Analysis and optimization of the J-T valve control logic for offshore oil and gas field low-temperature separators based on K-Spice

This study focuses on the Joule–Thomson (J–T) valve of a low-temperature separator in a domestic offshore oil and gas field. To address the lack of systematic research on the existing control logic, a dynamic model consistent with field operating parameters was established using K-Spice software. The model was employed to simulate the impact of dry gas compressor shutdown on separator pressure and to optimize the J–T valve control strategy. The results indicated that under the original control logic, when one dry gas compressor was shut down due to a fault, the separator pressure rapidly increased to 82 barg within 10 s, triggering the high–high pressure alarm (PAHH) and causing production shutdown. After the control logic was improved, the J–T valve opening automatically decreased to 20% within 3 s once the compressor shutdown was detected. Under this condition, the separator pressure was effectively maintained below 82 barg, the PAHH alarm was avoided, and production continuity was ensured. Moreover, optimizing the separator temperature setpoint to − 20 °C reduced the risks of both degraded export gas quality and excessive flaring. Overall, the findings quantitatively describe the dynamic response of separator pressure to J–T valve adjustments and provide a valuable reference for improving J–T valve control logic in offshore oil and gas production systems.