Wettability is one of the main parameters affecting the distribution and flow of fluids in a porous medium, and has a great influence on the dynamics of the oil field development, especially when waterflooding and enhanced oil recovery methods are used. The knowledge based on theoretical and experimental studies allowed us to conclude that wettability is determined by the historical interaction of the reservoir rock and fluids, surface properties of reservoir rocks’ pore channels, and physical and chemical properties of the oil. In this regard, it is extremely important to study the relationship of wettability with the pore space structure, the mineral composition of the reservoir rock and the residual oil saturation in the conditions of intensive fluid displacement by waterflooding.
The core samples were selected in two wells through the crossection of heterogeneous clastic layers D1 in South-Romashkino and West-Leninogorsk areas of the Romashkinskoye oil field. There were determined wettability, the clay content on the structure of the pore space and the model residual oil saturation and oil displacement efficiency in these samples after extraction of organic matter. The insoluble organic substance formed by the irreversible adsorption of oil components on the clay mineral surface and carbene-carboid compounds formed from asphaltenes after prolonged development of the oil reservoir by flooding with insufficiently treated river water was noticed in the rock, the presence of which modified the wettability of the rocks in the direction of increasing hydrophobicity. It was confirmed that hydrophilicity was more typical for rock samples with smaller pore radius. It was shown that the wettability of the reservoir correlated with the permeability and pore size and that the residual oil saturation increased in the more hydrophilic and less permeable parts of the reservoir. No direct correlation between the wettability and clay content was detected. The obtained results should be taken into account in developing technological solutions for waterflooding and enhanced oil recovery.
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