Analysing Gas-Liquid Flow Effects on the Performance of ESP by Nodal Analysis

Abstract

Electrical submersible pumps (ESPs) are one of the most effective artificial lift methods for increasing hydrocarbon production in high-rate wells; however, free gas in the production stream frequently causes issues such as gas locking, reduced pressure head, increased mechanical wear, and eventually pump failure, particularly in reservoirs with gas breakthrough or active gas caps. Traditional diagnostic workflows relied on pump performance curve matching with nodal analysis, which were unable to detect dynamic performance anomalies. In this study, an enhanced nodal analysis methodology was applied to assess the ESP performance under gas–liquid flow conditions using real-time field data. The methodology combined downhole intake and discharge pressures, surface well testing data, and Variable Speed Drive (VSD) output current. The field baseline was validated with Petex PROSPER software, achieving high predictive accuracy with a relative error of 2.82% for the oil production rate and <0.50% for the downhole pressures. The framework was used on Well A in the Peshkabir field (Kurdistan Region of Iraq), where gas breakthrough caused discharge pressure collapse from 2,572 psi to 1,360 psi (47.12%), a 23.08% reduction in VSD output current from 390 A to 300 A, and an intake pressure rise from 1788 to 1860 psi, signifying dynamic motor unloading and ESP head degradation. Following a gas shut-off intervention using coil tubing to close Sliding Side Door (SSD) #1, #2, and #3 in the lower completion, the discharge pressure climbed to 2850 psi (109.56%), the intake pressure remained steady at approximately 1770 psi, and VSD current restored to approximately 380 A (26.67%). The results indicated that the intake–discharge pressures, well test data, and VSD current telemetry serve as a reliable method for diagnosing gas interference in packer-completed wells, allowing better reservoir management without requiring pump curve details.