Wettability and Relative Permeability of Lower Cretaceous Carbonate Rock Reservoir, Saudi Arabia

Abstract

Abstract Results and discussions in this paper relate to a Lower Cretaceous carbonate reservoir located in southeastern Saudi Arabia. It is a heterogeneous carbonate formation with various facies due to diagenetic alteration of the original rock fabric. The reservoir is large and prolific with mixed-wet characteristics. Because of the economic importance and variety of oil-recovery mechanisms operative or possible in the reservoir, the multi-phase recovery behavior has been extensively studied. Also, various wettability tests were carried out using Amott and USBM methods. This paper describes the variation in wettability and relative permeability of Lower Cretaceous carbonate reservoir and the multi-phase simulations of the experimental results. It shows that measurements are consistent with recent theories of the relationship between water saturation, relative permeability, and wettability as described by Jadhunadan and Morrow, 1991.1 However, the results indicate that the wettability of the reservoir changes from water-wet low on structure near the oil/water contact to intermediate and/or oil-wet behavior higher on structure. Oil-wetting character increases towards the top of oil column and is correlated to decreasing water saturation. The results revealed that changes in wettability are accompanied by changes in waterflood efficiency and facies of deposition.