【摘要】 为了探讨礁滩储集岩的分布规律,以层序地层学理论与方法系统研究了四川盆地北部下三叠统飞仙关组地层。通过露头、岩芯、测井、地震数据综合分析,识别出两个三级层序及四个准层序组,确定蒸发台地、局限台地、开阔台地、台地边缘滩、斜坡和盆地相六类沉积类型。层序划分及层序界面的确定,依据陆上暴露和向上变浅两个方面的识别标志。暴露界面表现为泥岩表面干裂,淡水选择性溶蚀、白云化现象,白云岩、石膏,伽玛曲线高值。向上变浅层序有向上变厚、变粗序列,向上变细、变泥、变红序列,向上γ值变低序列。对比发现高水位体系域后期发育台地边缘鲕滩和台地内鲕滩。广泛白云岩化作用的台地边缘鲕滩相,具有很好的孔渗性,成为最有利的储集层。对指导进一步的勘探与开发具有重要意义。更多还原

【Abstract】 The Sichuan Basin is China’s largest natural gas producing area.In recent years,gas exploration achieved major breakthroughs in the eastern part of the basin.A number of oil and gas reservoirs,large and medium-sized gas fields,and natural gas prospects have been discovered in Permian and Triassic successions.Oil and gas reservoirs are mainly carbonate rocks of reef and beach facies.To explore reservoir rocks distribution,we applied sequence stratigraphy in the study of the Triassic Feixianguan Formation in the northern Sichuan Basin.On the basis of outcrop,core,logging,and seismic data,we have identified two sequences and four parasequence sets in the Feixianguan Formation.We recognized six sedimentary facies:evaporative platform facies,restricted platform facies,open platform facies,platform margin beach facies,slopes facies,and basin facies.Sequence division and identification were based on exposure surfaces and upward shallowing trends.Subaerial exposure surfaces are characterized by mudcracks,freshwater dissolution structures,dolomitization,dolomite and gypsum,and high gamma ray values.Shallow upward sequences can be upward-coarsening,upward-thickening,upward-fining,upward-shalining,upward-reddening,and upward-gamma-value-lowering.Stratigraphic correlation shows that in highstand systems tracts are characterized by late platform margin oolitic facies and intra-platform oolitic facies.Extensive dolomitization of platform margin oolitic facies led to greater porosity and permeability,hence the formation of favorable reservoirs.This research has implications for further exploration of the Sichuan Basin.更多还原