页岩等温吸附实验及实验误差分析

Shale isothermal adsorption experiment and experimental error analysis

根据容积法对渝东南地区页岩样品进行吸附实验时发现,高温高压下吸附等温线出现异常,甚至产生负吸附现象。通过误差分析认为:容积法的直接测量量的不确定度在计算吸附量时会发生累积传播,使测量结果出现较大误差,引起吸附等温线异常。为此,笔者改进了传统容积法的实验流程,提出"一注多吸"容积法,并对吸附量进行不确定度评定。结果表明:改进的容积法可以显著降低测量结果的不确定度,30℃时,其平均相对误差为9.42%,远小于传统"一注一吸"容积法的50.84%。通过影响不确定度的因素分析发现,压力不确定度对传统容积法的测量结果影响最大,其次是温度;而对于改进的容积法,温度不确定度影响最大,其次是压力,体积、压缩因子的影响很小。随着压力的升高,温度、体积和压缩因子的影响均会逐渐增强。

According to volumetric method,a series of methane adsorption experiments on shale samples from the area of southeast Chongqing were conducted. The adsorption isotherms under the high temperature and high pressure conditions were abnormal,even shown negative adsorption phenomenon. Through the error analysis,it is found that the cumulative propagation of uncertainty in direct measurement using volumetric method when calculating adsorption amounts leads to the big error of measurement results,causing abnormal adsorption isotherm. Thus the process of experiment needs to be improved. A new 'one injection for more adsorption'volumetric method was proposed and the adsorption amount uncertainty was evaluated. It shows that this improvement can significantly reduce the uncertainty: at30 ℃,the average relative deviation of the new method is 9. 42%,far less than that of the traditional'one injection for one adsorption'volumetric method,50. 84%. Through factor analysis,pressure uncertainty has the greatest influence for the traditional method,followed by temperature,while temperature uncertainty has the greatest influence for the new method,followed by pressure,the influence of volume and compressibility factors are small. With the increase of pressure,the effect of temperature,volume and compressibility factor will be gradually enhanced.