Wettability Effects on Oil Recovery Mechanisms in Fractured Reservoirs

Abstract

Abstract Iterative comparison between experimental work and numerical simulations has been used to predict oil recovery mechanisms in fractured chalk as a function of wettability. Selective and reproducible alteration of wettability, by aging in crude oil at elevated temperature, produced chalk blocks which were strongly-water-wet and moderately-water-wet, but with identical minerology and pore geometry. Large scale, nuclear-tracer, 2D-imaging experiments monitored waterflooding these blocks of chalk, first whole, then fractured. This data provided in-situ fluid saturations for validating numerical simulations and evaluating capillary pressure- and relative permeability input data used in the simulations. Capillary pressure and relative permeabilities at each given wettabilities were experimentally measured and used as input for the simulations. Optimization of either Pc- data or kr-curves gave indications of which of these input data could be trusted. History matching both the production profile and the in-situ saturation distribution development gave higher confidence in the simulations.