High Resolution, Three-Dimensional Facies Architecture Analysis Using Sequence Stratigraphy and Seismic Sedimentology: Example from Dongying Formation in BZ3-1 Block, Bozhong Sag, Bohai Bay Basin, China
Bohai Bay basin is a classic non-marine rift-basin. The Paleogene Dongying Formation is the main hydrocarbon-bearing stratigraphic unit in the basin. Using the recent 3D seismic data and sparse well control in the BZ3-1 Block in western slope of Bozhong Sag, we analyzed high-resolution, three-dimensional facies architecture of Dongying Formation. Based on principles of sequence stratigraphy, the second-order sequence of the Dongying Formation was subdivided into three third-order sequences (from base to top: SQd3, SQd2L and SQd2u); analysis of high resolution three-dimensional facies architecture was further developed using seismic sedimentology.
Sediment provenance is referred to have been derived from the northern Shijiutuo Uplift. The major sediment transport pathway was probably the paleo-channels found within Dongying Formation, which can be subdivided as four types, including type V, U, W and Compound. These facies are characterized by unique seismic facies and geometries. A seismic stratal slice movie delineates in detail the branching and converging characteristics of these channels from up-stream to down-stream and their evolution history. On the basis of an integrated analysis of seismic facies and multiple seismic attributes, two sedimentary facies have been recognized. The sand-rich facies is the fan-delta facies located in the footwall of growth faults with fan-shaped distribution of seismic anomaly, and the shale-rich facies is the coast-shallow lake facies characterized by various seismic attributes.
Finally, seismic stratal-slice analysis and 3D visualization revealed high-resolution, three-dimensional evolution of the fan-delta depositional systems. The number and scale of fan-delta have a close relationship with the system tracts in sequences of different order. The fan-deltas in third-order sequence SQd3 was mainly developed in lowstand period, and fan-deltas in third-order sequence SQd2u occured in highstand period. Channel-filled and fan-delta sand-bodies are excellent hydrocarbon reservoirs and potentially good exploration targets.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California