Parameterization of Petrophysical and Geomechanical Properties Alteration in Sandstone Formations by Water-Based Drilling Fluids

The alteration of the petrophysical and geomechanical properties of sandstone formations by exposure to barite-weighted water-based drilling mud is described by a physically based kinetics model satisfying the low-end and high-end limit values. This model leads to a modified power-law equation for variation of various properties of porous rocks as a function of time. The variations of the porosity, permeability, unconfined compressive strength, tensile strength, Young's modulus, Poisson's ratio, bulk modulus, rigidity or shear modulus, uniaxial compaction or oedometer modulus, and Lamé's parameter of Buff Berea sandstone core samples by exposure time to water-based drilling fluids are described accurately by the modified power-law equation. The application of the modified power-law equation leads to more accurate and proper correlations of the experimental data of the petrophysical and geomechanical properties alterations of sandstone in a physically meaningful manner. Further, the conditions and limitations of the previous correlations are investigated and compared with the new improved correlations developed using the modified power-law equation. The previous correlations predict unrealistic end-point values, such as plus or minus infinity for the initial and the final long-time limit conditions, and therefore they are valid only for applications in the range of the experimental data. The modified power-law equation circumvents the shortcomings of the previous correlations conveniently.