Build a more robust ESP or reduce the stress it endures? Run-life improvement requires finding the right balance to suit the local well conditions and economics. Utilizing key case studies, the paper examines how operational stress caused by low flow rates can be avoided with the correct utilization of instrumentation, surveillance, and automation thereby providing practical solutions for extending the run life of already installed ESPs. The method starts with an extensive review of ESP failure mechanisms and their causes, supported by case studies and pictures illustrating the symptoms that can be observed during dismantling. This holistic technique is supported by several case studies. The common "thread" found on most failure mechanisms is temperature rise inside the ESP, which deteriorates properties of materials, including polymer insulation, elastomer seals, and metallic parts. Heat rise is attributed to three main causes: motor thermal losses, pump hydraulic losses, and frictional heat. Case studies and data sets are provided to confirm that a paradigm shift in mitigation improvement can be achieved by automating the identification of low flow events utilizing a downhole real-time flowmeter. Three reasons are given. Firstly, it is a leading indicator, whereas surface flow meters and temperature sensors are lagging indicators due to pump-up time and heat exchange respectively. Secondly, automation enables more consistent and cost-effective identification in large ESP populations. Thirdly, it enables deeper diagnostics of the cause of low flow (i.e., gas lock versus slugging, and even the source of slugging such as horizontal lateral versus production tubing). The authors provide an exhaustive list of case studies identifying sand fallback and scale as well as low flow causes and how they can be diagnosed, including differentiation between ESP, wellbore hydraulics, and reservoir inflow causes (e.g. depletion and skin.)
Over the last 30 years, improvements in design and materials have tripled ESP run lives. Therefore, many fields attain six-year average run lives and 90-day survivability of 98%. Nevertheless, economics have tightened, which has raised the bar, and therefore, many operators still suffer uneconomical run lives. Case studies indicate that the next step-change in run life improvement will require a reduction in environmental stresses by mitigating the effect of low-flow events, scale, and sand.