 2:

[0043] This embodiment provides a specific structure for the construction method of a multi-functional tubing string for oilfield water wells, including the following steps:

[0044] The outer tubular column 2 is pre-assembled and delivered to the design depth;

[0045] Two outer tubular columns were sealed.

[0046] The inner tubing string 1 is pre-assembled and delivered to the designated depth;

[0047] Water injection / acidification / pressure drive / polymer injection construction.

[0048] Specifically, it also includes: when the tubing is replaced later, the inner tubing 1 is removed for replacement. When the control cylinder 14 on the inner tubing 1 is disengaged from the check valve 24, the piston of the check valve 24 is automatically reset under the spring thrust, the outlet of the check valve is closed, and then the inner tubing 1 is removed for replacement.

[0049] Specifically, the outer tubular column 2 is pre-assembled and delivered to the design depth, including:

[0050] Based on the design depth, the plug 25, check valve 24, Y-type packer 22, and positioning sealing cylinder 21 of the outer tubing string 2 are connected by a large oil pipe of appropriate length. The upper part of the positioning sealing cylinder 21 is connected to the delivery oil pipe, and the outer tubing string 2 is delivered to the design depth by using the delivery oil pipe.

[0051] Specifically, the two outer tube sets include:

[0052] After the outer tubing string 2 reaches the designed depth, steel balls are dropped into the wellhead. Then, hydraulic pressure is applied at the wellhead using a pressurizing device to set the Y-type packer 22, causing the rubber sleeve of the Y-type packer 22 to adhere to the casing 3. At the same time as the pressurization and setting, the packer is released, allowing the outer tubing string 2 to detach from the delivery tubing at the positioning sealing cylinder 21. The part below the positioning sealing cylinder 21 remains downhole, while the delivery tubing above the positioning sealing cylinder 21 is pulled out of the well.

[0053] Furthermore, the inner tubing 1 is pre-assembled and fed to a specified depth, including:

[0054] Based on the design depth, the control cylinder 14, positioning plug 13, and tubing anchor 12 of the inner tubing string 1 are connected to the small tubing 11. The inner tubing string 1 is lowered to the design depth, so that the positioning plug 13 of the inner tubing string 1 enters the positioning sealing cylinder 21 of the outer tubing string 2. The control mechanism of the control cylinder 14 contacts the piston of the check valve 24. The control mechanism pushes the piston open, so that the check valve is in the open state for the next step of construction.

[0055] Further, water injection / acidification / pressure displacement / polymer injection construction includes:

[0056] When the positioning insert of the inner tubing string enters the positioning sealing cylinder of the outer tubing string, the control mechanism of the control cylinder contacts the piston of the one-way valve. The control mechanism on the control cylinder will push the piston of the one-way valve, causing the one-way valve to open and remain in the open state. The inner tubing string and the outer tubing string are connected. Water / acid / pressure drive fluid / polymer injected from the wellhead enters the water injection layer through the one-way valve 24 to carry out water injection / acidification / pressure drive / polymer injection construction.

[0057] By adopting the above technical solution:

[0058] Working principle: such as Figure 1-3 As shown, the construction process is as follows:

[0059] 1. Lowering the outer tubing string 2: According to the construction design depth, the various components of the outer tubing string 2 are transported to the design depth using oil pipes.

[0060] 2. Setting of Outer Tubing String 2: After all components of outer tubing string 2 reach the designed depth, a ball is dropped and hydraulic pressure is applied to set the Y-type packer 22 and attach the rubber sleeve to the casing 3. At the same time, the packer is released, causing outer tubing string 2 to detach from the delivery tubing at the positioning sealing cylinder 21, so that the part below the positioning sealing cylinder 21 remains downhole. The detached delivery tubing is then pulled out of the well.

[0061] 3. Lowering the inner tubing string 1: After connecting all components of the inner tubing string 1 according to the construction design using small tubing, lower it to the depth specified in the design. Ensure that the positioning seal of the inner tubing string 1 is inserted into the positioning sealing cylinder 21 of the outer tubing string 2.

[0062] 4. Water Injection / Acidizing / Pressure Drive / Polymer Injection: When the positioning insert 13 of the inner tubing string 1 enters the positioning sealing cylinder 21 of the outer tubing string 2, the control cylinder 14 on the inner tubing string 1 will simultaneously contact the one-way valve 24 on the outer tubing string 2. The control mechanism on the control cylinder 14 will push the piston of the one-way valve 24, causing the one-way valve 24 to open and remain open. At this time, the inner tubing string 1 and the outer tubing string 2 are connected. Water / acid / pressure drive fluid / polymer injected from the wellhead enters the water injection layer through the one-way valve 24 of the inner tubing string 1 and the outer tubing string 2, realizing water injection / acidizing / pressure drive / polymer injection. At this time, the positioning insert 13 and the positioning sealing cylinder 21 cooperate to realize the function of the top packer of the tubing string, and together with the Y-type packer, they also play the role of top sealing, protecting the casing above the top seal.

