Geological Structure of Deep-Submerged Complexes of Sedimentary Basins: Hydrogeological Anomalies and Oil and Gas Potential as a Result of Implementation of Deep-Seated Fluids (on Example of the South Mangyshlak Fields)

Abstract

The authors of the article substantiate the induced nature of hydrogeological anomalies in deep-submrged complexes of sedimentary basins. As a result of significant catagenetic transformations, the rocks of the lower hydrogeological floor have practically lost their primary capacitance-filtration properties. The water saturation of the rock matrix, the focal nature of the development of secondary reservoirs against the background of extremely low permeability of the surrounding strata makes it impossible to develop elision flows. This causes the high sensitivity of the lower floor to various compression processes, including those caused by the intrusion of the deep high-energy fluid flows. The injection of these fluid flows into low-permeability strata leads to the formation of centers of desalinated waters of various hydrochemical types, from hydrocarbonate-sodium to calcium chloride, and also to the formation of hydrodynamic anomalies. When moving away from the intrusion channels, the hydrodynamic and hydrochemical parameters gradually level off, approaching the background value. It is shown that when fluids are difficult to move upward, hydraulic fracturing occurs in the layers into which the oil-water mixture enters under high pressure. The injection of fluids into the formation is accompanied by the decompression of low-permeability strata, the formation of additional fractures, and the formation of secondary voids of metasomatic origin. As a result, secondary reservoirs of complex morphology are formed, filled with hydrocarbons. The coincidence in terms of hydrogeochemical and hydrodynamic anomalies, areas of secondary reservoirs with distinct traces of metasomatosis and associated accumulations of oil and gas indicate their genetic relationship. The oil and gas reservoirs and their accompanying hydrogeological anomalies are considered on the example of the fields of the South-Mangyshlak oil and gas region, which is part of the North Caucasian-Mangyshlak oil and gas province.