Structural controls on petroleum migration and entrapment within the faulted basement blocks of Szeghalom Dome (Pannonian Basin, SE Hungary)
The basement of the Pannonian Basin contains several fractured metamorphic hydrocarbon reservoirs that typically form structural highs between the Neogene sedimentary sub-basins. One of the largest reservoirs, the Szeghalom Dome, is located on the northern margin of the Békés Basin and is mainly composed of Variscan gneisses and amphibolites with different metamorphic evolutions. These petrologically incompatible blocks were juxtaposed by post-metamorphic tectonic activity that was accompanied
... at was accompanied by the formation of brittle fault zones with higher transmissibilities. The aim of this study was to define the spatial arrangement of these fault zones and their internal architecture by integrated evaluations of borehole core and well-log data from a group of wells in the central part of the field. Spatial correlations between the reconstructed 1D lithologic columns revealed the main structural elements of the Szeghalom Dome. The low-angle (<15°) thrust faults most likely developed due to north-northwest vergent Cretaceous nappe tectonics, which were probably responsible for the juxtaposition of the different metamorphic blocks. A complex system of normal faults throughout the basement high provides evidence of intense Miocene extensional tectonic activity. This phase of the geodynamic evolution of the basin is believed to be responsible for the horst-graben structure of the Szeghalom Dome. The integration of the structural results with datasets of the palaeo-fluid evolution, recent production and fracture network geometry, indicates the importance of these fault zones in both the migration of hydrocarbons from the adjacent sub-basins to the overlying sediments and the development of significant storage capacity within the strongly fractured rock masses, (mainly the amphibolite bodies). These observations of fluid flow also emphasized the impact of strong anisotropic permeability anisotropy of the faults throughout the fractured reservoir.