论文部分内容阅读
页岩气吸附机理的研究对于页岩气成藏和储量评价具有重要意义.甲烷在地层温度和压力条件下处于超临界状态,页岩气的吸附实际上为超临界吸附,但其机理目前尚不明确.在建立Ono-Kondo格子模型的基础上,结合低温氮气吸附和高压甲烷等温吸附实验,对龙马溪组页岩的微观孔隙结构和超临界吸附曲线进行了分析.结果表明,页岩中发育的孔隙尺度较小,比表面积较大,吸附气主要赋存于微孔和中孔中;页岩的等温吸附曲线在压力较大时,必然存在下降的趋势,这并非异常现象,而是超临界甲烷过剩吸附量的本质特征.Ono-Kondo格子模型对页岩高压等温吸附曲线的拟合效果很好,相关系数均在0.99以上,说明该模型可以表征页岩纳米孔隙中超临界甲烷的吸附特征.基于拟合得到的吸附相密度可将过剩吸附量转换为绝对吸附量,并直接计算地层温度和压力下甲烷的吸附分子层数,计算层数均小于1,表明甲烷分子并没有铺满整个孔隙壁面.因此受流体性质、吸附剂吸附能力和孔隙结构3个方面的影响,页岩气的吸附机理为单层吸附,不可能为双层甚至多层吸附.
The study of shale gas adsorption mechanism is of great significance to the shale gas accumulation and reserves evaluation.Mathane is in the supercritical state under the conditions of formation temperature and pressure and the sorption of shale gas is actually supercritical adsorption, Is not clear.On the basis of Ono-Kondo grid model, the microscopic pore structure and supercritical adsorption curve of the Longmaxi shale are analyzed combining with low-temperature nitrogen adsorption and high-pressure methane isothermal adsorption experiments.The results show that in shale The developed pore scale is smaller and the specific surface area is larger. The adsorption gas mainly exists in the micropores and mesopores. The isothermal adsorption curve of shales tends to decrease when the pressure is high, which is not an abnormal phenomenon but an abnormal phenomenon Supercritical methane over-adsorption capacity of the nature of the.Inno-Kondo lattice model for shale high pressure isothermal adsorption curve fit good results, the correlation coefficient above 0.99, indicating that the model can characterize the adsorption of supercritical methane in shale nano-pores Based on the fitted adsorption phase density, the excess adsorption capacity can be converted into the absolute adsorption capacity, and the methane adsorption molecular layer number can be directly calculated under the formation temperature and pressure, The calculated layer numbers are all less than 1, indicating that methane molecules do not cover the entire pore wall, so the adsorption mechanism of shale gas is monolayer adsorption, which is impacted by fluid properties, adsorbent adsorption capacity and pore structure. Double or even multi-layer adsorption.