基于分形理论的多孔介质稠油启动压力梯度计算与分析

Calculation and analysis of threshold pressure gradient of heavy oil in porous media based on fractal theory

胡心玲 曹晨光 梁文川

中国石化江汉油田分公司勘探开发研究院，湖北 武汉 430223

Exploration and Development Research Institute, Jianghan Oilfield Company, SINOPEC, Wuhan 430223, China

准确掌握稠油启动压力梯度产生机理及影响因素，对实际油藏开发中研究压力场分布、确定井网井距具有重要意义。文中根据力学平衡关系及多孔介质分形理论，建立了考虑多孔介质孔喉结构、边界层性质异常及流体结构性的稠油启动压力梯度数学模型；分析了岩心孔隙结构参数、流体黏滞阻力及固￣液、液￣液流体表面力对启动压力梯度的影响规律，对稠油流体的流变性及非线性渗流特征进行了探讨，模型计算结果与室内岩心实验数据吻合较好。由建立的数学模型得出：研究稠油拟启动压力梯度不能忽略孔隙结构参数（最大孔喉半径、最小孔喉半径、孔喉半径分形维数、迂曲度分形维数）、流体的结构性，以及表面力的影响；拟启动压力梯度与最大孔喉半径负相关，与稠油极限剪切应力和表面力正相关。

It is of great significance to accurately know the mechanism and influencing factors of threshold pressure gradient of heavy oil for studying the pressure field distribution, well pattern and well spacing in actual reservoir development. Based on the mechanical equilibrium relationship and fractal theory of porous media, a mathematical model of threshold pressure gradient of heavy oil considering pore throat structure of porous media, abnormal boundary layer properties and fluid structure is established. The influence of pore structure, fluid viscosity resistance and surface force of solid-liquid and liquid-liquid fluid on the threshold pressure gradient is analyzed. The rheological properties and nonlinear seepage characteristics of heavy oil fluid are discussed. The calculation results of the model are in good agreement with the experimental data of the core in the laboratory. The mathematical model established in this paper shows that the influence of pore structure（maximum pore throat radius, minimum pore throat radius, pore throat radius fractal dimension, tortuosity fractal dimension）, fluid structure, surface force can not be ignored in the study of pseudo-threshold pressure gradient of heavy oil. The proposed pseudo-threshold pressure gradient is negatively related to the maximum pore throat radius and positively related to the ultimate shear stress of heavy oil and the surface force.

10.6056/dkyqt202204013