Flow field and performance analysis of downhole pipe string in single-well injection-production technology

High water content is a critical issue that must be urgently addressed in the current oilfield development, and the single-well injection-production technology (SWIPT) is an effective approach for achieving economical extraction in high-water-content oilfields. To meet the 5.5-inch casing size requirements, further improve SWIPT performance, and minimize the impact of pump pressurization on the subsequent oil–water separation process, dual-pump suction-SWIPT is proposed and an axial-flow cyclone separation pipe string is designed. A theoretical fluid–solid interaction (FSI) model of the downhole pipe string (DHPS) applicable to SWIPT is established through vibration testing and data analysis. Based on the new FSI model-corrected numerical simulation method, single-factor experiments are performed to analyze the medium transport process and oil–water separation performance within the flow field under structural vibration disturbances. The results indicate that the separation of fluid media within the single-well injection-production DHPS is not significantly affected by structural interference. The simulation results closely matched the experimental data, with the average error of the axial velocity at different test points being within 0.041 m/s. In the transport pipe regions, minor variations in the velocity and pressure fields are observed under vibration conditions. Under an inlet flow rate of 4 m3/h, split ratio of 30%, and oil volume fraction of 1%, the optimal separation efficiency of 97.26% is achieved. This study provides new insights for the development and application of SWIPT.