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首页> 外文期刊>Brazilian Journal of Geology >Primary composition and diagenetic patterns of sandstones from Barra de Itiúba Formation in Atalaia High, Sergipe Sub-Basin
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Primary composition and diagenetic patterns of sandstones from Barra de Itiúba Formation in Atalaia High, Sergipe Sub-Basin

机译：Sergipe次盆地Atalaia High Barra deItiúba组砂岩的初级成分和成岩模式

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The petrologic analyses of 40 thin sections from two wells located in Atalaia High, offshore of Sergipe Sub-Basin, allowed the identification of primary composition and diagenetic patterns of Barra de Itiúba Formation. The original detrital compositions included arkoses, sublithic, and lithic sandstones. The main diagenetic processes observed were: compaction of metamorphic rock fragments and mud intraclasts, generating pseudomatrix; precipitation of quartz and feldspar overgrowths and outgrowths, cementation and grain replacement by kaolinite; dolomite and ferrous dolomite/ankerite; pyrite; iron oxides and hydroxides; and diagenetic titanium minerals, in addition to dissolution phases during eo-, meso- and telogenesis. The macroporosity in the two studied wells is primary intergranular, but there is secondary porosity due to dissolution of primary and diagenetic constituents, as well as fracture porosity. Thirteen reservoir petrofacies were defined and grouped into four reservoir petrofacies associations. They reflect the reservoir quality in microscale: good, medium and low-quality and non-reservoir. The good-quality is characterized by average total porosity greater than 15%, whereas the medium shows average total porosity greater than 7%. Low-quality presents average total porosity between 1 and 4%, and the non-reservoir has an average total porosity consistently less than 1%. Overall, the studied reservoirs consist on low-quality and non-reservoir rocks, which are intercalated with levels of medium- and good-quality. The loss of original porosity was mainly due to mechanical compaction (generating pseudomatrix), and cementation by kaolinite and dolomite. Preservation of primary porosity was favored by the presence of quartz overgrowths.
机译：通过对位于Sergipe Sub-Basin海上Atalaia High的两口井的40个薄片进行岩石学分析，可以识别Barra deItiúba组的主要成分和成岩模式。原始的碎屑成分包括阿科糖，亚岩性和岩性砂岩。观察到的主要成岩作用是：变质岩碎屑和泥质碎屑的压实，产生假基质;石英和长石的过度生长和过度沉积，高岭石的胶结作用和晶粒替代;白云石和亚铁白云石/马来石;黄铁矿氧化铁和氢氧化铁;以及成岩，中观和成岩作用期间的溶解阶段以及成岩钛矿物。在两个研究井中，大孔是主要的粒间孔，但是由于主要和成岩成分的溶解以及裂缝孔隙，所以存在次要孔隙。定义了13个储集岩相并将其分为4个储集岩相组合。它们从微观角度反映了储层质量：优质，中质和劣质以及非储层。优质的特征在于平均总孔隙率大于15％，而介质的平均总孔隙率大于7％。劣质岩层的平均总孔隙度在1-4％之间，而非储层的平均总孔隙度始终低于1％。总体而言，所研究的储层由低质量和非储层岩石组成，中间夹有中等质量和优质水平。原始孔隙度的损失主要归因于机械压实（产生假基质）以及高岭石和白云石的胶结作用。石英过度生长的存在有利于保留主要孔隙度。

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