Impact of Fracture Permeability on Oil Recovery in Moderately Water-Wet Fractured Chalk Reservoirs

Abstract

Abstract The impact of fracture permeability on oil recovery from moderately-water-wet chalk has been determined. Nuclear Tracer Imaging was used to measure local fluid movement and to identify locations of trapped oil resulting from waterflooding a sleeved, fractured chalk block. Increasing the confinement pressure between experiments decreased the permeability of an interconnected fracture network for each sequential waterflood. The experiments showed that the dominant oil recovery mechanism was spontaneous imbibition, however, viscous oil recovery added significantly to the total oil production when the permeability ratio between the fractured system and the matrix was less than 20. The amount of oil viscously recovered increased as the fracture permeability decreased.