The Analysis and Prediction of Electric-Submersible-Pump Failures in the Milne Point Field, Alaska

Electric Submersible Pumps (ESPs) are the predominant lift method used in the Milne Point Field (MPU), Alaska. Each year some 50 ESP failures occur, adversely effecting lifting costs, rig utility and production. Statistical methods based on the Weibull distribution and the Bathtub reliability model have been used to analyse ESP reliability data collected over a thirteen year period. The analysis differs from earlier works by treating a portion of the infant failures (the early part of the Bathtub model) as a series of Bernoulli trials. Analysis shows the three main factors effecting ESP reliability in MPU are reservoir, sand control and if the ESP is newly installed or a replacement. Further, the ESP failure rate is shown to be dynamic, influenced by the delivery of new wells and the time lag between failure and replacement. The results have been incorporated in to a computer based failure simulator which uses Monte-Carlo techniques to simulate the failure rates. Numerical values for the statistical parameters are included together with details of the simulator. The simulator is currently used within the MPU asset as a planning tool to establish changes in rig utility, production loss and ESP replacement strategies in a cash constrained environment. It is also used to assess improvements in ESP performance and to secure commercial terms for ESP lease and purchase options. In the future it is recommended that the simulator be used, with suitable analogue data, to predict the economic impacts of ESP failures on development programs prior to sanction.