Methodology of prediction of terrigenous reservoir rocks (deposits of the Serpukhovian stage of the Dnieper-Donets depression cited as an example)

A sedimentational model of terrigenous reservoir rocks is based on the results of structural-paleogeomorphological and lithological-facies investigations. The reconstruction of the paleolrelif in time of the deposition of sandstones is carried out on the basis of the analysis of small thicknesses of one-aged deposits enclosing these sandstones. Minimum values of deposits thickness will correspond to the paleorelief rasing, and maximum ones – to its lowering. The information on the facies composition of rocks was obtained according to the result of studies of their composition, structure, texture, plant and fauna remnants, mineral inclusions, contacts and transitions between layers, interaction with hydrochloric acid and other diagnostic indications. It was also taken into consideration that sand material, which is carried over by linear sedimentary flows with one-directed dynamics of the water surroundings (rivers, their deltas, sewering and marine currents), is accumulated in the lover forms of the relief. Feedback is characteristic of lithofacies of litorial formations: beaches, bars and spits (wave dynamics of water surroundings). As an example we have constructed a sedimentational model of the Upper Serpukhovian productive horizon C-4 that contains the information on the distribution of alluvial, deltaic, avandeltaic, beach sandstones, their contents in the section of the productive horizon. On the basis of the sedimentation model and data of geophysical studies of wells, the regional map of reservoir rocks of the productive horizon C-4 was compilled which contains data on the sandstones thickness and their collecting properties.