Abstract Reservoir studies in the Sandakan sub-basin NW Borneo are challenging and inexplicable due to complex diagenetic effects such as compaction, cementation, dissolution and depositional means including grain size, sorting and packing with reference to clay texture. These diagenetic effects together impart significant amounts of uncertainty on reservoir quality assessment. In this regard, we documented the mineralogical, diagenetic and reservoir properties of sandstones from the Sandakan Formation, NW Borneo through thin sections, SEM, XRD, XRF, He-porosimeter and poroperm. In order to analyze the influential parameters, we used matrix, grain rearrangement and clay coating around detrital grains for the reservoir quality. Our results show that the sub-litharenites to quartz arenite that dominate in the sandstones are drawn from recycled orogenic sand. Furthermore, reservoir properties of the sandstones were ascertained to be controlled by diagenesis, micro quartz with clay coatings and pressure dissolution of feldspar with the alteration of lithic fragments. The result shows that the physical compaction, rearrangements and ductility of grains were the reasons that reduced porosity and permeability. The main reason for porosity reduction in the present study is pressure dissolution that resulted in the form of chemical compaction induced by micas with grain contacts. Nonetheless, through SEM and petrography, clay coatings around the grains and dissolution of feldspar were found to optimally contribute to the preservation of reservoir properties. Dissolution of feldspar and kaolinization resulted in the formation of secondary porosity that allows meteoric water to percolate through the open and detachment spaces of quartz or other grains. This percolation is also responsible in enhancing the pore throat radii in the reservoir media of the analyzed sandstones. These traits are obliging to diagenetic effects on porosity and permeability, which are linked with the physical compaction and clays coating to reduce and preserve the reservoir properties respectively of same type of reservoirs globally.

中文翻译：

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将成岩性质和粘土质地对婆罗洲西北砂岩储层质量的影响联系起来

摘要 山打根子盆地西北婆罗洲的储层研究具有复杂的成岩作用，如压实、胶结、溶解和沉积方式，包括粒度、分选和堆积与粘土质地，因此具有挑战性且难以解释。这些成岩作用共同给储层质量评估带来了很大的不确定性。在这方面，我们通过薄片、SEM、XRD、XRF、He 孔隙率计和孔隙率记录了来自婆罗洲西北山打根组砂岩的矿物学、成岩和储层特性。为了分析影响参数，我们使用基质、颗粒重排和碎屑颗粒周围的粘土涂层来评估储层质量。我们的结果表明，在砂岩中占主导地位的亚岩屑岩到石英砂岩是从再生造山砂中提取的。此外，确定砂岩的储层性质受成岩作用、具有粘土涂层的微石英和长石的压力溶解以及岩屑的蚀变控制。结果表明，颗粒的物理压实、重排和延展性是降低孔隙度和渗透率的原因。本研究中孔隙率降低的主要原因是压力溶解，导致由云母与颗粒接触引起的化学压实形式。尽管如此，通过扫描电镜和岩相学，发现颗粒周围的粘土涂层和长石的溶解对储层特性的保存做出了最佳贡献。长石的溶解和高岭土化导致次生孔隙的形成，使大气水能够渗透通过石英或其他颗粒的开放和分离空间。这种渗流也是导致分析砂岩储层介质中孔喉半径增大的原因。这些特征必然对孔隙度和渗透率产生成岩作用，这与物理压实和粘土涂层有关，以减少和保护全球同类型储层的储层性质。