The Structural
Styles and Strike-slip Movement of Tan Lu Fault Zone in Late Pleistocene and
The Formation of Oil Traps in Bohai Bay Area
Gong, Zaisheng1, Sitian Li2 (1) China National Offshore Oil
Corporation, Beijing, China (2) China University of Geosciences, Beijing, China
In the 1990's, seven important oil
fields, including the giant oil field PL19-3 have been found in Bohai Bay area and located in or
near the Tan Lu fault zone---the largest strike-slip fault zone in eastern China. Based upon the 3D
seismic data analysis, the detailed structural images of the oil bearing areas
in Tan Lu fault zone have been revealed. During the rifting phase in Paleogene, the evolution of Tan Lu fault zone was
controlled by right-lateral tenso-shear tectonic
regime and a series of NNE and EW trending depressions and uplifts were formed,
which were the primary controlling factors on the depositional processes and
framework. After a relative quiescent post-rifting stage in Neocene, the
evolution of Tan Lu turned into right-lateral compresso-shear
regime in late Quaternary. 3D seismic images shows that lots of close NE
trending faults in en echelon style distributed in Tan Lu zone in many
districts, and the anticline traps with flower structures, including the traps
PL19-3 and PL25-6, were developed in the same processes. Dating ages of carbon
isotope and uranium series analysis revealed that the unconformity on the top of
the anticline trap PL19-3 were formed in late Pleistocene which indicate the
oil migration and accumulation processes have been developed in a very short
geological period.