含油气盆地中天然气汞含量的主要影响因素

AFFECTING FACTORS OF HG CONTENTS IN GASES IN PETROLIFEROUS BASINS

天然气中汞的含量变化范围较大 (可达 3个数量级 ) ,主要受源岩母质类型的影响 ,但盆地构造背景和深部地质过程的影响也应引起足够的重视。中国东部地区拉张活动型盆地天然气中汞含量相对较高 ;而中部稳定克拉通盆地天然气中汞含量相对较低 ;西北亚稳定型盆地天然气中汞含量介于上述二者之间。天然气中汞含量的这种变化趋势在油型气中表现尤为明显。天然气中汞含量与稀有气体3 He/ 4He比值具有明显的正相关关系 ,表明天然气中一部分汞可能是来自地球深部的挥发分或与深部地质过程有关。

The contents of mercury(Hg) in natural gases can vary from less than 1 to n×10 3 μm/m 3.The main affecting factors are the types of the parent matter,the tectonic background and deep geological process.The content of Hg in coal type gas generated from typeⅢorganic matter is relatively higher.On the contrary,that of oil type gas generated from type Ⅰto Ⅱorganic matter is relatively lower.So the concentration of Hg in natural gas is regarded as geochemical index in determining the source rock of the gas.Research result shows that the concentration of Hg in natural gas is affectde by tectonic movement of basins and deep geological process.The contents of Hg in the natural gases from tensile active basins located in East China is relatively higher;that of natural gases from stable basins in Central China is relatively lower;that of natural gases from sub stale basins in Northwest China is between the above mentioned two.This variation of Hg contents in oil type gas is particularly considerable.The Hg contents in natural gas bear positive correlation with the 3He/ 4He ratio,indicating that Hg may be partly originated from deep earth degassing or be affected by deep geological action.