鄂尔多斯盆地南部页岩气地化特征及成因

对鄂尔多斯盆地南部页岩气井进行井口生产气取样、岩心解析气取样，进行天然气组分分析和碳氢同位素测试。明确了延长组长7段、长9段天然气组分特征，碳氢同位素特征，结合天然气分析相关图版探讨了天然气的成因类型及来源。结果表明，研究区天然气为有机成因气，干燥系数小，含有一定量的重烃成分，属于典型的湿气，排除了生物气及高温裂解气的可能。乙烷碳同位素特征及天然气类型图版分析表明该区页岩气为典型的油型气。长7段页岩气碳同位素组成序列整体为δ13 C1﹤δ13 C2﹤δ13 C3﹤δ13 C4，为正常序列，少量样品显示同位素反转，长9段长7段页岩气碳同位素组成序列为δ13 C1﹤δ13 C2﹤δ13 C3﹤δ13 C4。认为长7段页岩气来自本层段张家滩页岩，但局部地区存在运移通道，发生了天然气混合，长9段页岩气来自于长9段李家畔页岩。

Geochemical Characteristics and Genesis of Shale Gas in the South of Ordos Basin

Shale gas samples from production and core desorption were collected in the south of Ordos basin. Com-position and isotopes of carbon and hydrogen were tested and analyzed. Combining with diagram of natural gas type,we discussed the shale gas type and its origin in the chang7 and chang9 member. The result showed as fol-lows：the natural gas of the two members was organic origin. With small dry coefficient and a certain amount of heavy hydrocarbon,the gases were typical wet gas,not biogenic and thermal -cracking. 13C of ethane showed that the natural gases were typical organic genetic oil type gas. In general,the isotope of chang7 shale gas carbon was characterized by δ13 C1 ﹤δ13 C2 ﹤δ13 C3 ﹤δ13 C4 ,while small amount of samples showed reversal sequence. The iso-tope of chang9 shale gas carbon was characterized by δ13 C1 ﹤δ13 C2 ﹤δ13 C3 ﹤δ13 C4 . We could draw the conclusion that the origin of chang7 shale gas was Zhangjiatan shale,in some part of which migration pathway developed. Free gas may come through the pathway and mixed. The chang9 shale gas came from Lijiapan shale.