Sequence Stratigraphic Model for Incised Channels in a Continental Ramp Setting: From Example from the Lower Permian Shanxi Formation, Ordos Basin, China

Zhu Hongtao¹, Liu Keyu², and Chen Kaiyuan^3
1Faculty of Earth Resources, China University of Geosciences (Wuhan), Wuhan, China
²Petroleum Resources, Commonwealth Scientific and Industrial Research Organisation, Perth, WA, Australia
³Resources Department, China University of Geosciences (Beijing), Beijing, China

The Lower Permian Shanxi Formation is an important hydrocarbon-bearing reservoir unit in the northeastern Ordos Basin, China. The sediment succession is thought to have been deposited in a fluvial-lacustrine environment within an intra-cratonic basin under warm and humid climatic conditions. The formation is characteristic of a Type I sequence deposited in a lacustrine basin margin ramp setting with widespread incised valley sediment developed above the sequence boundaries. No basin-floor fans, which are typically associated with the classic Type I sequence, are present. Based on detailed sedimentological and stratigraphic analyses, it is concluded that the extremely gently sloped intra-cratonic ramp setting coupled with the strongly erosion-resistant vegetated wetland plain promoted the development of a unique incised channel fill sedimentary system, which include (1) the development of extensive belting-shaped sand-bodies in the N-S direction; (2) the alternating deposition of the belting sand-bodies and coal, high carbonaceous shale, and shale; (3) the presence of numerous scouring surfaces of fluvial origins; (4) the development of large-scale characteristic normal grading successions with distinct erosional bases; and (5) the deposition of multistorey cut-and-fill channel sand-bodies.

The development and the spatial and temporal distribution of the high-efficient belting reservoirs appear to be primarily controlled by the incised channel fill sedimentary system. The multistorey cut-and-fill channel sand-bodies developed during the lowstand systems tracts are excellent reservoirs. They may form excellent reservoir-seal combinations in conjunction with the associated fine-grained sediments, controlling the accumulation of hydrocarbons.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas