Opuwari Mimonitu, Afolayan Blessing, Mohammed Saeed, Amaechi Paschal Ogechukwu, Bareja Youmssi, Chatterjee Tapas
Petroleum Geosciences Research Group, Earth Sciences Department, University of the Western Cape, 7535, Bellville, Republic of South Africa.
Sci Rep. 2022 Jan 11;12(1):510. doi: 10.1038/s41598-021-04447-6.
This study aims to generate rock units based on core permeability and porosity of OW oilfield in the Bredasdorp Basin offshore South Africa. In this study, we identified and classified lithofacies based on sedimentology reports in conjunction with well logs. Lucia's petrophysical classification method is used to classify rocks into three classes. Results revealed three lithofacies as A (sandstone, coarse to medium-grained), B (fine to medium-grained sandstone), and C (carbonaceous claystone, finely laminated with siltstone). Lithofacies A is the best reservoir quality and corresponds to class 1, while lithofacies B and C correspond to class 2 and 3, which are good and poor reservoir quality rock, respectively. An integrated reservoir zonation for the rocks is based on four different zonation methods (Flow Zone indicator (FZI), Winland r35, Hydraulic conductivity (HC), and Stratigraphy modified Lorenz plot (SMLP)). Four flow zones Reservoir rock types (RRTs) were identified as RRT1, RRT3, RRT4, and RRT5, respectively. The RRT5 is the best reservoir quality composed of a megaporous rock unit, with an average FZI value between 5 and 10 µm, and HC from 40 to 120 mD/v, ranked as very good. The most prolific flow units (RRT5 and RRT4 zones) form more than 75% of each well's flow capacities are supplied by two flow units (FU1 and FU3). The RRT1 is the most reduced rock quality composed of impervious and nanoporous rock. Quartz is the dominant framework grain, and siderite is the dominant cement that affects flow zones. This study has demonstrated a robust approach to delineate flow units in the OW oilfield. We have developed a useful regional petrophysical reservoir rock flow zonation model for clastic reservoir sediments. This study has produced, for the first time, insights into the petrophysical properties of the OW oilfield from the Bredasdorp Basin South Africa, based on integration of core and mineralogy data. A novel sandstone reservoir zonation classification criteria developed from this study can be applied to other datasets of sandstone reservoirs with confidence.
本研究旨在根据南非近海布雷达斯多普盆地OW油田的岩心渗透率和孔隙度生成岩石单元。在本研究中，我们结合测井资料，根据沉积学报告对岩相进行了识别和分类。采用卢西亚的岩石物理分类方法将岩石分为三类。结果显示有三种岩相，即A相（砂岩，粗粒至中粒）、B相（细粒至中粒砂岩）和C相（碳质泥岩，与粉砂岩呈细层状互层）。A相储层质量最佳，对应1类，而B相和C相对应2类和3类，分别为储层质量良好和较差的岩石。基于四种不同的分区方法（流动带指标（FZI）、温兰德r35、水力传导率（HC）和地层修正洛伦兹图（SMLP））对岩石进行了综合储层分区。确定了四种流动带储层岩石类型（RRTs），分别为RRT1、RRT3、RRT4和RRT5。RRT5储层质量最佳，由大孔隙岩石单元组成，平均FZI值在5至10μm之间，HC为40至120 mD/v，评级为非常好。产量最高的流动单元（RRT5和RRT4区）占每口井流动能力的75%以上，由两个流动单元（FU1和FU3）提供。RRT1岩石质量最差，由不透水和纳米孔隙岩石组成。石英是主要的骨架颗粒，菱铁矿是影响流动带的主要胶结物。本研究展示了一种在OW油田划分流动单元的可靠方法。我们为碎屑岩储层沉积物开发了一个有用的区域岩石物理储层岩石流动分区模型。本研究首次基于岩心和矿物学数据的整合，深入了解了南非布雷达斯多普盆地OW油田的岩石物理性质。从本研究中开发的一种新颖的砂岩储层分区分类标准可以自信地应用于其他砂岩储层数据集。
