高温高压下蒙脱石水化特性的分子模拟

李立宗; 苏俊霖; 赵洋; 左富银

doi:10.3969/j.issn.1001-5620.2021.03.001

高温高压下蒙脱石水化特性的分子模拟

doi: 10.3969/j.issn.1001-5620.2021.03.001

西南石油大学石油与天然气工程学院·油气藏地质及开发工程国家重点实验室, 成都 610500

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中图分类号: TE254
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- 收稿日期: 2021-02-25

Molecular Simulation of the Hydration of Montmorillonite under High-temperature and Highpressure

SouthWest Petroleum College, Petroleum Enginneering School·State Key Laboratory of Reservoir Geology and Development Engineering, Chengdu Sichuan 610500

摘要

摘要: 页岩中黏土矿物的水化膨胀是影响页岩气井井壁稳定性的一个重要因素，蒙脱石作为黏土矿物的主要成分，其水化机理对于解决页岩气井井壁失稳问题至关重要。为了深入探索高温高压地层环境下蒙脱石的水化机理，利用分子模拟软件从微观角度研究了不同水化程度的蒙脱石在不同温度压力条件下的晶层间距、晶层间物质的移动规律、离子水化参数以及力学参数的变化。研究结果表明：温度增加、压力降低时，蒙脱石层间距随之增加，且温度对层间距的影响较大，层间距范围在1.823～2.042 nm之间；层间水分子和钠离子的扩散速率随温度增加而加快，随压力升高而减慢；低温高压时钠离子的水化配位数较大，配位数范围在2.35～4.35之间；温度增加时，蒙脱石晶体的体积模量、剪切模量以及弹性模量随之减小，泊松比随之增加，而压力对蒙脱石晶体力学参数的影响却恰恰相反。可见，本文的研究结果对于高温高压地层环境下页岩地层水化机理的研究具有重要的理论指导意义。
- 蒙脱石 /
- 水化 /
- 分子模拟 /
- 高温 /
- 高压 /
- 力学参数
Abstract: The hydration expansion of clay minerals in shale is an important factor affecting the sidewall stability of shale gas well. The montmorillonite is the main constituent of clay minerals, and its hydration mechanism is very important to solve the problem of borehole wall instability in shale gas well. In order to further explore the hydration mechanism of the montmorillonite under high temperature and high pressure, molecular simulation software was used to study the inter-layer spacing, inter-layer material movement, ionic hydration properties and mechanical parameters of the montmorillonite under different temperature and pressure conditions from a microscopic perspective. The results show that when the temperature increases and the pressure decreases, the inter-layer spacing of montmorillonite augments, and relatively the temperature has a great influence on the inter-layer spacing, which ranges from 1.823-2.042 nm. The diffusion rate of inter-layer water molecules and sodium ions increases with the increase of temperature and decreases with the increase of pressure. The hydration coordination number of sodium ion is large at low temperature and high pressure, and the coordination number varies from 2.35 to 4.35. When the temperature goes up, the volume modulus, shear modulus and elastic modulus of montmorillonite crystal goes down and poisson's ratio increases, while the effect of pressure on the mechanical parameters of montmorillonite crystal is the opposite. It can be seen that the research results of this paper have important theoretical guiding significance for the research of shale formation hydration mechanism under high temperature and high pressure formation environment.
- Montmorillonite /
- Hydration /
- Molecular simulations /
- High temperature /
- High pressure /
- Mechanical parameters

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参考文献(18)

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