Lawrence Berkeley National Laboratory

Leakage of CO2 from a primary disposal reservoir is presumed to occur along a fault or fracture zone, which has been modeled as a slab of porous and permeable material embedded in wall rocks of negligibly small permeability. Numerical simulations presented here include multiphase flow, boiling of liquid CO2, transitions between supercritical and subcritical conditions, phase partitioning between CO2 and water, and non-isothermal effects. Depressurization of rising CO2 is found to produce strong cooling. Conductive heat transfer from the impermeable wall rocks is an important aspect of system evolution. Pressure and temperature conditions are drawn towards the critical point of CO2 and the CO2 saturation line. The interplay between multiphase flow in the fracture zone and heat conduction perpendicular to it may produce non-monotonic, quasi-periodic variations in thermodynamic conditions.