Lock open and control system access apparatus and method for a downhole safety valve

A lock open device for a flapper is disclosed. The tool engages in the sub-surface safety valve (SSSV) body and rotates the flapper to the open position, without shifting the flow tube. The flapper base is preferably held by a shearable thread and has a groove for engagement by the tool. The tool jars down on the flapper base to shear the thread and force the held open flapper into a retaining groove. Optionally, a penetrating tool can be connected so that, in a single trip, the flapper can be locked open and the pressurized control system can be accessed. Shearing the thread allows the flow tube spring to bias the held open flapper into its retaining groove.

FIELD OF THE INVENTION

The field of this invention is lock open devices for sub-surface safety valves (SSSV) and related techniques for gaining access to the pressurized control system for subsequent operation of an inserted replacement.

BACKGROUND OF THE INVENTION

SSSVs are normally closed valves that prevent blowouts if the surface safety equipment fails. Conditions can arise where the SSSV fails to function for a variety of reasons. One solution to this situation has been to lock open the SSSV and to gain access into the pressurized control system that is used to move the flow tube to push the flapper into an open position against the force of a closure spring that urges the valve into a closed position. Thereafter, a replacement valve is delivered, normally on wireline, and latched into place such that the newly formed access to the control system of the original valve is now straddled by the replacement valve. This allows the original control system to be used to operate the replacement valve.

There have been several variations of lock open devices in the past. U.S. Pat. No. 4,577,694 assigned to Baker Hughes teaches the use of a flapper lock open tool (FLO) which delivers a band of spring steel to expand when retaining sleeves on the FLO tool are retracted. The tool latches inside the SSSV and with the flow tube in the flapper-closed position the band is released. This design offered the advantages of the lockout device not being integral to the SSSV. Instead it was only introduced when needed through a wireline. Another advantage was that the release of the band did no damage to the SSSV or the FLO tool. The band expanded into a recessed area so as to allow full-bore through-tubing access. The flow tube did not have to be shifted so that no spring forces acting on the flow tube had to be overcome to actuate the FLO tool. Subsequently, when the SSSV was retrieved to the surface, the band was easily removed by hand without special tools. The FLO tool had safety features to prevent premature release or incorrect placement. The FLO tool did not require fluid communication with the control system, as its purpose was solely flapper lock out.

The FLO tool did have some disadvantages. One was that the band could become dislodged under high gas flow rates. The tool was complicated and expensive to manufacture. The expanding ring presented design challenges and required stocking a large variety to accommodate different conditions. The running method required two wireline trips with jar-down/jar-up activation.

U.S. Pat. No. 4,574,889 assigned to Camco, now Schlumberger, required latching in the SSSV and stroking the flow tube down to the valve open position. The flow tube would then be outwardly indented in the valve open position so that the indentations would engage a downwardly oriented shoulder to prevent the flow tube from moving back to the valve closed position. This design had some of the advantages of the Baker Hughes FLO design and could accomplish the locking open with a single wireline trip. The disadvantages were that the flow tube was permanently damaged and that the flow tube had to be forced against a closure spring force before being dimpled to hold that position. This made disassembly of the SSSV with the flow tube under spring pressure a potentially dangerous proposition when the valve was later brought to the surface.

U.S. Pat. No. 5,564,675 assigned to Camco, now Schlumberger, also involved forcibly pushing the flow tube against the spring to get the flapper into the open position. In fact, the flow tube was over-stroked to push the actuator piston out of its bore in the pressurized control system, at which point the piston would have a portion splay out preventing its re-entry into the bore, thereby holding the flow tube in the flapper open position. This design had the safety issues of disassembly at the surface where the flow tube was under a considerable spring force. Additionally, fluid communication into the control system was not an option when locking open using this tool.

