致密储层润湿性定量表征及其对致密油赋存状态与流动规律的影响研究

With the breakthrough of exploration and development in Ordos and Dzungaria Basins, tight oil became a new star of unconventional oil and gas exploration and development in China. The surface property of reservoir, mainly refers to wettability, is weaker researched than characterization of reservoir space. Wettability is controlled by the interaction among oil, water and rock, and wettability in pore throat structure of tight reservoir could affect the occurrence and flow pattern of tight oil. The impact of mineral composition, oil and water property, pore-throat structure, curvature, and its surficial physical and chemical property, and temperature and pressure condition on wettability are conducted by various methods with various scales of pore-throat structure. Specifically, macro-scale ( >1μm) used experimental method, and mesoscopic (0.01~1μm ) used experiment and meso-simulation, and micro-scale (1~10nm ) used experiment and molecular dynamics simulation. Based on X diffraction experiment and meso-wetting experiment results, the force field parameters of molecular dynamics potential and the Thermodynamic parameters of the Dissipative particle dynamics simulation could be acquired, then the wettability and the absorption thickness of tight oil could be calculated. Considering the impact of the change of pore-throat surficial wettability before and after the filling of oil in tight reservoir on its flow pattern, the slip type, degree and flow rate in different mining conditions could be calculated, and the flow ability could be evaluated.

由于在鄂尔多斯、准噶尔等盆地获得重大突破，致密油成为我国非常规油气勘探开发的新亮点。学者们对储层孔喉结构表征表现出极大的热情，但对致密储层表面性质——润湿性的研究较为薄弱。润湿性是油水岩相互作用的一种表现。致密储层孔喉系统的润湿性对于致密油赋存状态、流动规律具有重要的影响。针对不同尺度孔喉，拟采用宏观尺度（>1μm）实验研究、介观尺度（0.01~1μm）实验+介观模拟、微观尺度（1~10nm）实验+分子动力学模拟的手段，研究矿物组成、油水性质、孔喉尺度和曲率、孔喉表面物理化学性质、温压条件等因素对润湿性的影响，实现对致密储层全尺度孔喉系统润湿性的定量表征。根据X衍射、润湿性实验标定分子模拟中的力场参数、介观模拟中的热力学参数，进而模拟计算致密油润湿性及吸附厚度。考虑致密储层在致密油充注前后孔喉表面润湿性的改变对致密油流动规律的影响，计算不同开采条件下致密油的流动规律，评价致密油的可流动性。

继页岩气之后，北美致密砂岩油、致密碳酸盐岩油、页岩凝析油获得重大突破，我国在鄂尔多斯、准噶尔等盆地致密砂岩和致密碳酸盐岩中获得了油气的重大发现，致密油成为全球非常规油气发展的新亮点。与北美海相致密油相比，我国陆相致密油储层分布稳定性差、非均质性强、赋存和流动机制复杂，传统成藏理论和评价方法遇到极大挑战，成为制约我国致密油工业化发展的瓶颈。润湿性被认为是存在非混相流体时，某种液体延伸或附着在固体表面的倾向性，是固体材料表面特性中最重要的性质之一。油藏工程领域已开展大量润湿性方面的分析和研究，但主要评价对象是常规的砂岩或碳酸盐岩储层，对于致密（页岩）储层中润湿性表征工作研究较少。由于致密储层本身具有低孔低渗、矿物组成复杂和非均质性较强等特征，致密储层润湿性对致密油赋存特征和可流动性影响较大，其作用不可忽略。依托本基金，分别开展了宏观尺度、介观尺度润湿性定量表征实验，通过与分子动力学模拟致密储层润湿性方面的研究结合形成从宏观、介观实验分析到微观模拟上的全尺度的致密储层润湿性定量表征。通过实验分析矫正平衡态分子动力学模拟的力场参数，研究了致密储层润湿性对致密油赋存状态的影响，建立了致密油赋存状态模型，计算了研究靶区致密储层中致密油的吸附游离态比例。通过开展格子玻尔兹曼模拟研究了润湿性对致密油流动规律的影响，并以鄂尔多斯盆地、准噶尔盆地和松辽盆地为靶区，应用研究的方法技术表征了研究区致密储层的润湿性，分析了润湿性对致密油赋存状态与流动规律的影响，评价相应地质条件下致密油的可流动性。