基于数字岩心的泥浆侵入数值模拟及微观机理

Numerical Simulation and Micro-mechanism Study of Mud Intrusion Based on Digital Core

石油钻井中由于钻井液压力略大于地层压力,使得钻井泥浆侵入到原始地层中,改变地层的电阻率,进而影响电阻率测井的准确性。以岩心CT扫描得到的数字岩心模型为基础,利用格子玻尔兹曼方法来模拟泥浆侵入的过程,结合有限元方法计算泥浆侵入过程中岩心电学特性参数的变化,并结合岩心孔隙结构参数,从微观尺度上认识泥浆侵入过程,从而系统地分析泥浆侵入的微观机理。孔隙微观结构参数中,渗透率、孔隙连通性及孔喉半径对泥浆侵入和电阻率影响显著,在实际测井解释中,有必要针对不同渗透率的岩心建立相应的电阻率校正模型。

In oil drilling,because the drilling fluid pressure is slightly higher than the formation pressure,the drilling mud will invade original formation,which changes the resistivity of the formation,and then affects the accuracy of resistivity logging.Based on the digital core model obtained by core CT scanning,the process of mud intrusion is simulated using lattice Boltzmann method.The changes of core electrical parameters in the process of mud intrusion are obtained by using the finite element method,combined with the pore structure parameters of core,the process of mud intrusion is fully understood from the micro-scale,and the micro-mechanism of mud intrusion is systematically analyzed.Among the pore microstructure parameters,permeability,pore connectivity and pore throat radius have significant effects on mud invasion and formation resistivity.In practical logging interpretation,it is necessary to establish corresponding resistivity correction models for cores with different permeability.