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The Influence of Transient Evaporation and Geometric Characteristics on Shale Gas Transmission in Inorganic Nanopores
Gas Science and Engineering ( IF 5.285 ) Pub Date : 2020-12-01 , DOI: 10.1016/j.jngse.2020.103694
Weihong Peng , Wei Zhang , Donghui Zhao , Yunchao Qi , Hongmei Cheng

Abstract Transient evaporation characteristics of water film in inorganic nanopores play an important role in the shale gas storage and transmission. Meanwhile, Inorganic nanopores in shale minerals exhibit complex geometric characteristics. In this work, TESCAN MAIA3 is used to observe the pore shape and size of inorganic nanopores. The pore shapes of rectangular or wedge-shaped are frequently occurred in inorganic nanopores. Water distribution characteristic influenced by surface wettability and disjoining pressure in slit-like nanopores is then analysed in detail. We divide the water film attached to the surface of the inorganic nanopores into two layers: the high-viscosity water film and the bulk water film. The Moving Mesh Method is used to simulate the evaporation of water film and a mass flow prediction model synthetically considering the pore shape, evaporation, water film slip and layering is established in a single inorganic nanopore. Based on this model, the influence of four different parameters including pressure gradient, water-methane diffusivity coefficient, pore size and wedging coefficient on the shale gas production are investigated. The results show that the presence of water film and its evaporation have significant influence on the production of shale gas. This phenomenon can be interpreted by the increase of pore size caused by evaporation. However, the water film slip and layering have little effect on the shale gas flow rate. With the increase of pressure gradient, the mass flow rate increases significantly. The water-methane diffusion has a considerable influence on the time to reach the steady state. Lower wedging coefficient and larger pore size contribute to higher mass flow rate. Meanwhile, as the wedging coefficient increases from 1.0 to 1.8, the contribution of evaporation increases from 39.34% to 45.33%. Generally, the effective migration space of shale gas directly determines the amount of gas production.

中文翻译:

瞬态蒸发和几何特征对无机纳米孔中页岩气传输的影响

摘要 无机纳米孔中水膜的瞬态蒸发特性对页岩气的储输具有重要作用。同时,页岩矿物中的无机纳米孔表现出复杂的几何特征。在这项工作中,TESCAN MAIA3 用于观察无机纳米孔的孔形状和大小。矩形或楔形的孔形状经常出现在无机纳米孔中。然后详细分析了受表面润湿性和分离压力影响的狭缝状纳米孔中的水分分布特性。我们将附着在无机纳米孔表面的水膜分为两层:高粘度水膜和本体水膜。采用移动网格法模拟水膜蒸发,在单个无机纳米孔中建立综合考虑孔隙形状、蒸发、水膜滑移和分层的质量流量预测模型。基于该模型,研究了压力梯度、水-甲烷扩散系数、孔径和楔入系数4个不同参数对页岩气产量的影响。结果表明,水膜的存在及其蒸发对页岩气的产量有显着影响。这种现象可以解释为蒸发引起的孔径增加。但水膜滑移和分层对页岩气流速影响不大。随着压力梯度的增加,质量流量显着增加。水-甲烷扩散对达到稳态的时间有相当大的影响。较低的楔入系数和较大的孔径有助于提高质量流量。同时,随着楔入系数从 1.0 增加到 1.8,蒸发的贡献从 39.34% 增加到 45.33%。通常,页岩气的有效运移空间直接决定了产气量。
更新日期:2020-12-01
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