Classification and Diagenetic Characteristics of the Cretaceous Sandstones in the Southern Bredasdorp Basin, Offshore South Africa,Acta Geologica Sinica-English Edition

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Classification and Diagenetic Characteristics of the Cretaceous Sandstones in the Southern Bredasdorp Basin, Offshore South Africa
Acta Geologica Sinica-English Edition ( IF 3.5 ) Pub Date : 2021-04-01 , DOI: 10.1111/1755-6724.14701
Temitope Love Baiyegunhi ₁ , Kuiwu Liu ₁ , Oswald Gwavava ₁ , Christopher Baiyegunhi ₂

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A systematic petrographic and geochemical studies of 92 representative sandstone samples from exploration wells E-AH1, E-AJ1, E-BA1, E-BB1 and E-D3 in the southern part of the Bredasdorp Basin was undertaken to classify the sandstones as well as unravel the main diagenetic processes and their time relations. Petrographic study shows that the sandstones are largely subarkosic arenite and arkosic litharenite, which have underwent series of diagenetic processes as a result burial, rifting and subsequent uplift. The main diagenetic processes that have affected the reservoir properties of the sandstones are cementation by authigenic clay, carbonate and silica, growth of authigenic glauconite, dissolution of minerals and load compaction. The major diagenetic processes reducing the porosity are calcite cementation in the subarkosic arenite, and compaction and quartz cementation in arkosic litharenite. On the other hand, the formation of secondary porosity due to the partial to complete dissolution of early calcite cement, feldspars and minor grain fracturing has improved the reservoir property of the sandstone to some extent. The clay minerals in the sandstones commonly acts as pore choking cement, which reduces porosity. In general, there is no particular diagenetic process that exclusively controls the type or form of porosity evolution in the sandstones.

中文翻译：

南非近海 Bredasdorp 盆地南部白垩纪砂岩分类及成岩特征

对 Bredasdorp 盆地南部勘探井 E-AH1、E-AJ1、E-BA1、E-BB1 和 E-D3 的 92 个代表性砂岩样品进行了系统的岩石学和地球化学研究，以对砂岩进行分类以及解开主要的成岩过程及其时间关系。岩石学研究表明，砂岩主要是亚长质砂岩和长长质岩屑岩，它们经历了埋藏、裂谷和随后的隆升等一系列成岩过程。影响砂岩储层性质的主要成岩过程是自生粘土、碳酸盐和二氧化硅的胶结作用、自生海绿石的生长、矿物的溶解和载荷压实。降低孔隙度的主要成岩过程是亚长质砂岩中的方解石胶结作用，长石质岩屑岩中的压实作用和石英胶结作用。另一方面，早期方解石胶结物、长石和细小颗粒压裂部分至完全溶解形成的次生孔隙，在一定程度上改善了砂岩的储层物性。砂岩中的粘土矿物通常充当孔隙阻塞胶结物，从而降低孔隙度。一般来说，没有特定的成岩过程专门控制砂岩中孔隙度演化的类型或形式。砂岩中的粘土矿物通常充当孔隙阻塞胶结物，从而降低孔隙度。一般来说，没有特定的成岩过程专门控制砂岩中孔隙度演化的类型或形式。砂岩中的粘土矿物通常充当孔隙阻塞胶结物，从而降低孔隙度。一般来说，没有特定的成岩过程专门控制砂岩中孔隙度演化的类型或形式。

更新日期：2021-04-01

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