Abstract The late Cretaceous Naparima Hill Formation in the South Trinidad Basin (southeast Caribbean) is a prolific source rock with a potential for unconventional hydrocarbon exploration. It is exposed across the Central Range and extends to the city of San Fernando. This study characterized the Naparima Hill source rock using petrographic analysis techniques (X-ray diffraction and thin section analysis) and petrophysical techniques. These techniques were applied to outcrop samples that were collected from 11 locations. Firstly, petrographic analysis was used to determine the mineral composition and lithofacies. Secondly, plugs were taken perpendicular to bedding and the bulk density was determined in dry conditions. Thirdly, porosity and grain density were determined using a porosimeter at ambient conditions. Finally, permeability measurements were obtained at 10 MPa to 130 MPa effective pressures using the transient pulse decay technique. The results show that the source rock is dominated by silica with carbonate as secondary minerals. Four lithofacies were identified: (a) siliceous-calcareous mudstone (b) calcareous mudstones interbedded with black chert, (c) carbonate-rich mudstone with nodular chert and (d) siliceous mudstone. Ranges of 5.9 to 30.8%, 2362 to 2668 kg/m3 and 1804 to 2350 kg/m3 were determined for porosity, grain density and bulk density, respectively. The permeability ranges from 3.96 × 10−20 to 5.94 × 10−18 m2 and shows very little dependence on the effective pressure. Permeability and porosity are moderately correlated (R2 = 0.6). There is no relationship between permeability and mineralogical composition. The observed microfractures, diagenetic processes and grain sorting, are factors that have affected the permeability-porosity relationship to varying degrees. However, none of these factors can be considered as the main intrinsic factor controlling the permeability of the samples. Overall, it is difficult to predict the permeability of the Naparima Hill Formation with any of the proxies (density, mineralogy and porosity) determined in this study. .

中文翻译：

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西印度群岛特立尼达中央山脉晚白垩世 Naparima Hill 地层的岩石学和岩石物理特征

摘要 南特立尼达盆地（加勒比海东南部）晚白垩世 Naparima Hill 组是一个多产的烃源岩，具有非常规油气勘探潜力。它横跨中央山脉并延伸至圣费尔南多市。本研究使用岩相分析技术（X 射线衍射和薄片分析）和岩石物理技术对 Naparima Hill 烃源岩进行了表征。这些技术应用于从 11 个地点收集的露头样本。首先，通过岩相分析确定矿物成分和岩相。其次，塞子垂直于层理并在干燥条件下测定堆积密度。第三，在环境条件下使用孔隙率计测定孔隙率和颗粒密度。最后，渗透率测量是在 10 MPa 到 130 MPa 有效压力下使用瞬态脉冲衰减技术获得的。结果表明，烃源岩以二氧化硅为主，碳酸盐为次生矿物。确定了四种岩相：(a) 硅质-钙质泥岩 (b) 钙质泥岩与黑色燧石互层，(c) 富含碳酸盐的泥岩与结节状燧石，(d) 硅质泥岩。孔隙度、颗粒密度和堆积密度的范围分别为 5.9 至 30.8%、2362 至 2668 kg/m3 和 1804 至 2350 kg/m3。渗透率范围为 3.96 × 10-20 至 5.94 × 10-18 m2，对有效压力的依赖性很小。渗透率和孔隙率中等相关（R2 = 0.6）。渗透率和矿物组成之间没有关系。观察到的微裂缝，成岩过程和颗粒分选是不同程度影响渗透率-孔隙度关系的因素。然而，这些因素都不能被认为是控制样品渗透率的主要内在因素。总体而言，很难用本研究中确定的任何替代指标（密度、矿物学和孔隙度）来预测 Naparima Hill 地层的渗透率。.