Evaluation of CO2 enhanced oil recovery and sequestration potential in low permeability reservoirs, Yanchang Oilfield, China

Sequestrating CO2 in reservoirs can substantially enhance oil recovery and effectively reduce greenhouse gas emission. To evaluate the potential of CO2 enhanced oil recovery (EOR) and sequestration for Yanchang Oilfield in China, a screening standard which was suitable for CO2-EOR and sequestration in Yanchang Oilfield was proposed based on its characteristics of strong heterogeneity, high water content and severe fluid channeling after water flooding. In addition, an efficient calculation method – stream tube simulation method was presented to figure out CO2 sequestration coefficient and oil recovery factor. After screening and evaluating, it turned out that 148 out of 176 blocks in 22 oilfields were suitable for CO2-EOR and sequestration. CO2 flooding after water flooding can produce 180.21 × 106 t more crude oil and sequestrate 223.38 × 106 t CO2. The average incremental oil recovery rate of miscible reservoirs was 12.49% and the average CO2 sequestration coefficient was 0.27 t/t while the two values were 6.83% and 0.18 t/t for immiscible reservoirs. There are comparatively more reservoirs that are suitable for CO2-EOR and sequestration in Yanchang Oilfield than normal, which can obviously enhance oil recovery and means a great potential for CO2 sequestration. CO2-EOR and sequestration in Yanchang Oilfield has a bright application prospect.