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萨克蒙托盆地天然气中氦的同位素比值(~3He/~4He≈0.11R_A～2.75R_4)研究表明,该盆地所产天然气部分具有幔源的特征,即1～34％的氦是地幔来源的。同时,~3He/~4He比值与CH_4/~4He比值之间的回归方程,提供了地壳和岩浆末端层之间的二元组分混合的证据。将该回归方程外推,使CH_4/~4He=0,则可得到一个3.84R_A的岩浆末端层的~3He/~4He比值,即相当于一半的典型地幔氦的同位素比值。这说明岩浆末端层实际可能代表的是一个地幔和地壳氦的混合层。由这种二元组分混合层来源的气体,可用纯甲烷、放射性成因的~4He,或~3He/~4He≈06R_A—1.0R_A的高N_2—He气体的加入所解释。岩浆末端层的CH_4/~3He比值变化很大(0～3×10~9),且人类是无法改变的。因此,萨克蒙托盆地某些气田中相当一部分甲烷可能是地球深部来源的。然而,具有最高~3He/~4He比值(2.75R_A)的气田(穆恩本德气田)是与潜伏的上新统-更新统侵入岩相关的,因为这些侵入体上拱沉积岩层而形成了烃类聚集的圈闭。这些气田中的甲烷可能是通过入侵岩体向沉积物迅速传递热能而使有机质热解形成的。此外,盆地西部气田中的甲烷表现出深源沉积物形成运移的特征,但局部地区甲烷可能是由微生物作用形成的。
The isotope ratio of helium (~ 3He / ~ 4He≈0.11R_A ~ 2.75R_4) in the natural gas of the Sacmonte Basin shows that the natural gas produced in this basin has the characteristic of mantle, that is, 1 ~ 34% of the helium is derived from the mantle . Meanwhile, the regression equation between the ~ 3He / ~ 4He ratio and the CH_4 / ~ 4He ratio provides evidence of binary component mixing between the crust and the magma tip layer. Extrapolating the regression equation such that CH_4 / ~ 4He = 0 yields a ~ 3He / ~ 4He ratio for a 3.84R_A magmatic tip, which is equivalent to half the isotopic ratio of a typical mantle helium. This shows that the magma tip layer may actually represent a mixed layer of mantle and crustal helium. The gas originating from this binary component mixed layer can be explained by the addition of pure methane, ~4He of radiogenic origin, or high N 2 -He gas of ~ 3He / ~ 4He ~ 06R_A-1.0R_A. The CH_4 / ~ 3He ratio of the magma tip layer varies greatly (0 ~ 3 × 10 ~ 9), and human beings can not be changed. As a result, a significant portion of methane in some of the Saccmonto Basin gas fields may be of deep Earth origin. However, the gas field (Muenbend gas field) with the highest (~ 2.75R_A) ratio (2.75R_A) is associated with the latent Pliocene-Pleistocene intrusive rocks because these intrusions have formed the hydrocarbon Class gathered traps. Methane in these fields may be formed by pyrolysis of organic matter by rapidly transferring thermal energy to the sediment through the intrusion of rock mass. In addition, the methane in the western gas field of the basin shows the formation and migration of deep-source sediments. However, the methane in some areas may be formed by microorganisms.