Studying the influence of formation of authigenic clayey mineral deposits on the physical properties of rocks is a current issue today. The lithological features of reservoirs predetermine their physical properties, the main of which are filtration-capacitance characteristics and are divided into primary and secondary. The primary factors include the granulometric composition of the clastic part of rocks and structural characteristics (sorting, grain size). Secondary factors include the nature of compaction of sedimentary rocks (intergranular contacts) and superimposed transformations of rock fragments and cement, among which authigenic mineral formation of clay minerals is distinguished. Clay minerals, which are found in cement of terrigenous rocks, have a direct impact on the reservoir properties. The purpose of the work is to study the interdependence between reservoir properties of the rock and the composition of clay minerals and their forms of selection. The object of the study were core samples of the А, В, С layers. The analysis of lithological, petrophysical, petrographic, mineral and geochemical data was carried out in the work. The research results showed that clay cement simultaneously with stage changes underwent superimposed epigenetic processes, which led to the transformation of the mineral composition of clay particles (kaolinization, chloritization and hydromica of cement), a change in the structural characteristics of clays and the emergence of new structural polytype modification. The comprehensive study made it possible to establish the authigenic nature of kaolinite and chlorite, as well as staging of their formation. Late generation kaolinite is represented by large, thick particles resembling pseudohexagonal crystals in their shape. The chlorite component of an earlier generation in the most cases directly contacts the surface of a detrital grain, while flakes of hidromicaceous composition are the latest in generation. The authigenic clay formation in the pores of terrigenous peservoirs leads to deterioration of reservoir properties. It should be noted that an increase in the hydromicaceous and, to a greater extent, mixed-layer component in the stone leads to a complication of the structure of the pore space and to a noticeable decrease in reservoir properties. Secondary mineral formation is an indicator for identifying reservoir zones with increased filtration-capacitance properties for rocks of various facies complexes.
References
1. Teodorovich G.I., Autigennye mineraly osadochnykh porod (Authigenic minerals of sedimentary rocks), Moscow: Gostoptekhizdat Publ., 1958, 572 p.
2. Yapaskurt O.V., Geneticheskaya mineralogiya i stadial’nyy analiz protsessov osadochnogo porodo- i rudoobrazovaniya (Genetic mineralogy and stage analysis of processes of sedimentary rock and ore formation), Moscow: ESLAN Publ., 2008, 356 p.
