Control of paleogeomorphology on sedimentation in Sha-3 member of J oilfield in Liaoxi uplift

Sha-3 member of J oilfield in Liaoxi uplift of Bohai bay basin has become an important target for lithologic reservoir exploration in recent years. There are many kinds of complex lithology in the bottom of Sha-3 member, while its genesis and distribution are not clear. By means of core description, thin section identification, seismic facies analysis and restoration of paleo geomorphology, the lithology, lithofacies and reservoir space characteristics of the complex lithologic section at the bottom of Sha-3 member are comprehensively studied. The results indicate that the paleogeomorphology in the early sedimentary period of Sha-3 member in J oilfield can be divided into two secondary structural units: sub-uplift and sub-sag. Among them, sub-uplift can further identify four types of tertiary structural units, including high steep slope, low gentle slope, platform area and valley. In the sub-sag unit, shore shallow lacustrine mudstone is developed, and in the high part of the sub-uplift and steep slope zone, slope facies red mudstone is developed. The gravelly sandstone of slope facies is developed in the sullage zone of the sub-uplift, with low maturity and poor physical properties. Beach bar sandstones are developed in the platform area and gentle slope zone of the sub-uplift, which are favorable exploration targets because of good physical properties and high productivity.