ABSTRACT:

The petrophysical analysis of carbonate rocks is often made challenging by the cumulative effects of varying sedimentary/diagenetic rock textures and in-situ mechanical conditions. Given all the variables involved, a relatively high number of measurements is needed to evaluate these rocks. In the approach presented in this paper, recently developed features of the sonic and electrical log measurements are associated for a thorough investigation of carbonate reservoirs. These techniques coordinate in three successive stages with increasing focus of investigation.1.At the greater scale of investigation, the compressional and shear acoustic properties allow the detection of the rock matrix and provide the estimation of the overall porosity. In the studied cases, typical acoustic-porosity trends are recognized and related to the permeability estimated by the sonic tube wave.2.At an intermediate scale of investigation, the azimuthal anisotropy of shear waves provides the distinction of isotropic vs. anisotropic zones, along with the strike direction of main fractured belts.3.At the finest scale of resolution, the electrical images of the borehole allow the direct visualization of both individual fractures and the diffused textural pattern. The latter is described in terms of small-scale heterogeneity distribution and connectivity, so to physically explain the permeability observed at a higher scale of observation. This approach leads to maximize the detection of productive zones in carbonates reservoirs, as illustrated by examples from wells in Central and Southern Italy

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