Recovery Factor is one of the key elements in determining commercial viability of hydrocarbon fields. It has been recognized that the recovery factor, apart from other parameters, depends on wettability of the reservoir rocks which in turn affects calculations of other parameters used in the volumetric equation. This study is concerned with the impact of wettability alteration due to production on resistivity saturation exponent used in the Archie equation and its subsequent effect on reserves calculations.
The idea is to compare capillary pressure derived saturations measured from laboratory tests on water wet samples and those derived from total porosity resistivity model with cementation and saturation exponents also measured under the same laboratory conditions. The discrepancy between the two is then used as part of the methodology for identification of potential wettability alteration. If discrepancy between the two methods isn’t caused by anomalously high permeabilities or wrong Free Water Level estimations, then by the way of iteration, saturation exponent can be varied until the match between the resistivity model and height function saturations is achieved. The workflow for integration of all saturation estimation sources is developed to back propagate the errors in hydrocarbon volume calculations.