Study on the Injection and Production Characteristics During the Process of CO₂ Flooding and Storage in Tight Oil Reservoirs

Tight oil reservoirs have strong heterogeneity and well-developed micro-fractures, and the adaptability of water flooding in some oil reservoirs is poor. Dynamically, it is manifested as problems such as a large initial decline, uneven areal water flooding, water break-through in multiple directions of oil wells, and great difficulty in water control. Therefore, based on the multi-scale physical simula-tion experiments after water flooding in tight oil reservoirs, the CO₂ displacement mechanism and the injection-production relationship under different phase state characteristic conditions are analyzed, taking into account the influence of reservoir characteristics and the dominant channels of water flooding. The oil displacement effect and main controlling factors are evaluated, and the process parame-ters of CO₂ flooding in tight oil reservoirs are optimized and formu-lated. The research results show that: ① Under the non-miscible condition, the improvement of oil recovery by CO₂ flooding is small; under the miscible condition, the component exchange be-tween CO₂ and crude oil is the main phenomenon in the displace-ment process, and the remaining oil is fully mobilized, increasing the oil recovery rate by 20–30 percentage points. ② The injection gas rate is optimized and formulated as 50,000 m3/d, the injection-production ratio is 1.2, and the upper limit of the producing gas-oil ratio is 1000 m3/m3 under the continuous injection condition. It is concluded that the research results provide a theoretical basis for determining the optimal technical policy for the CO₂ displacement and storage mechanism after water flooding development, and ef-fectively guide the development of tight oil reservoirs with scale benefits.