A Case History: The Installation of a System to Restore Full Safety Valve Functionality to a Malaysia Offshore Well with Damaged Control Line

Abstract

The loss of functionality of the surface controlled subsurface safety valve (SCSSV) due to blockage of, or damage to, the hydraulic control line can present a major problem to Operators. The subsequent loss of hydraulic pressure to the valve means the valve will close resulting in loss of production and hence alternative methods for re-establishing control of the SCSSV are required. Performing a full scale work-over to replace the inoperable control line can require major expense and may not be justifiable in a mature well, while installation of a velocity or dome charged subsurface controlled safety valve may not meet well integrity or production requirements. Hence the preferred alternative is to install a System to Restore Full Safety Valve Functionality that is cost effective, restores production, and maintains well integrity requirements. The Tubing Retrievable SCSSV on well C-02 in the Sabah water of East Malaysia lost its functionality due to a leak in the control line. The SCSSV body was also found to be leaking from tubing to annulus which resulted in the failure to successfully lock open the SCSSV. Initially a major rig work-over had been anticipated to pull the tubing and replace the safety valve and control line. This operation would have required the use of a Hydraulic Work-over Unit (HWU) to perform the work which would have incurred a major expense. An alternative method was proposed that would allow replacement of the safety valve and control line, and to straddle the leak in the SCSSV body without pulling the production tubing or making changes to the wellhead configuration. This alternative method was a unique concept not previously attempted by any operator in Asia Pacific. This innovative approach would involve four elements: Installation of a Lock Mandrel and Separation Sleeve to straddle the leak in the SCSSV body & hold open the SCSSV flapper. Installation of a Wireline Retrievable Subsurface controlled safety valve with wet connector to connect to a new control line installed through the tubing (WDCL Safety Valve) which is anchored and located in the Tubing above the Tubing Retrievable SCSSV by means of a packer system. A new control line and special control line connector installed from the wellhead to the WRSCSSV through the production tubing. A new penetration in the Wellhead Lower Master Valve for the injection of hydraulic power fluid to control the WRSCSSV. These 4 elements provided a unique solution and the installation was successfully completed under a severe deadline. This was achieved by a high level of cooperation and collaboration between all parties throughout all phases of the project including and not limited to the planning, design and installation. This paper will describe in detail the system components and the decision processes and evaluations that led to the selection of this alternative solution. The collaborative efforts between the operator and two major service providers will be examined and discussed and the installation procedure described in detail. The paper will describe why the successful completion of this project marks a significant milestone in the remediation of older producing wells.