Determination of Archie’s Tortuosity Factor from Stoneley Waves in Carbonate Reservoirs

One of the fundamental equations in calculate the saturation of fluid in hydrocarbon reservoirs is the Archie’s equation. In addition to the parameters measured by well logging such as porosity and resistivity, there are others parameters that called Archie’s coefficients. Archie provides constant values for this coefficient base on experimental core’s data, accordance with saturation formula in sandstone. In carbonate reservoirs nevertheless the sandstone reservoirs, high heterogeneity, variety in lithology and texture, shape and distribution of pores, due to this coefficient is not constant. So, variation of tortuosity as a coefficient that depends on the way correlation between pores, is high and considering a constant value due to error in calculation of fluid saturation. In this study, with the stoneley waves measured from DSI tools and required calculation, the value of tortuosity coefficient calculated continuously in well no.10 Darkhovin field. The regression of calculated values with the core data is 83.16 percent, that showed this method is useable for calculation the tortuosity.

Stoneley wave velocity variation

Stoneley wave velocity variation is analyzed by solving the modified Scholte secular equation for velocity of Stoneley waves, allowing to find dependency of the Stoneley wave velocity on the Wiechert parameter and construct a set of inequalities that confines region of existence for the appropriate root of the secular equation. Numerical analysis for Stoneley wave velocity dependence on the Wiechert parameter for both auxetics (materials with negative Poisson’s ratio) and nonauxetics revealed the presence of (i) asymptotes indicating degeneracy of Stoneley waves into the corresponding Rayleigh waves; and (ii) common extremums relating to degeneracy of Stoneley waves into the corresponding bulk shear waves.