Seal assembly energized with floating pistons

Methods and apparatus for sealing a plug within tubing that the plug is designed to be landed and set in are disclosed. The plug includes a seal assembly having a seal on the plug that is acted on by a piston. Wellbore fluid pressure acts on the piston when the valve is closed, thereby moving the piston to force the seal into sealing contact with an inside surface of the tubing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the invention generally relate to tools having a seal assembly for sealing an annulus between a tubular seat in the wellbore and the outside of the tool disposed in the tubular seat.

2. Description of the Related Art

Surface-controlled, subsurface safety valves (SCSSVs) and plugs are commonly used to shut-in oil and/or gas wells. The SCSSV or plug fits into tubing in a hydrocarbon producing well and operates to block upward flow of formation fluid through the tubing. The tubing may include a landing nipple designed to receive the SCSSV or plug therein such that the SCSSV or plug may be installed and retrieved by wireline. During conventional methods for run-in of the SCSSV or plug to the landing nipple, a tool used to lock the SCSSV or plug in place within the nipple also temporarily holds the SCSSV or plug open until the SCSSV or plug is locked in place.

Most SCSSVs are “normally closed” valves, Le., the valves utilize a flapper type closure mechanism biased to a closed position. During normal production, application of hydraulic fluid pressure transmitted to an actuator of the SCSSV maintains the SCSSV in an open position. A control line that resides within the annulus between production tubing and a well casing may supply the hydraulic pressure to a port in the nipple that permits fluid communication with the actuator of the SCSSV. In many commercially available SCSSVs, the actuator used to overcome the bias to the closed position is a hydraulic actuator that may include a rod piston or concentric annular piston. During well production, the flapper is maintained in the open position by a flow tube acted on by the piston to selectively open the flapper member in the SCSSV. Any loss of hydraulic pressure in the control line causes the piston and actuated flow tube to retract, which causes the SCSSV to return to the normally closed position. Thus, the SCSSV provides a shutoff of production flow once the hydraulic pressure in the control line is released.

The landing nipple within the tubing may become damaged by operations that occur through the nipple prior to setting the SCSSV or plug in the landing nipple. For example, operations such as snubbing and tool running using coiled tubing and slick line can form gouges, grooves, and/or ridges along the inside surface of the nipple as the operations pass through the nipple. Further, any debris on the inside surface of the nipple or any out of roundness of the nipple may prevent proper sealing of the SCSSV or plug within the nipple. Failure of the SCSSV or plug to seal in the nipple due to surface irregularities in the inner diameter of the nipple can prevent proper operation of the actuator to open the SCSSV and can prevent the SCSSV or plug from completely shutting-in the well when the SCSSV or plug is closed since fluid can pass through the annular area between the SCSSV or plug and the nipple due to the irregularities. Operating the well without a safety valve or with a safety valve or plug that does not function properly presents a significant danger. Thus, the current solution to conserve the safety in wells having damaged nipples includes an expensive and time consuming work over to replace the damaged nipples.

Therefore, a need exists for improved apparatus and methods for disposing a plug or SCSSV within tubing regardless of whether the tubing has a damaged or irregular inside surface.

SUMMARY OF THE INVENTION

According to some embodiments, a plug for obstructing a bore of a tubing located in a well includes a mandrel, a seal disposed on an outer circumference of the mandrel, wherein the seal is compressible against an outer surface of the mandrel and an inner surface of the bore, and a piston disposed below the seal and movable relative to the mandrel to compress the seal in response to a pressure differential across the plug.

For some embodiments, a plug for obstructing a bore of a tubing located in a well includes a bore blocking assembly to divide the bore with a fluid tight seal, a moveable piston disposed on an outside of the assembly and having an outside diameter that forms initial sealing contact with an inside diameter of the bore, wherein the piston is exposed to wellbore fluid pressure in the bore below the plug, and a seal disposed on an outer circumference of the assembly, wherein the seal is compressible against an outer surface of the assembly and an inner surface of the bore in response to movement of the piston.

In yet other embodiments, a method of plugging a bore of a tubing located in a well includes disposing a plug in the bore, the plug having a mandrel, a seal disposed on an outer circumference of the mandrel, and a piston disposed below the seal, and creating a pressure differential across the piston due to wellbore fluid pressure below the plug acting on the piston, thereby urging the piston toward the seal to compress the seal into sealing contact with an outer surface of the mandrel and an inner surface of the bore.

DETAILED DESCRIPTION

Embodiments of the invention generally relate to seal assemblies for any type of safety valve, dummy valve, straddle or plug designed to be landed and set within a tubular member. For some embodiments, the tubular member may form a ported landing nipple to enable fluid actuation of the safety valve, a side pocket mandrel, a sliding sleeve valve or a solid walled landing nipple. The seal assembly may be implemented with other variations of plugs, dummy valves, and subsurface safety valves different than exemplary configurations and designs shown and described herein since many operational details of these tools function independent of the seal assembly. For example, the seal assemblies may be used in all types of tools designed for landing in a nipple including wireline retrievable tools that may utilize flapper type valves or concentric type valves.

