裂缝性潜山油藏分形迂曲二叉树模型渗吸机理

裂缝性潜山油藏基质系统包含了10μm以下的小裂缝及微细裂缝,孔隙结构复杂。为了更好地描述基质系统孔隙结构,分析渗吸机理,文中运用分形理论建立分形迂曲二叉树模型,推导出渗吸机理判别参数NB~(-1)计算公式;运用刘卫东等的实验数据完成模型验证;借助MATLAB编程,绘制渗吸机理影响因素图版,进一步分析渗吸机理。结果表明,渗吸机理与毛细管力、润湿角、迂曲分形维数、管径分形维数、二叉树分叉系数、二叉树分级数、重力差、孔隙度及渗透率等多种因素有关,并且管径分形维数、迂曲分形维数、二叉树分叉系数、毛细管管径及润湿角越小,二叉树分级越多,越易发生逆向渗吸,渗吸效果越明显。

Imbibition mechanism of fractal tortuosity binary tree model for buried-hill fractured reservoirs

The matrix system of buried-hill fractured reservoirs is generally composed of small fractures and micro fractures below 10 μm,so the pore structure of matrix system is very complex.In order to describe the pore structure and analyze imbibition mechanism more accurately,fractal tortuosity binary tree model was established using fractal theory in this paper.The calculation formula of the NB-1 number was derived,and a model validation was conducted by the experimental data of LIU Weidong,et al.Finally,the influence factor chart was drawn and imbibition mechanism was analyzed.The results show that imbibition mechanism is affected by capillary force,wetting angle,tortuosity fractal dimension,diameter fractal dimension,branching coefficient of binary tree,branch number of binary tree,gravity difference,porosity,permeability and other factors.The smaller the tortuosity fractal dimension,diameter fractal dimension,branching coefficient of binary tree,capillary diameter and wetting angle are,the easier the occurrence of reverse imbibition is.The more the branch number of binary tree is,the more obvious the effect of imbibition is.