In Pakistan, carbonate rocks of Jurassic age are present entirely throughout the Indus Basin. The Jurassic carbonate rocks present in the Attock-Cherat requires a more detailed investigation as of recent discovery of gas in Jurassic carbonate rocks in the lower Indus basin. The evaluation of these Jurassic carbonate units in the Nizampur Basin of Attock-Cherat ranges should integrate the aspects of the depositional sediments, diagenetic history, and geochemistry to understand the reservoir behavior. In this study, the Samanasuk Formation of 90 m was sampled and measured in detail, and samples were collected with ~ 0.3 m interval and some samples were collected where reckoned necessary. Petrographic and microfacies analysis were conducted on about 100 samples; moreover, XRD analysis were performed. The present study aims to determine the depositional facies, diagenetic processes, and geochemical elements of this carbonate succession of the in an effort to explore their effect on reservoir quality. The Samanasuk Formation comprises eight microfacies assigning three facies belts including peritidal, lagoon, and shoal of a carbonate ramp. The recorded diagenetic processes include dolomitization, compaction, micritization, neomorphism, dissolution, and cementation in which dolomitization played an important role in enhancing the reservoir quality. In relation of their impacts on reservoir properties, the grainstone facies associated with peritidal facies and dolomudstone facie associated with carbonate sand and shoal shows the greatest reservoir quality, whereas lagoonal facies has the lowest reservoir quality. This study represents an approach to use the depositional facies, diagenetic alterations, and geochemical framework of carbonate succession in the reservoir characterization.

中文翻译：

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巴基斯坦喜马拉雅西北部 Nizampur 盆地 Kahi 剖面侏罗系 Samanasuk 组的微相分析、成岩叠印、地球化学和储层质量

在巴基斯坦，侏罗纪碳酸盐岩遍布整个印度河流域。由于最近在印度河流域下游侏罗系碳酸盐岩中发现了天然气，因此需要对 Attock-Cherat 中的侏罗系碳酸盐岩进行更详细的调查。对 Attock-Cherat 山脉 Nizampur 盆地的这些侏罗纪碳酸盐岩单元的评估应结合沉积沉积物、成岩历史和地球化学等方面，以了解储层行为。在这项研究中，对 90 m 的 Samanasuk 组进行了采样和详细测量，并以 ~ 0.3 m 的间隔采集了样品，并在认为必要时采集了一些样品。对大约 100 个样品进行了岩相和微相分析；此外，还进行了XRD分析。本研究旨在确定该碳酸盐岩系列的沉积相、成岩过程和地球化学元素，以探索它们对储层质量的影响。Samanasuk 组包括八个微相，分配了三个相带，包括潮汐带、泻湖和碳酸盐斜坡浅滩。记录的成岩过程包括白云石化、压实、微晶化、新形作用、溶解和胶结，其中白云石化在提高储层质量方面发挥了重要作用。从其对储层性质的影响来看，与周缘相伴生的颗粒岩相和与碳酸盐岩砂滩相伴生的白云岩相储层质量最好，而泻湖相储层质量最低。