FIG. 1illustrates a production well12having an SCSSV10installed therein according to aspects of the invention as will be described in detail herein. While a land well is shown for the purpose of illustration, the SCSSV10may also be used in offshore wells.FIG. 1further shows a wellhead20, surface equipment14, a master valve22, a flow line24, a casing string26and a production tubing28. In operation, opening the master valve22allows pressurized hydrocarbons residing in the producing formation32to flow through a set of perforations34that permit and direct the flow of hydrocarbons into the production tubing28. Hydrocarbons (illustrated by arrows) flow into the production tubing28through the SCSSV10, through the wellhead20, and out into the flow line24. The SCSSV10is conventionally set in a profile within the production tubing28. Surface equipment14may include a pump, a fluid source, sensors, etc. for selectively providing hydraulic fluid pressure to an actuator (not shown) of the SCSSV10in order to maintain a flapper18of the SCSSV10in an open position. A control line16resides within the annulus35between the production tubing28and the casing string26and supplies the hydraulic pressure to the SCSSV10.

FIG. 2illustrates a sectional view of the SCSSV10within a landing nipple100in the production tubing. The SCSSV10is shown in a run-in position prior to setting of the SCSSV10within the landing nipple100. As shown, the SCSSV10includes an upper and a lower seal assembly101,103around an outside thereof, a packing mandrel124disposed inside the seal assemblies101,103and an actuator/spring housing152connected to the lower end of the packing mandrel124. The upper seal assembly101includes an upper compressible seal111formed by an upper sealing element114located between concave portions of upper V-seals or chevrons110on each side of the upper sealing element114, an upper first piston102in contact with a top of the chevrons110, and an upper second piston106in contact with a bottom of the chevrons110. Similarly, the lower seal assembly103includes a lower compressible seal113formed by a lower sealing element116located between concave portions of lower V-seals or chevrons112on each side of the lower sealing element116, a lower first piston104in contact with a bottom of the chevrons112, and a lower second piston108in contact with a top of the chevrons112. The pistons102,106,108,104are preferably annular or concentric pistons. While both the upper and lower seal assemblies101,103are shown in the embodiment inFIG. 2, the SCSSV10may include only one of either the upper or lower seal assemblies101,103. Additionally, other variations of the seals111,113may be used so long as the pistons102,106,108,104can operate to force the seals111,113into sealing contact with the nipple100.

The packing mandrel124includes an upper sub126, a middle sub128, and a lower sub130connected together such as by threads. However, the packing mandrel124may be made from an integral member or any number of subs. An annular shoulder138on the upper sub126provides a decompression stop for the upper first piston102, which is slidable along a portion of an outer diameter of the upper sub126. The upper compressible seal111located proximate to an increased outer diameter portion139of the middle sub128seals against the increased outer diameter portion139. Additionally, the increased outer diameter portion139on the middle sub126provides a compression stop for both the upper first and second pistons102,106. A snap ring136fixed relative to the middle sub126engages a portion of an upper nut132connected to a lower nut134to secure the nuts132,134relative to the middle sub. The upper and lower nuts132,134located between the second pistons106,108operate to longitudinally separate the upper and lower seal assemblies111,113. Thus, a face140of the upper nut132provides a decompression stop for the upper second piston106and a face142of the lower nut134provides a decompression stop for the lower second piston108. Both the upper and lower second pistons106,108are slidable along portions of the outer diameter of the middle sub128on each side of the nuts132,134. The lower compressible seal113located proximate to an increased outer diameter portion143of the lower sub130seals against the increased outer diameter portion143. Additionally, the increased outer diameter portion143on the middle sub126provides a compression stop for both the lower first and second pistons108,104. An end face144of the actuator/spring housing152provides a decompression stop for the lower first piston104.

The compression and decompression stops operate to limit the sliding movement of the pistons102,106,108,104of the sealing assemblies101,103. Inner seals120on the inside of the pistons102,106,108,104provide a seal between each piston and the packing mandrel124that the pistons slide along. Outer seals118on the outside of the pistons102,106,108,104provide an initial seal between each piston and the nipple100. The outer seals118may be soft O-rings with a large cross section to help ensure a sufficient initial seal between the pistons102,106,108,104and the nipple100. Thus, the initial seal provided by the outer seals118sufficiently seals against the nipple100such that fluid pressure applied to the large surface areas of the pistons102,106,108,104that are shown in contact with the decompression stops138,140,142,144causes the pistons to slide along the packing mandrel124toward the respective seal111,113.

