摘要
作为川南志留系页岩气重点拓展区,宁西地区经历多次断裂活动,龙一段普遍发育方解石脉体,同时由于热演化程度极高,出现石墨化现象,致使页岩气富集规律不明.本次研究以区内重点探井——宁西202井的龙一段为研究对象,通过系统岩心描述、薄片镜下观察、阴极发光、激光拉曼光谱和显微测温等实验分析,进行了古温压恢复研究.研究表明:龙一段主体分布高角度方解石脉体(A类),局部发育顺层脉体(B类).A类脉体中主要发育高密度甲烷包裹体、部分样品出现特殊的沥青包裹体.沥青包裹体中沥青的拉曼R(o RmcRo)为3.52%~4.16%,处于过成熟至石墨化阶段.甲烷拉曼散射峰介于2910.7112~2912.4951 cm^(‒1),均一温度介于-99.8~-96.3℃.通过拉曼参数位移法和显微测温法分析得出的密度值分别介于0.2536~0.3445 g/cm^(3)和0.2916~0.3032 g/cm^(3),呈典型的高密度特征.综上,高密度甲烷包裹体可能捕获于燕山构造运动抬升初期,处于超压状态,指示页岩系统封闭性较好,有利于页岩气的富集.
As a key exploration area for Silurian shale gas in southern Sichuan basin,Ningxi area experienced multiple fracture activities.Calcite veins are generally developed in the Longmaxi Member Ⅰ.At the same time,graphitization occurs due to the extremely high degree of thermal evolution,resulting in shale gas enrichment pattern which remains unknown.This paper presents an estimation of paleotemperatures and paleopressures of the key exploration well in the region-the Well Ningxi 202 of Longmaxi Member Ⅰ,through integrated analyses on systematic core description,thin section microscopic observation,cathodoluminescence observation,laser Raman spectroscopy,and microscopic temperature measurement.Results show that:High-angle calcite veins(type A)are distributed in the main body of the Longmaxi Member Ⅰ,and bedding veins(type B)are locally developed.Methane inclusions are mainly developed in Type A veins,and some samples show special bitumen inclusions.The RmcRo of bitumen in bitumen inclusions are 3.52%-4.16%,indicating that they are in the overmature to graphitization.The methane Raman scattering peak is between 2910.7112-2912.4951 cm^(‒1),with the homogenization temperature between-99.8 to-96.3℃.The density obtained by Raman parameter displacement and microscopic temperature measurement ranged from 0.2536-0.3445 g/cm^(3) and 0.2916-0.3032 g/cm^(3),showing typical high-density characteristics.In conclusion,the high density methane inclusions may be trapped in the early stage of Yanshan tectonic movement and in overpressure state,indicating that the shale system has good sealing property and is conducive to shale gas enrichment.
作者
柳卓
郝芳
刘鑫
吴伟
全力
田金强
冯子齐
Liu Zhuo;Hao Fang;Liu Xin;Wu Wei;Quan Li;Tian Jinqiang;Feng Ziqi(School of Geosciences,China University of Petroleum,Qingdao 266580,China;Key Laboratory of Deep Oil and Gas,China University of Petroleum,Qingdao 266580,China;PetroChina Southwest Oil&Gasfield Company,Chengdu 610051,China;Shale Gas Research Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu 610051,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2021年第9期3157-3171,共15页
Earth Science
基金
国家自然科学重大基金项目⁃04课题(No.41690134)
国家自然科学面上基金项目(No.42072167).
关键词
宁西地区
龙一段
方解石脉体
高密度甲烷包裹体
沥青包裹体
石油地质
Ningxi area
Longmaxi Member I
calcite vein
high density methane inclusions
bitumen inclusions
petroleum geology