The petroleum industry has made significant changes and improvements to extend the run life and the operating envelope of ESP systems. Design improvements have dominantly focused on motors, seals, and pumps through improved material selection, bearings, etc.; changes accepted and deployed by operators without consideration of technology which can be applied to cable design and packaging. The ESP power delivery system (downhole cables and associated components) have remained largely unchanged for nearly 90 years.
The ESP cable system is responsible for greater than 20% of ESP failures, with a large portion occurring early in the system life (<2 years). In the last 10 years, offshore cable system failures have risen to more than 30% due to installation in harsher operating conditions.
In 2015, two major operators and a rigless ESP provider launched an extensive R&D program to develop a "life-of-well ESP" cable system to complement Wireline Retrievable ESP (WRESP) systems planned for deployment in West Africa and the Middle East. The logic was simple – if a life-of-well cable system could be developed, this could be used with a WRESP to provide rigless ESP operation throughout the life of a well, greatly reducing intervention costs while maximizing production. Once developed, it became apparent that the same technology could also be used in conventional ESP deployments to eliminate cable system failures while reducing the lost rig time and HSE risk associated with traditional ESP cable installations.
The proposed ESP cable system is essentially a repackaging of existing, proven components that have been adapted and qualified to the high voltage and high current requirements of an ESP. This new topology was rigorously tested to industry standards by a joint committee of operators under laboratory and field conditions to confirm the thermal, mechanical, and electrical performance of the system. An installation test was performed in an onshore well to validate reliability of the cable system, packer/wellhead penetrations and downhole splices.
Qualification testing has proven that a "life-of-well" ESP cable system is achievable. Discussion with other operators indicates the system to be scalable to both onshore and offshore applications for improved reliability at a minimal additional cost.