In the run in position of the SCSSV10as shown inFIG. 2, the seal assemblies101,103are in uncompressed positions with all the pistons102,106,108,104contacting their respective decompression stops138,140,142,144. Therefore, the upper and lower seals111,113are not compressed and may not provide sealing contact with the inside surface of the nipple100and the outside of the packing mandrel124. During run-in all parts of the SCSSV10are in equal pressure so that the pistons102,106,108,104do not move. In the run-in position, the SCSSV10is temporarily held open by a running tool (not shown) using a run-in prong or other temporary opening member. Since the SCSSV10is open, wellbore fluid pressure does not act on the first pistons102,104to compress the upper and lower seals111,113. Further, fluid pressure is not supplied through the control line16such that the second pistons102,106are also not acted on to compress the upper and lower seals111,113.

Once the SCSSV10is set or locked in the nipple100by conventional methods, the temporary opening member disengages and permits normal functioning of the SCSSV10. Thus, the flapper18biases to a closed position unless fluid pressure is supplied through the control line16to a port150in the nipple100in order to actuate the SCSSV10.

FIG. 3is a sectional view of the SCSSV10in an actuated open position with the seal assemblies101,103in a first compressed position. Fluid pressure supplied through the control line16to the port150in the nipple100passes through a fluid passageway154in the upper nut132and the middle sub128of the packing mandrel124into an annular area outside the upper sub126. The fluid pressure acts on a piston rod158connected to a flow tube122to force the flow tube down against the bias of a biasing member such as a spring146. The longitudinal displacement of the flow tube122causes the flow tube122to displace the flapper18and place the SCSSV10in the actuated open position. As an example of an SCSSV actuated by a concentric piston, the fluid pressure may alternatively act on an outward facing shoulder of a flow tube located concentrically within the packing mandrel to force the flow tube down and open a flapper.

The fluid pressure supplied through the control line16used to actuate and open the SCSSV10additionally operates to place the seal assemblies101,103in the first compressed position. The fluid pressure supplied from the control line16enters the port150where the fluid enters the interior of the nipple100and acts on the second pistons106,108to slide the second pistons toward the respective seals111,113. Any wellbore pressure on the first pistons102,104is less than that on the second pistons106,108such that the first pistons102,104remain in contact with their respective decompression stops138,144. The sliding movement of the second pistons106,108pushes on the chevrons110,112, which in turn pushes on the sealing members114,116. Compression of the seals111,113caused by the sliding of the second pistons106,108forces the sealing members114,116and/or the chevrons110,112into sealing contact with the inside surface of the nipple100. Preferably, the sealing members114,116are soft O-rings with a large cross section made from a material such as Viton® (65 duro). Additionally, the chevrons110,112are preferably made from a material such as Kevlar® filled Viton®. Once the SCSSV is actuated open, wellbore fluid passes through the SCSSV10such that wellbore fluid pressure does not act to slide the first pistons102,104, and the first pistons102,104remain in contact with their respective decompression stops138,144.

FIG. 4is a sectional view of the SCSSV10set in the nipple100and biased to the closed position with the seal assemblies101,103in a second compressed position and the flapper18blocking fluid flow through the SCSSV10. As fluid pressure bleeds from the control line16during closure of the SCSSV10, the fluid pressure acting on the second pistons106,108approaches hydrostatic pressure, which along with the wellbore pressure acting on the first pistons102,104keeps the seals111,113compressed. When the wellbore pressure is greater than the pressure supplied by the control line16, the wellbore pressure acts on the first pistons102,104to slide the first pistons toward the respective seals111,113. For example, wellbore fluid pressure above the SCSSV10acts on the upper first piston102, and wellbore fluid pressure below the SCSSV10acts on the lower first piston104. The second pistons106,108slide into contact with their respective decompression stops140,142. The sliding movement of the first pistons102,104pushes on the chevrons110,112, which in turn pushes on the sealing members114,116. Therefore, compression of the seals111,113caused by the sliding of the first pistons102,104maintains sealing contact with the inside surface of the nipple100since the sealing members114,116and/or the chevrons110,112remain forced against the inside surface of the nipple100.

In both the first and second compressed positions as illustrated byFIGS. 3 and 4respectively, the upper and/or the lower seals111,113form a fluid seal with an inside surface of the nipple100that may have irregularities, grooves, recesses, and/or ridges that would prevent prior SCSSVs from properly sealing within the nipple100. Additionally, the sealing ability of the upper and/or the lower seals111,113with the chevrons110,112around the sealing members114,116increases with increased pressure to the pistons102,106,108,104. As shown, the SCSSV provides a large inner diameter flow path, and the seal assemblies101,103do not reduce or significantly reduce the inner diameter flow path through the SCSSV10.

