Invasion patterns derived from inversion of logging- while-drilling measurements

The measured electromagnetic resistivity from the logging-while-drilling (LWD) tool is affected by mud-filtrate invasion. An inversion method is carried out to obtain accurate formation resistivity, resistivity of flushed zone, and invasion depth. We studied the invasion pattern of mud-filtrate based on the data of inversion. We observed that the invasion depth can be expressed as a function of parameters such as formation porosity, permeability, mud column pressure, mud invasion time, and difference between arrayed resistivity.