CH4-H2O体系流体包裹体均一过程激光拉曼光谱定量分析

对南黄海盆地二叠纪地层中某石英脉中的CH4-H2O体系流体包裹体均一过程进行了激光拉曼光谱定量分析。利用甲烷与水的拉曼峰面积比值计算不同温度下流体包裹体中水溶液相中甲烷的浓度,除了在100℃附近出现最小值,随温度增加甲烷浓度呈指数增大。包裹体在214℃完全均一,均一时甲烷的浓度为0·1347mol/L。同时利用甲烷的拉曼特征对流体包裹体均一过程的内压变化作了分析。压力变化可以分为三个区间:19~100℃,随温度升高压力增大;100~150℃压力随温度升高减小;150℃之后压力迅速增大。均一温度下的内压为21·92MPa。流体包裹体内压的变化主要是由甲烷溶解行为和封闭体系的热力学特征决定的。实验表明激光拉曼光技术可以作为定量分析含甲烷流体包裹体的一种有效方法。

Quantitatively analyzing the homogenization process of CH4-H2O fluid inclusion by laser Raman spectroscopy

We have quantitatively analyzed the homogenization process of CH_4-H_2O fluid inclusion from a Permian quartz vein in the South Yellow Basin by laser Raman spectroscopy. Methane concentrations in the liquid aqueous phase of the examined fluid inclusion were computed from the ratios of CH_4 area / H_2O area at different temperatures. The methane concentration increases exponentially with increasing temperature, except for a minimum at 100 ℃. The concentration of methane is 0.134 7 mol/L at 214 ℃ when the fluid inclusion homogenized. We have also obtained the internal pressure of the fluid inclusion at different temperature. The variation of internal pressure behavior was observed within three temperature-controlled intervals. The internal pressure increases with increasing temperature between 19~100 ℃, then decreases between 100 ℃ and 150 ℃, but increases rapidly once temperature reaches 150 ℃. These changes of internal pressure may be caused by the dissolution behavior of methane and by the thermodynamic characteristics of the closed bearing methane system. Therefore, this study shows that laser Raman spectroscopy can be regarded as an effective method for analyzing quantitatively methane bearing fluid inclusions.