The sedimentation of the Banqiao reservoir in the Banqiao oilfield occurred during the most active tectonism of the Huanghua Depression in the Bohai Bay Basin.The basin expanded so quickly that the accommodation space it provided was far more spacious for sedimentation.The typical deep-water gravity flow deposits were formed in the northern and central parts of the oilfield

while the shallow-water beach-bar deposits were formed in the southern part under the control of palaeo-geomorphology.Eight sedimentary micro-facies were identified in the study area through core observation and study of facies markers and logging facies.The gravity flow channel facies can be divided into 4 microfacies including main channel

distributary channel

channel flank and overflow.The beach-bar facies also can be divided into 4 microfacies

including main bar

bar flank

inner-margin beach and outer-margin beach.The sedimentary scale shrunk vertically due to many factors such as lake basin expansion

sediment input

palaeo-geomorphology and palaeo-climate.At the end of deposition

the gravity flow channel deposits were only developed in the northern part and the winding and forking phenomenon can be easily observed

while the beach-bar disappeared.The fine study of the sedimentary characteristics and evolutions in the area lays a sound foundation for adjustment of development well pattern.