页岩气在孔隙表面的赋存状态及其微观作用机理

陈国辉; 卢双舫; 刘可禹; 许晨曦; 薛庆忠; 田善思; 李进步; 卢书东; 张钰莹

doi:10.3799/dqkx.2019.194

页岩气在孔隙表面的赋存状态及其微观作用机理

doi: 10.3799/dqkx.2019.194

陈国辉^{1, 2, 3, 4, ,},
卢双舫^{2, 3, 4, ,},
刘可禹^2, ,,
许晨曦²,
薛庆忠²,
田善思²,
李进步²,
卢书东⁵,
张钰莹^{1, 2}

1.
中国地质大学资源学院, 湖北武汉 430074
2.
中国石油大学地球科学与技术学院, 山东青岛 266580
3.
中国石油大学重质油国家重点实验室, 山东青岛 266580
4.
陕西省页岩气成藏与开发重点实验室, 陕西西安 710000
5.
北京中油瑞飞信息技术有限责任公司, 北京 100000

基金项目:

博士后创新人才支持计划项目 BX201700289

国家自然科学基金项目 41802157

国家自然科学基金项目 41330313

国家自然科学基金项目 41672130

中国博士后科学基金项目 2017M620296

中国博士后科学基金项目 2018M630811

山东省自然科学基金项目 ZR2018BD017

青岛市博士后资助项目 BY20170216

详细信息

作者简介:
陈国辉(1986-), 博士, 主要从事非常规油气地质学及分子模拟方面的研究

通讯作者:
卢双舫

刘可禹

中图分类号: P593
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- 被引次数: 0
出版历程
- 收稿日期: 2019-08-06
- 刊出日期: 2020-05-15

Occurrence State and Micro Mechanisms of Shale Gas on Pore Walls

Chen Guohui^{1, 2, 3, 4
,
,},
Lu Shuangfang^{2, 3, 4
, ,},
Liu Keyu^{2
, ,},
Xu Chenxi²,
Xue Qingzhong²,
Tian Shansi²,
Li Jinbu²,
Lu Shudong⁵,
Zhang Yuying^{1, 2}

1.
Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China
2.
School of Geosciences, China University of Petroleum, Qingdao 266580, China
3.
State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao 266580, China
4.
Shaanxi Province Key Laboratory of Lacustrine Shale Gas Accumulation and Development, Xi'an 710000, China
5.
Richfit Information Technology Co., Ltd., CNPC, Beijing 100000, China

摘要

摘要: 吸附态是页岩气的主要赋存状态之一，对吸附气含量的准确评价是页岩气勘探开发中的重要环节.在页岩吸附气含量评价过程中，所选用的等温吸附模型是否遵循页岩气的赋存状态及其微观作用机理，是决定模型适用性的关键所在，也是决定吸附气含量评价准确性的重要因素.因此，需要对页岩气在孔隙表面的赋存状态及其微观作用机理开展深入研究，为科学地优选或建立吸附气评价模型提供理论依据.利用巨正则蒙特卡洛（Grand Canonical Monte Carlo，简称GCMC）法分别模拟甲烷在有机质和伊利石孔隙中的吸附特征并得到分子构型，并进行分子动力学（MD）模拟使体系达到充分平衡.在此基础上，根据气体浓度分布、密度场分布以及分子间相互作用等特征阐明页岩气在孔隙表面的赋存状态及其微观作用机理.研究表明，页岩气在孔隙表面的吸附作用并非单层吸附，吸附相可划分为强吸附层、弱吸附层和二者之间的吸附层波谷.强吸附层主要受到矿物表面的吸附作用；吸附层波谷与弱吸附层既受到矿物表面的吸附作用，又受到不同吸附层之间的吸附作用.Langmiur模型与BET模型的假设条件与此机理不严格相符，可能对模型评价精度造成一定影响.对页岩气在孔隙表面赋存状态及其微观作用机理的研究，有望为吸附模型的优选或建立提供理论依据.
- 页岩气 /
- 吸附机理 /
- 有机质 /
- 伊利石 /
- 分子模拟 /
- 油气地质
Abstract: The adsorption gas is one of the main occurrence states of the shale gas, so the accurate evaluation of the adsorption gas amount is important for exploration. The key for the applicability of the models lies in whether the adsorption model obeys the occurrence state and its micro mechanisms of shale gas on the pore walls, which is the critical factor influencing the accuracy of the evaluation of the adsorption gas amount. The occurrence state and its micro mechanisms of shale gas on the pore walls are investigated in this study, aiming at optimizing the adsorption model. By the Grand Canonical Monte Carlo (GCMC) method, the adsorption behavior of CH₄ in both organic and illite pores was simulated, and the molecular dynamic (MD) was performed on the molecular structure at a certain temperature and pressure. Based on the simulations, the gas distribution, the interaction distribution and density field were investigated to document the occurrence state and its micro mechanisms of shale gas on pore walls. It is found that the adsorption of shale gas on pore walls is not the single layer adsorption, and the adsorption phase can be divided into the strong adsorption layer, the weak adsorption layer and the trough of adsorption layer. The strong adsorption layer is mainly adsorbed by the pore walls, while the weak adsorption layer and the trough of adsorption layer are not only adsorbed by pore walls, but also adsorbed by the adsorption layers. This is inconsistent with the hypothetical condition of the Langmiur model or the BET model, so the reasonability of the models and the accuracy of the evaluating results would be limited. The occurrence state and its micro mechanisms of shale gas on pore walls revealed in this study can provide theoretical basis for optimizing and establishing adsorption models.
- shale gas /
- adsorption mechanism /
- organic matter /
- illite /
- molecular simulation /
- petroleum geology

HTML全文

图 1 有机孔隙（a）与伊利石孔隙（b）模拟单元剖面

气体和钾离子为球状模型，有机质和伊利石骨架为球棍模型.色标：氧，红色；氢，白色；硅，黄色；铝，粉色；钾，紫色；有机质骨架：灰色，甲烷联合原子：橙色

Fig. 1. Snapshots of organic pore (a) and illite pore (b) with CH₄ molecules

下载: 全尺寸图片幻灯片

图 2 等温吸附实验与分子模拟结果对比

Fig. 2. Comparison between molecular simulation results and experimental measurements

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图 3 伊利石与干酪根孔径分布

Fig. 3. Pore size distribution of illite and kerogen

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图 4 有机孔隙（a）与伊利石孔隙（b）表面气体分布特征与结合能分布特征对比

Fig. 4. Gas distribution and interaction distribution of gas on organic pore walls (a) and illite pore walls (b)

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图 5 垂直于有机质（a）与伊利石（b）孔隙表面的CH₄密度场分布

Fig. 5. Density field of CH₄ perpendicular to organic pore walls (a) and illite pore walls (b)

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图 6 孔隙内气体分布结构

a.垂直于有机质孔隙表面；b.垂直于伊利石孔隙表面；c.平行于有机质孔隙表面；d.平行于伊利石孔隙表面

Fig. 6. Structure of gas molecules in pores

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图 7 孔隙表面与不同吸附层内气体分子之间结合能

a.有机质孔隙; b.伊利石孔隙

Fig. 7. Interaction energy among pore walls and different adsorption layers

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