Pressure equalization device for downhole tools

A pressure equalizing tool can be run into a downhole tool on wireline or coiled tubing preferably and temporarily secured before being actuated to separate two components in a downhole tool that are in a sealing relation but are configured to be temporarily movable so as to allow pressure equalization before the downhole component is actuated. Once pressure is equalized the equalizing tool is released, usually with an applied pick up force and the downhole tool being equalized as to differential pressure can be operated with the preexisting actuation parts that are on the downhole tool. In a preferred embodiment the downhole tool is a ball valve and the equalizing tool is temporarily secured to the ball valve housing to temporarily part the ball from the uphole seat to equalize an annular space around the ball with tubing pressure. The ball is allowed to go back to contact with the seat when the equalizing tool is released and removed from the tubing.

FIELD OF THE INVENTION

The field of the invention is downhole tools that are constructed in a manner that make it possible to trap high differential pressures on movable components, which makes the components hard to move with actuation equipment unless such pressure differentials are equalized. In that context various tool embodiments are used to equalize pressure to enable subsequent operation using the normal actuation components.

BACKGROUND OF THE INVENTION

Downhole tools are controlled from the surface or locally by control systems to move a component between two or more positions. The movable components are exposed to highly variable tubing pressures and can be constructed in ways where pockets that trap pressure at some pressure level can form with a resulting high differential pressure across a tool component that is high enough to prevent the normal actuation system from operating the tool into another position.

One example of such a tool is a barrier valve that uses a 90 degree rotating ball. In some designs the ball turns between opposes seats that can have a resilient seal in contact with the ball. The actuation system can be in part in an annular space that is in communication with the passage in the ball around its pivot axis. When the valve is open tubing pressure and the annular space equalize through the small passage around the ball pivot axis. The ball can be closed during a time when the tubing pressure is low. Thereafter with the ball in the closed position and the annular space around the ball and the passage in the ball isolated from tubing pressure, pressure can build on the ball under conditions where the differential across the ball from tubing to the annular space results in increased contact frictional force so that the mechanism that would rotate the ball under normal operation is not strong enough to turn the ball back to the open position. Merely adding pressure above the ball during these circumstances just increases the differential across the ball with respect to the annular space and aggravates the contact loading problem.

The present invention in its various embodiments addresses this problem by equalizing pressure into the annular space by separation of a ball from its uphole seal in a rotating ball environment for a downhole valve. Other applications where trapped low pressures create loading to the point where the tool will not move normally are envisioned.

Equalizing devices in downhole tool and more particularly flapper type safety valves are well known as shown in Fineberg U.S. Pat. No. 4,478,286 and which included a spring loaded plug in the flapper that is actuated by a flow tube. Other equalizing devices are shown in U.S. Pat. Nos. 7,204,313; 6,848,509; 3,799,204; 6,644,408; 6,296,061; 6,283,217; 6,079,497 and 5,752,569. These valves generally have an equalizing valve built into a flapper to be actuated by the advancing flow tube before the flow tube tries to move the flapper. Alternatively the valve can be built into the housing to equalize across a closed flapper as a result of initial flow tube movement that occurs before the flow tube engages the flapper.

While the objective of the present invention is equalization to enable operation when large pressure differentials are present, its execution of that objective is different from the above described equalizing mechanism. Rather, in one embodiment a tool is delivered to the downhole tool needing pressure equalization. The tool is anchored and actuated to separate two members that are in sealing contact using built in flexibility of these parts to move relatively to each other. There after the tool is released and removed. It can be delivered quickly by wireline with a jar actuated to operate the tool or in another embodiment it can be delivered on coiled tubing and respond to pressure applied through the coiled tubing to operate. It can be released with a pickup force on the coiled tubing. Other embodiments are envisioned. Those skilled in the art will more fully appreciate the various aspects of the present invention by reviewing the descriptions of the embodiments described below in conjunction with the associated drawings while recognizing that the full scope of the invention is found in the appended claims.

