Design of hybrid artificial lift system with dual electric submersible pumps for ultra-deep oil wells

Ultra-deep hydrocarbon reservoirs have enormous resource potential, and oil production from ultra-deep wells contributes significantly to energy supply, imposing increasingly stringent demands on extraction technologies. To address the research gaps in previous research in ultra-deep well artificial lift systems and tackle the technical bottlenecks restricting long-term and efficient oil extraction, this paper comprehensively analyzes the advantages and limitations of six existing composite artificial lift methods. Focusing on the interconnection difficulties of upper and lower electric submersible pump (ESP) units in dual-ESP hybrid lift systems, three structural deployment schemes are proposed, and a detailed comparative analysis of their technical advantages and drawbacks is conducted. The optimization analysis reveals that dual-ESP hybrid lifting is the most viable solution, with a packer-setting connection identified as the optimal linkage scheme between the upper and lower ESP units. Taking a typical ultra-deep well in the Tarim Basin as a field case, corresponding software models were constructed using a commercial program to design key lifting parameters. The results demonstrate that the packer pressure differential is affected by the total pressure head, which is boosted by the lower pump. In the pump configuration, the lower-power ESP should be used as the lower pump unit, and the higher-power ESP as the upper pump unit. These findings are helpful for advancing artificial lifting and enhancing oil recovery in ultra-deep wells.