摘要
鄂西宜昌斜坡是四川盆地外寒武系页岩气勘探新区,与盆内勘探不同,宜昌斜坡发育于黄陵隆起之上,页岩气富集地质条件研究薄弱。利用最新的地震、钻探和测试资料,分析认为研究区沉积、构造演化具有特殊性,先后经历了印支期隆起雏形、燕山期快速抬升剥蚀、喜马拉雅期充填改造3个关键沉积—构造阶段。宜昌地区相对稳定的构造条件,对页岩气富集成藏有4个方面的影响:①桐湾运动末期形成早寒武世隆、凹相间的古地理格局直接影响宜昌地区寒武系水井沱组富有机质页岩的展布,对页岩气的形成分布有重要的源控作用,水井沱组页岩含气量与TOC含量具有较好正相关性,指示有机质丰度是影响页岩气富集的关键因素。②印支期开始隆升、燕山期迅速隆升的黄陵岩体控制宜昌斜坡区构造沉降,使下古生界页岩层埋藏深度适中、抬升早、有机质热成熟度相对低,在中、下扬子区下古生界页岩过成熟演化背景下尤为特殊。适宜的热演化条件下,水井沱组页岩有机质纳米孔发育,构成页岩气重要储集空间。③受黄陵隆起的砥柱作用,宜昌斜坡在南方中、新生代多期次强烈构造活动中免遭构造破坏和强改造,表现为隆升剥蚀为主、局限断裂活动为辅、整体构造变形弱的特点,构造保存条件较临区优越,加之页岩渗透性极低,使宜昌单斜构造上水井沱组页岩气仍有效保存,是当前该区勘探的主体。④寒武系页岩裂缝发育,早期构造作用形成的高角度裂缝、晚期由于重力顺层滑脱作用形成的低角度剪切缝,共同构成页岩气运移、储集的重要空间。宜昌地区页岩气的勘探突破表明,古隆起、古斜坡等稳定古构造周缘是中下扬子区古生界页岩气勘探的潜在有利区。
The Yichang slope,located in western Hubei Province,is a new area for shale gas exploration of the Cambrian strata outside the Sichuan Basin.Few studies have focused on the shale gas enrichment characteristics of the Yichang slope,which developed on the ancient Huangling anticline.Based on the analysis of sedimenta⁃ry,structural and the latest seismic and drilling data,as well as laboratory test,the sedimentary,tectonic and hydrocarbon accumulation characteristics are analyzed.Compared to other region of the Middle Yangtze,it is conformed that the study area has experienced three important key tectonic stages,namely the embryonic uplift in the Indosinian Period,the rapid uplift and denudation in the Yanshan Period,and the filling and reconstruc⁃tion in the Himalayan Period,respectively.The relatively stable tectonic conditions in Yichang area have impor⁃tant influences on shale gas accumulation:(1)At the end of the Tongwan tectonic movement,the paleogeo⁃graphic pattern of early Cambrian had a direct influence on the distribution of organic shale in Yichang area,and played an important role in controlling the formation and distribution of shale gas.A positive correlation between gas content and TOC content indicate that the abundance of organic matter is the key factor influencing shale gas enrichment.(2)The Huangling anticline,which began to rise in the Indosinian tectonic movement and rose rap⁃idly in the Yanshan movement,controlled the structural subsidence of the Yichang area.The Lower Paleozoic shale strata is characterized by suitable burial depth,earlier tectonic uplifting than the west Hubei area.This rel⁃atively lower thermal maturity of the organic matters in the Sinian-Early Paleozoic shale is particularly special among the high maturity background in the south China.Organic nanopores formed an important shale gas stor⁃age space.(3)This ancient anticline played an important role in protecting the Yichang slope from suffering structural alteration and destruction during the multi-stage stro
作者
罗胜元
陈孝红
岳勇
李培军
蔡全升
杨睿之
LUO Sheng-yuan;CHEN Xiao-hong;YUE Yong;LI Pei-jun;CAI Quan-sheng;YANG Rui-zhi(Wuhan Center of China Geological Survey,Wuhan 430205,China;Wuhan Zondy Cyber-Tech co.,Ltd.,Wuhan 430074.China)
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2020年第8期1052-1068,共17页
Natural Gas Geoscience
基金
国家科技重大专项“中扬子高演化页岩气赋存机理与富集规律研究”(编号:2016ZX05034001-002)
中国地质调查局项目“宜昌斜坡页岩气有利区战略调查”(编号:DD20179615)联合资助.
关键词
页岩气
古隆起
构造演化
下寒武统水井沱组
宜昌斜坡
鄂西地区
Shale gas
Uplift
Hydrocarbon accumulation
The Lower Cambrian Shuijingtuo Formation
Yichang slope
Western Hubei
