Characteristics and model of meandering-river-delta reservoir architecture of member Chang-6 in Fuxian area, Triassic Ordos Basin

Abstract

To elucidate the spatial architecture of sand bodies within the Member Chang 6 in the Fuxian area of the Ordos Basin, a comprehensive analysis was conducted leveraging core samples, logging data, mud logging, and other pertinent information. This analysis was guided by both sedimentology theory and the theory of architecture element analysis. Additionally, a detailed investigation of outcrop features was carried out to augment the understanding. The sedimentary characteristics and sand bodies architecture of the Member Chang 6 were meticulously examined at the outcrop locations of Yanhe in Yanchang County, and the Fuxian area. Through this comprehensive examination, a well-defined sand body architecture model was successfully established. The study reveals the presence of nine distinct lithofacies types within the Member Chang 6 of the Fuxian area. Additionally, four primary architecture elements have been identified, namely underwater distributary channels, interdistributary bays, estuary bar, and distant sand bars. The vertical stacking pattern of delta front sand bodies within the meandering river system of the Member Chang 6 can be classified into connected and disconnected types. In terms of lateral arrangement, the superposition pattern is further categorized into butted and cut-stacked types. The sedimentary period of Member Chang 6 in Fuxian area is mainly meandering river delta front. The prevailing water energy is characterized by its subdued nature, resulting in limited sand-carrying capacity. This dynamic leads to the development of a meandering river delta sedimentary model characterized by a gentle near-source slope. The outcomes of this research will serve as a valuable reference for in-depth investigations into the internal architecture of the Chang 6 reservoir and the detailed characterization of oil and gas reservoirs within the Fuxian area.