Interpretation of Lithofacial Characteristics of the Productive Series to Predict Hydrocarbon Potential of Pliocene Deposits

The article examines the influence of the diagonal fault system and tectonic uplifts on the processes of migration and generation of hydrocarbons in the Lower stage of the Productive Series (PS) of the studied region. It is shown that the structures of the region were subjected to intense lateral compression and were formed as a result of the development of plicative and disjunctive dislocations along the diagonal system. Fault dislocations are characterized by northwest-southeast directions in the form of tectonic uplifts, faults, and thrusts. Plicative dislocations are represented by linearly asymmetric brachyanticlinal folds that are aligned along faults, accompanied by the formation of diapir folds and mud volcanoes. These tectonic surfaces not only act as screens for fluids, but also create conditions for their vertical and lateral migration to the upper horizons. The study of vertical and lateral zonation confirms that hydrocarbons move from the center of the depression to its marginal uplifts. For example, within the Zirinsky trough of the Absheron archipelago, in the deep horizons of the productive layer (4500–5000 m), a zone of gas condensate phase with residual oil was identified. The main hydrocarbon accumulations are shifted towards tectonic uplifts and are concentrated in such deposits as Kohna Gala, Gala, and Buzovna. The purpose of the work: re-evaluation of theoretical and practical data considering the specific features of the South Caspian Depression (SCD), such as the dependence of the spatial position of fluids on evolutionary facies conditions, which requires a new approach to assessing the prospects of the region. Objects: The Apsheron archipelago and its structures, sedimentary cover, sedimentation conditions, lithofacies characteristics of rocks, areas of abnormally high reservoir pressure (AHRP), and other aspects. The study was based on data from exploration and production drilling, field geophysics, laboratory studies, and rock samples, as well as published scientific articles and materials. Results: The alternation of permeable and screening layers in the section creates favorable conditions for the generation and accumulation of hydrocarbons even at significant depths (9–10 km). In the southwestern direction (Kura facies), there is an intensive increase in clay content, while in the south (Absheron and Kura facies) and southeast (Cheleken facies), this trend is weakly expressed. In the southeastern direction, the deterioration of reservoir properties is replaced by areas with good sorting of sandstones, enrichment in quartz, and the presence of AHRP, which is typical for structures with high reservoir characteristics. These parameters are naturally manifested in large-sized structures, which allows us to consider them promising for exploration work.