The application of diamondoids indices for oils from Block 4 of the Muglad Basin in the middle of Africa

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences Pub Date : 2024-08-15 DOI:10.1016/j.jafrearsci.2024.105384

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Abstract

The abundances and distribution diamondoids were studied with a series of crude oil samples from Block 4 of the Mugald Basin in Sudan, to investigate the validity of various diamondoid parameters on the oil source, thermal maturity and biodegradation information. All crude oils of Block 4 were generated by lacustrine source in lower part of the Abu Gabra Formation as a whole, and can be further divided into two crude oil groups: oil group of the Neem-Azraq Uplift and oil group of K-3 well and B-1 well. They are all mature oils within oil window and four crude oils from the Neem-Azraq Uplift were slightly biodegraded. The concentrations of diamondoids in oils of K-3 well and B-1 well, especially the concentration of diamantanes, are higher than those of oils from the Neem-Azraq Uplift. The concentrations of diamondoids are mainly controlled by source of oil, while the influence of thermal maturity and biodegradation may be limited. The isomerization ratios as indicators of thermal maturity are inapplicable at the mature stage, but DMDI-2, 4,8/3,4-DMD and 1-EA/3-EA can clearly distinguish the two groups of crude oils. The concentration ratios of oils from K-3 and B-1 wells are significantly lower than these of oils from Neem-Azraq Uplift, and these concentration ratios including newly proposed parameters such as MAs/DMAs, DMAs/TMAs, D/MDs, MDs/DMDs and so on, are effective indicators on organofacies and oil group division within oil window.

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非洲中部穆格莱德盆地 4 号区块石油的金刚石指数应用

对苏丹穆加尔德盆地 4 号区块的一系列原油样本进行了菱形类丰度和分布研究，以探讨各种菱形类参数对石油来源、热成熟度和生物降解信息的有效性。4 号区块的所有原油均由阿布-加布拉地层下部的湖泊源整体生成，并可进一步分为两个原油组：尼姆-阿兹拉克隆起区的油组以及 K-3 井和 B-1 井的油组。它们都是石油窗口内的成熟油，尼姆-阿兹拉克隆起带的四种原油略有生物降解。K-3 井和 B-1 井石油中的类钻烃浓度，尤其是二烷烃浓度高于尼姆-阿兹拉克隆起带的石油。类钻石的浓度主要受石油来源的控制，而热成熟度和生物降解的影响可能有限。作为热成熟度指标的异构化比率在成熟阶段并不适用，但 DMDI-2、4,8/3,4-DMD 和 1-EA/3-EA 可以明显区分两类原油。K-3 和 B-1 井的石油浓度比明显低于楝树-阿兹拉克隆起区的石油浓度比，这些浓度比包括新提出的参数，如 MAs/DMAs、DMAs/TMAs、D/MDs、MDs/DMDs 等，是石油窗口内有机层和石油组划分的有效指标。

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来源期刊

Journal of African Earth Sciences 地学-地球科学综合

CiteScore

4.70

自引率

4.30%

发文量

240

审稿时长

12 months

期刊介绍： The Journal of African Earth Sciences sees itself as the prime geological journal for all aspects of the Earth Sciences about the African plate. Papers dealing with peripheral areas are welcome if they demonstrate a tight link with Africa. The Journal publishes high quality, peer-reviewed scientific papers. It is devoted primarily to research papers but short communications relating to new developments of broad interest, reviews and book reviews will also be considered. Papers must have international appeal and should present work of more regional than local significance and dealing with well identified and justified scientific questions. Specialised technical papers, analytical or exploration reports must be avoided. Papers on applied geology should preferably be linked to such core disciplines and must be addressed to a more general geoscientific audience.