For the purposes of winning economic performance and environmental performance, the application of CO2 displacement might be a viable option due to enhancing oil recovery significantly and sequestrating part of CO2 permanently.

Molecular diffusion is the key migration style of sequestrated CO2 due to concentration gradient in geologic body, so in the process of CO2 concentration goes to a balance condition, the sealing performance of cap rock for CO2 is influenced by some extent.

According to actual geologic parameters of Jilin CO2 flooding pilot test, CO2 diffusion coefficients were investigated in cores of super-low permeability saturated with in place oil under both miscible and immiscible pressure. Results obtained from these experiments were used to gas saturation field prediction for 1000 years after CO2 flooding on 12 homogenetic models considering immiscible, near-miscible and miscible conditions and cap rock thickness from 10m to 100m.Based on the prediction, CO2 geology sequestration safety template was built considering both miscible condition and the thickness of cap rock, which allows getting optimum reservoir and geological parameters for CO2 sequestration.

This research has reference value on the evaluation for CO2 geology sequestration ability and safety in low permeability oil reservoir.

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