[0063] 5. Subsequent Replacement: During subsequent tubing string replacement, only the inner tubing string 1 needs to be removed for replacement. When the control cylinder 14 on the inner tubing string 1 disengages from the check valve 24, the piston of the check valve 24 automatically resets under spring thrust, closing the outlet of the check valve 24. At this time, the outer tubing string 2 forms a sealed space, preventing overflow water or other backflow materials from the formation from entering the tubing string, effectively preventing backflow. Furthermore, for wells experiencing overflow, currently, the inner tubing string 1 is generally only retrieved for replacement after the overflow has been completely drained. This is because the process of retrieving the tubing string creates a suction negative pressure at the bottom of the well, exacerbating the overflow and potentially causing a well kick and production accidents. With this tubing string, because the outer tubing string 2 seals the overflow within the formation, the formation overflow will not affect the retrieval and replacement of the inner tubing string 1, thus achieving the purpose of non-pressure well replacement.

[0064] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A method for constructing a multi-functional tubing string for oilfield water wells, wherein the tubing string is installed inside the casing (3) of the oilfield water well, characterized in that, include: The inner tubing string (1) includes a tubing anchor (12), a positioning plug (13), and a control cylinder (14) arranged sequentially from top to bottom. The tubing anchor (12) and the positioning plug (13), and the positioning plug (13) and the control cylinder (14) are respectively connected by small tubing (11) of corresponding length. The top of the tubing anchor (12) is provided with a small tubing (11) of corresponding length. An outer tubing column (2) is fitted onto the lower end of the inner tubing column (1). The outer tubing column (2) includes a positioning sealing cylinder (21), a Y-type packer (22), a check valve (24), and a plug (25) arranged sequentially from top to bottom. The positioning sealing cylinder (21) and the Y-type packer (22), the Y-type packer (22) and the check valve (24), and the check valve (24) and the plug (25) are all connected by large oil pipes (23) of corresponding lengths. The positioning insert (13) is located at the top of the positioning sealing cylinder (21) and is engaged with the positioning sealing cylinder (21). The check valve (24) is located below the control cylinder (14). The construction method for multi-functional tubing strings in oilfield water wells includes the following steps: The outer tubular column (2) is pre-assembled and delivered to the design depth; External tube column (2) seat seal; The inner tubular column (1) is pre-assembled and delivered to the specified depth; Water injection / acidification / pressure drive / polymer injection construction; When the tubing is replaced later, the inner tubing (1) is pulled out. When the control cylinder (14) on the inner tubing (1) is disengaged from the check valve (24), the piston of the check valve (24) is automatically reset under the spring thrust, the water outlet of the check valve is closed, and then the inner tubing (1) is pulled out for replacement.

2. The construction method for a multi-functional tubing string for oilfield water wells as described in claim 1, characterized in that: The tubing anchor (12), the positioning plug (13), and the control cylinder (14) are all connected to the small tubing (11) by threaded connections.

3. The construction method for a multi-functional tubing string for oilfield water wells as described in claim 1, characterized in that: The positioning sealing cylinder (21), the Y-type packer (22), the one-way valve (24), and the plug (25) are all connected to the large oil pipe (23) by threaded connection.

4. The construction method for a multi-functional tubing string for oilfield water wells as described in claim 1, characterized in that, The outer tubular column (2) is pre-assembled and delivered to the design depth, including: Based on the construction design depth, the plug (25), check valve (24), Y-type packer (22), and positioning sealing cylinder (21) of the outer tubing (2) are connected by a large oil pipe of appropriate length. The upper part of the positioning sealing cylinder (21) is connected to the conveying oil pipe, and the outer tubing (2) is conveyed to the design depth by using the conveying oil pipe.

5. The construction method for a multi-functional tubing string for oilfield water wells as described in claim 1, characterized in that, The outer tube column (2) seat includes: After the outer tubing string (2) reaches the designed depth, steel balls are dropped from the wellhead, and then hydraulic pressure is applied at the wellhead using a pressurizing device to set the Y-type packer (22). The rubber sleeve of the Y-type packer (22) is attached to the casing (3). While pressurizing and setting the seal, the outer tubing string (2) is released, so that the outer tubing string (2) is separated from the delivery tubing at the positioning sealing cylinder (21). The part below the positioning sealing cylinder (21) remains in the well, and the delivery tubing above the positioning sealing cylinder (21) is pulled out of the well.

6. The construction method for a multi-functional tubing string for oilfield water wells as described in claim 5, characterized in that: The inner tubular column (1) is pre-assembled and delivered to a specified depth, including: Based on the construction design depth, the control cylinder (14), positioning plug (13), and tubing anchor (12) of the inner tubing string (1) are connected to the small tubing (11). The inner tubing string (1) is lowered to the design depth so that the positioning plug (13) of the inner tubing string (1) enters the positioning sealing cylinder (21) of the outer tubing string (2) so that the control mechanism of the control cylinder (14) contacts the piston of the flow valve (24).

7. The construction method for a multi-functional tubing string for oilfield water wells as described in claim 6, characterized in that: The water injection / acidification / pressure displacement / polymer injection construction includes: Water / acid / pressure-driven fluid / polymer is injected from the wellhead and enters the water injection layer through the one-way valve (24) for water injection / acidification / pressure-driven / polymer injection construction.

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