Underwater release rubber plug and well completion pipe string

Abstract

The invention provides an underwater release rubber plug and a well completion pipe string, the underwater release rubber plug comprises a sleeve top plug, a sealing cavity and a balance valve connected with the sleeve top plug through a connecting part, part of the balance valve is arranged in the sealing cavity, the inner wall of the sleeve top plug is provided with a sealing ring groove, and the sealing ring groove is arranged above the connecting part. Stress concentration at the position of the sealing ring groove can be avoided, the risk that a casing top plug is released in advance and blocks an overflowing channel is eliminated, the later plug drilling time is shortened, and normal well completion construction is guaranteed; and meanwhile, the quick-mounting structure can improve the field mounting efficiency and reduce the field stop time.

Description

Technical Field

[0001] The invention relates to the field of oil and gas well drilling and completion, and in particular to an underwater release plug and a completion string. Background Art

[0002] In recent years, exploration and development have gradually developed into deepwater areas. In deepwater development, semi-submersible platforms are usually used to complete wellbore development, and underwater release plug technology is adopted in the cementing process.

[0003] During the cementing construction process, the pressure at the underwater release plug changes in real time, and the rubber bowls of the casing top plug and casing bottom plug can achieve one-way sealing. When the circulating pressure increases, the pressure can enter the sealing chamber of the annulus through the rubber bowl. When the circulating pressure decreases, due to the one-way sealing effect of the rubber bowl, the underwater release plug cannot release the pressure through the rubber bowl. The balancing valve starts to open the circulation channel, and the piston of the balancing valve can move back and forth in the sealing chamber with the fluctuation of the circulation pressure to achieve pressure balance. The piston of the balancing valve slides upward and exposes the leakage hole to release the pressure. After the pressure is balanced, the piston of the balancing valve resets under the action of the spring and closes the channel to achieve sealing.

[0004] Before cementing, release the lower drill pipe rubber plug and use cement slurry to replace it. When the lower drill pipe rubber plug reaches the casing bottom plug, it forms a seal with the impact seat. When the pressure reaches 5-6MPa, cut the shear nail to release the casing bottom plug; after the rubber plug is compounded, the casing bottom plug and the casing top plug run down to the floating collar together and impact seal. When the pressure reaches 8-10MPa, break through the rupture disk to achieve flow, and the cement slurry passes through the floating collar through the flow channel and enters the annulus after circulation. After cementing is completed, release the upper drill pipe rubber plug and use drilling fluid to replace the cement slurry; when the upper drill pipe rubber plug runs to the casing top plug, it is sealed through the impact seat. When the pressure reaches 17-18MPa, cut the shear nail to release the casing top plug. After the rubber plug is compounded, the casing bottom plug and the casing top plug run down to the floating collar together to achieve cementing construction.

[0005] The balancing valve is sealed by the sealing ring in the sealing ring groove, and the balancing valve is connected to the casing top plug. After multiple reciprocating movements, the reliability of the balancing valve will be reduced. Once the sealing ring cannot be retracted into the sealing ring groove and is squeezed out of the sealing ring groove by the piston, the balancing valve will fail and cannot release pressure through reciprocating sliding. As a result, the pressure that cannot be released in the sealing cavity will directly act on the casing top plug. The sealing ring groove is subjected to the downward pulling force F1 applied by the sealing cavity, and is also subjected to the upward pulling force F2 applied by the connection between the balancing valve and the casing top plug (such as Figure 1As shown in the figure, under the combined action of the two pulling forces, the sealing ring groove is tensilely broken, which leads to the premature release of the casing top plug. The casing top plug and the casing bottom plug run to the floating collar position together and cannot penetrate the rupture disk, resulting in high pressure holding phenomenon. The cement slurry in the casing cannot circulate into the annulus, resulting in a "sausage stuffing" accident.

[0006] In summary, the existing underwater release plug technology has the risk of premature release of the top plug. Therefore, it is urgent to propose an underwater release plug that can prevent the casing top plug from being released prematurely. Summary of the invention

[0007] One object of the present invention is to provide an underwater release plug and a completion string, so that the sealing ring groove is located between the connecting part and the sealing cavity, and the sealing ring groove is subjected to the downward pressure applied by the sealing cavity, and is also subjected to the upward pressure applied by the connecting part, thereby avoiding stress concentration at the sealing ring groove, eliminating the risk of premature release of the casing top plug and blocking the flow channel, reducing the later drilling plugging time, and ensuring the normal progress of the completion construction.

