Riglessly Restoring the Functionality of Subsurface Safety Valves
Authors: Carpenter Chris 
Published: February 2015

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 164370, ’Innovative Methodology To Riglessly Restore the Functionality of Subsurface Safety Valves (SC-SSSVs) With Damaged Control Lines,’ by Mohamed Fahim, Hossam Elnaggar, Abd Allah ElBarbary, Mohammed Abu Arab, Ashraf Keshka, Hamdi Bouali Daghmouni, and Mohamed Al Karra, ADCO, and Ammar Soufan, Joseph O'Connor, and Magdi Elasmar, Baker Hughes, prepared for the 2013 SPE Middle East Oil and Gas Show and Exhibition, Manama, Bahrain, 10-13 March. The paper has not been peer reviewed.

The surface-controlled subsurface safety valve (SC-SSSV) is an integral part of the overall safety system of any well, and it is the only method that provides subsurface isolation in case of emergency caused by uncontrolled surface or subsurface events. The effectiveness of these valves can be threatened by leaks, plugs, or breaks in the control lines (CLs). This paper describes a methodology that deploys CLs on the inside of the tubing, reducing cost and ensuring continued effectiveness of SC-SSSVs.

Introduction

Functional SC-SSSVs must be installed in production tubing in all gas and oil wells, irrespective of location, as a safety barrier to halt flow in case of a catastrophic failure. SC-SSSVs are held in the open position by introducing hydraulic positive pressure from the surface. This pressure is applied through a CL in the tubing/ casing annulus running from the valve to the surface. In case of an emergency shutdown, the hydraulic pressure will be lost, forcing the safety valve to close.

CLs for SC-SSSVs could leak, plug up, or break, leading to loss of the capability to control the valves’ operating condition, causing environmental and safety concerns in addition to a loss of production upon closure of the valve.

In one of the giant Abu Dhabi onshore oil fields, approximately 160 strings have with damaged-CL problems. In the past, the only way to rectify SCSSSV problems was to pull out the production tubing through a rig workover. Hence, all affected wells were enrolled in a drilling workover schedule. Rig availability is one of the major challenges affecting field-development plans, and so any rigless technologies that can be used in place of rig workovers are of high importance to save on rig time.

A multidisciplinary team was formed to survey the market and carry out an evaluation of technologies that could remedy the problem of the damaged CL by replacing or modifying the existing SC-SSSV riglessly. The findings of this survey indicated that there were two technologies that could restore the functionality of the SC-SSSV riglessly. One of these is an SC-SSSV with a CL line deployed inside the tubing (Fig. 1). This can be compared with conventional CLs, which are set in the annulus (outside the tubing string) and hence require rig intervention in case of damage. The running and retrieval of this modified SCSSSV are performed by a conventional slickline unit; however, the CL requires special equipment (a capillary unit) for installation and retrieval.