中-上扬子地区下寒武统筇竹寺阶泥页岩差异成气过程分析  

Differential shale gas generation in the Lower Cambrian Qiongzhusi stage in the Middle-Upper Yangtze region

作　　者：何陈诚 陈红汉 肖雪薇 刘秀岩 苏奥 HE Chencheng;CHEN Honghan;XIAO Xuewei;LIU Xiuyan;SU Ao(Wuxi Research Institute of Petroleum Geology,SINOPEC,Wuxi 214126,China;Department of Petroleum Geology,Faculty of Earth Resources,China University of Geoscience(Wuhan),Wuhan 430074,China;School of Geosciences,Yangtze University,Wuhan 430100,China)

机构地区：[1]中国石化石油勘探开发研究院无锡石油地质研究所,江苏无锡214126 [2]中国地质大学(武汉)资源学院石油地质系,湖北武汉430074 [3]长江大学地球科学学院,湖北武汉430100

出　　处：《地学前缘》2023年第3期44-65,共22页Earth Science Frontiers

基　　金：国家重点自然科学基金项目(41730421)。

摘　　要：中上扬子地区下寒武统筇竹寺阶黑色泥页岩具有很高的总有机碳丰度(TOC含量)和生烃潜力而被认为是继上奥陶—下志留统五峰组—龙马溪组页岩气取得突破之后最有潜力的后备勘探层系。其优质烃源岩主要分布于绵阳长宁裂陷槽、湘鄂西裂陷槽、川东黔北深水陆棚相和斜坡盆地相。优质烃源岩层段受沉积相带控制主要分布于筇竹寺阶下部,其TOC具有不对称单峰型分布样式;若受到热水沉积影响,则出现两个TOC峰值;在深水陆棚和斜坡盆地相中上部则发育多个稳定分布的TOC峰值。烃源岩生烃史数值模拟、流体包裹体分析、超低浓度U-Pb定年和页岩气组分与同位素组成成因分析综合结果表明,中上扬子地区下寒武统筇竹寺阶黑色泥页岩存在两种成烃演化模型:(1)以湘鄂西和川东地区为代表,筇竹寺阶烃源岩经历一期生油和原油/干酪根裂解生气过程,加里东晚期(430 Ma)第一次生油,温度95.7~105.2℃;海西晚期(270 Ma)原油开始裂解成气,温度144.7℃左右;燕山早期湿气二次裂解,温度215.3℃;成气时限270~130 Ma;燕山晚期至今(130~0 Ma)页岩气泄漏。(2)以陕南、川南、川中和川西南等地区为代表,筇竹寺阶烃源岩经历了两期生油和原油/干酪根裂解生气过程;第一期生油时间421.5 Ma,温度115.8~128.9℃;第二期生油时间262.4~256.4 Ma,温度137.1~150.0℃;海西晚期((259.4±3.0)Ma)裂陷槽筇竹寺组原油在140℃左右开始裂解成气;燕山中—晚期(175~133 Ma)湿气二次裂解,温度220℃左右;至今由于保存条件较好仍处于聚集和调整过程之中。不同成烃演化模型的出现主要是受区域构造沉积演化控制的。研究区下寒武统筇竹寺阶泥页岩气主要为有机成因的“油型气”,是干酪根裂解气和原油裂解气混合气;黔北地区和渝东南地区内因断层发育,早期生成的页岩气受到地表水和大气的冲洗,使得页岩气组分和同位素The Lower Cambrian Qiongzhusi black shale of the Middle-Upper Yangtze region is considered the best candidate for shale gas exploration after the breakthrough of shale gas development in the Upper Ordovician Wufeng Lower Silurian Longmaxi Formations because of its high total organic carbon(TOC)content and high hydrocarbon-generating potential.The high-quality argillaceous source rock is mainly distributed in the Mianyang Changning trough in Sichuan,the Xiang’exi trough in western Hunan and western Hubei,and the deep-water shelf and slope basins in eastern Sichuan and northern Guizhou,with source-rock intervals mainly developed at the bottom of the troughs and in the middle and upper parts of the deep-water shelf and slope basins,as indicated by TOC profile studies.In this paper,fluid inclusion analysis and super-low-concentration U-Pb dating were performed on collected shale specimens,in combination with comprehensive literature research,to investigate the hydrocarbon generation history in the Lower Cambrian Qiongzhusi stage.In addition,the shale gas composition and isotopic characteristics are discussed.There are two possible modes of shale gas generation and accumulation:(1)Source rock developed in western Hunan,western Hubei and eastern Sichuan experienced a single-stage oil/gas generation process,where oil generation started in the late Caledonian(430 Ma),at temperatures of 95.7105.2℃,followed by crude oil cracking in the late Hercynian(270 Ma),at~144.7℃,wet gas secondary cracking in the early Yanshanian(270130 Ma),at 215.3℃,and shale gas leakage from the late Yanshanian to present(1300 Ma).(2)Source rock from southern Shaanxi and southern,central and southwestern Sichuan experienced a two-stage oil/gas generation process,where the 1st and 2nd stage oil generation occurred at 421.5 Ma and 262.4256.4 Ma,at temperatures of 115.8128.9℃and 137.1150.0℃,respectively;crude oil and/or kerogen cracking in the Mianyang Changning trough started in the Late Hercynian(259.4±3.0 Ma),at~140℃,on average,follow

关 键 词：中上扬子地区 筇竹寺阶 泥质烃源岩 生烃史模拟 页岩气 流体包裹体 U-PB定年 

分 类 号：P618.130.1[天文地球—矿床学]