This work evaluated the hydrocarbon potentiality and petrophysical properties of the Paleocene Zelten Formation in the Libyan Sirte Basin. It aimed to delineate the influence of the microfacies composition of the studied sequence on the reservoir characteristics. The study was based on petrographical and petrophysical data derived from six wells. The petrophysical data included well-logging data (gamma-ray, caliper, PEF, sonic, neutron porosity, density, spectral gamma-ray, and deep and shallow resistivity) and conventional core data (density, porosity, permeability, and fluid saturations). Lithologically, the carbonate Zelten reservoir sequence is composed of four non-clastic lithofacies: (1) argillaceous limestone; (2) calcareous shale; (3) fossiliferous limestone, sometimes slightly dolomitic; and (4) dolomite lithofacies. Petrographically, four microfacies were defined: (1) oolitic grainstone; (2) dolomitic bioclastic packstone; (3) dolomudstone; and (4) ferruginated bioclastic wackestone microfacies. The petrophysical characteristics of the studied sequence were deduced by analyzing well-logging data sets to evaluate the effective and total porosities, shale volume, fluids saturations, and thickness of the net pay. Moreover, detailed processing of the core dataset was applied to estimate the average reservoir pore radius (R₃₅) and the reservoir quality parameters. Petrophysically, the Zelten reservoir was sliced into four reservoir rock types (RRTs), with the RRT1 group having much better reservoir quality than the other RRTs; it forms the topmost parts of the Zelten Formation, averaging 78 ft thick and primarily composed of oolitic grainstone microfacies. It has fair to very good permeability (2.3–479.0 mD), poor to excellent porosity (8.1–41.8%), good to tight reservoir quality parameters, and micro- to meso-pore sizes (0.97–8.08 µm). Besides, the oil saturation was in the range of 0.70–44.6%. In contrast, the RRT4 is a compact reservoir rock type; it primarily consists of ferruginated bioclastic wackestone microfacies and is characterized by excellent porosity (10.5–34.8%), fair to tight permeability (0.013–1.4 mD), tight reservoir quality index (RQI) and flow zone indicator (FZI) values (0.011 and 0.153 µm, respectively), micropore sizes (0.05–0.34 µm), and 0.9–31.5% oil saturation. The petrophysical characters of the RRT2-3 samples have transitional reservoir quality (average porosity = 22.7 and 24.8 %, average permeability = 12.34 and 2.789 mD, RQI_av = 0.198 and 0.091 μm, FZI_av = 0.588 and 0.291 μm, and R₃₅ = 1.29 and 0.53 μm for RRT2 and RRT3, respectively) between the tight RRT4 and the best RRT1 reservoir samples. Also, the Zelten reservoir was sliced vertically into six zones, with the best reservoir quality assigned for zone 5 (net-pay thickness = 348.3 ft, average porosity = 18.7%, average water saturation = 48.3%, and shale volume = 27.9%). The proposed integrated petrophysical and petrographical workflow is applicable to other analogues in Sirte Basin and other basins in Libya and North Africa.

这项工作评估了利比亚苏尔特盆地古新世 Zelten 组的碳氢化合物潜力和岩石物理性质。它旨在描述所研究序列的微相组成对储集层特征的影响。该研究基于来自六口井的岩石学和岩石物理数据。岩石物理数据包括测井数据（伽马射线、卡尺、PEF、声波、中子孔隙率、密度、光谱伽马射线以及深电阻率和浅电阻率）和常规岩心数据（密度、孔隙度、渗透率和流体饱和度）。在岩性学上，碳酸盐岩 Zelten 储层序列由四个非碎屑岩相组成：（1） 泥质石灰岩;（2） 钙质页岩;（3） 石灰岩化石，有时略带白云岩;（4） 白云岩岩相。在岩石学上，确定了四个微相：（1） 鲕粒岩;（2） 白云质生物碎屑堆石;（3） 白泥岩;（4） 铁质生物碎屑 Wackestone 微相。通过分析测井数据集来推断所研究序列的岩石物理特征，以评估有效孔隙度和总孔隙度、页岩体积、流体饱和度和净层厚度。此外，对岩心数据集进行详细处理，以估计平均储层孔隙半径 （R₃₅） 和储层质量参数。在岩石方面，Zelten 储层被切分为 4 种储集层岩石类型 （RRT），其中 RRT1 组的储集层质量远优于其他 RRT;它构成了 Zelten 组的最顶部，平均厚度为 78 英尺，主要由鲕粒岩微相组成。它具有一般到非常好的渗透性 （2.3–479.0 mD），差到极好的孔隙率 （8.1–41.8%）、良好至紧密的储层质量参数以及微孔至中孔尺寸 （0.97–8.08 μm）。此外，油饱和度在 0.70-44.6% 的范围内。相比之下，RRT4 是一种致密的储集层岩石类型;它主要由铁质生物碎屑 Wackestone 微相组成，其特点是孔隙度优异 （10.5-34.8%）、一般至紧密渗透性 （0.013-1.4 mD）、紧密储层质量指数 （RQI） 和流区指标 （FZI） 值（分别为 0.011 和 0.153 μm）、微孔尺寸 （0.05-0.34 μm） 和 0.9-31.5% 的油饱和度。RRT2-3 样品的岩石物理特征在致密 RRT4 和最佳 RRT1 储层样品之间具有过渡储层质量 （平均孔隙度 = 22.7 和 24.8 %，平均渗透率 = 12.34 和 2.789 mD，RQI_av = 0.198 和 0.091 μm，FZI_av = 0.588 和 0.291 μm，RRT2 和 RRT3 的 R₃₅ = 1.29 和 0.53 μm）。此外，Zelten 储层被垂直切分为 6 个区域，最佳储层质量分配给 5 区（净储层厚度 = 348.3 英尺，平均孔隙度 = 18.7%，平均含水饱和度 = 48.3%，页岩体积 = 27.9%）。拟议的综合岩石物理和岩石学工作流程适用于苏尔特盆地以及利比亚和北非其他盆地的其他类似物。