Overcoming Deployment and Retrieval Challenges with Killed Well Cable Deployed Electric Submersible Pump Systems – Lessons Learned from Five Years of CDESP History

Abstract

The advantage of cable deployed electric submersible pump (CDESP) systems are beginning to be understood and realized as experience has been gained with the deployment and retrieval of these systems. Cable deployed ESP systems have at times been touted as a temporary system for failed conventional ESP systems. Long-term successes have demonstrated the value of permanently installed CDESP systems, which provide the benefit of reduced production deferral, less costly change-out, and reduced HSE risk. The decision to change from conventional ESP to a rigless CDESP system is not necessarily a simple conclusion. The decision must consider technical, economic, and operational considerations to gain the full benefit from the technology. The learnings developed over multiple deployments and retrievals will benefit decision makers in the evaluation of the technology use. The technology application presented in the paper sheds the light on a journey to develop and bring alternative ESP deployment from concept to reality, overcoming technical and operational challenges. The current CDESP requires a rig to initially construct the permanent completion to accept the rigless CDESP system. Production rates requirements determine the ESP size, and in turn the tubing and wellhead size. Pressure control equipment is installed on top of the Christmas tree. Rigless installation and retrieval of the CDESP is performed on an elevated tower with the wellhead in place. The tower design has been improved to allow the production flowline to remain in place. A minimum of two well barriers, with one barrier well kill fluid, are in place at all times. A key learning of the killed well CDESP system is the need to understand the potential changes to the reservoir after sustained production in planning the replacement of a failed ESP. Kill fluid losses can be higher than expected with restorative well cleanup and production. Actual deployment or retrieval time can be improved with successive change-outs. Long-term operational robustness of the CDESP is proven with a system continuing to operate after 5 years of cumulative operations. This paper shares the lessons learned from an early technology adopter with multiple deployment and retrievals in various well environments including highly fractured reservoirs and high hydrogen sulfide wells.