鄂尔多斯中部气田下古生界水溶气成因

ORIGIN OF LOWER PALEOZOIC DISSOLVED GASES IN CENTRAL GAS FIELD OF ORDOS

鄂尔多斯中部气田下古生界水溶气以高甲烷含量为特征 ,含有少量重烃和非烃组分 ,基本显示出高成熟过成熟的干气特征 (C1/C1～ 5>0 95 )。该区下古生界水溶气组成存在“东、西差异”(东部区块水溶气的C+2 重烃、苯和甲苯含量较高 ,而西部区块水溶气的C+2 重烃、苯和甲苯含量低或缺失 ) ,揭示了东部、西部区块水溶气的来源是不同的。东部区块水溶气具有上古生界煤成气和下古生界油型气的混合贡献 ,西部区块水溶气主要来自下古生界的油型气。

Characterized by higher contents of methane , the lower Paleozoic dissolved gases in central gas field in Erdos have a little amount of heavy hydrocarbon and non- hydrocarbon compositions basically indicating a dry gas feature of high-over maturation(C 1/C 1-5>0.95). Differences between 'East block & West block' in compositions of the lower Paleozoic dissolved gases(high contents of heavy hydrocarbon C 2+,benzene,toluene in compositions of dissolved gas in the east block while in the west block above compositions are either very low or absent) reveal that east and west block dissolved gases come from different sources. Dissolved gases from the east block are combinations of coal-formed gas in the upper Paleozoic and oil-type gas in the lower Paleozoic, whereas dissolved gases from the west block mainly come from oil-type gas in the lower Paleozoic.