WETTABILITY CHARACTERIZATION BY NMR T2 MEASUREMENTS IN CHALK

Nuclear Magnetic Resonance (NMR) T2 relaxation properties for oil- and water-saturated outcrop chalk were measured using the CPMG sequence at various wettabilities and at various fluid saturations in order to their usefulness for wettability characterization. Slower T2 relaxation times and increased intensity are associated with the water phase signal as the water saturation increases during spontaneous imbibition. The assumption that the shifts in the water phase T2 relaxation time would decrease at less water-wet conditions due to reduced surface relaxation, and be a non-linear function of saturation was not corroborated. The relative shift for T2 relaxation time for the oil phase during spontaneous imbibition as a function of increasing water saturation, Sw, was observed to consistently and gradually change from a shift toward slower relaxation for strongly water-wet conditions to a shift toward faster relaxation for more neutral wet conditions.