The Relationships between Hydrocarbon Accumulation of Neogene Shallow Water Delta and Tanlu Fault Zone in the Huanghekou Sag, Offshore Bohai Bay Basin, Eastern China

Xia, Qinglong; Zhang, Xintao; Tian, Lixin; Zhou, Xinhuai; Nin, Chengmin

The Huanghekou sag is located in the south part of the offshore Bohai Bay Basin, eastern China. The Tanlu fault zone traverses the west side of the Huanghekou sag, where it is characterized by the complicated and typical NNE-trending dextral strike-slip faults. The assemblage of strike-slip faults system indicates a right-handed wrenching action which occurred in the Late Neogene-Quaternary. The EW direction faults could act as the adjusting faults between the uplifts and depressions in the southern region, and have quasi-flower structures composed of the major listric faults and branching strike-slip faults in seismic lines,and their formation should be controlled by the early EW extension and the late strike-slipping movement of the Tanlu fault.

The controlling factor of reservoir enrichment in Huanghekou sag can be summarized as follows:First,the strike-slipping movement of the Tanlu fault controlled the development of hydrocarbon kitchens and promoted the fast maturation of source rocks. Second, the Neogene strike-slipping activities shaped many structural traps and helped the hydrocarbon migration and late aecumulation.Third, the shallow-water delta deposit system provide the safeguard for the forming of the high quality reservoir.

A great number of late adjusting faults and young traps formed along the Tanlu fault zone after 5.1Ma, and the traps were not finally shaped until about 2.0Ma. The coincidence of neotectonic movement since the Neogene and the peak of hydrocarbon generation in the sag created excellent basis for the formation of high-quality shallow water delta. Recently, some oil fields in the Neogene with oil reserves of about 400 million cubic meter have been discoveried in the shallow water deltaic reservoirs, approximately constituting 70% of the total reserves which are related to the strike-slip fault belt.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013