巴西桑托斯盆地湖相微生物碳酸盐岩储层内幕刻画及定量表征方法

Internal characterization and quantitative characterization of lacustrine microbial carbonate reservoirs in Santos Basin of Brazil

微生物碳酸盐岩研究是近年来国内外关注的热点,虽然已经取得了一定的成果和认识,但是在储层精细描述方面研究相对薄弱。以巴西桑托斯盆地盐下白垩系湖相微生物碳酸盐岩油田为例,利用露头、岩心、测井、地震等资料综合分析了研究区储层沉积特征、岩性、物性特征及其主控因素,并在此基础上对储集体内幕结构进行分类和描述,初步建立其定量表征方法。结果表明:(1)研究区由3个独立的碳酸盐岩台地沉积组成,可细分为微生物灰岩丘、高能颗粒滩、丘间洼地和台间洼地4个亚相;(2)微生物灰岩、生物碎屑颗粒灰岩、介壳颗粒灰岩、层纹岩等是主要的储层岩石类型;(3)储层物性较好,孔隙度4%~27%,集中在5%~15%,平均12.5%;渗透率为(0.01~3 000)×10^(-3)μm^(2),平均120×10^(-3)μm^(2);(4)储层发育受沉积和成岩双重作用,古构造控制优势储层的发育,准同生期溶蚀作用对储层改造作用加强,周期性暴露溶蚀使生物碎屑颗粒填充至丘间洼地形成高孔高渗条带;(5)研究区储层的内幕结构以微生物灰岩丘群为基础,细分为丘基、丘核、丘翼、丘间和丘间甜点。建立以沉积相和成岩相控制因素为基础的丘群组合模式定量表征方法,在应用中获得了较好的效果。

In recent years,microbial carbonate reservoir development technologies are the research frontier all over the world,with a certain number of achievements and cognition,while the refined reservoir description is relatively weak.Taking Cretaceous lacustrine microbial carbonate oil field in Santos Basin as an example,the authors in this paper have used outcrop,core,logging and seismic data to comprehensively analyze the lithologic characteristics,sedimentary,physical characteristics and main controlling factors in the study area.And the internal structure of the reservoir was classified and described,and the quantitative characterization method was thus established.The results show that:①The study area was composed of three independent carbonate platform deposits,which could be subdivided into four subfaces:microbial limestone mound,high-energy grain bank,inter-mound depression and inter-platform depression.②Microbial limestone,bioclastic granular limestone,scale granular limestone and stratified rock were the main reservoir rock types.③The reservoir was with good physical properties:the porosity was 4%-27%with an average of 12.5%,and the permeability was(0.01-3000)×10^(-3)μm^(2)with an average of 120×10^(-3)μm^(2).④The development of reservoir was influenced by sedimentation and diagenesis,and the development of dominant reservoir was controlled by paleo structure.The effect of quasi-syngenetic dissolution on reservoir transformation was strengthened,and the bioclastic particles by periodic exposure and dissolution were filled into the inter-mound depression to form the high-porosity and high-permeability bands.⑤The inner structure of the reservoir in the study area was based on microbial limestone mound groups,which were subdivided into mound foundation,mound core,mound wing,inter-mound,and inter-mound sweet spot.The quantitative characterization method of cluster assemblage model had been established based on sedimentary facies and controlling factors of diagenetic facies,which has achieved good application effects in oil field development.