Management of mature carbonate reservoirs depends critically on good porosity data. For many western Canadian carbonate pools discovered and developed in the late forties and fifties little reliable porosity data exists. Lack of good porosity data hinders the computation of reserves and the monitoring of gas-liquid contacts. To supplement existing porosity data, we have explored the use of porosities derived from cased-hole sonic data. We have utilized both a special research shear-wave sonic tool and new generation, commercially available long-spaced, full waveform, digital sonic tools.