Vertical evolution and seismic interpretation of the microfacies from the littoral and shallow lake subfacies in the fourth member of the Shahejie Formation, northern Guangrao region, Shandong

The integration of the data on lithology, well-logs and seismic facies shows that the fourth member of the Paleogene Shahejie Formation in northern Guangrao region, Dongying depression, Shandong represents the littoral and shallow lake depositional systems including the microfacies such as sand bar, mixed sand-mud beach and mud beach in the littoral lake subfacies, and offshore bar, sheet sand and shallow-lake mud in the shallow-lake subfacies. There are vertical gradations, from the base upwards, from the shallow lake subfacies(ES₄⁶) through the littoral lake subfacies (ES₄³,ES₄⁴,and ES₄⁵) to the shallow lake subfacies (ES₄¹ and ES₄²) again, indicating a transgression-regression-transgression cycle. The correlation has been made between the sedimentary microfacies outlined above and seismic facies on the basis of the correlation of seismic profiles and interpretaion of seismic facies. The approaches are also made for the oil and gas accumulation in different microfacies.