358 S. G. KoMAROv and Z. I. Keivsar 



(c) The mean and mean square values of these deviations, calculated 

 from formulae similar to (6) and (7), 



These mean and mean square deviations characterize the error introduced 

 when, instead of the actual value of permeability for the stratum, we take 

 the mean value of permeabihty for the stratum. 



There are small differences between the errors in determining the perme- 

 ability of the stratum from the specific resistance and the errors which are 

 obtained when, for the permeability of the stratum of a given section, 

 we take the mean value of permeability for the stratum. 



Thus, the use of the method for determining permeability from the 

 specific resistance, in accordance with the existing instructions, does not 

 lead to a noticeable improvement in accuracy of the data on stratum perme- 

 abihty. The stratum permeabihties obtained by averaging the values are 

 used more effectively since it is not necessary to process a large amount of 

 materia;!. 



Thus, the method for determining permeabihty by the specific resistance 

 in the variant recommended for the Devonian sandstones of the Bashkiria, 

 Takaria and Nizhnii Povolzh'e deposits lead to large errors. 



CERTAIN PROBLEMS IN THE METHOD FOR DETERMINING PERMEABILITY 

 FROM THE SPECIFIC RESISTANCE 



It was assumed that the large error in determining permeabihty from the 

 specific resistance for the Tuimazinskian, Shkapovskian and Romashlcinskian 

 deposits is connected with the incorrect choice of the same specific resistance 

 of the water-bearing stratum for all cases (0.7 O/m). Consequently for the 

 deposits mentioned, a second determination of the permeability from the 

 specific resistance was conducted; the specific resistance of the water- 

 bearing stratum being taken as its value obtained for each separate well. 



Calculations showed that the values of the errors are about the same (see 

 Table 2, corrected by Do una results). Apparently, the main reason for the 

 error is not the initial geophysical data, but the poor connection between 

 the interstitial water saturation and the permeability or the error in deter- 

 mining it. 



The determination of permeability of petroleum strata by the specific 

 resistance is based on the assumption that in the petroleum stratum there 

 is only interstitial (connate) water. 



Apparently, apart from interstitial water in the petroleum stratum there 

 is also the so-called free water, the quantity of which near the top surface of 

 petroleum-bearing deposits or water-petroleum contact can be sufficiently 



