Encapsulated ESP System: An Innovative Solution for Extended Run Life in High H2S Environments

Abstract

The electric submersible pump (ESP) is one of the most reliable artificial lift methods for delivering high flow rates in oil wells. If well designed for reservoir properties, ESPs may run for several years before failing. Despite many ESP design advancements, electrical connections remain within the most prominent points of failure in high H2S environments. This paper presents an innovative approach to mitigate electrical connection failures by encapsulating the ESP system for extended ESP run life in high H2S environments. Following an ESP design review to explore current practices in mitigating ESP electrical-connection failures in sour wells, an innovative ESP system was designed to eliminate electrical-connections’ contact with well fluid. The ESP is connected from the top to a production tubing, encapsulated within a pressure-retaining pod, and located above a deeply set production packer. The motor head is designed to partially set outside the pod to accommodate electrical-cable connection, while partially encapsulated within the pod to deliver the necessary electrical supply to the ESP motor. The tubing-casing annulus (TCA) is then filled with inhibited-brine to protect the electrical connections. Experts in the field typically select special ESP metallurgy and electrical connections (i.e., metal to metal) in high H2S wells to extend the run life of ESP systems. Although the development of multiple versions of electrical connections can mitigate H2S attacks, field experience has shown progress in sour environments where ESP run life is not yet matching mild environments. Most efforts were made to minimize H2S attacks on ESP electrical-connections by developing robust ESP systems, but little to no effort was made to eliminate the risk. This challenge can be undertaken by encapsulating the ESP system to avert electrical connection contact with well fluid. Thus, it provided a radical solution to one of the most common ESP failure points in sour environments. The encapsulated ESP system is a new concept, for which a patent is pending, designed to address electrical connection failures for an extended run life in high H2S environments. This paper will discuss the background and design of the system and its potential to eliminate electrical connection integrity issues.