Simulations of Carbon Dioxide Leakage from Uncased Boreholes Into Formations Lying Above a Sequestration Reservoir.

We present calculations showing how leakage of CO2 up an uncased section of a borehole can move into formations overlying a sequestration reservoir. Relationships between the invaded formation permeability structure, phase-state of the CO2 in the borehole at the depth of contact, and reservoir pressure are explored. Preliminary results suggest that the most important parameters governing the invasion of borehole CO2 into formations are 1) the pressure gradient between the borehole fluids and the formation waters, and 2) the relative permeability to the available phase that is being transported from the borehole to the surrounding formation. We show that fractured formations overlying a storage reservoir are the most likely to allow significant invasion when leaking boreholes are overpressured with single phase CO2. Finally, we discuss how these results can be abstracted into a system modeling approach during the performance assessment phase of CO2 sequestration site selection.