Characteristics of pore dynamics in shale reservoirs by CO2 flooding
The pore utilization characteristics of CO2 during shale oil displacement are a crucial indicator for evaluating its effectiveness in enhancing shale oil reservoir recovery rates.Therefore,experiments on supercritical CO2 displacing shale cores were conducted in the laboratory,and nuclear magnetic resonance(NMR)online core scanning technology was used to study the pore utilization characteristics and patterns of CO2 displacement in shale oil reservoirs.The results indicate that immiscible flooding by supercritical CO2 mainly develops the oil in shale pores with radius of 0.1～3.0 µm,but the oil content in pore radius less than 0.008 μm actually increases.The analysis shows that CO2 brings shale oil from large pores into small pores through pressure difference and diffusion effect in the shale layer and makes oil undergo adsorption and retention.After a displacement time of five hours,the recovery rate of shale oil by CO2 displacement reached 35.7％,indicating a relatively effective oil displacement result.
supercritical CO2shale oilnuclear magnetic resonancepore development characteristicoil recovery
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