A method for sealing a SCSSV within a nipple located in a well is provided by aspects of the invention. The method includes locating the SCSSV in the nipple using conventional running methods. The SCSSV includes at least one seal assembly disposed about an outer surface thereof, and the at least one seal assembly includes a seal, a first piston disposed on a first side of the seal, and a second piston disposed on a second side of the seal. Urging the first piston, the second piston or both the first and second piston toward the seal forces the seal into sealing contact with an inside surface of the nipple. Urging the first piston is caused by wellbore fluid pressure applied to the first piston when the SCSSV is closed. Urging the second piston is caused by fluid pressure supplied from a control line to a fluid port in fluid communication with an inside portion of the nipple.

FIG. 5illustrates a sectional view of a plug510within a landing nipple500during run-in of the plug510such that a compressible seal513of the plug510remains in an uncompressed position. The plug510includes the seal513around an outside thereof, a packing mandrel524disposed inside the seal513, and a lower bore closure housing552coupled to the lower end of the packing mandrel524. The seal513may include a middle ring515disposed between first and second sealing elements514,516with the first sealing element514located adjacent concave portions of first V-seals or chevrons512and the second sealing element516disposed proximate concave portions of second V-seals or chevrons517. The middle ring515may support without compressing and space the sealing elements514,516from one another during squeezing of elastomeric material making up the sealing elements514,516. A sliding piston504, such as an annular or concentric piston, bears on the second chevrons517either through direct contact at one end of the piston504with convex portions of the second chevrons517or through indirect coupling. The bore closure housing552contains the piston504and seal513in place around the mandrel524between an end face544of the bore closure housing552and an outward shoulder542of the mandrel524.

During run-in of the plug510, a running tool (not shown) using a run-in prong or other temporary opening member temporarily holds the plug510open by, for example, displacing a flapper valve518. Since the plug510is open, wellbore fluid pressure does not act on the piston504to compress the seal513. All parts of the plug510remain in equal pressure in the run-in position so that the piston504does not move from resting against the end face544of the bore closure housing552. One or more ports505through the wall of the packer mandrel524may ensure that no differential pressure occurs across the piston504during run-in since both sides of the piston504are therefore at the wellbore pressure. The seal513while uncompressed may not provide sealing contact with the inside surface of the nipple500and the outside of the packing mandrel524.

For some embodiments, mechanical setting of the plug510in the nipple includes engaging dogs509on the plug510within a profile507in the nipple500. Once the plug510is set or locked in the nipple500, the temporary opening member disengages and permits closure of the plug510. The disengagement may occur upon retrieval of the running tool. According to some embodiments, biasing or otherwise moving the flapper valve518to a closed position obstructs, blocks and/or seals the bore of the nipple500.

FIG. 6shows a sectional view of the plug510in a closed position and set in the nipple500with the seal513in a compressed position. Once the plug is closed, bleeding off pressure above the plug510occurs to relieve pressure at the wellhead. Inner seal520on the inside of the piston504provides a seal between the piston504and the packing mandrel524that the piston504slides along. Outer seal519on the outside of the piston504provides an initial seal between the piston504and the nipple500. The outer seal519may be a soft O-ring with a large cross section to help ensure a sufficient initial sealing between the piston504and the nipple500. Thus, wellbore fluid pressure applied to the piston504causes the piston504to slide along the packing mandrel524toward the seal513due to the initial sealing against the nipple500provided by the outer seal504. Once locked in place, the mandrel524remains stationary with respect to the nipple500such that movement of the piston504occurs relative to the mandrel524and the nipple500.

In operation, the bleeding of pressure from above the plug510may create a pressure differential across the piston504. Accordingly, wellbore pressure below the piston504acts on the piston504to urge the piston504toward the seal513as the bleeding lowers the pressure above the piston504. The ports505may facilitate draining of pressurized fluid above the piston504during the bleeding. The piston504then slides along a portion of an outer diameter of the packing mandrel524to push the seal513against the shoulder542of the mandrel524. In response to the movement of the piston504, the seal513must occupy a shorter longitudinal distance accommodated for by an increase in radial volume of the seal513. The seal513hence compresses against the outside of the mandrel524and the inside of the nipple500to ensure fluid tight separation between areas above and below the plug510. Lack of movement between the mandrel524and the nipple500during this active contact with respective inner and outer surfaces of the seal513prevents excess binding and wear of the seal513.

The seal513forms a fluid seal with the inside surface of the nipple500that may have irregularities, grooves, recesses, and/or ridges that would prevent prior plugs from properly sealing within the nipple500. Additionally, the sealing ability of the seal513with the chevrons512,517around the sealing elements514,516increases with increased pressure to the piston504. Any increase in pressure below the plug504therefore tends to improve sealing properties and thereby ensure safe containment of fluids below the plug504.