Abstract: In order to determine the spatial distribution of the architectures of the multi-stage superimposed braided-river tight sandstone reservoirs in the He 8 member, Sulige gas field, by using well logging and core data and referring to modern rivers, the architecture division scheme of the braided river reservoirs in the study area was determined, and the reservoir architecture units were dissected hierarchically. Through the joint simulation based on pixel and target methods, a 3D architecture model of the braided river reservoir including multi-level architecture units was established to finely depict the spatial distribution of different reservoir architectures. The reservoirs in the He 8 member formed due to the vertical or lateral cutting and stacking of multi-phase sandbodies of braided channel. The mid-channel bar of a single braided belt appears in form of lens. The interior of mid-channel bar is separated by discontinuous fall-silt seam, and the braided channels are distributed around the mid-channel bar. According to the 3D architecture model, the reservoir can be divided into different hierarchical architectures, among which the favorable reservoir interval is He 8₄ sublayer which is mainly distributed in two major braided belts extending north-south in the east and west of the study area, and high-quality sandbodies are distributed in a lenticular shape inside the braided belt. The research results were applied to horizontal well deployment and geosteering drilling, and the drilling results show a high coincidence rate with model predictions.

Key words: Ordos basin, Sulige gas field, Shihezi formation, He 8 member, braided river, reservoir, architecture unit, mid-channel bar sandbody