Abstract

A combination of wireline log data and sedimentological characterization provides insight into the sequence stratigraphic framework of the carbonate rocks. The Cenomanian Rumaila Formation is considered one of the Cretaceous representative carbonate units in the Middle East. In Iraq, limited information regarding the regional distribution of the Rumaila Formation within a sequence stratigraphic framework prompted this work. This study integrates geophysical well logs (i.e. gamma ray, sonic and density logs) and a detailed microfacies study of the core and cutting samples to suggest the sequence stratigraphic framework of the studied sections. The detailed carbonate microfacies study of over 100 samples from the four available wells (WQA, WQB, WQC, and WQD) within the West Qurna Oil Field suggests deposition from the outer to the middle ramp with the influence of the shoal environment. The Rumaila Formation could be correlated to the early part of the highstand face of the Wasia Group with a Cenomanian to Early Turonian age. There is no clear evidence of unconformity or a time gap between the Ahmadi and Rumaila formations in the studied area. The sequence stratigraphic study of 80 m of the Rumaila Formation revealed the identification of three 4^th-ordered stratigraphic sequences (RLS1, RLS2 and RLS3). Moreover, this study identified a potential regional correlative maximum flooding surface that correlates with the regional established one (i.e. K-130). Two marine flooding surfaces were identified within the studied sections and could be further correlated regionally. Because of the intercalation between the Rumaila and Mishrif formations in southern Iraq, identifying these regional marine intrusion episodes (i.e. K-130 and K-135) provides credible evidence to clearly differentiate them. In the transgressive system tracts (TST), the deepening upward trend is invariably accompanied by an increase in gamma-ray and density log values, a decrease in acoustic and neutron log values, and vice versa in the high stand system tracts (HST). Thus, wireline logs provide insight into the sequence stratigraphic framework in carbonate rocks, especially when sedimentological data is missing.

中文翻译：

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综合电缆测井和沉积学数据预测碳酸盐岩层序地层框架：以伊拉克南部西库尔纳油田 Rumaila 组（Cenomanian）为例

摘要

电缆测井数据和沉积学特征的结合提供了对碳酸盐岩层序地层结构的深入了解。Cenomanian Rumaila 组被认为是中东地区白垩纪具有代表性的碳酸盐单元之一。在伊拉克，关于 Rumaila 组在层序地层框架内的区域分布的有限信息促成了这项工作。本研究将地球物理测井（即伽马射线、声波和密度测井）与岩心和切割样品的详细微相研究相结合，以提出所研究剖面的层序地层框架。对来自四个可用井（WQA、WQB、WQC、West Qurna 油田内的 WQD) 表明受浅滩环境的影响，沉积从外斜坡到中斜坡。Rumaila 组可能与 Wasia 组高位面的早期部分相关，具有 Cenomanian 到早期 Turonian 时代。没有明确的证据表明所研究区域的 Ahmadi 和 Rumaila 地层之间存在不整合或时间间隔。Rumaila 组 80 m 层序地层研究揭示了三个 4^th-有序地层序列（RLS1、RLS2 和 RLS3）。此外，这项研究确定了一个潜在的区域相关最大泛滥面，该面与区域已建立的泛滥面（即 K-130）相关。在研究剖面内确定了两个海洋泛滥表面，并且可以在区域上进一步关联。由于伊拉克南部 Rumaila 和 Mishrif 地层之间的夹层，识别这些区域性海洋入侵事件（即 K-130 和 K-135）为明确区分它们提供了可靠的证据。在海侵体系域（TST）中，不断加深的上升趋势总是伴随着伽马射线和密度测井值的增加，声波和中子测井值的下降，反之亦然。因此，