中文摘要：

阐明鄂尔多斯盆地东胜气田天然气地球化学特征并厘清其天然气成因及来源.基于该气田的6口井及前人已经发表的其它主要气田25口井天然气组分、碳等同位素特征,轻烃组分特征及实际地质背景,对该气田天然气地球化学特征及来源进行了较详细分析,认为东胜气田天然气具有与上古生界其它气田相似的成因,为典型的煤成气;该气田天然气组分、同位素及轻烃特征与其南部苏里格气区存在明显差异,该气田天然气主要来自于其下伏煤系并非来自于南部烃源岩.研究结果表明：东胜气田天然气以烷烃气为主,表现为干气,天然气中甲烷体积分数为93.69%-93.96%,乙烷体积分数为3.57%-3.71%,丙烷体积分数为0.85%-0.92%,丁烷体积分数为0.21%-0.37%;含少量非烃气体CO2和N2;烷烃气碳同位素具有正碳同位素系列,表现为原生特点;C7轻烃化合物表现为甲基环己烷优势,庚烷值及异庚烷值分布区间分别为14.3%-16.0%和1.9%-2.6%,结合碳同位素认为该气田为烃源岩成熟-高成熟过渡带阶段形成的天然气;天然气K1值[K1=（2-甲基己烷＋2,3-二甲基戊烷）/（3-甲基己烷＋2,4-二甲基戊烷）]为1.2.

英文摘要：

Geochemical characteristics, genesis and source rocks of the natural gas in Dongsh- eng gas field, Ordos basin, were discussed in this paper. Data of 6 wells in Dongsheng gas field and 25 wells in other major gas fields of the Ordos basin selected from published researches were collected. On the basis of natural gas composition, isotope and light hydrocarbon analy- sis, combining with the geological background of the study area, natural gas from the Dongsh-eng gas field is found to have the same genesis characteristics with gas in other gas fields of the upper Paleozoic, both of which are typical coal derived gases. Furthermore, obvious differences from Sulige gas field in terms of isotope and light hydrocarbon characteristics indicate gases of the Dongsheng gas field is mainly sourced from the underlying coal seam rather than migration from the south area. Research results show that the Dongsheng gas field is mainly composed of alkane gases, characterized by dry gas. The content of methane, ethane, propane and butane are 93.69%-93.96%, 3.57%-3.71%, 0. 85%-0.92% and 0. 21%-0. 37 % respectively. Also, there is a small amount of non-hydrocarbon gases including CO2 and N2. Alkane gases have positive carbon isotopic series, indicating the primarily sourced feature. C7 light hydrocarbon compounds show dominance of methyl cyclohexane. The distribution intervals of heptane and isoheptane value are 14.3%-16.0% and 1.9%-2.6% respectively. Isotope and light hy- drocarbon characteristics suggest that the gases were generated when the source rocks were in the transition zone of mature to high mature stage. The value of K1, [（2-methylhexane ＋2, 3- dimethyl pentane）/（3-methylhexane ＋2, 4-dimethyl pentane）], is 1.2.