The results of petrophysical and geochemical studies of limestones of the Lower Carbon age sampled from productive and water-bearing intervals are considered. Based on the integration of capillarometry data and the determination of relative phase permeabilities, the forecast of the nature of saturation along the height of the reservoir from the free water level (OWC1) to transition zone (OWC2) was carried out. Reservoir models using samples taken from productive and water-bearing intervals, and the thickness of the transition zone in each of these models was determined. The studies made it possible to establish that the residual oil in the pore space of the aquifer is oil bitumen rich in asphalt-resinous components. On the contrary, the residual oil in the pore space of samples taken from producing intervals is similar in composition and properties to the oil produced from these deposits. Samples from aquifers have lower reservoir properties than samples obtained from productive intervals. All boundaries distinguished by the height of the reservoir (from OWC1 to OWC2) in the reservoir model built using samples from the aquifers are located higher than the same boundaries obtained on the model of the same reservoir, built from samples taken from productive interval. There is a high content of residual oil (oil bitumen) in the limestones under consideration, especially those taken from the aquifer near the OWC2 boundary, which necessitates the development of methods for enhancing oil recovery from these rocks.
References
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