Geophysical and geochemical studies on the delineation of volcanogenic rocks to improve the efficiency of prospecting for non-anticlinal hydrocarbon deposits

An important characteristic of effusive rocks for predicting their possible hydrocarbon saturation is the presence of reservoirs (fractured, pore-cracked, pore-cracked-cavernous) within them, especially in those parts of the volcanogenic section that are in contact with ordinary sedimentary formations. For this purpose, issues related to the methodology of complex studies aimed at improving the efficiency of prospecting for hydrocarbon (HC) deposits in the buried weathering crusts of effusives are considered. Although, the initial data for the development of the proposed methodology were mainly materials from the study of volcanogenic rocks in oil-and-gas-bearing regions of the Middle Kura Depression, this methodology can be used to search for HC deposits in other oil-and-gas-prospective regions. In the method under consideration, in addition to the main criteria for oil and gas potential, the specific occurrence of hydrocarbons in effusive-pyroclastic formations is considered, as well as paleogeomorphological features of buried paleorelief, the presence and duration of interruptions in sedimentation after the formation of the effusive-pyroclastic massif, and the age, lithological, and petrophysical characteristics of the overlying rocks. The presence and thickness of distinct geochemical zones in weathering crusts are also considered. As a result of complex studies of traps in volcanogenic strata, it is proposed to construct a number of additional cartographic materials – historical and paleogeographic maps of the unconformity surface of the sedimentary cover and weathered volcanics, cross-sections of weathered volcanic rocks with precise identification of individual geo- chemical weathering zones, and maps showing the distribution and thickness of the most favorable zones for hydrocarbon saturation in the geochemical weathering crust, which exhibit enhanced reservoir properties. Consistent application of the developed methodology of complex studies in forecasting, searching, and exploration of hydrocarbon deposits in combined-type traps in weathering crusts will significantly increase the efficiency of exploration work in areas where buried effusive massifs may be encountered in the oil and gas regions of Azerbaijan.