Abstract:
This paper is the result of oil and gas exploration engineering.
Objective Debris flow represents an important mechanism of sediment transport and dispersal in deep-water environment, the related sandstone reservoir constitute one of the important targets for petroleum exploration in petroliferous basins, while deep-water systems dominated by debris flows are still poorly understand compared to well-studied turbidity currents and turbidite systems.
Methods The depositional process and model of gravity flows which developed in the Middle Sub-member of the 3rd Member of the Eocene Shahejie Formation, Dongying Depression, Bohai Bay Basin have been studied through the integration of core data examination, well logging data and 3D seismic data interpretation.
Results It is suggested that nine base types of lithofacies can be recognized in slump-derived gravity flow deposits, which can be summarized into four main origin types, which indicate mass transport and flow transport processes, respectively. Quantitative lithofacies analysis suggests that the slump-derived gravity flow depositional system is dominated by debris flows, while turbidity currents are less important, and sandy debris flows represent the most important debris flow type. The slump-derived gravity flows undergo five evolution stages including slide, slump, sandy debris flow, muddy debris flow and turbidity currents, which correspondingly develop five types of deep-water depositional elements during transportation and evolution, including slide, slump, debrite channel, debrite lobe and turbidite sheet. Sandy debrite channels, lobes and sandy slides constitute the most important deep-water reservoirs in the study area according to their wide distribution and reservoir property.
Conclusions It is proposed that adequate sediment supply, high depositional rate on delta-front, frequent tectonic activities and short transport distance are the main controlling factors. Accordingly, a depositional model is proposed to depict slump-derived gravity flow systems based on depositional processes, sedimentary patterns and basin morphology. This study seeks to improve deep-water sedimentary theories and provide guidance for petroleum exploration of deep-water sands in deep-lacustrine basins.
下载: