Temperature and pressure prediction of offshore high CO2-content associated gas lift and analysis of influencing factors

Abstract

With the continuous injection of CO2 into the reservoir, a portion of the sequestered CO2 is co-produced with crude oil, resulting in a significant concentration of CO2 in the associated gas. Utilizing high CO2-content associated gas for offshore gas lift operations improves the reutilization of such gas and reduces costs related to sourcing and transporting it. To ensure smooth activation of the gas lift valve, conducting a thorough study on temperature and pressure within the wellbore during the gas lift process is essential. This study developed a dynamic model for calculating the transient temperature and pressure within offshore gas lift wellbores and fitted equations to calculate the physical properties of high CO2-content associated gas for specific compositions. This refinement minimized computational discrepancies arising from fluctuations in physical property parameters. When applying this model to oilfield scenarios, the maximum error observed was 3.83%, which aligned well with the accuracy standards required for oilfield computations. By integrating oilfield production data, this research explored the influence of injection parameters on temperature and pressure dynamics within the gas lift wellbore. The results revealed that variations in injection temperature and pressure had minimal impact on the temperature at the gas lift valve. Yet, they induced significant changes in the pressure at that point. An increase in CO2 concentration within the gas source composition was associated with considerable shifts in temperature and pressure gradients throughout the wellbore. At high mass flow rates, the temperature gradient of the wellbore was notably reduced, while the pressure gradient was significantly enhanced. These research findings provided a theoretical basis for optimizing gas lift operations using high CO2-content associated gas in offshore settings.