基于分子动力学模拟的深部储层原油赋存特征研究

With the development of petroleum exploration, deep oil & gas have become important area for oil & gas exploitation discovering and scale increase storage in china. Clarifying the occurrence characteristics of oil & gas in deep reservoirs has great practical significance for the evaluation of deep reservoir reserves and optimization of exploration program. According to the structural characteristics of deep reservoir rocks, crude oil has mainly three status: bulk free crude oil inside large fractured cavity, crude oil adsorbed on the rock surface and crude oil inside micropore of rock. Currently, due to the high temperature and high pressure of deep reservoir, studies on the occurrence characteristics of deep oil & gas via experimental means exists many difficulties. Therefore, in this project, collecting the rock cores and oil samples of deep reservoir located at Shunbei-Yuejin area in Tarim basin, based on the characterization of these rock cores structure and analysis of crude oil components, the corresponding simulation systems of reservoir rock and crude oil will be constructed. Adopting molecular dynamics simulations, the occurrence characteristics of bulk crude oil, crude oil adsorbed on rock surface and crude oil inside rock micropore will be studied systematically, and the influencing rule of temperature, pressure and gas oil ratio on the occurrence characteristics of crude oil will also be investigated. This project provides a new idea and method for studying the occurrence characteristics of oil & gas in deep reservoirs, and the results will provide basic data and theoretical reference for the exploitation and exploration of deep oil & gas resources.

随着石油勘探工作的不断推进，深层油气已经成为我国陆上油气勘探突破发现与规模增储的重要领域。明确深部储层原油赋存特征对于油藏储量评估和开发方案优化具有重要的现实意义。依据深部储层岩石的结构特征，原油存在三种赋存状态：大尺度缝洞中的体相游离原油、缝隙岩石表面的吸附原油和岩石微孔隙中的赋存原油。目前，由于深部储层高温高压的特点，实验上开展深层原油赋存的研究存在诸多困难。鉴于此，本课题采集塔里木盆地顺北-跃进地区的深层岩心和油样，基于深部储层岩石结构表征和原油组分分析的实验结果，构建储层岩石/原油赋存分子模拟体系；采用分子动力学模拟方法，系统考察体相游离原油、岩石表面吸附原油和微孔隙内原油的赋存特征；明确温度、压力和气油比等因素对原油赋存的影响规律。本课题的开展可为深层油气赋存特征研究提供新的思路和方法，研究工作将为深层油气的勘探开发提供基础数据和理论依据。

明确深部储层原油赋存特征对于油藏储量评估和开发方案优化具有重要的现实意义。由于深部储层高温高压的特点，实验研究存在诸多困难。鉴于此，本课题采集塔里木盆地顺北-跃进地区的深层岩心和油样，基于深部储层岩石结构表征和原油组分分析的实验结果，构建储层岩石/原油赋存分子模拟体系；采用分子动力学模拟方法，系统考察体相游离原油、岩石表面吸附原油和微孔隙内原油的赋存特征；明确温度、压力和气油比等因素对原油赋存的影响规律。具体研究成果如下：.（1）岩石/原油的模拟体系构建及力场优化：① 采集了顺北-跃进地区典型的深层岩心进行表征，得到了深层典型的储层岩石类型并依此构建了岩石模型；② 选取该区块具有代表性的深层油样，通过实验表征得出原油组分及占比，依此构建了原油分子模拟体系；③ 对于常见力场在深层条件下的适用性进行测试，得出了符合深层条件的分子力场。.（2）体相游离原油结构及物性研究：① 构建了体相原油体系模型，模拟了原油的赋存状态，揭示了原油的分布特征；② 对于原油的物性进行研究，阐述了深层原油的物性规律；③ 考察了常见注入气对于原油赋存的影响，揭示了注气类型对于原油赋存的影响规律，阐明了注入气与原油之间的相互作用机理。.（3）岩石表面吸附原油结构及稳定性研究：① 构建了原油在岩石表面的吸附模型，采用全原子分子动力学模拟方法模拟了原油的赋存状态，对于原油的吸附层和游离层进行了区分；② 研究了原油在岩石表面的吸附过程，揭示吸附态原油的结构特征；③ 研究了温度和压力变化对于对于吸附油赋存结构的影响，揭示了储层温压条件对于原油赋存影响的本质规律，并且发现芳香烃是原油吸附中贡献最大的组分；④ 对于不同气体类型影响原油赋存过程进行研究，揭示了气体影响原油赋存的微观机理。.（4）微孔隙赋存原油结构及可动性研究：① 构建了岩石微孔隙模型，采用全原子分子动力学模拟方法研究了孔隙内原油赋存特征，探究了孔隙尺寸对于原油密度分布的影响；② 对于孔道内游离态与吸附态原油进行划分，确定了典型深层条件下游离态原油赋存的空隙下限，探究了温压条件变化对于孔道内原油赋存结构的影响规律；③ 研究了恒温度下压强变化和恒压强下温度变化对于原油扩散性能和稳定性的影响，揭示了温压变化对于原油稳定性影响的微观规律。