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

Abstract

To investigate the dynamic invasion process of drilling fluid, the parameters of the physical model in laboratory were optimized based on numerical simulation and 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. Key words: mud invasion, physical modeling, numerical simulation, mudcake, resistivity, porosity, permeability