Abstract:

Foreland basin is an orogenic foredeep filled with terrigenous clastics,that has been developed on a craton and has been converted from a passive margin and platform-type sedimentary area.Complex structural deformation,from thick skinned to thin-skinned structures,has occurred in the orogenic belt and its frontal region along with compressional deformation;and structural styles are varied,due to the control of tectonic settings,sedimentary sequences and movement characteristics.Although foreland basin is the most prolific basin type,hydrocarbon accumulations can only be preserved in regions where there are synorogenic sedimentary covers.Since thrust-fold structures are clear,and there are oil and gas seepages in the area neighboring the orogenic zone,thus the mountain front became the main objective area in the early stage of exploration.The exploration campaign in foreland overthrust zone since 1975 has been the result of advances in 3-D seismic survey and drilling technologies which make it possible to recognize structural features and trap conditions beneath the thrusts.Failures often occur in exploration when the thrust zones are taken as the main targets for exploration of hydrocarbon accumulations.Practices have shown that only the basins that have preserved both the synorogenic sediments and underlying pre orogenic sediments would have exploration potentials.

Key words: foreland basin, thrust, hydrocarbon occurrence, exploration history, experiences and lessons