Numerical Simulation of Mud Invasion and Its Array Laterolog Response in Deviated Wells

Abstract

AbstractIn order to study the petrophysical properties of mud‐invaded formation in deviated wells, a generalized curvilinear coordinate system is used to simulate the characteristics of mud invasion, and then the array laterolog response during mud invasion is researched. Numerical simulation shows that the phenomena of saw tooth in mesh generation on the border of the dip borehole, which is unavoidable in the Cartesian coordinate system, can be effectively eliminated in the curvilinear coordinate system. The heterogeneity of formation results in non‐uniform mud invasion, the better the reservoir permeability is, the more deeply mud filtrate invades. And mud invasion changes the distribution of both fluid saturation and salinity around the borehole, thus leading to the complexity of rock resistivity distribution around the deviated well. The variation of apparent resistivity from array laterolog and the difference between its deep and shallow resistivity during mud invasion reflect the characteristics of mud invasion. In this paper a four‐parameter inversion of array laterolog based on Marquardt method is adopted to effectively recover the invasion profile and then obtain the original formation resistivity in the deviated well. The analysis of invasion characteristics and array laterolog response simulation in the deviated well contributes to the correct understanding of petrophysical properties around the well and reservoir evaluation with array laterolog in the deviated well.