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.

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