Study and Experiment on CCUS-EOR Technology for Shale Oil in Dagang Oilfield

The recovery efficiency of shale oil depletion development in Dagang oilfield is low and there is no effective technology to enhance recovery efficiency. Through physical simulation and numerical simulation, the technology of enhancing oil recovery by injecting CO2 in shale oil was studied. At the same time, research on supporting technology of injection and production integration, corrosion prevention and control, production gas recovery and injection is carried out. Through the construction of CCUS-EOR technology system of shale oil in Dagang oilfield, this paper guides the safe and efficient implementation of field CO2 pumping to enhance oil recovery technology. The results show that the mechanism of CO2 in shale oil to improve oil recovery is miscibility to improve oil displacement efficiency, dissolution and permeability, plugging extraction and so on. The optimal CO2 injection volume in a single well is 800–1500 tons, and the best smothered time is 30–40 days. The injection and production integration technology can realize the construction and drainage without moving the pipe string. Three slug corrosion inhibitor filling mode in the process of operation and intermittent dosing mode in the production process can effectively alleviate CO2 corrosion; Output gas back injection process can realize the recycling of output CO2, and can avoid the corrosion of gathering and transportation system. Field test results show that CO2 injection is effective in improving oil recovery in shale reservoir. The supporting technologies, such as injection and production integration, corrosion prevention and control, produced gas recovery and injection, have strong adaptability, which is not only conducive to the green and low-carbon development of the oilfield, but also conducive to the realization of the national “double carbon” goal. The implementation of shale oil CCUS-EOR technology has better economic and social benefits. The research results have certain reference significance for the efficient development of shale oil and the green development of oil and gas field enterprises.