川东卧新双地区天然气特征及上三叠统须家河组天然气来源  

Analyses of features and source of natural gas in the Upper Triassic Xujiahe Formation,Woxinshuang area,eastern Sichuan Basin

作　　者：林世国[1] 王昌勇[2] 易士威[1] 高阳[1] 李明鹏[1] 李世宁[3] 李爽[3] 

机构地区：[1]中国石油勘探开发研究院天然气地质研究所,河北廊坊065007 [2]成都理工大学沉积地质研究院油气藏地质及开发工程国家重点实验室,四川成都610059 [3]中国石油西南油气田分公司重庆气矿,重庆400021

出　　处：《石油与天然气地质》2017年第5期913-921,共9页Oil & Gas Geology

基　　金：国家科技重大专项(2016ZX05007)

摘　　要：天然气来源分析是一个重要的石油地质问题,直接关系到勘探决策。四川盆地川东地区须家河组勘探和开发相对滞后,基础地质研究的欠缺导致卧新双地区须家河组天然气的来源一直存在争议。天然气组分及碳同位素分析结果表明:卧新双地区须家河组天然气具有甲烷含量较低、重烃含量较高、干燥系数较低等特点;天然气中甲烷碳同位素值δ^(13)C_1<-40‰,具有δ^(13)C_3>δ^(13)C_2>δ^(13)C_1的特征;须家河组天然气为干酪根初次裂解的陆相油型气和混合气;须家河组天然气目前主要处于成熟-高成熟的湿气阶段。卧新双地区须家河组暗色泥岩较为发育,有机地球化学分析结果表明:须家河组泥岩主要以Ⅱ1和Ⅱ2型干酪根为主,具有较高的有机碳含量和氯仿沥青"A"含量,总体具有较好的生烃能力,泥岩中有机质处于成熟-高成熟的湿气阶段。卧新双地区须家河组天然气成熟度与烃源岩成熟度相当,结合须家河组天然气组分特征、同位素特征及成因类型等与下伏石炭系、茅口组、龙潭组、长兴组、飞仙关组、嘉陵江组及雷口坡组天然气存在明显区别,推测该区须家河组天然气主要为自生气。Source analysis of natural gas is one of the geological challenges involving exploration decision-making.Exploration and development of the Xuejiahe Formation in eastern Sichuan Basin is relatively lagged behind and the source of natural gas there is still a mystery due to the fact of lacking basic geological study.Gas composition and isotope analyses show that the natural gas from the Xuejiahe Formation of Woxinshuang area features in low content of methane,high content of heavy hydrocarbon,and lower aridity coefficient.The carbon isotope values were measured to be δ^13C1-40‰ and δ^13C3〉δ^13C2〉δ^13C1.The gas from the Xuejiahe Formation is continental oil-type gas or mixed gas from primary cracking of kerogen and is now at the mature and highly mature wet gas stage.The Formation in the area has well developed dark mudstone.Organic geochemical analyses indicate a kerogen Ⅰ and Ⅱ dominated mudstone with high content of organic carbon and chloroform bitumen ＂A＂,indicating relatively high hydrocarbon generation potential.The organic matter of the mudstone was measured to be at the mature to highly mature wet gas stage.Gas from the Formation in the area has a maturity as same as that of source rocks.Combining this understanding with the gas composition and isotope analyses results,we suggest that the gas in the Xuejiahe Formation is mostly autogeneous gas and differs utterly from thatin the underlying Carboniferous,the Maokou,the Longtan,the Changxing,the Feixianguan,the Jialinjiang and the Leikoupo Formations.

关 键 词：天然气 须家河组 上三叠统 卧新双地区 川东地区 

分 类 号：TE121.1[石油与天然气工程—油气勘探]