Abstract:

The Damintun Sag, situated in the Liaohe Valley of the north part or the Bohai Bay Basin, is a small oil-generation sag of the Meso-Cenozoic. It co-vers an area or 800km². The greatest thickness of sedimental rocks is up to 6600m. Oil exploration was initiated in 1970. but once stopped due to the existence of the red bed on the basin bottom, the basalt within the basinand humic mother substance and high condensate point in the oil nature. Since 1981, we carried out a thoroughly comprehensive geological research for key problems which we have no knowledge of basement strucures,covering structures,the greatest thickness and the productivity of the high condensate oil by adopting new technique of the digital seismics and thermal recovery to reevaluateoil productivity and to choose the most favourable traps for prior drilling. As the result, high yield oil pools in a buried-hill were discovered. By means of tectonic geology and seismic stratigraphy, the sedimentary system ofthe main hydrocarbon-bearing formations as well as the assemblage and distribution regularity of complex pools were further known and Tertiary hydrocarbon resources were consecutively discovered. The source beds in the seg are the 3rd and 4th members of the Shahejie Formation, the reservoir rocks are carbonate rocks of the Proterozoic, andthe mixed rocks and granite gneiss of the Archaeozoic in the buried-hill, the sandstone of the 3rd member of the Shahejie Formation. The sag contains 3 secondary uplift and subsidence belts respectively, in which not only the up-lifts are oil-bearing, but also the subsidence belts contain either source beds or oil reservoirs. Therefore, in later belts, complex hydrocarbon pools will also be expected to be discovered.