Is There Unusual Hysteresis Between Primary Drainage and Imbibition Relative Permeability for Supercritical Carbon Dioxide?

Abstract The objective of this paper is to investigate supercritical CO2 (scCO2) hysteresis behavior between primary drainage and primary imbibition and to directly compare results with known non-wetting nitrogen (N2) gas using the same core, the same experimental apparatus, and the same test conditions. Carbon dioxide injection is a drainage process, whereas post-injection scCO2 plume migration involves imbibition. Typically, supercritical carbon dioxide in aquifer is assumed to be water wet. In this work, we will perform drainage and imbibition relative permeability tests with supercritical carbon dioxide - brine and nitrogen - brine under reservoir conditions and evaluate if there is any unexpected hysteresis specifically associated with scCO2. Relative permeability experiments are conducted using a steady-state recirculation coreflooding unit with equilibrated fluids. Both scCO2 and nitrogen are equilibrated with brine to generate high confidence data. We use Berea sandstone core to reduce any potential rock-fluid effects. Carbon dioxide and brine typically cannot be directly treated as simple immiscible fluids due to their mutual solubility and sensitivity of phase behavior to temperature and pressure. Thus, carbon dioxide relative permeability studies require the use of equilibrated fluids, close control on temperature, control of pressure differential across the core, corrosion resistant materials, and specialized equipment. We completed both scCO2 – brine and N2 – brine relative permeability tests at the same reservoir conditions and using the same core sample. The results indicate that scCO2 relative permeability is similar to nitrogen, where both fluids show strongly water-wet hysteresis behavior.