[0008] According to the present invention, there is provided an underwater release rubber plug, comprising: a casing top plug, a sealing cavity and a balancing valve connected to the casing top plug via a connecting portion, wherein a portion of the balancing valve is arranged in the sealing cavity, and a sealing ring groove is provided on the inner wall of the casing top plug, and the sealing ring groove is arranged above the connecting portion.

[0009] In a preferred embodiment, the casing top plug is connected to the balancing valve via threads.

[0010] In a preferred embodiment, the plug core of the casing top plug is made of phenolic resin material.

[0011] In a preferred embodiment, the outer wall of the sleeve top plug is provided with a rubber bowl in contact with the inner wall of the sleeve, and the rubber bowl can leak by turning over under a certain pressure.

[0012] In a preferred embodiment, the underwater release rubber plug also includes: a casing bottom plug arranged below the casing top plug and connected thereto, a rupture disk being arranged inside the casing bottom plug, and when the casing top plug and the casing bottom plug descend to the floating collar, the rupture disk can be pierced by holding pressure to achieve flow.

[0013] In a preferred embodiment, the underwater release plug further includes: a drill rod joint and an upper joint arranged above the sealing cavity and the balancing valve, the drill rod joint is arranged above the upper joint, and its lower end can be inserted into the upper joint.

[0014] In a preferred embodiment, the inner wall of the upper joint and the outer wall of the drill rod joint are respectively provided with a first retaining ring groove and a second retaining ring groove, a retaining ring is arranged in the first retaining ring groove, and a plurality of fixing screws extend axially inward from the inner wall of the first retaining ring groove, and after the lower end of the drill rod joint is inserted into place, the fixing screws can squeeze the retaining ring and press the retaining ring into the second retaining ring groove to connect the drill rod joint with the upper joint.

[0015] The present invention also provides a completion tubular column, comprising: a float shoe, a second casing string, a float collar, a first casing string, an underwater release plug, a drilling tool and a drill pipe cement head, which are arranged in sequence from bottom to top, wherein the underwater release plug comprises: a casing top plug and a casing bottom plug arranged below the casing top plug and connected to the casing top plug.

[0016] In a preferred embodiment, the interior of the drill pipe cement head is provided with an upper drill pipe plug and a lower drill pipe plug in sequence from top to bottom. The upper drill pipe plug can form a seal by impacting and pressing with a collision and pressure seat provided inside the casing top plug after descending, and the lower drill pipe plug can form a seal by impacting and pressing with a collision and pressure seat provided inside the casing bottom plug after descending.

[0017] In a preferred embodiment, an anti-rotation tooth is provided at the upper end of the floating collar, and the casing top plug and the casing bottom plug can engage with the floating collar through the anti-rotation tooth after descending.

[0018] The present invention has at least the following technical effects:

[0019] According to the present invention, a casing top plug, a sealing cavity, and a balancing valve connected to the casing top plug through a connecting portion are provided. Since part of the balancing valve is arranged in the sealing cavity, a sealing ring groove is provided on the inner wall of the casing top plug, and the sealing ring groove is arranged above the connecting portion, so that the sealing ring groove is between the connecting portion and the sealing cavity, and the sealing ring groove is subjected to downward pressure applied by the sealing cavity, and also subjected to upward pressure applied by the connecting portion, thereby avoiding stress concentration at the sealing ring groove, eliminating the risk of the casing top plug being released in advance and blocking the flow passage, reducing the later drilling plugging time, and ensuring the normal progress of the well completion construction.

[0020] According to the present invention, the outer wall of the casing top plug is provided with a rubber bowl in contact with the inner wall of the casing. The rubber bowl can leak by flipping under a certain pressure. Even if the balancing valve fails in a complex situation and high pressure is generated inside the sealing chamber, the casing top plug will not be released prematurely, affecting the normal cementing construction.

