摘要
为探讨下扬子区上二叠统龙潭组海陆过渡相页岩地球化学特征及其地质意义,对皖南地区港地1井、昌桥剖面、稻山冲剖面的泥页岩样品系统开展了有机地球化学测试、矿物组成分析、氩离子抛光—扫面电镜观察等工作。结果表明:皖南地区龙潭组泥页岩TOC含量介于0.96%~9.54%之间(平均为5.11%),R_(O)值介于1.23%~1.63%之间(平均为1.41%),处于有利的生气阶段,整体为一套非常好—极好的烃源岩。饱和烃气相色谱图单峰、双峰、多峰均有分布,主峰碳数较为分散,介于nC_(15)—nC_(24)之间,且单个样品低、高碳数饱和烃单体δ^(13)C差值超过了3.5‰,明显高于单一来源饱和烃单体的δ^(13)C变化(<1.6‰),反映龙潭组海陆过渡相泥页岩中的有机质母质具有低等水生生物和高等植物的混源特征,其中龙潭组下部以低等水生生物为主,龙潭组中部和上部以陆源高等植物为主。TOC与TS相关性、Pr/Ph值、Pr/nC_(17)—Ph/nC_(18)图解及黄铁矿形态及粒径,共同指示研究区龙潭组泥页岩形成于贫氧—氧化的水体环境。
In order to find out the organic geochemical characteristics and geological significance of the marinecontinental transitional shale in the Upper Permian Longtan Formation in the Lower Yangtze area,a case study was carried out from one core(Well Gangdi-1)and two different types of outcrops(Daoshanchong outcrop and Changqiao outcrop)for the analyses of organic geochemistry,mineral composition and pyrite morphology.Results show that the Longtan Formation shale in southern Anhui Province belongs to very good to excellent source rock with high total organic carbon(TOC)content ranging from 0.96%to 9.54%(average 5.11%).The vitrinite reflectance(R_(O))is between 1.23%and 1.63%(average 1.41%),demonstrating that the Longtan Formation shale is in a favorable gas generation stage.Moreover,the gas chromatograms(GC)display unimodal,bimodal and multimodal distributions with carbon peak in the range of nC_(15)-nC_(24).The variations of the δ^(13)C values of n-alkanes for the target samples exceeding 3.5‰offset,which is obviously higher than the corresponding value(<1.6‰)of n-alkanes from a single source.All these pieces of information demonstrate that the organic matters in Longtan Formation transitional shale belong to a mixed source of lower aquatic organisms and terrestrial higher plants.To be specific,the organic matters in the Lower Longtan Formation are dominated by lower aquatic organisms,whereas those in the middle and upper Longtan Formation are mainly composed of terrestrial higher plants.Furthermore,the crossplot of TOC vs.TS combined with Pr/Ph ratio,the Pr/nC_(17)-Ph/nC_(18) diagram,and pyrite characteristics together indicate that the Longtan Formation black shale in southern Anhui Province was deposited in a dysoxic-to-oxic water environment.
作者
丁江辉
孙金声
张金川
杨向同
石刚
王如意
黄波
李会丽
DING Jianghui;SUN Jinsheng;ZHANG Jinchuan;YANG Xiangtong;SHI Gang;WANG Ruyi;HUANG Bo;LI Huili(CNPC Engineering Technology R&D Company Limited,Beijing 102206,China;PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China;School of Energy Resources,China University of Geosciences,Beijing 100083,China;Nanjing Center of China Geological Survey,Nanjing 210061,China)
出处
《天然气地球科学》
CAS
CSCD
北大核心
2023年第3期510-524,共15页
Natural Gas Geoscience
基金
国家科技重大专项(编号:2016ZX05034-002-001)
国家自然科学基金项目(编号:41927801)联合资助.
关键词
过渡相页岩
生物标志物
有机质生源
龙潭组
皖南地区
Transitional shale
Biomarkers
Organic matter provenance
Longtan Formation
Southern Anhui Province
作者简介
丁江辉(1990-),男,内蒙古乌兰察布人,博士后,工程师,主要从事非常规油气地质评价研究.E-mail:djhdream2015@163.com.
