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The main focus of this work is the investigation of the hydraulic function of faults, which is dependent upon the fluid-potential field, based mainly on theoretical considerations. The study displays the joint application of different research techniques, particularly hydrogeological methods for the western part of the Trans-Tisza region, Hungary, where thermal water and hydrocarbon accumulations are known. During the research, seismic, well-log, lithostratigraphic, and hydraulic data were analyzed to determine the hydrogeological framework and the fluid-potential field of the study area. As a result, the heterogeneity of a thick (∼1000 m [∼3281 ft]) and regionally extensive argillaceous aquitard unit was established, which is divided by structural elements and relatively thin (150–200 m [492–656 ft]) sandy aquifer units. Furthermore, two major strike-slip fault zones connecting the overpressured sub-Neogene basement with the uppermost aquifer unit and also intersecting each other were identified. Based on the complex investigation, we determined that the identified faults represent direction-dependent control over the fluid-flow systems of the study area. Both proved to act vertically as conduits but transversely as barriers; they enable pressure dissipation and intensive water upwelling from the sub-Neogene basement, resulting in a fluid-potential anomaly and, at the same time, in hydrocarbon entrapment. Consequently, during hydrocarbon exploration, it is not definitely necessary to search for low-permeability faults because high-permeability faults can also be acting as direction-dependent barriers for fluid flow. Moreover, the research also pointed out that hydrogeological methods are effective in hydrocarbon exploration during the evaluation of hydraulic function of faults.
Brigitta Czauner, M.Sc. geologist, is a Ph.D. student at the Eötvös Loránd University (ELTE), Budapest, Hungary. Her research interests include hydrogeology, petroleum hydrogeology, structural geology, and tectonics. Her Ph.D. research topic is the hydraulic behavior of structural elements, such as fractures and faults, and particularly their function in groundwater flow systems and hydrocarbon entrapment.
Judit Mádl-Szőnyi is associate professor of hydrogeology at Eötvös Loránd University (ELTE), Hungary. She received her M.Sc. degree in geology and her Ph.D. in hydrogeology. Her main research interest is evaluation of regional groundwater flow in drainage basins in sedimentary and karst environments. Besides vulnerability topics, transport of matter and energy as manifestations of groundwater flow are her favorite subjects.