The restoration of Pre-Jurassic paleogeomorphology and its influence on oil accumulation in Longdong area

With logging, seismic, core and other geological data，the paleogeomorphology was rebuilt according to the impression method and comprehensive geological method. The results reveal various paleogeomorphic patterns, such as high land, valley, brae, mound and river terrace. Based on the relationships between the paleomorphology and the formation of Yan'an oil reservoir, the authors inferred that reservoirs are mainly distributed in the brae near high land and other relatively high zones. Favorable conditions for petroleum accumulation included the upward migration pathway of hydrocarbon from source rock of Yanchang Formation via the incised valley, the type and distribution of reservoirs and sand bodies were controlled by the brae, and the relatively high zones of later structural traps were formed by the "impression" of layers.