预交联凝胶颗粒分散体系微观渗流的LBM-DEM模拟方法研究

The microscopic flow of the suspensions of Preformed Particle Gel (PPG) in porous media is a complicated problem. It has not only the basic flow properties of particle-fluid suspensions, but also swelling and deformation characteristics. This study is carried out by both microscopic experiments and microscopic simulations. Based on micro-focus tomographic imaging experiments, the 3-dimensional pore-throat structure of reservoir rocks is reconstructed and then used as the flow constraints of the suspensions. The Lattice Boltzmann Method (LBM) is used to simulate the flow and evolution of the fluid. The Discrete Element Method (DEM) is used to simulate the collision and movement of the particles. The Immersed Boundary (IB) method is improved to simulate the deformation of the PPG. Therefore, the LBM-DEM methods simulating the migration, deposition, restart, clogging and deformation behavior of the suspensions of PPG in porous media can be established, and then validated and improved by microscopic experiments. On this basis, microscopic flow mechanism of PPG in porous media will be investigated thoroughly, which are listed as follows: The critical flow parameters of the suspensions of PPG will be obtained; Rules of permeability and porosity variation as well as its influential factors will be studied; Related filtration parameters including the maximum retention volume, breakthrough pressure gradient, deposition coefficient and restart coefficient will be computed. This study will contribute greatly to further development and improvement of the percolation theory of particle-fluid suspensions such as deformable PPG.

预交联凝胶颗粒分散体系在多孔介质中的渗流是一个复杂的流动问题，它不仅具有颗粒悬浮流的基本渗流特征，同时还具备溶胀、变形等特性。本项目采取微观实验与微观模拟相结合的研究手段：基于层析成像实验建立岩石三维孔喉结构提供模拟边界约束，采用格子玻尔兹曼方法(LBM)模拟流体的流动和演化，离散元方法(DEM)处理颗粒的碰撞和运动，改进浸入边界(IB)法模拟颗粒的变形特征，建立起能够描述凝胶颗粒分散体系在多孔介质中运移、沉积、重启动、堵塞和变形通过特征的LBM-DEM微观模拟方法，并借助微观渗流实验进行验证和完善。在此基础上，确定凝胶颗粒流动参数临界条件，讨论该分散体系流动过程中多孔介质渗透率和孔隙度的变化规律及其影响因素，求取颗粒最大滞留量、突破压力梯度、沉积系数、重启动系数等渗滤相关参数。该研究内容有助于进一步发展和完善凝胶颗粒分散体系等含颗粒流体在多孔介质中的渗流理论。

非均相复合驱是高含水油田提高采收率的重要方法，预交联凝胶颗粒驱油剂是其主要的化学注入剂。而预交联凝胶颗粒分散体系在多孔介质中的渗流是一个复杂的流动问题，它不仅具有颗粒悬浮流的基本渗流特征，同时还具备溶胀、变形等特性。本项目将微观实验与微观模拟相结合研究了预交联凝胶颗粒分散体系在多孔介质中的微观渗流机制，取得的代表性研究成果包括：基于可视化微观驱替实验，阐明了孔喉分布特征、凝胶颗粒粒径、溶胀程度等对预交联凝胶颗粒分散体系微观渗流和驱油特征的影响，实现了微观渗流特征的定量化分析；发展了基于微观受力分析的颗粒变形处理方法，建立了能够描述预交联凝胶颗粒弹性变形特征的微观渗流LBM-DEM-IMB模拟方法，通过微观渗流实验验证了该方法的有效性；基于层析成像的岩石骨架开展微观流动模拟研究，建立了临界压力梯度定量表征模型，确定了凝胶颗粒变形通过孔喉的临界条件，揭示了凝胶颗粒分散体系具有“颗粒暂堵变形运移、固液增阻扩大波及”的微观渗流机制。.研究成果已发表相关论文21篇，分别发表在《Chemical Engineering Science》、《Transport in Porous Media》、《International Journal of Heat and Mass Transfer》、《SPE Journal》等国内外期刊及国际会议上，其中SCI检索13篇、EI检索8篇。授权美国发明专利1项、中国发明专利3项，获中国石油和化学工业联合会技术发明一等奖1项，登记计算机软件著作权2项。目前，培养青年教师3名，培养毕业博士和硕士4名，侯健教授获国家杰出青年科学基金资助，并获第三批国家“万人计划”科技创新领军人才等荣誉称号。.通过本项目的研究，全面完成了研究计划内容，达到了预期指标要求。形成了预交联凝胶颗粒分散体系微观渗流的LBM-DEM-IMB模拟方法，揭示了预交联凝胶颗粒分散体系在多孔介质中的微观渗流机制，研究成果为凝胶颗粒等弹性颗粒分散体系微观渗流机制研究提供有效的模拟研究手段，有助于进一步发展和完善含颗粒流体渗流理论。