SPE 168271: Tubing Retrievable Surface Controlled Subsurface Safety Valve Floating Flapper Remediation

Background

A requirement within a conventional offshore well’s completion design per operator standard design and/or governmental regulation is the installation of a “subsurface safety device.” Among the list of permitted safety devices, subsurface safety valves (SSVs), if maintained properly, can fulfill such a requirement in well control and isolation.

Whether it is of the surface-controlled (SC), subsurface-controlled (SSC), wireline-retrievable (WR), tubing-retrievable (TR), ball check, or flapper valve variety, subsurface safety valves can easily be damaged during through-tubing (wireline, coiled tubing [CT], etc.) deployment through the valve if steps, such as equalization before opening, slowing toolstring running speed, etc., are not taken to properly safeguard valve integrity. A problem that could occur during these deployments, specifically in reference to the SSV flapper-type valve, is shearing of the hinge pin on which the valve flapper rotates, allowing the flapper to “float” in a cavity directly below its rotation point, creating an effective downhole obstruction.

A traditional intervention operation to repair this includes using a slickline (SL) rotating wedge to manipulate the flapper to a position that will allow a subsequent, suitably3 sized sleeve installation through the cavity, bypassing the flapper. This will allow for both toolstring deployment past the obstruction to assist in future uphole recompletion operations and continued production without slugging from unexpected valve flapper reseating.

This paper discusses a case history in which the above-mentioned conventional SL manipulation toolstring was deemed not suitable, as it was currently designed for a small cavity-type Tubing Retrievable Surface Controlled Subsurface Safety Valve (TRSCSSV), and alternative intervention means were developed. Five full-scale4 tests were performed with four different toolstrings (one SL and three electric line [EL]) engineered to provide a method of inserting a bypass sleeve with predetermined minimum inside diameter requirements for future tubing cutter deployment. Of the four toolstring options developed, two were deemed field ready and deployed with the offshore operation itself, while the other two required additional engineered modifications. Details of the successful intervention deployment are also given in which desired flapper orientation and isolation was not only achieved by toolstring manipulation but also by well-production characteristics.

Three benefits can instantly be noted from the developments and lessons learned. First, the toolstring solutions could be used for obstruction isolation of many varieties. Second, this rigless operation is part of the ongoing efforts in the Gulf of Mexico and elsewhere in the world to intervene in wells in the most economically feasible, least hazardous, and most expedited manner. Lastly, the intervention means employed here incorporates toolstring components readily available on the market. Lead time and operational use are minimized, and rig campaign schedules can be maintained almost without delay.

Find the full paper at onepetro.org

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