[0021] According to the present invention, after all casings are lowered, the drill pipe joint is hoisted by the top drive to vertically place the underwater release plug next to the wellhead of the drilling platform, and then the top drive is lowered to allow the lower end of the drill pipe joint to be inserted into the upper joint and enter the inner hole of the plug, thereby eliminating the need to manually lift the plug for buckling and eliminating the need to rotate the plug. After the drill pipe enters the inner hole of the plug, it is tightened by the set screw, thereby simplifying the connection operation and improving the buckling efficiency.

[0022] According to the present invention, an anti-rotation tooth is provided at the upper end of the float collar, and the casing top plug and the casing bottom plug can engage with the float collar through the anti-rotation tooth. During the drilling process, the casing top plug and the casing bottom plug will not rotate with the drill bit, thereby effectively improving the drilling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The force diagram of the sealing ring groove of the underwater release plug in the prior art is schematically shown;

[0024] Figure 2 The structure diagram of the completion string including the underwater release plug of the present invention is schematically shown;

[0025] Figure 3 The force diagram of the sealing ring groove of the underwater release plug according to the present invention is schematically shown;

[0026] Figure 4 Another structural diagram of the underwater release plug according to the present invention is schematically shown.

[0027] In the present application, all drawings are schematic drawings, which are only used to illustrate the principles of the present invention and are not drawn according to the actual scale. DETAILED DESCRIPTION

[0028] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be understood that the terms "upper", "lower", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the 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 the present invention, "multiple" refers to two or more.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixed" and the like 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, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] like Figures 2 to 3 As shown, the underwater release plug 100 of the present invention comprises: a casing top plug 206, a sealing cavity 205, and a balancing valve 204 arranged above the casing top plug 206 and connected to the casing top plug 206 through a connecting portion b. The sealing cavity 205 is arranged above the casing top plug 206, and part of the balancing valve 204 is arranged in the sealing cavity 205. The sealing cavity 205 is an annulus formed between the drill pipe and the casing. The piston of the balancing valve 204 can reciprocate in the vertical direction under the cyclic pressure inside the sealing cavity 205 to achieve pressure relief. The casing top plug 206 is connected to the drill pipe by threads, and a sealing ring groove a is provided on the inner wall of the casing top plug 206. A sealing ring is arranged inside the sealing ring groove a to achieve sealing between the drill pipe, the sealing cavity 205 and the balancing valve 204. The sealing ring groove a is close to the balancing valve 204 relative to the connecting portion b, and the sealing ring groove a is arranged above the connecting portion b. Optionally, the casing top plug 206 is connected to the balance valve 204 by threads, that is, the connection part b is a thread. In the description of the present invention, "above" is closer to the drill pipe cement head 1 in the vertical direction, and correspondingly, "below" is farther away from the drill pipe cement head 1 in the vertical direction.

[0032] According to the present invention, a casing top plug 206, a sealing cavity 205, and a balancing valve 204 connected to the casing top plug 206 through a connecting portion b are provided. Since part of the balancing valve 204 is arranged in the sealing cavity 205, a sealing ring groove a is provided on the inner wall of the casing top plug 206, and the sealing ring groove a is arranged above the connecting portion b, so that the sealing ring groove a is between the connecting portion b and the sealing cavity 205, and the sealing ring groove a is subjected to a downward pressure F1' applied by the sealing cavity 205, and is also subjected to an upward pressure F2' applied by the connecting portion b, thereby avoiding stress concentration at the sealing ring groove a, eliminating the risk of the casing top plug 206 being released in advance and blocking the flow passage, reducing the later drilling plugging time, and ensuring the normal progress of the completion construction.

[0033] In one or more embodiments, the core strength of the casing top plug 206 is improved by optimizing the material formulation and structural design, and the core of the casing top plug 206 is made of phenolic resin material.

[0034] In one or more embodiments, the outer wall of the casing top plug 206 is provided with a rubber bowl in contact with the inner wall of the casing, and the strength of the rubber bowl of the casing top plug 206 is reduced by adjusting the formula or reducing the thickness of the rubber bowl, so that the rubber bowl can flip and leak under a certain pressure (for example, 8 to 10 MPa).

[0035] According to the present invention, by reducing the hardness of the rubber bowl of the casing top plug 206 so that the rubber bowl can flip over and leak under a certain pressure, even if the balancing valve 204 fails in a complex situation and high pressure is generated inside the sealing chamber 205, the casing top plug 206 will not be released prematurely, affecting normal cementing construction.