U.S. Pat. No. 6,059,041 assigned to Halliburton uses a tool that forces the flow tube down to get the flapper in the open position. It then releases a band above the flow tube that lodges on a downwardly oriented shoulder to hold the flapper open. This system has the risk of a flow tube under a spring force causing injury when later disassembled at the surface. This tool is fluid activated and must overcome the spring force to get the flow tube to the flapper open position. Finally, the tool is fluid pressure actuated, which will require a long fluid column to eventually communicate with the formation, a particular disadvantage in gas wells.

Also of interest in the area of lock open devices for SSSVs are U.S. Pat. Nos. 4,624,315; 4,967,845 and 6,125,930 (featuring collet fingers on the end of the flow tube that engage a groove in the SSSV body).

The present invention addresses these shortcomings by providing a technique to use a tool to get the flapper open without shifting the flow tube. In the preferred embodiment the flapper base is shifted with the flapper in the open position to trap the flapper in the open position. The closure spring that normally biases the flow tube into the flapper closed position is employed after the flapper base is liberated to bias the held-open flapper into its retaining grove. The lock open feature can be combined with stroking an oriented penetrating tool into the control system conduit for access to operate a subsequently installed valve to replace the locked open SSSV. The penetration step is not required to obtain the lock open state. Optionally the flapper base can be retained in its normal operating position by a shearable thread to allow taking advantage of a metal-to-metal sealing feature of the thread. These and other advantages of the present invention will become more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the claims appended below.

SUMMARY OF THE INVENTION

A lock open device for a flapper is disclosed. The tool engages in the sub-surface safety valve (SSSV) body and rotates the flapper to the open position, without shifting the flow tube. The flapper base is preferably held by a shearable thread and has a groove for engagement by the tool. The tool jars down on the flapper base to shear the thread and force the held open flapper into a retaining groove. Optionally, a penetrating tool can be connected so that, in a single trip, the flapper can be locked open and the pressurized control system can be accessed. Shearing the thread allows the flow tube spring to bias the held open flapper into its retaining groove.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The sub-surface safety valve is illustrated in the closed position for the flapper12, in FIG.1. Spring16bearing on shoulder18biases the flow tube14upwardly. Flapper12is secured to flapper base20at pivot22. Spring24biases flapper12to the closed position shown inFIG. 1d. Flapper base20is secured by sleeve26to body28. That connection is preferably by a thread30. Thread30is designed to release under a predetermined force applied to flapper base20. Other retainers that selectively release such as shear pins or collets can be used instead of thread30as contemplated in alternative forms of the present invention. A piston32sees pressure from a control line extending from the surface (not shown) and connected to port34. Piston32engages groove36to push the flow tube14down against the force of spring16. Grooves38and40are for locating the lock open tool T as shown inFIG. 2b.FIG. 1dshows an enlargement of the area around thread30.

FIGS. 2a-2eillustrate the initial insertion of the tool T. Tool T has a mandrel42made up of a top sub44connected to segment46at thread48. Segment50is connected to segment46at thread52with the connection held locked by screws54. Segment56is held to segment50at thread58with the connection locked by screws60. Segment56further comprises a tapered shoulder62. Collet retainer64is secured by thread66to segment56by screws67. Collet retainer64comprises an extension segment68that defines an annular groove70in which the lower ends71of the collets82are disposed. The outer assembly72fits over the mandrel42and comprises a top sub74retained to segment46of mandrel42by a shear pin or pins76. Segment75is retained to top sub74at thread77. Projections79and81latch respectively into grooves38and40of body28due to the flexible nature of segment75. Segment78is retained to segment75by a shear pin or pins80. Collets82are secured to segment78by shear pin or pins84. Collets82have an internal shoulder86for jarring down and an external shoulder88to engage groove90on flapper seat20. Flapper seat20can be made of several interconnected parts. Spring16bears on flapper seat20for reasons to be explained below. Insertion of tool T results in a partial rotation of the flapper12toward the fully open position. The flapper is in the fully open position when in alignment with groove92in body28asshown inFIGS. 3d-3e.

