GEOCHEMICAL CORRELATIONS BETWEEN PETROLEUM SAMPLES FROM THE POTIGUAR BASIN AND DEFINITION OF THEIR POSSIBLE GENERATING ROCKS

Eight petroleum samples from Potiguar Basin were submitted for determination of saturated biomarkers by gas chromatography (fingerprint), liquid chromatography (saturates, aromatics, resins and asphaltenes), gas chromatography-mass spectrometry (GC-MS), nickel and vanadium by high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS). The geochemical parameters provided information on type of depositional paleoenvironment in which organic matter that gave rise to each oil sample and level of thermal maturation reached by generating rocks that make up the Potiguar Basin were deposited. The relationships between the stable isotopes of carbon (δ13C) and between Ni and V concentrations of each petroleum sample were also evaluated. The evaluations separated for oil samples into two distinct groups. Group 1 formed by samples P1, P2, P5 and P8, with characteristics of generating rock that was deposited in a marine hypersaline environment. Group 2 composed of samples P3, P4, P6 and P7 with freshwater lacustrine depositional paleoenvironment, which were elucidated through the geochemical parameters studied. The hierarchical cluster analysis was presented as promising chemometric tool for characterization of petroleum samples in the according to their origin of the generating rock by ratio parameters of hopane/sterane , tetracyclic polyiprenoids/diastereomers and diastereos R+S/cholestane R+S.本研究选取波蒂瓜尔盆地（Potiguar Basin）的8件石油样品，开展如下分析：采用气相色谱（指纹法）测定饱和生物标志物，液相色谱分离饱和烃、芳香烃、树脂与沥青质组分，气相色谱-质谱联用仪（GC-MS）进行组分分析，以及高分辨率连续光源石墨炉原子吸收光谱法（HR-CS GF AAS）测定样品中的镍、钒元素含量。所得地球化学参数可揭示各原油样品对应母质的沉积古环境类型，以及波蒂瓜尔盆地烃源岩的热演化程度。本研究还分析了各石油样品的碳稳定同位素（δ¹³C）组成与镍、钒浓度之间的相关性。基于上述分析可将所有石油样品划分为两个截然不同的组别：第1组包含样品P1、P2、P5和P8，其对应的烃源岩形成于海相超盐度沉积环境；第2组由样品P3、P4、P6和P7组成，对应陆相淡水湖沉积古环境，该分类结果通过本次研究的地球化学参数得以验证。层级聚类分析是一种极具应用前景的化学计量学工具，可通过藿烷/甾烷、四环多聚异戊二烯/重排甾烷以及重排甾烷R+S/胆甾烷R+S比值参数，基于烃源岩成因对石油样品进行精准表征。