深层页岩气等温吸附数学模型研究

Isothermal Adsorption Mathematical Model of Deep Shale Gas

摘要: 我国深层页岩气储量占比大，明确深层页岩气吸附规律对于准确评价深层页岩气储量具有十分重要的意义。然而，深层页岩储层温度压力高，远超实验测试范围，导致深层页岩气吸附规律尚不清楚。因此，采用分子模拟技术构建深层页岩干酪根模型，模拟深层页岩甲烷高温高压吸附行为，揭示深层页岩气储层原位吸附规律，在此基础上，研究了深层页岩气等温吸附数学模型。结果表明：随着温度的增加，深层页岩气吸附量减少；随着压力的增加，深层页岩气吸附量呈现先快后慢的增加，并在高压段趋于平缓；通过采用Langmuir模型、Freundlich模型以及Langmuir-Freundlich模型对模拟数据进行拟合，明确了Langmuir-Freundlich模型能够更好描述深层页岩气吸附规律。

Abstract: Deep shale gas reserves account for a large proportion in China. It is of great significance to clarify the adsorption law of deep shale gas for accurate evaluation of deep shale gas reserves. However, the high temperature and pressure of deep shale reservoirs far exceed the experimental test range, leading to the unclear adsorption law of deep shale gas. Therefore, a deep shale kerogen model was constructed by molecular simulation technology to simulate the adsorption behavior of methane in deep shale at high temperature and high pressure, and to reveal the in-situ adsorption law of deep shale gas reservoirs. On this basis, the isothermal adsorption mathematical model of deep shale gas was studied. The results show that with the increase of temperature, the adsorption amount of deep shale gas decreases, and with the increase of pressure, the adsorption amount of deep shale gas increases first fast and then slowly, and tends to be flat in the high pressure section. By using the Langmuir model, Freundlich model and Langmuir-Freundlich model to fit the simulated data, it is clear that the Langmuir-Freundlich model can better describe the adsorption law of deep shale gas.