塔中地区天然气氦、氩同位素地球化学特征

氦同位素组成对大构造背景下的构造演化特征具有指示性，而对同一盆地内部较小区块的构造演化差异特征指示性不明显。塔中地区天然气的3^He／4^He组成具有典型壳源天然气特征，和塔里木盆地整体大地构造背景一致。与中国其他油气区寒武系一奥陶系天然气氩同位素组成相比，塔中地区天然气氩同位素。40^Ar／36^Ar组成有一定特殊性。原因是该区中、下寒武统和中、上奥陶统烃源岩中氩的母体元素钾的丰度较低。利用元素衰变原理估算塔中地区天然气40^Ar的母体元素钾的百分含量表明，塔中地区中、下寒武统和中、上奥陶统烃源岩中的泥质和泥质条带对该区天然气具有重要贡献。图2表3参17

Helium and argon isotopic compositions of natural gases in the Tazhong area, Tarim Basin

Helium isotopic compositions in natural gases have a good relationship with geology tectonic background,which indicate the features of tectonic evolvement in a great region but don't work for a small region in the same basin.The ~(3)He/(~4He) ratio of natural gas in the Tazhong area,Tarim Basin,has typical crust-source characteristics,and is consistent with the tectonic background in the basin.The ~(40)Ar/~(36)Ar ratio of the gases in the Tazhong area is different from that in other basins with Cambrian-Ordovician source rocks,which could be caused by the low potassium abundance in Cambrian-Ordovician source rock in the Tazhong area.The calculation of potassium abundance indicates that the argillite and argillaceous stripe in Cambrian-Ordovician source rocks make significant contribution to natural gases in the study area.