川南地区须家河组天然气地球化学特征及成藏过程  

Geochemical characteristics and accumulation process of natural gas of Xujiahe Formation in southern Sichuan Basin

作　　者：王鹏 沈忠民[2] 何崇康 陈刚 潘树林 王君泽 WANG Peng;SHEN Zhongmin;HE Chongkang;CHEN Gang;PAN Shulin;WANG Junze(College of Resources and Environmental Engineering,Yibin University,Yibin 644000,Sichuan,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploration,Chengdu University of Technology,Chengdu 610059,China;Department of Oilfield Development,PetroChina Changqing Oilfield Company,Xi’an 710021,China)

机构地区：[1]宜宾学院资源与环境工程学院,四川宜宾644000 [2]油气藏地质及开发工程国家重点实验室(成都理工大学),成都610059 [3]中国石油长庆油田分公司油田开发处,西安710021

出　　处：《岩性油气藏》2017年第5期19-27,共9页Lithologic Reservoirs

基　　金：国家自然科学基金项目"川西坳陷上三叠统须家河组储层水岩相互作用机理研究"(编号:41172119);油气藏地质及开发工程国家重点实验室项目"四川盆地T3-K碎屑岩油气成藏机理和分布规律研究"(编号:国重科研C08);宜宾市科技局重点科技项目"长宁地区页岩气储层特征研究"(编号:2015QD09)联合资助

摘　　要：为探究川南地区须家河组天然气地球化学特征及成藏机理,以天然气地球化学分析数据为基础,对该区天然气地球化学特征、成因、成藏期次及成藏过程进行了分析。结果表明:研究区天然气以烷烃气为主,甲烷体积分数大于80%,重烃体积分数低,天然气干燥系数大于0.85;部分天然气含H2S,这是研究区与四川盆地其他地区须家河组天然气组分特征的最大差异;天然气δ^(13)C_1为-43.17‰^-30.80‰,δ^(13)C_2为-33.81‰^-24.90‰,δ^(13)C_3为-28.65‰^-22.70‰,总体具有正碳同位素系列特征。碳同位素与轻烃分析均证实,研究区须家河组天然气以煤型气为主,同时存在部分油型气;煤型气主要来自须家河组煤系烃源岩,油型气主要来自下伏海相层系。成藏年代分析表明,研究区须家河组天然气主要有3期成藏:晚侏罗世中期—早白垩世,须家河组煤系烃源岩生成的少量煤型气进入须家河组成藏;晚白垩世,须家河组煤系烃源岩大量生成煤型气并进入须家河组成藏,该时期是须家河组天然气的主要成藏期;喜山期,部分下伏油型气经断裂进入须家河组成藏,该阶段的流体充注是研究区出现异常高温包裹体与天然气含H_2S的主要原因。Based on the geochemical analysis data,the characteristics,origin,hydrocarbon accumulation stages and process of natural gas of Xujiahe Formation in southern Sichuan Basin were analyzed.The results show that the drying coefficient of natural gas is greater than0.85,the gas composition is mainly alkane,some contains H2S,which is the most remarkable feature of gas component of Xujiahe Formation in southern Sichuan Basin.Theδ13C1,δ13C2andδ13C3values are-43.17‰to-30.80‰,-33.81‰to-24.90‰and-28.65‰to-22.70‰,respectively,which has the characteristics of positive carbon isotope.The analyses of carbon isotope and light hydrocarbon show that the natural gas is dominated by coal type gas,with some oil type gas existing.The coal type gas is mainly derived from coal-bearing source rocks of Xujiahe Formation,and the oil type gas is mainly derived from underlying marine strata.Base on the hydrocarbon accumulation history,there are mainly three stages of gas accumulation of Xujiahe Formation:(1)From the middle of Late Jurassic to Early Cretaceous,the coal-bearing source rocks of Xujiahe Formation generated a small amount of coal type gas,and then the gas accumulated inXujiahe Formation.(2)During the Late Cretaceous,the coal-bearing source rocks of Xujiahe Formation generated a large amount of coal type gas,which then accumulated in Xujiahe Formation,and this stage is the most important accumulation period.(3)During Himalayan movement,some oil type gas derived from underlying strata and entered reservoir of Xujiahe Formation along the fault,the fluid charging is the origin of abnormal high temperature inclusions and higher H2S content.

关 键 词：天然气成因 成藏期次 成藏过程 须家河组 川南地区 

分 类 号：TE122.113[石油与天然气工程—油气勘探]