Zuo Guoping, Wang Hongping, Fan Guozhang, Zhang Jiazhen, Zhang Yonggang, Wang Chaofeng, Yang Liu, Ding Liangbo, Pang Xu, Zuo Yinhui
PetroChina Hangzhou Research Institute of Geology, Hangzhou 310023, China.
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China.
ACS Omega. 2022 Jul 12;7(29):25715-25725. doi: 10.1021/acsomega.2c03018. eCollection 2022 Jul 26.
The Santos Basin in Brazil is a hot area of oil and gas exploration in recent years, and its subsalt lacustrine mudstones are the main source rock of the basin. However, there is a lack of studies on the source rocks of the subsalt Picarras and Itapema formations, which is not conducive to the accurate evaluation of the source rock characteristics. Based on logging data of 51 wells and geochemical data of 16 wells, this paper makes detailed evaluations of the organic matter abundance, type, maturity, and distribution characteristics of source rocks of the subsalt Picarras Formation and Itapema Formation in the Santos Basin. The results show that the characteristics of source rocks of the Itapema and Picarras formations are similar, both of which have a high abundance of organic matter. The types of organic matter are mainly type I and II, and the maturities are in the low-maturity to the high-maturity stage, which meets the standard of good source rocks. The total organic carbon content of the source rocks of the Picarras Formation ranges from 0.4 to 4.0%, much lower than that of the source rocks of the Itapema Formation, 0.8-5.6%. In addition, the hydrogen index average value of the source rocks of the Itapema Formation is 712.8 mg/g TOC, higher than that of the Picarras Formation, 697.5 mg/g TOC, both revealing a great hydrocarbon potential. The quality of source rocks of the Itapema Formation is better than that of the Picarras Formation. The two sets of source rocks have great hydrocarbon generation potential and are mainly developed in the eastern and western sags of the central depression. Therefore, the surrounding uplift areas will be the target for further oil and gas exploration.
巴西的桑托斯盆地是近年来油气勘探的热点地区，其盐下湖相泥岩是该盆地的主要烃源岩。然而，目前缺乏对盐下皮卡拉斯组和伊塔佩马组烃源岩的研究，不利于准确评价烃源岩特征。本文基于51口井的测井资料和16口井的地球化学资料，对桑托斯盆地盐下皮卡拉斯组和伊塔佩马组烃源岩的有机质丰度、类型、成熟度及分布特征进行了详细评价。结果表明，伊塔佩马组和皮卡拉斯组烃源岩特征相似，均具有较高的有机质丰度。有机质类型主要为Ⅰ型和Ⅱ型，成熟度处于低成熟到高成熟阶段，均达到优质烃源岩标准。皮卡拉斯组烃源岩的总有机碳含量为0.4%4.0%，远低于伊塔佩马组烃源岩的0.8%5.6%。此外，伊塔佩马组烃源岩的氢指数平均值为712.8mg/g TOC，高于皮卡拉斯组的697.5mg/g TOC，两者均显示出巨大的生烃潜力。伊塔佩马组烃源岩质量优于皮卡拉斯组。这两套烃源岩具有巨大的生烃潜力，主要发育于中央坳陷的东部和西部凹陷。因此，周边隆起区将是进一步油气勘探的目标。
