Features of Estimating the Thickness of the Water-Oil Transition Zone Depending on Various Physico-Geological Factors

Abstract

. Significant oil reserves may be contained in the part of the oil reservoir related to the water-oil saturation transition zone, but a comprehensive description of the relationship between capillary pressure, relative phase permeability and saturation with oil and water is a constant problem in carbonate deposits due to complex wettability changes, difficulties with assessing the nature of reservoir saturation by well logging, pore geometry and lithofacies heterogeneity throughout the reservoir thickness in the saturation transition zone.

In the course of the work, it is shown that a reliable interpretation of the constructed capillary pressure curves and relative phase permeability, including taking into account various physical and geological factors of productive formations, has a significant impact on predicting the initial oil saturation coefficient and the thickness of the two-phase filtration zone for complex carbonate reservoirs. The paper examines various factors influencing the size of the transition zone in a carbonate reservoir: lithofacies and filtration-capacitive properties of reservoirs, age of sediments, properties of saturating fluids, surface properties by wettability of the solid surface of capillaries, and structural features of the pore space of reservoirs.