Exploring for Hydrocarbons Under Thrust Belts--A Challenging New Frontier in the Carpathians and Elsewhere

Abstract

New significant reserves of hydrocarbons may occur in subthrust autochthonous and parautochthonous series buried below the frontal zones of thin-skinned thrust belts. The subthrust plays have been tested in several orogenic belts of the world, the Carpathians being one of the best examples. The arcuate thin-skinned Carpathian orogenic belt, which evolved during the Mesozoic and Cenozoic, is thrust tens of kilometers over its Neogene foredeeps and the underlying European plate. Various structural and stratigraphic settings and potential hydrocarbon plays have been recognized within the buried margins of the European plate, including a late Paleozoic Hercynian compressional system, Mesozoic rifted margins of the Tethys, and a Cenozoic synorogenic foreland-type fault system. Possibly, deeper parautochthonous structures, documented on examples from the southern Apennines, may also be present below the thin-skinned frontal zone of the Carpathian thrust belt. In addition to these structural settings, large Paleogene valleys/submarine canyons have been found within the margins f the European plate. These structural and morphologic features, if combined with source rocks, reservoirs, and proper burial history, represent potential hydrocarbon plays. Generation of hydrocarbons from sources within the subthrust plate was greatly enhanced by emplacement of the wedge-shaped thrust belt, which may also provide a regional seal; therefore, the combination of the long and complex geological history of the European plate with the impact of the Alpine thrusting and foreland deformation created unique conditions for generation, entrapment, and preservation of hydrocarbons in subthrust settings.