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. 4,574,889 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.
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.
a-1e are a section view of the SSSV in the closed position;
a-2e are a section view of the SSSV with the lock open tool latched;
a-3e show the collets freed at the base of the tool to push the flapper into the fully open position;
a-4e are a section view showing the flapper base engaged by the tool just before the threads shear;
a-5e are a section view with the flapper base sheared and the flow tube spring acting on the flapper base to retain the flapper in the lock open recess;
a-6e show the SSSV in section with the lock open tool removed;
a-7c shows the addition of the penetrating tool above the lock open tool;
The sub-surface safety valve is illustrated in the closed position for the flapper 12, in FIG. 1. Spring 16 bearing on shoulder 18 biases the flow tube 14 upwardly. Flapper 12 is secured to flapper base 20 at pivot 22. Spring 24 biases flapper 12 to the closed position shown in
a-2e illustrate the initial insertion of the tool T. Tool T has a mandrel 42 made up of a top sub 44 connected to segment 46 at thread 48. Segment 50 is connected to segment 46 at thread 52 with the connection held locked by screws 54. Segment 56 is held to segment 50 at thread 58 with the connection locked by screws 60. Segment 56 further comprises a tapered shoulder 62. Collet retainer 64 is secured by thread 66 to segment 56 by screws 67. Collet retainer 64 comprises an extension segment 68 that defines an annular groove 70 in which the lower ends 71 of the collets 82 are disposed. The outer assembly 72 fits over the mandrel 42 and comprises a top sub 74 retained to segment 46 of mandrel 42 by a shear pin or pins 76. Segment 75 is retained to top sub 74 at thread 77. Projections 79 and 81 latch respectively into grooves 38 and 40 of body 28 due to the flexible nature of segment 75. Segment 78 is retained to segment 75 by a shear pin or pins 80. Collets 82 are secured to segment 78 by shear pin or pins 84. Collets 82 have an internal shoulder 86 for jarring down and an external shoulder 88 to engage groove 90 on flapper seat 20. Flapper seat 20 can be made of several interconnected parts. Spring 16 bears on flapper seat 20 for reasons to be explained below. Insertion of tool T results in a partial rotation of the flapper 12 toward the fully open position. The flapper is in the fully open position when in alignment with groove 92 in body 28as shown in
The significant components now having been described, the operation of the tool will be reviewed in detail. The tool T is lowered into the valve 10 until projections 79 and 81 spring into grooves 38 and 40 for latching contact. This position is shown in
Referring to
While the rotation to get alignment for penetration is going on, the tool T is opening the flapper 12 and latching into groove 90 as shown in
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.
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Number | Date | Country | |
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20040065442 A1 | Apr 2004 | US |