Petrographical and petrophysical characterization of the late cretaceous Naparima Hill Formation, Central Range, Trinidad, West Indies
Petrographical and petrophysical characterization of the late cretaceous Naparima Hill Formation, Central Range, Trinidad, West Indies
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DOI：
10.1016/j.coal.2020.103592
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发表时间：
2020-09
影响因子：
5.6
通讯作者：
U. C. Iyare;R. Ramsook;O. Blake;D. Faulkner
中科院分区：
文献类型：
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作者：
U. C. Iyare;R. Ramsook;O. Blake;D. Faulkner
南特立尼达盆地（加勒比海东南部）的白垩纪晚期纳帕里马山组是一个丰富的烃源岩，具有非常规油气勘探的潜力。它横跨中央山脉并延伸至圣费尔南多市。本研究利用岩相分析技术（X 射线衍射和薄片分析）和岩石物理技术对纳帕里马山烃源岩进行了表征。这些技术应用于从 11 个地点采集的露头样本。首先，利用岩相分析确定矿物成分和岩相。其次，垂直于垫层取出塞子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，使用瞬态脉冲衰减技术在 10 MPa 至 130 MPa 有效压力下获得渗透率测量结果。结果表明，烃源岩以硅石为主，次生矿物为碳酸盐。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核状燧石和（d）硅质泥岩。孔隙率、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 × 10−18m2，对有效压力的依赖性很小。渗透率和孔隙度具有中等相关性 (R2= 0.6)。渗透率和矿物成分之间没有关系。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，这些因素都不能被视为控制样品渗透性的主要内在因素。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）来预测纳帕里马山地层的渗透率。 。
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/m3and 1804 to 2350 kg/m3were determined for porosity, grain density and bulk density, respectively. The permeability ranges from 3.96 × 10−20to 5.94 × 10−18m2and 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. .