基于Ono-Kondo格子模型的页岩气超临界吸附机理探讨

发布时间：2018-04-02 02:03

  本文选题：页岩气　切入点：Ono-Kondo模型　出处：《地球科学》2017年08期

【摘要】：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.
[Abstract]:The study of shale gas adsorption mechanism is of great significance for shale gas reservoir formation and reserve evaluation. Methane is in supercritical state under formation temperature and pressure, and shale gas adsorption is actually supercritical adsorption. However, the mechanism is still unclear. Based on the Ono-Kondo lattice model, the micropore structure and supercritical adsorption curves of Longmaxi formation shale are analyzed by combining the experiments of nitrogen adsorption at low temperature and isothermal adsorption of methane at high pressure. The pore scale developed in shale is smaller, the specific surface area is larger, and the adsorption gas mainly occurs in micropores and mesoporous areas, and the isothermal adsorption curve of shale is bound to decrease when the pressure is high, which is not an abnormal phenomenon. But the essential characteristics of supercritical methane excess adsorption. The Ono-Kondo lattice model fits well the isothermal adsorption curve of shale at high pressure, and the correlation coefficient is above 0.99. This model can be used to characterize the adsorption characteristics of supercritical methane in shale nano-pores, and the excess adsorption capacity can be converted into absolute adsorption capacity based on the fitted adsorption phase density. The number of adsorbed molecular layers of methane under formation temperature and pressure is calculated directly, and the calculated layers are less than 1, which indicates that methane molecules are not covered with the whole pore wall. Therefore, it is affected by the fluid properties, adsorbent adsorption ability and pore structure. The adsorption mechanism of shale gas is monolayer adsorption, which can not be bilayer or even multilayer adsorption.
【作者单位】： 中国石油勘探开发研究院;国家能源页岩气研发(实验)中心;中国石油非常规油气重点实验室;
【基金】：国家重点基础研究发展计划(973计划)项目(No.2013CB2281)
【分类号】：P618.13
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本文编号：1698271