Sequence Stratigraphy Characteristics of the Yanchang Formation in Ordos Basin

Based on the drilling,logging and seismic data,the right scour erosion surfaces and the unconformities as sequence boundaries can be found.There is time through in the division of lithostratigraphic units in Yanchang formation.In the sedimentary period of Yanchang formation,Ordos basin is a craton basin,which have special sedimentation sequence features.①The three-order sequences growth are stable totally,with little change of the thickness in Ordos basin.②Sedimentary slope-break belt is the main type in the glacis depression basin,it can not form thick sand bodies in the low stand systems.③Above the lake level,the distribution of sand-bodies is controlled by sediment source.Below the lake level,the distribution of sand-bodies is controlled by slope-break belt.④The whole sequence has the filling characteristics with multiprovenance and multicycle.