Experimental Permeability Tensor for Fractured Carbonate Rocks

This paper presents a novel petrophysical experiment for measuring the 3D permeability tensor at reservoir conditions in fractured vuggy carbonate rock. The permeability variation with confining pressure is demonstrated through the experimental investigation; the permeability ellipse plots show the decrease of permeability, as a function of the increase in effective stress. The experiment was developed at reservoir conditions (120 °C temperature and variable confining pressure) in a native whole rock sample, from the Gulf of Mexico naturally fractured and vuggy reservoir. The analysis of the laboratory data reveals the elliptical behavior of permeability. Two ellipses were generated, one corresponding to the fracture network (secondary porosity system) and another for matrix porosity and permeability (primary porosity system). An important result is the compaction of the representative fracture network ellipse until it fuses with the matrix porosity ellipse at a high confining pressure state. The test contributes to the understanding of the mechanical and flow aspects of permeability, for naturally fractured reservoirs. The experimental results provide a basis for improving reservoir simulation studies, to obtain realistic predictions of reservoir behavior.