Primarily the wells Blumau1 and 2 were examined with respect to the characteristics of the carbonates reservoir. Already a survey of the Palaeozoic Carbonate reservoir of Graz has shown that next to the texture yards of variety with respect to the pore space of the carbonates also a variation in the mineral composition appears. For the revision, the available logs have been digitized. The combination of logs for a carbonate analysis is not optimal. As a deficiency, the missing of the"combination density-Neutron turns out. A computer supported analysis with different techniques was undertaken. Problems of a porosity calculation are originated by the occurrence of minerals of high density and PE cross section. In the wells Blumau 1/1a, the upper carbonate area (2355-2612m) could in its dolomitic construction described and an estimation of the porosity (in the range of 10%) was carried out the lower area was not exact interpretable;all results shows that, this is practically not porous and accordingly not water-bearing. In the Well Blumau 2 the existing sonic log and the resistivity measurements, have been earlier taken place, the porosity estimation that carried out, delivers the similar results and also the upper section (2750-2770, 2810-2840 m) show hints to increased porosity. Connected with the encountered statements on the Porosity, methodical investigations to derive the Porosity, under relatively unfavourable conditions with regard to the available logs are discussed.