巴西桑托斯盆地L油田BV组湖相碳酸盐岩沉积特征及高精度层序划分

Sedimentary characteristics and high-precision sequence division of lacustrine carbonate rocks of BV Formation in L oilfield of Santos Basin,Brazil

巴西桑托斯盆地是世界上著名的大型含油气沉积盆地,其盐下湖相微生物碳酸盐岩储层近年来成为油气勘探的热点,而针对主力储层的高精度层序划分和沉积机理等方面的研究较少,制约了该地区油气田的勘探和开发。基于前人研究成果,结合盆内钻井、测井、地震资料,对桑托斯盆地L油田盐下Barra Velha组(简称BV组)进行高精度层序地层及沉积相划分,明确了湖盆沉积层序演化规律,建立了盆地内L油田BV组微生物礁的沉积模式。结果表明:BV组可划分成1个三级层序、4个次级旋回;湖相微生物礁相作为BV组重要的储集相带,分布在湖盆两侧台阶坡折带,且在高水位环境加积发育,主要受控于古地貌及火山作用。该研究成果可为桑托斯盆地乃至整个巴西东南部海岸含盐盆地盐下湖相碳酸盐岩油气勘探提供地质依据。

Santos Basin in Brazil is a famous large-scale petroliferous sedimentary basin in the world in recent years,and its sub lacustrine microbial carbonate reservoir has become a hot spot of oil and gas exploration.There are few researches on high-precision sequence division and sedimentary mechanism of main reservoirs,which restrict the exploration and development of oil and gas fields in this area.Based on the previous research results,combined with the drilling,logging and seismic data in the basin,this paper made high-precision sequence stratigraphic and sedimentary division of Barra Velha Formation in L oilfield in Santos Basin,clarified the evolution law of the sedimentary sequence in the lake basin,and established the sedimentary model of the microbial reef of BV Formation in L oilfield in the basin.The results show that the BV Formation can be divided into one third-order sequence and four fourth-order sequences.As an important reservoir facies belt of BV Formation,lacustrine microbial reef facies was distributed in the steep slope break belt on both sides of the lake basin and developed in high water level environment,which was mainly controlled by paleogeomorphology and volcanism.The research results could provide a geological basis for the exploration of the carbonate rocks in the sub salt lacustrine facies in Santos Basin and even in the whole coastal salt bearing basin in southeastern Brazil.