The significant components now having been described, the operation of the tool will be reviewed in detail. The tool T is lowered into the valve10until projections79and81spring into grooves38and40for latching contact. This position is shown inFIGS. 2a-2b. The collets82still have their lower ends71held by collet retainer64, but the insertion itself has resulted in partial rotation of flapper12towards its fully open position. Actuating the mandrel42downwardly with a wireline operated jarring tool (not shown) connected to top sub44forces down the mandrel42. Initially, shear pin or pins76break as the mandrel moves with respect to the outer assembly72, which is supported to body28at grooves38and40. Downward movement of the mandrel42moves collet retainer64away from lower ends71of collets82, allowing them to spring radially outwardly so that shoulder88engages groove90in flapper seat20. This is shown inFIG. 3d. The mandrel42continues moving down until shoulder51on segment50engages shoulder53on segment78of the outer assembly72. At this time shear pin or pins80will break after the application of a predetermined force. When shear pin or pins80break, segment78of the outer assembly72is driven down until lower end83engages shoulder86on collets82. By this time the collets82have pushed the flapper12into the fully open position so that it is in alignment with groove92in body28. Movement of the lower end83of segment78breaks shear pin or pins84, as shown inFIG. 4d. When a predetermined force is applied to shoulder86from lower end83the thread30holding flapper base20to sleeve26shears or otherwise fails and the flapper base20is driven down, now also with the help of spring16until the flapper12has entered groove92. Spring16retains flapper12in groove92. Collets82insure the alignment of flapper12with groove92as the flapper is driven down from the force of the jarring tool on the wireline (not shown) acting on mandrel42and from spring16. The tool T can now be removed by an upward force on the wireline (not shown) and the flapped remains locked in groove92under the force of spring16, as shown inFIGS. 6a-6e. The downward movement of flapper base20can be purely translation, as described for the preferred embodiment, or rotation or a combination of both movements to get the flapper12into groove92.

Referring toFIGS. 7a-7c, the penetration tool P can be added above the lock open tool T. The lock open tool terminates near shoulder51at thread95. The assembly of the tool T and the tool P are initially suspended in grooves38and40as collet94springs outwardly. Collet94comprises an internal shoulder96and a lower end98, which covers window100. Mandrel102is connected to the jarring tool (not shown). Shear pin104secures sleeve106to mandrel102so that the entire assembly is initially supported by collet94. Outer housing108has an exterior shoulder110near its upper end112. Window100is in outer housing108. At its lower end114, outer housing is attached by shear pin80to segment78, as previously described. Guide pin114is biased by spring116but lower end98of collet94holds in pin114until shear pin104is broken. When mandrel102is advanced after shear pin104is broken, pin114is pushed out by spring116to contact spiral ramp118that is part of the SSSV. Such contact coupled with advancement of the mandrel102creates rotation as pin114advances along spiral ramp118and toward longitudinal groove120. Eventually, all rotational movement is complete as pin114in groove120and shoulder110hits shoulder96. This is the position in FIG.8. Now shear pin122can break as mandrel102and wedge surface124push penetrator assembly126through window100and into control system128above piston32(see FIG.9).

While the rotation to get alignment for penetration is going on, the tool T is opening the flapper12and latching into groove90as shown inFIGS. 2e-4e. When the penetration occurs the shear out of thread30occurs and the flapper12is displaced into groove92. Thus both steps can occur in a single trip or either step can be done individually without the other.

FIGS. 10 and 11show a variation of holding the flapper12in the open position. It can be held open with a combination of groove92, as previously described as well as an enlarged diameter hinge130that is forced down into a reduced diameter segment132for an interference fit.FIG. 11shows that groove92can be eliminated and the interference fit between hinge130and reduced diameter segment132can be the sole mechanism to insure the flapper12stays open after the thread30is sheared out.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.