SUMMARY OF THE INVENTION

A pressure equalizing tool can be run into a downhole tool on wireline or coiled tubing preferably and temporarily secured before being actuated to separate two components in a downhole tool that are in a sealing relation but are configured to be temporarily movable so as to allow pressure equalization before the downhole component is actuated. Once pressure is equalized the equalizing tool is released, usually with an applied pick up force and the downhole tool being equalized as to differential pressure can be operated with the preexisting actuation parts that are on the downhole tool. In a preferred embodiment the downhole tool is a ball valve and the equalizing tool is temporarily secured to the ball valve housing to temporarily part the ball from the uphole seat to equalize an annular space around the ball with tubing pressure. The ball is allowed to go back to contact with the seat when the equalizing tool is released and removed from the tubing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1shows the equalization tool10. It has a lower body12and a dog housing14secured at thread16. Dog housing14has openings18through which dogs20can be extended. A top sub22retains ring24internally so that actuator26can be fully extended to the position inFIG. 1without coming out of the top sub22. Top sub22is secured to the dog housing14at threads28. Actuator26has a larger outer diameter30and a small outer diameter32separated by tapered surface36. In the run in position ofFIG. 1the tool10has the actuator26fully extended so that the small outer diameter32is under the dogs20so that the dogs20are retracted into the openings18. Actuator26has an internal groove38. The tool10is run in on wireline40with a jar tool or other known tool that can create a jarring force on actuator28preferably at groove38with the jarring force shown schematically as arrows42. Those skilled in the art will appreciate that in theFIG. 1position a snap ring44is held in groove46by the dog housing14. Inside the dog housing14is a release sleeve48that is shear pinned to dog housing14with a shear pin. A gap52is formed between the dog housing14and the release sleeve48to allow the lower end54of the actuator26to enter when the jar tool force42is applied. Internal recess56at the top of the release sleeve48can be grabbed by a fishing tool, not shown, for an emergency release of the dogs20as will be explained below. The jarring movement42puts the larger outer diameter30under the dogs20to cam them all out so that they can engage the tool to be equalized as will be discussed later in regard toFIG. 3. The only resistance offered by actuator26to moving down is any force required to make snap ring44jump out of a groove58that it sits in for run in and into another groove60where it snaps out with the dogs20in the extended position as shown inFIG. 2. The rating of shear pin50is considerably higher than the force required to drag the snap ring44from groove58to groove60and the friction force from it dragging on the inside surface of dog housing14.

Lower body12has a piston62that is initially secured with a shear pin64. Seals66and68define atmospheric or low pressure chamber70. Seals72and74seal the chamber70and the piston62initially to the release sleeve48. A hard seat76is secured at thread78to the piston62. A soft seat80is held by a retainer82to the hard seat76. In a ball valve application as shown inFIG. 3, the soft seat80lands on the ball84. The tool10has an open through passage86that gets obstructed when the soft seat80lands on the ball84. Because of the passage86the tool10can be run in with wireline40at a high rate of speed. After the tool10is locked in position with dogs20, surface pressure buildup acts on piston62to break the shear pin64to move the piston62against the low pressure chamber70. This movement of the piston62moves the ball84to equalize pressure to annular space96, as shown inFIG. 3. Passage73is exposed during emergency release when shear pin50is broken by an upward jar at fishing neck56of release sleeve48by a second jar tool schematically shown as43if the support for the dogs20by surface30cannot be undermined for removal of tool10. Moving the release sleeve48opens chamber70to tubing pressure to equalize tubing pressure on piston62.

FIG. 2shows the tool10landed on the ball84with the actuator26pushed down so that the dogs20are extended by surface30to lock the tool10in position as can be seen by looking atFIG. 3, which is the top of the ball valve88whileFIG. 4is the bottom of valve88. The tool10is shown inFIG. 3after equalizing has taken place with shear pin64broken.FIG. 2shows the dogs20extended before shear pin64is broken andFIG. 3shows how the dogs20lock the tool10to the ball valve88. As seen inFIG. 3, when the tool10lands on the ball84the dogs20are presented opposite groove90in upper seat assembly92. Groove90is longer than dogs20so that after dogs20are extended and the pressure is built up, there is room for lower housing to move up to break shear pin64so that the applied pressure on piston62can ultimately move the ball84away from seal94for pressure equalization. When actuator26is pushed down the dogs20are extended and locked to the groove90. Upper seat assembly92has a seal94that is against the ball84. When there is pressure equalization the ball84is pushed by the tool10away from seal94to equalize an annular space96with tubing pressure at98above the ball84. As the equalizing is done the pressure at98can be brought close to the pressure below ball84at100so that the ball84is equalized from above and below before it is to be rotated.

The workings of the valve88will now be briefly explained. Starting at the lower end there is an assembly that is preloaded by a spring102adjusted by changing the position of nut104. Nut104pushes on lower seat assembly106which has a lower seal108pushed against the ball84. An open cage110loosely secures the lower end of upper seat assembly92and its seal94to the ball84as well as securing the upper end of lower seat assembly106and its seal108to the ball84. The upper ball seat assembly92is ultimately pushed toward the ball84by a spring112putting a force on ring114which is mounted to the upper ball seat assembly92. The cage110supports ball84through opposed pins116and118for 90 degree rotation between an open position (not shown) and a closed position seen inFIGS. 3 and 4.

