Study On Lithofacies Paleogeography And Reservoirs Of Sinian Dengying Formation In North Middle-Yangzi In East Sichuan

In this paper,carbonate petrology,sedimentology,petroleum geology,reservoir geology is theoretical guide.Combined with synthetical analysis of regional outcrop,drilling core,well-logging data,The lithofacies paleogeography and reservoirs of Sinian Dengying Formation in the research area were studied.The results show that most of sedimentation of Dengying Formation in the research area is in the shallow water.The sedimentary facies of Dengying Formation are distributed according to the sedimentary model of carbonate platforms-epicontinental seas facies.It has restricted platform facies,open platform facies,platform margin facies and slope-basin facies.The paleogeographic environment of Dengying Formation in the area was influenced by the distribution of platform and trough.It has ‘two platform foiders one trough'.The high energy facies zones of the shoal facies in and around the platform provide the material basis for reservoir development.The lithology of reservoirs is dominated by arenaceous dolomite,fine crystal dolomite and algal dolomite.And the main reservoir space type is dissolution porosity The reservoir of Dengying Formation belongs to low porosity and low permeability reservoir.With the controlling of twice uplifting and sedimentation of platform and platform margin,the reservoir is greatly affected by the distribution of high-energy facies,karst and denudation.And the dissolution optimizes reservoir space.the stratum uplift causes lots of karstification and denudation in Dengying Formation.However,cementation and metasomatism destroy the reservoir space.The karst paleogeomorphology at the top Dengying formation is adopted by ‘Moldic method',So the favorable reservoirs are predicted to be distributed in the superposition areas of the high-energy facies zone and the high-terrain areas.