论鄂尔多斯盆地中部气田混合气的实质  

Feature of mixed gas in central gas field of Ordos basin

作　　者：陈安定[1] 

机构地区：[1]中国石化江苏油田分公司地质科学研究院

出　　处：《石油勘探与开发》2002年第2期33-38,共6页Petroleum Exploration and Development

摘　　要：对鄂尔多斯盆地中部气田气源问题主要有两种不同看法:一种看法认为它是以奥陶系碳酸盐烃源岩来源为主、腐泥气为主的混合气;另一种看法认为它是上古生界煤系气或煤系气为主的混合气。最近,有人提出混合气中的腐泥成分仍来自石炭系。气源问题直接关系到对低丰度碳酸盐烃源岩的评价。本文从介绍烃源岩入手,然后以乙烷碳同位素为主要判断依据,详细剖析了两种来源气体的各项特征。通过典型样品的氢同位素、δ13C2和轻烃异庚烷值指标关系分析,说明腐泥型气只能来自奥陶系,不可能来自石炭系。提出识别混合气的“分段解剖”、“特征转移”及“浓度特征贡献比相关性”原理,指出中部气田混合气的本质是石炭系高成熟腐殖型干气和奥陶系过成熟腐泥型更干的干气所形成的混合气,计算中部气田天然气总量中有大约80％来自奥陶系,解释了轻烃碳同位素资料不能用来说明天然气主成分来源的基本道理。表4图5参7（陈安定摘）There are two different opinions on origin of gases in Ordovician reservoir of the central gas field of Ordos basin: (1) Gases are mainly sourced from Ordovician carbonate source-rock, it is a mixed gas in which sapropelic gas dominates; (2) Gases are mainly sourced from Carboniferous coal-bearing source-rock, it is a mixed gas in which humid gas dominates. Recently it is proposed that sapropelic gas in mixed gas is still sourced from Carboniferous. The opinion on origin of gases is associated with estimating of 'low abundant' carbonate source-rocks. In this paper the nature of two source-rock and two types of gas distinguished mainly by ethane carbon-isotope have been introduced. Based on argon isotope and the relation of iso-heptane value with δ13C2, the sapropelic gas in mixed gas of the central gas field can but come from Ordovician, not Carboniferous. The methods to divide oil-gas into C1-5, C6-12 and C12+ fraction, the phenomenon of 'characteristic transfer' and principle of relation of concentration and feature-contribution should be used for discovering and research mixed gas. It is pointed that gas reservoir in the central gas field was formed by mixing both dry gas from Carboniferous and more dry gas from Ordovician, 80% of gross is sourced from Ordovician carbonates. It is explained why carbon isotopes of C6-12 light hydrocarbon cannot be used to prove gas origin.

关 键 词：鄂尔多斯盆地 大型气田 天然气成因 混合气 碳酸盐烃源岩 

分 类 号：P618.130.2[天文地球—矿床学] TE12[天文地球—地质学]