[0036] like Figure 2 As shown, the underwater release plug 100 of the present invention further includes: a casing bottom plug 207 arranged below the casing top plug 206 and connected thereto, a collision seat (not shown in the figure) is arranged inside the casing bottom plug 207, which can form a seal with the lower drill pipe plug 202 by collision and pressure, a collision seat (not shown in the figure) is arranged inside the casing top plug 206, which can form a seal with the upper drill pipe plug 201 by collision and pressure, and a rupture disk (not shown in the figure) is also arranged inside the casing bottom plug 207. When the casing top plug 206 and the casing bottom plug 207 descend to the floating collar 5, the rupture disk can be punctured by holding the pressure to achieve flow.

[0037] like Figure 2 , Figure 4 As shown, in one or more embodiments, the underwater release plug 100 of the present invention further includes: a drill pipe joint 203 and an upper joint 210 arranged above the sealing chamber 205 and the balance valve 204, the drill pipe joint 203 is arranged above the upper joint 210, and its upper end is connected to the drilling tool 3, and its lower end can be inserted into the upper joint 210. The inner wall of the upper joint 210 and the outer wall of the drill pipe joint 203 are respectively provided with a first retaining ring groove and a second retaining ring groove, a retaining ring 208 is arranged in the first retaining ring groove, and a plurality of set screws 209 extend inwardly along the axial direction from the inner wall of the first retaining ring groove, wherein the depth of the first retaining ring groove is greater than the thickness of the retaining ring 208, and the depth of the second retaining ring groove is less than the thickness of the retaining ring 208. A through hole is provided on the inner wall of the first retaining ring groove, and the set screw is installed in the hole and extends inwardly along the axial direction. Before installation, the retaining spring 208 is in an expanded state. Since the length of the first retaining spring groove from the upper end surface of the upper joint 210 is equal to the length of the second retaining spring groove from the limit step of the drill rod joint 203, after the lower end of the drill rod joint 203 is inserted into place, the set screw 209 can squeeze the retaining spring 208 and press the retaining spring 208 into the second retaining spring groove of the drill rod joint 203. At this time, a part of the retaining spring 208 is located in the first retaining spring groove, and the other part is located in the second retaining spring groove, thereby connecting the drill rod joint 203 with the upper joint 210 of the underwater release plug 2. Optionally, one or more set screws 209 can be provided in the circumferential direction of the inner wall of the first retaining spring groove of the upper joint 210 as required.

[0038] After the casing is lowered, an underwater release plug needs to be installed. The underwater release plug in the prior art has a large number of threaded circles for installing the drill bit, and when threading it, the underwater release plug system needs to be lifted to mate with the drill bit and rotate it to thread it. Due to the large size of the plug, which is heavy and time-consuming and labor-intensive to lift, the on-site threading efficiency is low, the waiting time is increased, and the cost is doubled accordingly.

[0039] According to the present invention, the inner wall of the upper joint 210 and the outer wall of the drill pipe joint 203 are respectively provided with a first retaining ring groove and a second retaining ring groove, a retaining ring 208 is arranged in the first retaining ring groove, and a plurality of set screws 209 are extended inwardly along the axial direction from the inner wall of the first retaining ring groove. After all the casings are lowered, the drill pipe joint 203 is hoisted by the top drive to vertically place the underwater release plug 2 next to the wellhead of the drilling platform, and then the top drive is lowered so that the lower end of the drill pipe joint 203 is inserted into the upper joint 210 and enters the inner hole of the plug. After the lower end of the drill pipe joint 203 is inserted in place, the set screw 209 can squeeze the retaining ring 208 and press the retaining ring 208 into the second retaining ring groove to connect the drill pipe joint 203 with the upper joint 210, so that there is no need to manually lift the plug for buckling, and there is no need to rotate the buckle. After the drill pipe enters the inner hole of the plug, it is tightened by the set screw 209, which simplifies the connection operation and improves the buckle efficiency.

