珠-坳陷湖盆古环境恢复与优质烃源岩发育模式  

Environmental reconstruction for the paleo-lake of ZhuⅠdepression and the depositional model for high-quality source rocks

作　　者：谢世文 王宇辰 舒誉 吴宇翔 张丽丽 刘冬青 王菲 XIE Shiwen;WANG Yuchen;SHU Yu;WU Yuxiang;ZHANG Lili;LIU Dongqing;WANG Fei(Shenzhen Branch of CNOOC Ltd.,Shenzhen 518067,China)

机构地区：[1]中海石油(中国)有限公司深圳分公司,深圳518067

出　　处：《海洋地质与第四纪地质》2022年第1期159-169,共11页Marine Geology & Quaternary Geology

基　　金：国家科技重大专项“珠一坳陷古湖泊演化与富烃凹陷优选”(2016ZX05024-002-008);海油重大生产科研项目“珠江口盆地(东部)浅水区古近系油气成藏条件及勘探突破方向”(SCKY-2020-SZ-21)。

摘　　要：珠-坳陷古近纪陆相湖盆发育优质烃源岩,通过对文昌组、恩平组泥岩系统取样,进行常量、微量元素、同位素含量等分析,优选出对环境敏感的元素与元素比值,系统分析了珠-坳陷烃源岩形成时的古环境,包括古盐度、古水深、氧化还原条件、古气候及古水体的封闭性,并建立了有机碳与环境敏感元素比值的定量关系。开展优质烃源岩发育的水化学性质研究,明确研究区优质烃源岩形成演化所具有的古环境特征,最终探讨了文昌组优质烃源岩的发育模式。研究结果表明,珠-坳陷(除韩江凹陷无样本点)文昌期温暖略干气候条件下,湖盆水体主要为淡水-微咸水,发育中-深湖相,整体表现为开放-半封闭、还原—强还原的环境,极利于有机质的保存和优质烃源岩的发育,各凹陷古环境差异不大。烃源岩质量与咸度、水深、还原条件呈正相关,共同影响了优质烃源岩的发育。总之,温暖略干、微咸、深水及强还原、开放-半封闭环境共同控制了珠-坳陷优质烃源岩的发育。High-quality source rocks are well occurred in the Paleogene lacustrine deposits of the ZhuⅠdepression. Element geochemistry and isotope analysis for mudstone cuttings from the Wenchang Formation and Enping Formation is carried out by this paper in order to optimize the study of element content and elements ratio which are sensitive to paleoenvironment reconstruction. Paleoenvironmental parameters for the source rocks in ZhuⅠdepression are systematically analyzed, which include paleosalinity, paleowater depth, redox conditions, paleoclimate,degree of environmental closure and so on. Upon the basis, we revealed the quantitative relationship between the organic matter content and the ratio of environmental sensitive elements, and established the depositional model for the high-quality source rocks in the Wenchang Formation.The results show that under the warm and slightly dry climate conditions during the Wenchang period, the ZhuⅠdepression was a medium to deep and open to semiclosed lake dominated by fresh water and brackish water under a reductive or strongly reductive environment, which was conducive to the preservation of organic matter and the formation of high-quality source rocks. The quality of source rocks is positively related to salinity, water depth and reduction conditions. In conclusion, in a warm and slightly dry lake with slightly salty deep water as the ZhuⅠdepression, the strong reduction and open-semiclosed environment jointly control the development of high-quality source rocks in ZhuⅠdepression.

关 键 词：优质烃源岩 发育模式 古环境 古湖泊 无机地球化学 珠一坳陷 

分 类 号：P736[天文地球—海洋地质]