Prospects for oil and gas presence of Lower Sarmatian deposits in the north-western part of the Outer zone of the Carpathian foredeep (by hydrogeochemical and hydrodynamic indicators)

The hydrogeochemical parameters of the Lower Sarmatian aquifer of the north-western part of the Outer Zone of the Carpathian Foredeep have been studied. The waters of the chloride-calcium type (according to the classification of V. O. Sulin) are dominated. Other types of water are distributed locally. On the basis of the calculated genetic coefficients, the conclusion on sedimentogenic conditions of their forming during a geological history of the region is made. It is established that the general tendency for the deposits of the Outer Zone is increasing of TDS of water with depth and stratigraphy. The waters of the north-western part of the Outer Zone are characterized by reduced values of sulfate content and sulfation coefficient rSO42– • 100/rCl–, indicating the conditions of hydrogeological closed structures. The genetic index of formation water metamorphism (rNa+/rCl–) is mainly inversely dependent on TDS. Its values greater than one are inherent in waters of hydrocarbonate-sodium and sulfate-sodium types, which are not typical for the hydrocarbon deposits. The nature of fluctuations in the values of the chlorine-bromine coefficient is fully consistent with other hydrochemical parameters and the results of paleohydrodynamic reconstructions. A detailed analysis of the current hydrodynamic situation of Lower Sarmatian aquifer in combination with geochemical features and paleohydrodynamic reconstructions allowed to identify the perspective structures of the studying region. Our forecasts for the gas potential of the Krukenychy depression are consistent with the forecasts of researchers of Ivano-Frankivsk National Technical University of Oil and Gas. The results of their research are based on gravitational field anomalies.