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ABSTRACT: One-, two-, and two-and-a-half dimensional combined depositional and fluid flow/maturation modeling of the southern portion of Bohai Bay, China

Matthews, Martin D.1, Kelly Dempster2, Jeff R. Johnson3, and Mona Bissada3
(1) Exploration Technologies, Inc, Sugar Land, TX 
(2) Texaco Upstream Technology, Bellaire, TX 
(3) Texaco Exploration, Bellaire, TX

Global cyclostratigraphic analysis is combined with well data and seismic stratigraphy in southern Bohai Bay to understand the spatial and time variation of stratigraphic patterns related to tectonics. A 3-dimensional model of the stratigraphic evolution of the basin is constructed to provide the framework for 2-dimensional fluid-flow/maturation cross-sections and 2-dimensional migration maps.

The early syn-rift, Kongdian and Shahejie 4, is characterized by locally derived rivers and sags in an alternating dry (saline lake) and wet (fresh lakes) climate, favoring the deposition of lith-arkosic sediments. Followed by syn-rift conditions, Shahejie 3 to Dongying, the river basins enlarged by headward erosion, providing a more constant water supply from multiple climates as the Himalayas rose. Subsidence rates increased, resulting in the potential for deeper lakes. Chemical weathering increased with sand compositions averaging 1/3 quartz, 1/3 lithics, and 1/3 feldspar, but locally up to 70% quartz. Post-rift conditions, Guantao to Recent, demonstrate reduced subsidence and through-going river systems that caused fine sediment bypass. Presently, the basin is covered by marine waters, but is rapidly being reclaimed to sub-areal conditions by river deposition.

The thermal history of the region is constrained by bottom hole temperatures and vitrinite data. Variation is due to local uplifts and depth to the moho. Pressure modeling, constrained by RFT and DST measurements, indicates both compaction and kerogen maturation are important pressure generation mechanisms in the region. Faults are believed to be important pathways for transmitting overpressure to the shallower sections.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia