地层模块尺度钻井液侵入模拟与储集层电阻率剖面特征

Simulation of mud invasion and analysis of resistivity profile in sandstone formation module

针对钻井液动态侵入,基于钻井液侵入数值模拟,确定实验室模型参数,研制钻井液侵入物理模拟系统,模拟原状地层条件下钻井液侵入规律。首先开展了砂岩地层钻井液侵入实验,测量岩石模块径向电阻率变化,获取不同侵入时刻泥饼,并提出了泥饼孔隙度和渗透率随侵入时间变化模型;然后将物理模拟与数值模拟结果进行对比标定,开展地层条件下钻井液侵入规律分析。结果表明:钻井液侵入开始后泥饼快速形成,其孔隙度和渗透率迅速降低,一定时间后钻井液侵入主要受泥饼控制,泥饼参数随侵入时间变化模型可以很好地反映泥饼参数在侵入过程中的变化,钻井液侵入情况下储集层电阻率剖面特征受地层岩石物性、泥饼参数及地层水矿化度等多种因素共同影响。

Aiming at the dynamic invasion process of drilling fluid, the parameters of the physical model in laboratory were optimized based on numerical simulation and then a physical simulation system for mud invasion in undisturbed zone was developed. Then, the experiment of fresh water invasion in sandstone formation was conducted to measure the radial resistivity and mudcake parameters over time, and a mudcake porosity and permeability calculation model with the invasion time was proposed based on the measurement. Finally, the numerical simulation results were compared and calibrated with the physical simulation results to find out the regularity of drilling fluid invasion under formation conditions. The results show that the mudcake forms quickly and the porosity and permeability of the mudcake decrease sharply after the beginning of drilling fluid invasion, and the invasion process is mainly controlled by the mudcake after a certain period. The mudcake parameters model developed in this study can depict the changes of mudcake parameters during the invasion process. The characteristics of radial resistivity profile under mud invasion are affected by sandstone physical properties, mudcake parameters and formation water salinity.