Sedimentary sequence and architecture analysis by integrating multidiscipline data - An example of a sandy conglomerate reservoir in the Qie12 block, Qaidam Basin, northwest China

Understanding the sedimentary sequence and architecture of a reservoir is important for planning its development strategy. We have developed a case study of analyzing the sequence and architecture of a sandy conglomerate reservoir by integrating geology, petrophysics, seismic, and development data. The analysis indicates that the depositional environment of the target lower part of the Ganchaigou Formation is an alluvial fan. We define eight lithofacies according to the core analysis and five sedimentary microfacies by integrating the core and petrophysical data. We next adopt four sedimentary architectural models by integrating the lithofacies result, microfacies analysis, and high-frequency sequence models. The four architecture models include the extensively connecting body sandwiched with intermittent channels, the composite channel formed by the overlapping and separation of stable channels, the lateral alternated braided channel and sheet flow sediment, and the runoff channel inlaid in flood plain mudstone. Finally, we build an architecture model for the alluvial fan. The model of the alluvial fan overall shows an upward-fining grain-size feature, and this feature indicates that the alluvial fan belongs to a retrograding sequence. The built model consists of six alluvial fan bodies that migrate from the north.