巴西下白垩统微生物灰岩沉积特征及优势相带预测

Sedimentary Features of Microbial Carbonate in Lower Cretaceous Formation and Prediction of Favorable Zone

通过岩心、薄片观察及测井曲线特征等资料,以揭示巴西桑托斯盆地下白垩统微生物灰岩的沉积特征及优势相带预测为目的开展工作,得到以下认识:巴西桑托斯盆地深水盐下碳酸盐岩储层发育在桑托斯盆地水下古隆起上,东部隆起区远离陆源碎屑供给区,沉积了厚层的湖相碳酸盐岩。湖泊的水体动荡且水深变化频繁,导致了Barra Velha组微生物灰岩结构组分多样,储层单层厚度薄、岩性变化快。Barra Velha组发育五个沉积微相,包括微生物礁、高能颗粒滩、低能颗粒滩、滩缘及深湖微相沉积。研究区的微生物灰岩的分布主要受到湖平面变化、古地貌、气候条件的影响,隆起带古地貌微环境的不同直接影响岩石类型和沉积微相的差异。微生物礁和高能颗粒滩是本区碳酸盐岩礁滩最有利的油气储集相带。通过沉积微相的研究和相模式的研究,为研究区A油田Bara Velha组微生物灰岩储层的预测和表征提供基础。

Carbonate rock type and sedimentary facies model of Barra Velha formation in the Santos basin,Brazil were studied by core observation,core thin section analysis and well logs characteristics.It can be seen that the aimed stratum in the studied area develops carbonate rock reef and shoal,which are located on the paleo-high of Santos basin,far away from land resulting in poor terrestrial debris.The significant features of Barra Velha microbial carbonate are various rock types with thin thickness of each layer and rapid change in lithology,which are the results of the turbulent and frequent change of the lake level.There are five sedimentary facies of Barra Velha formation:microbial reef,high-energy shoal,low-energy shoal,shoal ringe and deep lakes.The distribution of sedimentary facies is controlled by the water depth,paleo-terrain and paleo climate.Differences in paleo-geomorphic in paleo-high zone affect the rock types and sedimentary facies significantly.Microbial reef and high-energy shoal are the favorable sedimentary belt in the research zone.