Abstract:

      TOUGH2/ECO2N code was used to simulate transportation of CO2 plume in the deep saline aquifer of lower part of the
Yancheng Formation in Subei basin. A fault was added to the conceptual model to evaluate the leakage risk after CO2 injection. Simulation results indicate that the effect of multilayer capping for CO2 sequestration is not good because of the clay strata with small thickness and relatively high permeability, although the lower part of the Yancheng Formation has three sequences’ structure (multiple sand-clay layers) and the sand stratum has high permeability and high porosity. Especially when there is a fault conducting all layers the leakage risk for CO2 geological sequestration is significant. Morris method was used to analyze the global sensitivity of the parameters for two scenarios. When only the fault parameters are changed, the parameters related with the capillary pressure have great effect on CO2 leakage along the fault. When all the parameters of fault, sand and clay strata arevaried, the permeability of sand and clay has the highest sensitivity for the leakage risk, while the parameters related with the capillary pressure are secondary. For both scenarios, the sensitivity of porosity and salinity is very small.

Key words: Subei basin, CO2 geological sequestration, fault leakage, global sensitivity analysis, Morris method