Carbonate Porosity and Permeability from Sonic Log

Abstract

The main goal of this work was to estimate carbonate porosity from sonic log S-wave slowness measurement, practically insensitive to fluid effect. Methodology is empirical and had already been successfully tested in sandstones (Silva and Beneduzi (2018)). Oolitic carbonate reservoir log data were used and porosity is in good agreement with lab data. Small deviations were observed in more heterogeneous carbonate systems mainly composed by stromatolites or bivalves, being interpreted as porous geometry influence. Compressional velocity deviation log methodology (Eberli et al., 2003) is currently used to identify porosity type in carbonates. The present rock physics model used to estimate porosity allows to define shear velocity deviations. Combination between Vp (P-wave velocity) and Vs (S-wave velocity) deviation (Vp/Vs deviation log) shows good compatibility with flow zones. A significant linear correlation was observed between new deviation curve and the lab values, allowing calculate permeability for the entire well. Results are in good agreement with NMR log permeability. New method brings up important reservoir petrophysical information. Moreover, the results can give a very important technical support in the early stages of well evaluation.