Sequence stratigraphic framework and sedimentary types in the Block 5 and 6, Bonan Oilfield

The sequence stratigraphy and sedimentary system analysis suggest that the Bonan sub-sag could be subdivided into 2 tectonic sequences and 7 third rank sequences. The sub-sag was an asymmetry Tertiary fault-step basin, south of which was slow fault-step belts and are mainly delta plains and delta front sediments. But in the north part of the sub-sag, controlled by the syn-sedimentary fault, steep fault-step was developed with mainly deposition of sub-aqueous fan, turbidity fan, and front of fan-delta. The sandstone groups No. 0-9 were developed from the uplift in the SE direction and the sandstone groups No. 0-8 were developed in the fan-delta environment, suggesting a main process of lacustrine filling up and prorogation.