Experimental Simulation Study on the Impact of Gas Lift on the Flowability of Offshore Heavy Oil

Gas lift is a commonly used method for extracting heavy oil, which has the advantages of simple and reliable construction, free control of depth, and minimal damage to reservoirs. When applied in actual field conditions, there may be issues with accurately assessing oil well production, and the flow characteristics of wellbore fluids during gas lift for heavy oil still require further research. This study employs experimental methods to investigate the flow behavior of heavy oils with different viscosities during gas lift. In this context, 5# white oil, 68# white oil, and 300# white oil respectively represent low viscosity, medium viscosity, and high viscosity scenarios. Air injection is used to simulate the actual field injection of nitrogen. The experiments simulated the variations in wellbore friction pressure drop and total pressure drop under different gas injection rates and liquid flow rates for varying viscosity levels. It can be observed that as the viscosity of the crude oil increases, the impact of frictional pressure drops on the total pressure drop becomes more pronounced. Additionally, the study also examined the characteristics of bottom-hole pressure changes during the experimental process. Analysis of the experimental data indicates that reducing the gas injection rate at the beginning of the injection process can effectively mitigate the negative impact on bottom-hole pressure. Finally, utilizing the images of two-phase flow patterns captured during the experiments and the recorded data, flow regime maps were constructed for different viscosities. This will contribute to improving the accuracy of two-phase pressure drop calculations for highly viscous oil and gas flows.