渤海湾盆地渤中凹陷西南环古生界深埋碳酸盐岩潜山天然气获得重大突破,钻井资料揭示该地区碳酸盐岩岩溶储集层具有很强的非均质性.由于沉积相是岩溶储集层发育的主控因素之一,因此文中根据岩心和薄片资料、测井相、微量元素和古生物特征等多种手段综合分析沉积相特征.结果表明,研究区现存奥陶系纵向上表现为1个较为完整的海退一海进序列,主要发育开阔台地和局限台地2种沉积亚相,并可进一步划分为台内滩、滩间、潮下带知潮间带4种沉积微相.台内滩和潮下带微相横向分布连续稳定,水动力条件强,形成的储集层早期溶孔发育,且这2种沉积环境里发育的碳酸盐岩较纯净,经后期风化淋滤形成的岩溶储集层厚度大、质量好,因此是有利的岩溶储集层发育相带.该研究明确了研究区台内滩及潮下带的发育特征,对下一步油气勘探具有一定的指导意义.%A major hydrocarbon reservoir has been discovered in the deep Paleozoic carbonate buried-hill in southwestern Bozhong sag,Bohai Bay Basin.The strong heterogeneity of carbonate karst reservoir was revealed through well data.The sedimentary facies is determined to be the main controlling factor in the development of the karst reservoir.In this study,cores and thin sections were described in terms of sedimentary fabric,while log facies,trace elements and palaeontologic data were used to determine hydrodynamic condition and palaeo-depth.Petrological,geophysical and geochemistry data were integrated to characterize the sedimentary facies.The studied interval is considered to represent an early Ordovician transgression to middle-late Ordovician regression sequence.Two sedimentary sub-facies including open platform and restricted platform were identified,which could be further subdivided into four microfacies:Platform shoal,inter-shoal,sub-tidal and inter-tidal microfacies.The platform shoal and sub-tidal microfacies show a continuous distributed thick succession which suggests strong hydrodynamics during deposition.The hydrodynamic condition also favored the development of earlier dissolution pores of the reservoir.Moreover,the quality of the reservoir is further enhanced through later weathering and leaching.Therefore,the platform shoal and sub-tidal microfacies are promising in developing high-quality karst reservoir zones,which have important implication for future oil and gas exploration.
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