No abstract

No abstract

The results of study of hydrogeological conditions of oil and gas bearing deposit of the southern areas of Ob-Irtysh interfluves (southern regions of West Siberian basin) are presented. The hydrodynamic field is characterized by direct dependence and the presence of normal and increased pressure (formation anomalous pressure factor not exceed 1.13) is common in Apt-Alb-Cenomanian, Neokomian, Jurassic and pre-Jurassic complexes. The results of study of the reservoir properties and hydrodynamic conditions indicated that the elision water exchange play the dominant role in the modern hydrogeological structure formation. Two types of water drive system is established: elisional (lithostatical and termodehydrational) in the inner areas (southern part of Koltogor-Nyurolsky trench, Nyurolskaya megadepression, Verkhnevasyugansk anteclise and other structures) and infiltrational within the territory of Baraba-Pikhtovo monocline. Elisional system is replaced by the elisional-termodehydrational at the depth 2.0-2.2 km. Large piezo maximum zones (southern part of Koltogor-Nyurolsky trench and Nyurolskaya megadepression) become the inner regions of water pressure generation (the inner feed areas) with the maximal degree of hydrogeological closure of the interior. The region of piezo minima, tracing the structures of the Barabinsk-Pikhtovskaya megamonocline, relates to the external feed area. The hydrodynamic model of the southern areas of Ob-Irtysh interfluves is building for the first time and allow to predict the pressure change trends in the areas with poorly provided with the actual data.

No abstract

––For the first time in the last 35 years, hydrogeochemical data on pre-Jurassic complexes in West Siberia have been generalized. Groundwater and brines of Cl–Na and Cl–HCO3–Na type with total salinity (TDS) varying from 4 to 330 g/L are found to be widespread in the area under study, with the former type dominating. A detailed analysis of the hydrogeochemical data allowed us to assume the presence of three genetic groups of groundwater and brines in the hydrogeologic section: (1) sedimentogenic, (2) lithogenic (revived) and ancient infiltrogenic, and (3) condensatogenic. An integrated analysis of coefficients rNa/rCl, Ca/Cl, (Br/Cl)·10–3, and (Sr/Cl)·10–3 and integrated index S of brine metamorphization in the Siberian sedimentary basins has corroborated the fact that groundwater and brines in West Siberia are at the initial stage of metamorphization of their chemical composition. Groundwater and brines in the studied Siberian sedimentary basins show an increase in the degree of metamorphization (catagenetic changes) of their chemical composition in transition from the areas of igneous and metamorphic deposits at the base of the Meso–Cenozoic sedimentary cover of the young West Siberian sedimentary basin to the structures of the ancient Siberian Platform, where ultrastrong Ca–Na and Ca chloride brines are widespread.