[0040] like Figure 2 As shown, the present invention also provides a completion string 200 for a semi-submersible drilling platform for deep-ground tail pipe cementing or deep-water cementing, comprising: a floating shoe 7, a second casing string 6, a floating collar 5, a first casing string 4, an underwater release rubber plug 2, a drilling tool 3 and a drill pipe cement head 1 arranged in sequence from bottom to top, wherein the floating shoe 7 and the floating collar 5 can both achieve forward flow and reverse sealing. The underwater release rubber plug 2 is arranged on the upper part of the first casing string 4 and is connected to the drilling tool 3 through a drill pipe joint 203 at the underwater wellhead position. The drill pipe cement head 1 is arranged at the top of the completion pipe string 200, usually above the drilling platform, and an upper drill pipe plug 201 and a lower drill pipe plug 202 are arranged therein from top to bottom, wherein the upper drill pipe plug 201 can form a seal by impacting and pressing with a collision and pressure seat arranged inside the casing top plug 206 after descending, and the lower drill pipe plug 202 can form a seal by impacting and pressing with a collision and pressure seat arranged inside the casing bottom plug 207 after descending.

[0041] In one or more embodiments, an anti-rotation tooth is disposed at the upper end of the floating collar 5 , and the casing top plug 206 and the casing bottom plug 207 can both engage with the floating collar 5 through the anti-rotation tooth.

[0042] After the cementing construction is completed and the cement slurry solidifies, the drill tool is lowered to drill out the rubber plug and the cement below the rubber plug. According to the present invention, the upper end of the float collar 5 is provided with anti-rotation teeth, and the casing top plug 206 and the casing bottom plug 207 can be engaged with the float collar 5 through the anti-rotation teeth. During the drilling and removal process, the casing top plug 206 and the casing bottom plug 207 will not rotate with the drill bit, thereby effectively improving the drilling and removal efficiency.

[0043] Although the present invention has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. An underwater release plug, comprising: A casing top plug, a sealing cavity and a balancing valve connected to the casing top plug through a connecting portion, part of the balancing valve is arranged in the sealing cavity, and a sealing ring groove is opened on the inner wall of the casing top plug, and the sealing ring groove is arranged above the connecting portion.

2. The underwater release plug according to claim 1, characterized in that: The casing top plug is connected to the balancing valve through threads.

3. The underwater release plug according to claim 1 or 2, characterized in that: The plug core of the sleeve top plug is made of phenolic resin material.

4. The underwater release plug according to claim 3, characterized in that: The outer wall of the sleeve top plug is provided with a rubber bowl in contact with the inner wall of the sleeve, and the rubber bowl can leak by turning over under a certain pressure.

5. The underwater release plug according to claim 1, characterized in that: Also includes: A casing bottom plug is arranged below the casing top plug and connected thereto, and a rupture disk is arranged inside the casing bottom plug. When the casing top plug and the casing bottom plug descend to the float collar, the rupture disk can be punctured by holding pressure to achieve flow.

6. The underwater release plug according to claim 1, characterized in that: Also includes: A drill rod joint and an upper joint arranged above the sealing cavity and the balancing valve, wherein the drill rod joint is arranged above the upper joint, and the lower end of the drill rod joint can be inserted into the upper joint.

7. The underwater release plug according to claim 6, characterized in that: The inner wall of the upper joint and the outer wall of the drill pipe joint are respectively provided with a first retaining ring groove and a second retaining ring groove, a retaining ring is provided in the first retaining ring groove, and a plurality of set screws extend axially inward from the inner wall of the first retaining ring groove. After the lower end of the drill rod joint is inserted into place, the set screw can squeeze the retaining ring and press the retaining ring into the second retaining ring groove to connect the drill rod joint with the upper joint.

8. A completion string, characterized in that: The invention comprises the following components arranged in sequence from bottom to top: a float shoe, a second casing string, a float collar, a first casing string, an underwater release plug, a drilling tool and a drill pipe cement head, wherein the underwater release plug comprises a casing top plug and a casing bottom plug arranged below and connected to the casing top plug.

9. The underwater release plug according to claim 8, characterized in that: The interior of the drill pipe cement head is provided with an upper drill pipe plug and a lower drill pipe plug in sequence from top to bottom. The upper drill pipe plug can form a seal with the impact pressure seat provided inside the casing top plug by impacting and pressing after descending. The lower drill pipe plug can form a seal with the impact pressure seat provided inside the casing bottom plug by impacting and pressing after descending.

10. The underwater release plug according to claim 8, characterized in that: The upper end of the float collar is provided with anti-rotation teeth, and the casing top plug and the casing bottom plug can engage with the float collar through the anti-rotation teeth after descending.

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