桑托斯盆地湖相碳酸盐岩储层特征及控制因素

巴西桑托斯盆地盐下湖相碳酸盐岩领域油气资源十分丰富，是世界油气勘探的热点地区。利用桑托斯盆地41口井的岩芯、薄片等资料，明确了盐下湖相碳酸盐岩包括以微生物作用为主的微生物礁叠层石灰岩和以机械成因为主的生屑滩贝壳灰岩两种类型。盐下湖相碳酸盐岩储层整体上属于孔隙型灰岩储层，孔隙度整体上属于中等-好，渗透率中等。储层孔隙类型以原生孔隙为主，并受后期溶蚀改造。根据碳氧同位素地球化学资料、介形虫古生物等资料分析，总结出桑托斯盆地湖相碳酸盐岩储层发育主要受湖水古盐度、古构造格局和沉积相带3种因素控制。其中，湖水古盐度控制储层成因类型，古构造格局控制储层宏观分布，沉积相带控制储层物性特征。预测了桑托斯盆地东部隆起带和中央拗陷带的低凸起是湖相碳酸盐岩储层发育有利区带，对该地区油气勘探具有实践指导意义。

Characteristic and Developmental Controlled Factors of Pre-salt Lacustrine Carbonate,Santos Basin

The lacustrine carbonate of pre-salt in Santos Basin is rich in oil and gas resources,a hotspots of exploration in the world.Based on analysis of cores,thin sections from 41 wells,we determine two types of carbonate developed including microbial reef strobitolites limestone and bioclastic bank coquinas.The lacustrine carbonate is porous limestone reservoir,medium porosity and permeability.The main pore type is primary pore,which had undergone reconstruction from later dissolution.Analysis of C-O isotope data and Ostracoda materials leads to the conclusion that three main elements,paleo-salinity of water,paleo-structure,sedimentary facies,are the main control factors lacustrine carbonate reservoir development.Genesis types of carbonate reservoir is controlled by paleo-salinity of water.Distribution of reservoir is controlled by paleo-structure.And physical property of reservoir is controlled by sedimentary facies.Eastern uplift zone and lower horsts of central depression zone is the favorable area to develop lacustrine carbonate reservoir,helpful to direct exploration deployment.