Investigation of pore-scale mixed wettability

Abstract

The efficiency of secondary and tertiary-recovery processes can be improved by properly taking into account the reservoir's true wettability state. Most reservoirs are assumed to be mixed-wet, based on core-scale indices such as Amott-Harvey and USBM. Oil/brine/mineral contact-angle measurements on smooth substrates offer some molecular-scale input and estimates for network modeling. However, direct experimental techniques to characterize wettability and validate the mixed-wet model at the pore scale in real or model rocks remain elusive. One promising avenue is the use of microtomography (μ-CT) to map the pore-scale distribution of multiple phases in miniplugs. A second, complementary approach involves the study of model rocks based on bead packs to probe the surface chemistry of the minerals exposed to crude oil and brine in pore confinement. Integrating the two approaches described in the current study provides a promising means of explaining the observed multiphase-fluid occupancy in pores by combining the detailed knowledge of the 3D pore structure and information on the surface chemistry of its walls.