Research on Sequence Stratigraphy of Nantun Formation in Bayanhushu Depression of Hailar Basin and Favorable Target

摘要

Exploration in Bayanhushu depression has been published from time to time,showing great exploration potential,but the degree is low at present.We devided Nantun formation into two third sequences through comprehensive analysis and studied on the types and distribution of sedimentary facies.The conclusion shows that Nantun formation is mainly comprised of fan delta,braid delta and lacustrine facies.The fan delta sedimentary facies mainly distribute in the western steep slope zone,while the braided river delta develops in the eastern gentle slope zone,and the lacustrine facies mainly develops in the middle trough zone and the edge of the fan delta.The sedimentary pattern has the characteristics of"east-west zoning".From the steep slope to the gentle slope,the types of sedimentary facies gradually change from fan delta to shore-shallow lake,semi-deep lake to deep lake and then to braided river delta.The study of source-reservoir-cap assemblages and accumulation conditions shows that fan delta front and braided delta front have good physical properties and are close to high grade source.So it is easy to form inversion structural reservoirs in the steep slope break zone,while fault-lithologic reservoirs in gentle slope zone,a lithologic reservoirs near trough areas.