Hydrocarbon potential and depositional environment of the Lower Cretaceous black mudstones and shales in the coastal Guangdong Province, China
Hydrocarbon potential and depositional environment of the Lower Cretaceous black mudstones and shales in the coastal Guangdong Province, China
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DOI：
10.1016/j.marpetgeo.2018.10.008
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发表时间：
2019
影响因子：
4.2
通讯作者：
G. Hu;Ruofei Yang;Lichao Wang;Wenxuan Hu;Jian Cao
中科院分区：
文献类型：
--
作者：
G. Hu;Ruofei Yang;Lichao Wang;Wenxuan Hu;Jian Cao
南海北方中生界（特别是白垩系）是重要的油气勘探目标，但目前对它们的认识还很薄弱。本文运用有机岩石学和地球化学方法对广东大亚湾剖面白垩系黑色泥岩和页岩进行了生烃潜力评价和沉积环境研究。这些泥岩和页岩的总有机碳（TOC）含量为0.63%-2.76%，大多数样品符合较高TOC烃源岩的要求。泥岩和页岩中的有机质主要来源于高等植物和次级底栖大型藻类。有机岩石学和地球化学资料表明，有机质以Ⅲ型为主，Ⅱ型次之，热成熟度普遍较低。因此，我们评估了黑色泥岩和页岩具有生烃潜力（特别是天然气倾向）。Pr/Ph值、微量元素和有机质混合物来源表明，这些黑色泥岩和页岩形成于弱氧化-弱还原、低盐度的滨-湖环境。在剖面中部有海侵发育。总体而言，南海北方受海洋影响较大，可能含有TOC含量较高、有机质类型较好的烃源岩。珠江口盆地局部地区可能存在具有较高液态烃生成潜力的白垩系烃源岩。
The Mesozoic (especially the Cretaceous) sequences in the northern South China Sea (SCS) are important potential targets of oil and gas exploration; however, they are currently poorly understood. We use organic petrology and geochemistry to evaluate the hydrocarbon potential and study depositional environment of the Cretaceous black mudstones and shales from the Dayawan Section in the Guangdong Province, China. These mudstones and shales yield total organic carbon (TOC) contents of 0.63%–2.76% and most samples meet the requirement for higher TOC source rocks. Organic matters in the mudstones and shales were sourced mainly from higher plants as well as subordinate benthic macroalgae. Organic petrology and geochemical data suggested that the organic matters were dominated by Type-III and minor Type-II, and generally have low thermal maturity. Thus, we evaluated the black mudstones and shales have a potential for hydrocarbon generation (especially gas prone). Pr/Ph, trace elements, and mixture source of organic matter suggested that these black mudstones and shales formed in a coastal–lacustrine environment, characterized by weakly oxidizing−weakly reducing conditions and low-salinity. A marine transgression developing in the middle part of the section was recognized. Generally, the northern SCS, which exhibits the more marine influence, likely contains source rocks with higher TOC contents and better organic matter types. The Cretaceous source rocks with higher liquid hydrocarbon generation potential may occur locally in the Pearl River Mouth Basin.