Fluid Issues when Modeling CO2 Reinjection into a Fractured Reservoir Gas Field

CO2 reinjection into a fractured reservoir is challenging, as reinjected CO2 may recycle rapidly to the gas production wells, leading to potential gas production losses.

Development studies require performing screening studies, looking at many possible scenarios (as geological model, well location, process capacity). It is hence critical to speed up the simulation time in order to be able to investigate these many scenarios.

Various fluid models, with various degrees of simplification, may be used to study different phenomena that will impact the CO2 break through time. This includes convective flow in the fracture network, CO2 diffusive flow into the gas bearing matrix blocks, and CO2 dissolution in the formation water.

Specific fluid models, embedded in the reservoir model, were used in order to look at the impact of these various phenomena for the different scenarios, in order to speed up the developement process. This is presented in more details for the modeling of the molecular diffusion into the matrix blocks and the modeling of the convective flow in the fractures.