南盘江坳陷天然气地球化学特征及新认识  

GEOCHEMICAL BEHAVIORS OF NATURAL GAS IN NANPANJIANG DEPRESSION AND NEW COGNITION

作　　者：赵孟军[1] 张水昌[1] 赵陵[2] 刘培初[2] 

机构地区：[1]中国石油勘探开发研究院 [2]中石化南方勘探开发分公司研究院贵州科研所

出　　处：《天然气工业》2007年第2期23-28,共6页Natural Gas Industry

基　　金：国家"十五"重点科技攻关项目(编号:2001BA605A-06);中国石化集团公司项目(编号:P00045)部分研究成果

摘　　要：南盘江坳陷是目前油气勘探程度不高的地区,如何解释秧1井的天然气出现的高含N2和高含CO2两种情况,以及如何认识南盘江坳陷天然气的来源一直是人们关注的问题。为此,在讨论南盘江坳陷天然气(显示)地球化学特征基础上,得出了以下认识:①秧1井的天然气显示主要为高N2和高CO2两类非烃天然气为主,结合南盘江区域地质上气显示以高N2天然气为主的事实,认为高N2天然气是南盘江坳陷具有地质意义的天然气;②与前人观点不同的是,认为该地区天然气主要为中泥盆统泥质烃源岩的“晚期阶段聚气”造成的——尽管南盘江古油藏沥青为原油裂解后形成的焦沥青,但研究认为该地区高N2天然气不是原油裂解气,也不是源自上二叠统龙潭组的煤型气,而主要是源自中泥盆统泥质烃源岩的干酪根裂解气;同时强调中泥盆统泥质烃源岩的“晚期阶段聚气”是造成该地区天然气高N2、烃类组分碳同位素值偏重的主要原因。The less explored Nanpanjiang depression is a frontier worthy of further study.Based on a discussion of the geochemical behaviors of natural gas(show) in the study area,the followings are concluded.①The gas show in Well Yang-1 is dominated by nonhydrocarbon natural gas with high contents of N2 and CO2.Considering that the gas show in Nanpanjiang area is dominated by natural gas with high content of N2 from the perspective of regional geology,natural gas with high N2 content is believed to have geologic significance in Nanpanjiang depression.②The natural gas in the study area is resulted from 'gas accumulation at the late stage' generated by the Middle Devonian shaly source rocks.This is totally different from that of the previous understandings.Although the bitumen in the fossil oil pools in Nanpanjiang depression is pyrobitumen resulted from crude oil cracking,our study shows that the natural gas with high content of N2 in the study area is mainly kerogen-cracked gas generated by the Middle Devonian shaly source rocks,rather than oil-cracked gas or coal-related gas sourced from the Upper Permian Longtan Formation.Meanwhile,'gas accumulation at the late stage' generated from the Middle Devonian shaly source rocks is highlighted as the main cause of the high content of N2 and the relatively large carbon isotope value of hydrocarbon components in the natural gas of the study area.The new cognition of the source and genesis of natural gas in Nanpanjiang depression have directly influenced the analysis and evaluation of the hydrocarbon accumulation history of the fossil oil pools in the study area

关 键 词：南盘江坳陷 天然气 地球化学 组成 同位素 天然气成因 中泥盆世 泥质烃源岩 

分 类 号：P618.13[天文地球—矿床学]