Analysis of elastic velocities behavior and porosity in carbonates submitted to external pressure variation

Abstract

Carbonate rocks usually present a complex porous system that exhibits different behavior of porosity and elastic velocities when submitted to external pressure variation. This work aims to study compressional- and shear-wave velocity variation and porosity in carbonate rock samples submitted to external pressure variation. By analyzing the data set, it is intended to characterize carbonate rocks samples porous system. Experimental tests were carried out at the Rock Physics Laboratory of UENF/LENEP on a set of carbonate rocks. Those tests consisted of measurements of petrophysical properties, mineral composition and optical microscopy images that aid to characterize the pore system of such rocks. The Differential Effective Medium (DEM) theory was used to estimate the microporosity aspect ratio supposing a dual porosity scenario,macro-meso pores captured by optical microscopy and micropores that are out of the resolution of the image analysis. The influence of pressure variation in the aspect ratio was also studied as well as its impact on the behavior of porosity and elastic velocities for different rock textures.