CHARACTERIZATION OF DRILLING MUD FLUID INVASION

Donaldson, E.C. and Chernoglazov, V., 1987. Characterization of drilling mud fluid invasion. J. Pet. Sci. Eng., 1: 3-13. A method for the characterization of drilling mud fluid invasion of porous formations was developed. The oil saturation and resistivity profiles are determined as a function of radial distance from the well and time using a finite difference solution of the radial form of the diffusivity equation. The coefficient of dispersion and its variation with respect to time was determined for five sandstones using long cores. The effluent profile of a step increase of injected sodium chloride concentration is analyzed to determine the value of the coefficient. Values reported in the literature for the dependence of the mud filtration rate on time of filtration were used. The method gives a complete analysis of mud filtrate invasion and can be used for improvement of resistivity well log interpretation.