DEPOSITION OF THE ED₃ OF THE DONGYING FORMATION AND ITS RESPONSE TO TECTONIC-PALEOGEOMORPHOLOGY IN THE BLOCK QHD29-2 OF THE BOHAI BAY BASIN

The Shijiutuo Uplift, which is located in the southern part of the Block QHD29-2 in the Bohai Bay Basin, is bounded by faults which controlled not only the boundaries of the uplift, but also the paleogeomorphic pattern characterized by a steep horst in the center and flat slopes outwards. Faulting was intensive at the center and gradually became weaker to the out sides. The structural pattern was obviously the main factor which controls the types of depositional system and the filling sequences. Integrated study has been carried out for well logging facies, cumulative probability curve, CM diagram, thin sections and seismic multi-attributes. Results show that the distribution pattern of sedimentary facies of the Ed₃ of the Dongying Formation in the study area is consistent with the paleogeomorphic features of a steep center surrounded by flat sides. The fan-shaped or flower-shaped fan deltaic deposits are distributed around the steep slope of the central uplift where occurred intensive tectonic activity and rapid and near-source deposition, whereas the braided river deltas, which were in a zonal pattern, are distributed on both sides of the steep uplift,where the tectonic activity was weak.