等温吸附曲线在四川威远页岩气区块的应用与表征

Application and Characterization of Isothermal Adsorption Curve in Weiyuan Shale Gas Blockin Sichuan

基于四川威远页岩储层条件,在90℃下开展了对四川威远区块页岩气等温吸附实验,分析了影响吸附的主要因素。结合生产实际阐述了吸附气在生产中的变化规律。同时应用吸附势理论,建立不同深度下的吸附模型,对不同深度下的吸附气量进行了预测。研究表明,当地层压力较高时,解吸附气体较少,主要是游离气在贡献,随着地层压力降至10 MPa后,吸附气解析速率逐渐增大直至吸附气起主导作用;黏土含量越高,黏土与有机质的竞争吸附中占主导;吸附气含量越小,而TOC越高,有机质与黏土竞争吸附中占主导;吸附气量越高,另外压力越高、温度越低,吸附气量越高;基于吸附势理论的吸附模型比Langmuir等温吸附模型具有较好的拟合程度,具有较强的适用性;对异常高压的页岩气藏而言,随着深度的增加,吸附气含量逐渐增加,并未出现明显的极值,温度对吸附气量的影响没有压力的影响大,压力对吸附气的含量起主导作用。

Base on shale cores from Weiyuan block in sichuan,isothermal adsorption experiments have been conducted in 90 ℃. Main factors affecting the adsorption have been analyzed and gas changes absorbed on the shale are expounded in combination with production practice. Also adsorption model is established and adsorption capacity is predicted in different depth while relying on the adsorption potential theory. The results show that when the formation pressure is high,gas which is desorbed is less than that which is free. However,when the formation pressure drops down to 10 MPa,adsorbed gas desorbed more and more gradually until the adsorbed gas plays in a leading role. Higher clay content,adsorbed gas content is smaller,which is opposite for TOC. And the higher the pressure,the lower temperature,the higher adsorption capacity. Adsorption model based on adsorption potential theory has better fitting degree and applicability than the Langmuir isothermal adsorption model. For shale gas reservoir with abnormal high pressure,adsorbed gas content increased gradually with the increase of depth,it does not appear obvious extreme value. This shows that effect of temperature on the shale gas adsorbed is less than pressure.The reservoir pressure plays a leading role on the adsorbed gas.