Tuning VSDs in ESP Wells to Optimize Oil Production—Case Studies

Abstract

To maximize electrical submersible pump (ESP) uptime and production in North Kuwait's diverse reservoir conditions, it was necessary to combine variable speed drive (VSD) feedback control functionality with reservoir knowledge and real-time data and subsequently develop an operating strategy tailored to individual wells. The case studies in this paper show how well performance can be stabilized and production increased by incorporating motor current and downhole pressure into the VSD frequency control loop. In North Kuwait fields, engineers studied wells with ESPs running in unstable condition or suffering frequent tripping due to underload or high temperature. Their ESP design datasheets, production test results, historical VSD running parameters, and downhole gauge data were used to calibrate pump and well performance models and identify the pump operating point. From these simulation results, the VSD feedback control loop function was optimized to minimize tripping and/or enhance stability, thereby increasing production. The main causes of well instability and ESP downtime in North Kuwait are declining bottom hole flowing pressure and gas interference. The case studies illustrate how to select the appropriate VSD frequency feedback object function for each of these cases. For weak inflow, the VSD is configured to maintain constant intake pressure, especially where the intake pressure is less than 500 psia. For ESPs suffering from gas interference, constant current was implemented to avoid gas locking. The before and after results from the case study wells demonstrate the effectiveness of this technique for well stabilization and associated production increase. After the study, this method was implemented on 60 wells and resulted in a 21% reduction in the number of ESP trips over 6 months and an associated increase in uptime from 92% to 97%. This case study describes a workflow that integrates ESP historical running data, reservoir knowledge, and VSD feedback control functions to increase well uptime by preventing ESP tripping. In addition, the workflow enhances ESP system operating stability and optimizes the reservoir drawdown, which offers the operator a viable option to achieve production objectives.