摘要
珠江口盆地白云凹陷是中国近海盆地已证实的富气凹陷,对烃源岩的研究是该凹陷关键的地质问题之一。通过地震、钻井、地球化学和古生物资料综合分析认为恩平组沉积时期,白云凹陷北坡发育海陆过渡相三角洲,凹陷深部为浅海相沉积。受控于沉积相带的分布,烃源岩呈二元分布特征,分三角洲煤系烃源岩和浅海相泥岩。三角洲煤系分布在凹陷的缓坡区,烃源岩包括煤层、炭质泥岩和暗色泥岩,沉积有机质来自陆源,这类烃源岩地球化学指标以高双杜松烷、低奥利烷和高Pr/Ph值为特征。浅海相泥岩烃源岩分布于深凹陷部位,有机质可细分为2类:一类为陆源海相有机质,地球化学指标以低双杜松烷、高奥利烷和中等Pr/Ph值为特征;另一类为海生藻类,地球化学指标以不含双杜松烷及奥利烷、低Pr/Ph值为特征;这2种类型的烃源岩形成了2种不同类型的气藏。海陆过渡相烃源岩在中国近海外带多个凹陷中都发育,其生烃能力与热演化程度有关。成熟和过成熟时,生成大量天然气;成熟和低成熟时生成一定量的石油。烃源岩分布位置的差异导致天然气富集区主要在热成熟度足够高的煤系三角洲区,生烃灶处在"缓坡区";另外成熟度足够高的浅海相泥岩区,也是天然气的富集区域,生烃灶处在"深凹区"。
Baiyun Sag is a gas-prolific sag in the Pearl River Mouth Basin of the outer zone of China offshore basins.Hydrocarbon is derived from marine-continental transitional facies,and the source rocks distribute as duality,including deltaic coals and neritic mudstones.Deltaic coals develop on the northern slope of Baiyun Sag,that includes coal bed,carbonaceous mudstone and dark mudstone.Sedimentary organic matter of the source rock is terrigenous origin,and its kerogen type isⅡ-Ⅲ.Deltaic coals are regarded as good-excellent source rocks.Neritic mudstones develop in the deep of Baiyun Sag,and its kerogen type is mainlyⅡ2-Ⅲ.The organic matter of neritic source rock is mixed origin.Most of them are terrigenous source,and others are from marine algae.The abundance of organic matter of neritic source rocks is fair-high.The forming of hydrocarbon type depends on both kerogen type and geotherm.Gas is mainly enriched in coal delta which has high geothermal maturity,with source kitchens locating in the gentle slope area.Neritic environment with relatively high geothermal maturity can be another gas enriched area,with source kitchen locating in the deep of Baiyun Sag.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2014年第9期1299-1308,共10页
Natural Gas Geoscience
基金
国家"973"项目"南海深水盆地油气资源形成与分布基础性研究"(编号:2009CB219400)
国家科技重大专项"海洋深水区油气勘探关键技术"(编号:2008ZX05025
2011ZX05025)联合资助
关键词
海陆过渡相
二元模式
煤系烃源岩
海相烃源岩
源热共控论
Marine-continental transitional facies
Duality pattern
Coal source rock
Neritic source rock
Maturity
