塔里木盆地塔中地区天然气气源对比

Gas-Source Correlation in the Tazhong Region,Tarim Basin.

塔里木盆地塔中地区的天然气碳同位素值与其他地区相比普遍偏低 ,用常规的气源对比方法难以确定其母质来源。选择苯、甲苯、甲基环己烷碳同位素作为有效的气源对比新指标 ,同时应用天然气生物标志物、天然气的δ13 C1—δ13 C4和实际地质资料进行气源综合对比 ,认为 :塔中主垒带上的天然气主要来源于寒武系—下奥陶统烃源岩 ,部分为中、上奥陶统与下奥陶统的混合气 ;塔中北斜坡的天然气主要来源于中、上奥陶统 ,部分来源于寒武系—下奥陶统烃源岩。对塔里木盆地相关气源岩进行热模拟实验 ,建立了Ro 与δ13 C1回归方程 ,应用该方程确定的塔中地区天然气成熟度为 :塔中主垒带上天然气的Ro 值约为 1 .4% ,塔中北斜坡的天然气Ro 值约为 1 .1 % ,烃源区均为塔中地区。图 3表 2参 4(李剑摘 )

Many newly discovered natural gases present lower carbon isotope ratio of CH 4 in the center of Tarim basin.They are different from other natural gases.Selection new indexes for Gas Source Correlation is the first step of this article.Benzene,toluene and methylcyclohexane are selected to be as new indexes in many experiments.They are used in this article to probe the source rock of natural gases in the center of Tarim basin combined with biomarks of natural gas and δ 13C 1～ δ 13C 4.The conclusions are:Natural gases distributed in Tazhong major host belts come chiefly from the Cambrian Lower Ordovician,a few of them from the Middle Upper Ordovician.Natural gases distributed in the north slope of Tazhong uplift come chiefly from the Middle Uupper Ordovician,a few of them from the Cambrian Lower Ordovician.Related source rocks in Tarim basin are selected to do thermal simulation and R o～ δ 13C 1 are established at the end of this article.The maturity of natural gas are calculated from R o～ δ 13C 1 relational expression.The calculation results are: R o of natural gases distributed in Tazhong major host belts is 1.4%, R o of natural gases distributed in the north slope of Tazhong uplift is 1.1%.The source rocks of natural gases are distributed in the center of Tarim basin.