IntroductionThe Qibei slope is located within the Bohai Bay Basin, southwest of the Qikou sag between the Gangxi fault and the South Dagang fault (Figure1). West of the Qibei slope lies the Kongdian bulge, which is an eastward dipping slope structure with long-term development. Subject to different basement subsidence as well as the differential movements of the two major boundary faults, the Qibei slope can be divided into three flexural slope regions; from west to east, they include the: high slope, middle slope and low slope.The sandstones of the Es 2 and Es 3 Member of the Paleogene were supplied by the trough fault and distributed along the eastward dipping slope. The target layer is at the favorable burial depth and the reservoir property is good, correlating well with the slope break structure and the oil sources. It is a favorable zone for lithologic oil/gas accumulation. Identification and description of the lithologic trapBased on the drilled well, it has been verified that the Es 2 Member, which is one of the major target layer in the study area, is composed of thin interbeds of sandstones and mudstones. Deposition of the Es 2 was subject to the factors such as sedimentary source and palaeogeomorphology, such that the sand bodies exhibit strong variation in the vertical and horizontal directions, and the strata have complex geologic relations with the surrounding rocks. Consequently, uncertainties about the boundaries of the Es 2 Member exist. Therefore, the identification of the slope break and the division of the sedimentary facies were carried out using a sequence stratigraphic approach at the outset of the investigation. Subsequently, many geophysical methods such as seismic facies analysis, multi-parameter inversion and 3D visualization were applied within the range of the favorable sedimentary facies to predict the spatial distribution of the sand bodies, in order to effectively improve the prediction accuracy of the reservoir.

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