四川盆地下侏罗统页岩吸附扩散动态实验研究

Experimental study of dynamic gas adsorption and diffusion process of lower silurian shale gas reservoir in Sichuan Basin

针对气体在页岩中的吸附扩散过程,设计并搭建页岩气运移机理研究装置,对甲烷吸附扩散动态过程进行描述。通过等温吸附实验、吸附扩散动态实验和液氮吸附实验,验证了该实验方法的可靠性,分析了不同样品的性质差异,并对页岩气吸附扩散动态过程给出准确描述。实验结果表明：JY-2样品的饱和吸附量约为JY-1样品的3倍,二者分别为3.2、1.1mL/g;压力影响气体的吸附扩散过程,压力越高,平衡时间越短,运移速率越快;页岩样品微孔分布广泛,1~30nm范围内的孔径主要分布在3~5nm;JY-1与JY-2样品的TOC质量分数分别为1.7%和3.4%,对应比表面积分别为2.57m2/g和22.95m2/g;根据实验结果建立页岩气动态吸附扩散数学模型,可进行不同压力下的气体生产动态预测。通过与已有模型进行分析对比,证明所提出的实验方法可靠,所建立的数学模型误差为1.44%。为现场生产动态预测及生产方案制定奠定了实验基础并提供理论探讨的参数。

For investigating the process of methane adsorption-diffusion process,a new apparatus was designed and tests were conducted for shale samples from Lower Sichuan Basin.By comparing the results from the apparatus presented in this paper and from the adsorption isotherm,the accuracy is guaranteed.Specific surface area and distribution of pore diameter were studied by the results of low temperature nitrogen adsorption method.Results show that：the saturated adsorbed gas content of JY-2is three times higher than JY-1,which are 3.2mL/g and 1.1mL/g,respectively.Pressure has an obvious effect on the gas transport process：the higher the pressure,the faster the gas moved and the shorter the time needed for obtaining equilibration.The main pore diameter for two shale samples are between 3to 5nm in the range of 1to 30 nm.The shale sample of JY-1has the BET specific surface area of 2.57m2/g and total organic carbon（TOC）of 1.7%,while the BET specific surface area and TOC of JY-2are 22.95 m2/g and 3.4%.Based on the experimental results,a mathematical model was obtained to describe this dynamic process of gas moving in shale matrix.Compared with another model published in paper,the error for the model is 1.44%.This study could provide some basic and lab supports for the prediction of gas production in filed and deriving mathematical model to describe the whole gas migration process for shale reservoir.