Impact of the geometrical configuration of electrical submersible pump impellers on run life and sand stuffing: a case study and recommended practice

Abstract

The objective of this study was to identify the root cause of the premature failures of electrical submersible pumps installed in an artificially lifted brown oil field located in southeastern part of Sudan, and to mitigate the causes in order to extend the pumps run life so oil production is increased and lifting costs are reduced. One of the standard failure finding procedures, known as Dismantle, Inspection, and Failure Analysis (DIFA) was used in this study to systematically tear down and inspect the failed pumps to find out the root cause of the failures. It was found that sand accumulation (stuffing) in the radial flow impellers was the cause of premature pump failures. The study has further elaborated on the technical reasons and justification as to why radial flow impeller pumps, despite their seemingly perfect design, were unable to produce sand while the mixed flow, under designed for the same well conditions, did. This finding was then experimented on many wells and proved to be correct as demonstrated in this paper. Eventually, the result was technically proved as being attributed to the geometrical shape of the impeller flow path. The study has then correlated sand stuffing failure with the flow path geometry of the impellers and eventually projected these results to an established specific speed model ($N_{s}$) with the recommendation of adopting a pump sizing approach in mild sand- -producing oil wells to cater for the geometrical flow configuration of the pump impellers.