Dynamic simulation of gas-lock instability in an electrical submersible pump induced by annulus valve closure

This study employs a validated dynamic multiphase flow model to quantify the severe operational impacts of impaired annulus gas venting on Electrical Submersible Pump (ESP) performance. Utilizing high-frequency field data from a documented gas-lock incident-initiated by the inadvertent closure of a valve-the analysis demonstrates how a surge in the pump intake gas flow rate (from 0.2 to 0.4 MMSCFD) triggers a cascade of system failures. These include a severe oscillatory decline in the liquid flow rate of up to 300 STBD, leading to an overall production loss of 23%. The incident further induced significant system instability, manifested as amperage fluctuations between 40 and 58 A, Pump Intake Pressure (PIP) oscillations with an amplitude of ± 30 psi, and impaired motor cooling. The primary contribution of this work is a detailed causal analysis and dynamic quantification of the gas-lock progression, establishing a benchmark for its severity. These findings underscore the critical, non-negotiable requirement for proper annulus venting in both ESP design and operational procedures to prevent catastrophic production losses and equipment damage.