Verification of the Technology of Search for Hydrocarbon Pools on the Basis of the Studies of Water-Gas Equilibria (the Southern Regions of the Ob-Irtysh Interfluve)

Results obtained through the analysis of water-gas equilibria in formation waters are shown to form the basis of the technology aimed at search for hydrocarbon pools. A direct dependence of a decrease in total gas saturation, the concentrations of methane homologues and water composition on the distance from water-oil contacts was established. A connection between hydrogeochemical anomalies and hydrocarbon pools was also detected It was revealed from the nature of the equilibria that hydrocarbon pools in the Paleozoic and Mesozoic sediments of the southern parts of the Ob-Irtysh interfluve act as a conservative element of the lithosphere. Water-gas equilibria modeling revealed that the geochemical regime dominating at the major part of the territory under study is favourable for the formation and conservation of hydrocarbon pools, except for the marginal zones. Computer modeling of physicochemical equilibria and evasion-invasion processes in water-gas systems allowed us to establish the degree of groundwater saturation with gases and the nature of diffusion redistribution of gases at the boundary between hydrocarbon deposit and formation water. All waters with total gas saturation of 2.0 l/l become ultimately saturated with gases (Kg = 2.0), which means that theoretical prerequisites for the formation of hydrocarbon deposits arise. Calculations allowed us to reveal more than 30 promising objects with the high probability of detection of hydrocarbon deposits at the Bergul, Vitin, Chekovsky and other areas.