多孔介质中微生物非线性生长及弥散传质过程的分形描述

As a promising technology for enhanced oil recovery, a large amount of attention has been putting on microbial enhanced oil rocovery because of its advantages as low cost, non-damaging to formations, et al. Up to now, some experience has been accumulated through the already performed laboratory experients and field tests home and abroad. However, the theoretical studies are still very weak for microbial flooding. Many areas are still blank such as the matching transport laws of microbes, nutritions and metabolites, the contributions of different metabolites to oil recovery ratio and the fields coupling mechanisms between flowing fluid and microbes. Methods and technologies are still required to surport the revervoir evalution, program optimization and microbes development, et al. In this study, after selection of several microbes which is albe to live under revervoir conditions and can produce certain bio-surfactant and bio-polymer, the fractal theory is used to describe the non-linear evolution of bacterial colonies and the morphologic characteristics of the bio-film and its transporting capability. Further, its effect on fluid flow is also appraised. Consequently, in combination of the short and long cores experiments at lab, the following analyses are made about the convection-dispersion laws and the matching mechanisms among microbes, nutritions and metabolites inside porous media, the effect of their adsorption on the mass transportation of convection-dispersion and the scale effect of dispersion. Thus the mechamism of microbial flooding is explained detailedly to guide the field test of microbial flooding.

微生物采油以价格低、不伤害油层等优点，成为备受关注的一项提高采收率技术。国内外已开展了一些室内实验及现场试验，积累了一定的经验。但微生物驱的理论研究还十分薄弱，微生物、营养物及代谢产物在多孔介质中的运移规律以及代谢产物对提高采收率的贡献、多孔介质中的渗流场与微生物场、微生物与营养物传输的耦合机制等方面还是尚待研究的领域，在适合微生物驱的油藏条件评价、方案优化设计和菌种开发等方面还缺乏依据和理论支持。本课题在获得适应油藏条件的能产生生物表活剂、生物聚合物等代谢产物菌株的基础上，运用分形理论描述微生物菌落演化的非线性规律和生物膜的形态特征，评价其在多孔介质中的运移能力及其对流体渗流的影响。结合长、短岩心室内实验，分析微生物、营养物及代谢产物在多孔介质中的对流-弥散规律及耦合机制，分析吸附效应对对流-弥散传质规律的影响和弥散的尺度效应，深刻阐述微生物驱油机理，为微生物驱油试验提供技术支持。

在国内外微生物采油相关技术基础上，主要进行了菌种筛选与评价、微生物非线性生长演化过程、微生物代谢作用对油藏物性和流体渗流的影响、微生物体系运移规律、微生物体系对流-弥散规律和微生物体系组分传输耦合规律等相关实验和理论研究。筛选出了具有旺盛生命力的产生物表活剂、生物聚合物等代谢产物的优秀菌株各1株；通过不同生长条件下菌落非线性演化过程的描述，运用DLA团簇模型模拟菌落自组织生长过程，分析了菌落演化形态的复杂性和自相似特征，深刻阐述微生物扩散聚集的非线性机制；通过平板模型与蚀刻玻璃模型中生物膜演化特征的描述，运用分形理论分析了生物膜的运移能力及其对多孔介质渗流特征的影响；建立了微生物、营养物及代谢产物在岩心孔隙中的对流迁移模型和弥散迁移模型，结合理论与室内沿程分布实验研究了微生物体系在多孔介质中的对流-弥散规律，最后建立了考虑界面张力、毛管压力、相对渗透率等因素的微生物激活地层原油模型，结合微生物驱油组分运移方程、微生物新陈代谢动力学方程及岩石表面吸附作用方程，根据实验数据拟合模型参数，比较各组分其对传质规律的影响。通过模型求解与室内实验相互验证，深刻阐述了微生物体系在储层孔隙中的渗流机制和微生物体系提高原油采收率机理。研究成果为微生物驱油矿场试验提供了技术支持。