巴西盐下巨型湖相介壳灰岩储层是当前全球油气勘探的热点,潜力巨大但研究程度却较低.本文结合岩心、薄片、地震和综合地质录井数据等资料,对巴西坎波斯盆地西部隆起带盐下白垩系Lagoa Feia组湖相介壳灰岩的岩石学特征、沉积学特征、地震反射特征和沉积模式进行了深入分析.坎波斯盆地介壳灰岩包含生物礁灰岩和颗粒灰岩2种主要类型,是以双壳类硬质壳体为主,介形类和腹足类壳体为辅,并含有其他碳酸盐岩组分和部分硅质碎屑的岩性复合体.该盆地介壳灰岩总体发育于滨浅湖区域,可划分出湖缘、生物碎屑砂质滩、生物碎屑灰质滩、鲕粒滩、生物礁后滩、生物礁和生物碎屑滑塌扇等7种主要相带类型.分析了几种主要相带对应的地震反射特征,建立了断陷湖盆边缘镶边台地介壳灰岩沉积模式,其中生物礁相带的提出系基于新资料经研究后提出的新认识,与前人持有的介壳灰岩滩坝观点有所不同.本文研究结果对于类似地区的油气勘探具有指导作用.%The giant pre-salt lacustrine coquina reservoir in Brazil is one hotspot of globe oil and gas exploration with great potential but poorly studied.The lithology,sedimentation,seismic characteristics and depositional model of coquina in Cretaceous Lagoa Feia Formation in western uplift zone in Campos basin are analyzed based on core data,thin sections,seismic data and well logging.The coquina is dominated by fossils of bivalve mollusk with subordinate ostracods,gastropods and other carbonate and siliciclastic components,and can be divided into 2 main types:organic reef and allochem limestone.Coquina reservoir in Campos basin mainly developing in shorezone and offshore can be categorized into such 7 facies belts as marginal lake,bioclastic sandy beaches,bioclastic calcarenite beaches,oolitic beach,backreef shoal,organic reef and bioclastic slump fan.Several main seismic reflection characteristics are analyzed and depositional model of coquina in marginal rimmed platform of rift lake basin is built.The viewpoint of reef facies is proposed based on the new understanding of up-to-date data,which is different from the prior ideas of shoal and bar.The results in this paper can guide oil and gas exploration for similar region.
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