关键词: 巴彦呼舒凹陷, 　南屯组, 　沉积体系, 　沉积演化, 　成藏条件

Abstract: The Bayanhushu depression is in the initial stage of exploration, and its sedimentary characteristics and distribution are not clear. In this study, the types and characteristics of sedimentary system in Nantun Formation of Bayanhushu sag are discussed in detail by using core, well logging, seismic and grain size analysis data and combining with regional tectonic and geological background analysis. It is considered that there are 3 depositional systems of fan delta, braided river delta and lake in the study area. Braided River delta deposits and fan delta deposits are mainly developed in the gentle slope zone in the eastern part of the study area and the steep slope zone in the western part, is developed in the middle trough zone between the two.The braided river delta and fan delta deposits are mainly developed in the eastern gentle slope zon and the steep slope zone in the western part, while the lacustrine facies are developed in the middle trough zone. On the whole, the sedimentary pattern shows obvious characteristics of "North South Block and East West zoning". From the western steep slope zone to the eastern gentle slope zone, the sedimentary facies types transit from fan delta to deep lake⁃semi⁃deep lake and then gradually to the discriminate river delta. Reservoir physical properties of braided river delta front and fan delta front sand bodies are good and often adjacent to large⁃scale high⁃quality source rocks. Steep slope inversion structural reservoirs, fault⁃lithologic reservoirs and lithologic reservoirs are easy to form in steep slope zone, gentle slope zone and trough zone, respectively.

Key words: Bayanhushu depression, Nantun formation, Sedimentary system, Sedimentary evolution, Reservoir forming conditions