Demonstration of Sedimentary Facies Types of Shan31 in Qingyang Gas Field,Ordos Basin
The Shan1 member in the Qingyang Gas Field,Ordos Basin,constitutes one of the primary production layers.However,debates persist regarding its sedimentary environment and facies types.Divergent interpretations have resulted in discrepancies in sand body correlation patterns and distribution within each sedimentary facies,posing challenges in well-location exploration.Leveraging existing research,the author integrates seismic,logging,core,outcrop,and laboratory data.Employing diverse methods,including seismic reflection structure analysis,core-based examination of lithological grain size and bedding structure,logging sedimentary cycle characteristics,and comparisons with modern sedimentology,the sedimentary facies of the Shan31 strata were discussed,analyzed,and described comprehensively.Results indicate that the lithology in the study area is predominantly medium to coarse sandstone with pla-nar and small trough cross-bedding.Logging facies encompass sections with a characteristic upward thinning sequence,indicative of meandering fluvial depositions,and sections with coarse-grained sediments,associated with the sedimentation of braided rivers.Parti-cle size analysis reveals a prevalence of coarse particles,indicating robust paleohydrodynamic forces.Field outcrop data demonstrate the concurrent development of both meandering and braided rivers during the deposition period of the Shan1 member.Modern satellite images showcase the widespread development of meandering and braided rivers.In conclusion,the study identifies the sedimentary en-vironment of Shan31 as fluvial facies,characterized by the coexistence of meandering and braided rivers.Key factors contributing to the complexity of sand body distribution and rapid lateral facies changes include frequent lateral accretion of meandering rivers,planform changes in river patterns,and the multiple-phase stacking of vertical channels.
Qingyang Gas Fieldmeandering-braided coexistoutcropsedimentary model
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万方数据
