页岩气储层裂缝多尺度协同建模研究

Shale gas is a new field of petroleum exploration and development today. The coupling of shale reservoir fracture modeling and fluid simulation technology, has become the focus and difficulty of reservoir modeling and simulation at home and abroad. This project focuses on difficulty of coupling of multi-scale fracture modeling and fluid simulation. And intends to bring molecular dynamic simulation method , which has demonstrated great potential application value , to shale fracture modeling research. By combing the extended finite element method and macroscopically fault stress inversion method, this project could build a system, which combined information from fracture modeling at different scale and fluid simulation method. Firstly, by using of FIB-SEM three-dimensional imaging method, nano CT et al to analysis the composition of shale reservoir and characteristics of micro-fracture. Then establishes corresponding micro-scale fracture molecular dynamical model step by step, this project could reveal controlling factors of microscopic fracture propagation system. After that, this project would build a core-scale fracture simulation model based on stochastic fracture mechanics method. And this project would establish a large- scale fracture modeling under the controlling of main fault by using simulated annealing method. Finally, this project would realize multi-scale modeling of shale gas，to improve the precision and accuracy of fracture modeling.

页岩气是现代油气勘探开发的一个新领域。页岩裂缝建模技术的研究，已成为国内外储层建模技术的焦点和难点。本课题针对页岩裂缝多尺度建模难题，拟探索将分子动力学理论引入页岩微观裂缝研究，并综合扩展有限元模拟方法和宏观断层应力场反演模拟方法，建立多尺度协同的裂缝建模方法。首先利用FIB抛光-SEM扫描三维成像、纳米CT等实验手段，分析页岩储层成分及微裂缝结构特征，分层次建立对应的微观裂缝分子动力学模型，结合宏观力学实验不断调整分子动力学模型势能参数等，确立微观裂缝的主控因素和预测参数体系；而后基于裂缝扩展模型，采用模拟退火技术进行主构造控制下主断层扩展拟合模拟，建立储层大尺度断层构造应力场模拟模型；然后在区域应变和属性分布控制下，基于宏观裂缝的断裂力学和微观裂缝的控制规律，基于协同克里金建模方法，构建宏观裂缝和微观裂缝模拟预测模型，实现页岩气多尺度协同建模，提高裂缝建模的精度和准确性。

页岩储层微观裂缝扩展机理分析及多尺度建模研究是石油地质界的世界性难题，目前仍处于探索阶段。实际岩层裂缝受控于地层局域应力场、岩石属性及其空间分布。已有的离散裂缝网络模型主要依靠井约束数据进行模拟，不仅缺乏对断层尖端应力场的模拟分析，而且在裂缝建模时，缺少断层演变过程和对其进行三维外推的信息。本项目从裂缝的多尺度非均质特征出发，基于地质统计学、断裂力学和多相流理论的基本原理，综合随机建模理论的概率观点、断裂力学和多相流分析的数值模拟观点，建立多尺度裂缝建模耦合分析体系。基于分子动力学开展小尺度研究，分析了矿物纳米尺度力学性质；基于FIB-SEM和CT技术构建数字岩心，分析了介观尺度，岩石矿物的属性；将地质统计学中的泛克里金系统与断裂模拟的裂缝追踪系统，统合为单一系统，在建立多尺度裂缝分布模型之后，应用内聚单元和双重介质混合模型实现多尺度裂缝与多相流体场耦合分析。通过本次研究，共发表学术论文6篇，授权专利3项，授权软件2项，申请油田局级项目2项。