Patent Application
20100006296
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.
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. 4,579,889 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). More recently a combination tool has been disclosed that penetrates into an existing control system while locking the flapper open with a jarring force that moves a flapper base when the flapper is wide open so that the flapper becomes trapped in the housing in a retaining groove. This is described in U.S. Pat. No. 6,902,006. It has a fairly complex system for locating it in the proper position and as a result is expensive to manufacture.
The present invention focuses on a one trip operation to penetrate and lock the flapper open. It doesn't require flow tube movement or deformation or shifting a base for a flapper to obtain the locked open position. It doesn't deliver a sleeve to the flapper from the surface. Rather, in the preferred embodiment, the safety valve is put in service with the sleeve locked in position. A tool lands and is locked in a nipple adapter at the upper end. The lower end passes through the sleeve and no-goes below it. A jar up force unlatches the sleeve and shifts it under the flapper whereupon its position is secured. The no-go shoulder also moves the sleeve and is sheared off and retained to the tool for removal from the hole. Centralizers are provided to the sleeve circumferentially in alignment with the bore in the safety valve so that passing tools or an insert safety valve can be installed without interference. Those skilled in the art will more readily appreciate the full scope of the invention from the more detailed description of the preferred embodiment that appears below with its associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.
A combination penetration tool for access to the control system of a subsurface safety valve also has a lockout for the flapper that operates by latching into a nipple profile near its upper end as a series of collet fingers pass through a sleeve that is held in the locked position on the valve housing. One or more dogs on the collet fingers line up with the flapper already pushed open by the advancing collet fingers to push the flapper further back. A second series of dogs get past the sleeve after moving through it. With a jar up force the second series of dogs overcomes a lock on the sleeve and shifts the sleeve to overlap the open flapper and allow the lock ring that moves with the sleeve to latch into the housing. The second series of dogs is sheared off but retained by the tool for removal from the well. The penetrator portion of the tool is a known device that preferably works by jarring up.
Those skilled in the art can appreciate that the sleeve to lock out the flapper is already in the housing when it is deployed downhole and is secured in position until the tool 10 is in position to shift the sleeve. The dogs 22 can be matched to their landing shoulder 52 to reduce the chance of other tools moving through from unintentionally engaging the sleeve 42 and dislodging it prematurely. The flapper 50 is pushed back by dogs 20 to give the sleeve room to move into position without hitting the held open flapper. The dogs 22 that get sheared off are retained to avoid damage to other downhole equipment.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
