HYDRAULIC BEHAVIOUR OF FAULTS ON THE WESTERN PART OF TRANS-TISZA REGION, HUNGARY

The main focus of the present work was to investigate the possible hydraulic role of faults in groundwater flows and hydrocarbon entrapment. With this object, a study area was chosen in the Trans-Tisza Region of Hungary where a significant fluid-potential anomaly, as well as thermal water and hydrocarbon accumulations are also known. The geological framework was determined by the interpretation of seismic sections, well-log and lithostratigraphic subdivision data, whereas the fluid-potential field was analyzed by hydrogeological methods (hydraulics, hydrochemistry). As a result of the structural and stratigraphical interpretation, strike-slip fault zones were identified on the eastern and western margin of a N-S trending Pre-Neogene basement high. These fault zones approach the land surface and furthermore intersect each other in the south of Berekfürdõ. As a combination of the hydraulic and hydrogeochemical results, it could be determined that the identified faults represent direction dependent control over the fluid flow systems of the study area. Both proved to be vertically conduit, thus along them the overpressure can dissipate from the basement, and at the same time causes water upwelling, as well as the development of the fluid-potential anomaly. Incidentally, the orientation of these fault zones is approximately perpendicular to the recent compressional stress field, which superficially contradicts their conduit character. However, the overpressure prevailing in the Pre-Neogene basement may be able to open fractures and faults periodically, and thus it can explain the previous paradox. On the other hand, both fault zones are acting as a barrier for transversal fluid flow, and may act as lateral seals of the Tatárülés-Kunmadaras gas field. Finally, their junction near Berekfürdõ represents the southern limit of the hydrocarbon bearing aquifer units, and also causes more intensive water upwelling, providing reason for existence of the Berekfürdõ Spa.