利用氦气标定空余体积计算方法的推导及应用

Derivation and application of the calculated methods by helium calibration void volume

页岩气和煤层气是中国非常重要的非常规天然气资源,在对其资源量评价中需要用到等温饱和吸附量参数.该参数需要通过吸附实验建立等温吸附曲线来确定.按照目前吸附实验装置的特点,可将目前吸附仪分为称重仪和测压仪,这两种吸附仪的测试方法分别称为称重法和测压法.无论是称重法或是测压法,当称重法的测试桶和测压法的样品室装入岩样之后,都有一个空余体积需要标定,方能计算其中自由甲烷的摩尔量.空余体积内氦气的摩尔量与岩样吸附甲烷的摩尔量之和等于在某一稳定压力下注入甲烷的总摩尔量,因此,准确地标定空余体积是非常重要的.由于氦气物理性质稳定,不与岩样发生吸附作用,因此,通常采用氦气作为标定空余体积的介质,基于自由状态方程和仪器原理,分别建立称重法和测压法利用氦气标定空余体积的计算方法.实例应用对比结果表明,新建方法是正确有效的.

The shale gas and coalbed methane are very important unconventional natural gas resources in China.The iso⁃thermal adsorption parameters are used in resource evaluation.The determination of the parameters needs to be solved by setting up isothermal adsorption curve through the adsorption experiments.According to the characteristics of the adsorp⁃tion experimental device,the current adsorption instruments can be divided into weighing instrument and pressure testing instrument.When a rock sample is loaded into a sample cell or test barrel,the void volume needs to be calibrated before calculating the molar amount of free methane in them,either by pressure testing or by weighing method.The sum of the mo⁃lality of methane in the void volume and the molality of methane absorbed from the rock sample is equal to the total molality of methane injected at a certain stable pressure.Therefore,it is very important to accurately calibrate the void volume size.As helium(He)is stable in physical properties and does not adsorb with rock samples,helium gas is usually used as the me⁃dium to calibrate the volume of free space.Based on free state equations and instrumental principles,this paper provides the weighing method and pressure testing method to calibrate the void volume by using He.Application of an example indi⁃cates that the method presented in the paper is effective.