ESP Reliability Lessons Learned From Three H2S Saudi Arabian Fields

摘要

Previously, many Oil and Gas Production Companies elected not to develop hydrogen sulfide (H2S) producing fields, particularly offshore, in exchange for sweeter crude projects. A narrow number of H2S field developments resulted in a limited number of publications with empirical data on Electrical Submersible Pump (ESP) reliability producing in high H2S partial pressure offshore fields. This paper summarizes ESP reliability lessons learned and solutions implemented from more than 500 ESPs producing across three carbonate field wells characterized by high H2S/CO2 partial pressures, reservoir pressure and production rates; low bubble point pressure and low to mid-level water cut. This paper utilizes ESP field observations and pull failure findings from over 200 Dismantle Inspection and Failure Analysis (DIFA) to confirm H2S behavior and root causes of electrical and mechanical failures within multiple ESP components. Moreover, H2S affects where ESPs were initially idle and exposed to H2S for one to two years either in static conditions or in naturally high rate flowing wells prior to commissioning are discussed. DIFA observations over a wide range of ESP runlife was instrumental in establishing the need for technologies to slow H2S movement across ESP components inclusive of a tandem seal section. Several motor seal sections have failed mechanically from H2S attack thereby requiring upgrade to high alloy metals, ceramic radial bearings and upgraded mechanical seals. Laboratory testing of failed conductor insulations retrieved during DIFA further exposed H2S methodology in creating electrical shorts. Systematic approaches were adopted to identify any unnecessary contributors such as power quality, operational practices or human error that may have facilitated H2S attack. Following the investigation and identification of unnecessary contributors; H2S scavengers were introduced into the seal section to slow H2S migration into the motor, lead sheathed motor lead extension (MLE) was upgraded with new H2S resistant insulation materials and design along with other new technologies that were trial tested to further improve ESP reliability and run life in H2S producing wells. ESP component failure tracking and runlife statistics spanning an eleven year period are shared with the reader to validate the success of H2S resistant ESP component upgrades. Finally, methodology in calculating and measuring impact of varying degrees of H2S partial pressure and temperature from three high and two low H2S partial pressure ESP fields are provided.