A control system is used to rotate the ball84through control line connections120shown inFIG. 3 and 122shown inFIG. 4. Each connection has a piston124and126respectively. Pistons124and126are connected to opposite ends of a slide128that has a pin connection130shown in dashed lines inFIG. 3to the ball84that is offset from its center pivots116and118. Slide128slides through a recess (not shown) in the cage110. Relative movement between the moving slide128and the stationary cage110rotates the ball. The direction of rotation is determined by which port120or122is pressurized and which has the pressure removed. The exterior of the upper seat assembly92is sealed to the housing of the valve88at seal132. The lower seat assembly106is sealed to the housing of valve88at seal134. The passage136through the ball84communicates with annular space96through a weep hole138near pivot118. The annular space96extends from seal132to seal134and outside the ball84and the upper and lower seat assemblies92and106.

What can happen is that the ball84can be in an open position when tubing pressure at98and100is fairly low such as 300 PSIG for example. Through weep hole138with the ball84open, the annular space96will equalize to that same 300 PSIG pressure. When the ball84is then closed the annular space96and the ball passage136are now isolated from tubing pressure above and below the ball due to seals94and108literally on the ball and seals132and134outside the upper and lower seat assemblies92and106. The weep hole138just communicates the sealed off passage136inside the ball84to the annular space96. The pressure can then go up either above the ball84at98or below the ball84at100. The differential can rise to thousands of pounds to the point where the ball84can experience loading to the point where the pressure applied at the hydraulic connections120or122will not get the ball to turn or may result in shearing the drive pin130at the location that it extends from the ball84. Simply adding pressure above the closed ball84just causes additional loading as the pressure differential across it is enhanced.

This frictional loading problem caused by high differential pressure across the ball84is resolved by the tool10. As shown inFIG. 3the tool10is anchored using dogs20in groove90in the upper ball seat92. With soft seat80landed on the ball84and dogs20latched to groove90of upper ball seat assembly92, applying pressure in the tubing at98breaks shear pin64. Tubing pressure at98is present above piston62and low or atmospheric pressure is in chamber70allowing the piston62to move down forcefully and reduce the volume of chamber70while pushing down on ball84as the tool10is anchored at dogs24. The pushing of the ball84by the soft seat80separates the ball84from the seal94to allow the annular space96to equalize with whatever pressure was applied above the ball84at98. The gap is made possible by slack between the cage110and where it retains the upper and lower seat assemblies92and106respectively. In essence spring102is compressed and spring112is extended as a gap is created by the tool10between the seal94and the ball84. If the pressure at98is selected close to that below the ball84at100, the operation of the tool10essentially makes the pressure in the annular space96and inside the ball at136the same as in the tubing so that the hydraulic system can operate the ball84in the normal manner.

Referring nowFIGS. 5 and 6a different embodiment of the equalizing tool200is illustrated. It is run preferably on coiled tubing202but it can be run on rigid tubing in the alternative although it would take far longer to get it into position into a downhole tool such as a ball valve88located on a tubing string. The tubing202is connected to mandrel204at thread206. A passage208runs through the mandrel204to a port210that leads into an annular passage212. Piston214has seals216and218to allow pressure delivered through the coiled tubing202to reach the piston214to drive it along of mandrel204after breaking shear pin219. Also mounted to mandrel204is a cone220with a seal222. A slip ring224is supported by the mandrel204. It has a series of slips226that are initially retained to the mandrel204by a shear pin or pins228. As in the other embodiment there is at the lower end of piston214a soft seat230to contact the ball84and a retainer232surrounding the soft seat230for support.

In operation, as shown inFIG. 6, the soft seat230is landed on the ball84and pressure is built up in passage208so that the cone220is driven under the slips226to drive them out, while breaking pin228, against the upper seat assembly92that is shown inFIG. 3with the other embodiment. At this time pin219is not yet broken but the tool200is now anchored. A further pressure buildup breaks the pin219and the piston214is extended to push the ball84from its seal94shown inFIG. 3for pressure equalization. It should be noted that pressure outside the tool200is applied as pressure is equalized so that the annular space96will then be at a pressure close to the pressure downhole of the closed ball84to allow simple operation of the ball84without concern of breaking the actuation mechanism due to the frictional contact force from high pressure differential as the actuation systems attempts to rotate the ball84to the open position. Cone220can be biased to the retracted position by reducing pressure in annular space212to make the cone220and the piston214retract toward each other so that the tool200can be pulled out with the coiled tubing202because the slips226have become unsupported by the retraction of the cone220.

Those skilled in the art will appreciate that the tools10or200allow for pressure equalization for components operated in a downhole tool from a remote location. There are no additional valves added to an assembly within the tool housing. Instead an equalizing tool is rapidly deployed to the downhole tool and simply physically separates a downhole component from an adjacent seal to equalize pressure between formerly isolated zones affecting the component so the actuation system operated from outside the downhole tool can move the component without damage to the actuation system or the component from component loading that otherwise occur when there are significant pressure differences across the component before it is urged to move. In some cases such a valve the component can be a ball. Other applications where an actuated component can be placed under a pressure imbalance that needs to be equalized before the component is moved are also envisioned.