Bespoke Insert Safety Valve Design Installed in Deepwater Gulf of Mexico via Light Well Intervention

Abstract Deepwater Assets in the Gulf of Mexico (GoM) have been challenged in recent years by major production deferrals due to fail-close incidents of nitrogen (N) charged tubing retrievable surface controlled sub-surface safety valves (TR-SCSSVs). Remediation for these failure events were typically managed via a workover operation (Ramnath et al, 2017), which required a mobile offshore rig unit (MORU) at considerable cost. In non-Deepwater environments, the use of wireline retrievable surface controlled sub-surface safety valves (WR-SCSSVs) inserted within the failed TR-SCSSV is a common solution to restore a wellbore to production without having to workover the well (i.e. retrieve the tubing string with the failed TR-SCSSV and replace with a functional TR-SCSSV). The industry offers other alternative wireline retrievable valves, but these are all subsurface controlled designs that are not currently approved for use in GoM subsea wells due to federal regulations. However, due to the depths of the installed Deepwater Subsea TR-SCSSVs, N compensated modules are often employed to offset the high hydrostatic pressure of the hydraulic control line (CL) system, to prevent the valves from permanently being open. It is this N compensated system that complicated past considerations to use insert WR-SCSSVs as a solution to address failed TR-SCSSVs in Deepwater Subsea environments. The insert WR-SCSSV discussed in this paper was engineered to utilize a large-force power spring and an atmospheric chamber to compensate for the high hydrostatic pressures imposed by the hydraulic fluid in the CL system, functioning in water depths in excess of ~6,000 ft. With this new WR-SCSSV design, wellbores with failed TR-SCSSVs but a functioning CL system (i.e. control line integrity along the length of the installed completion and within the subsea infrastructure), could be restored to production via an intervention operation at much lower cost and within a shorter time-period, compared to historic workover alternatives. A key enabler is the usage of a Light Well Intervention Vessel (LWIV) to perform the operation, which normally has greater flexibility in response time and scheduling of operations. With the availability of the LWIV, a WR-SCSSV intervention installation can cost approximately 50% and 30% less than the cost of a workover to replace a failed TR-SCSSV on a horizontal and vertical tree respectively. The eventual installation of the WR-SCSSV was performed according to plan, achieving the objectives of not only restoring the well to production, but installing a functioning well barrier element to further manage the life of well. Furthermore, this has unlocked well intervention and well management capabilities, previously unavailable in Deepwater Subsea environments of the GoM and beyond.