关键词: 海拉尔盆地, 查干诺尔凹陷, 南屯组, 湖底扇, 沉积模式

Abstract: Sublacustrine fan is a very important place for oil and gas accumulation in continental rift basins. Establishing an accurate and reliable sedimentary model of sublacustrine fan is of great significance to the prediction of dominant reservoirs. Based on the data of lithofacies, seismic profile facies, logging facies and grain size analysis, the sedimentary characteristics and models of sublacustrine fan depositional system developed in Nantun formation of lower cretaceous in Chaganuoer depression of Hailar Basin are systematically studied in this paper. It is considered that there are three subfacies and five microfacies in the sublacustrine fan depositional system of Nantun formation in the study area. On this basis, the lake floor fan sedimentary model of Nantun Formation in Chaganuoer depression is established. It is considered that the planar microfacies sequence is characterized by the variation of "main channel of inner fan, braided channel of middle fan, turbidite of outer fan and mud of deep lake", and that the channel systems (main channel and braided channel) are separated by obvious scale mudstones of deep lake facies. Controlled by this sedimentary model, the sublacustrine fan deposits extend far from the eastern steep slope zone to the center of the lake basin in the southern part of the study area, while the sublacustrine fan deposits gradually transit to fan delta deposits from south to north with the weakening of the influence of structural slope breaks.

Key words: Hailar depression, Chaganuoer depression, Nantun formation, Sublacustrine fan, Sedimentary model