366 S, G. KoMAROv and Z, I. Keivsar 



value for the permeability of a stratum, determined from a core; while 

 in some cases (the strata D^ and Djj of the Tuimazinskian deposit, Dj^^ of 

 the Romashkiusldan deposit) they practically coincide. 



However, the difference between the values of the permeabiUty determined 

 from the specific resistance and from cores, increases sharply, if we compare 

 them separately for large and small permeabilities of the stratum. This is 

 illustrated in Fig. 4, where the average values of the permeability K^^, 

 determined from the specific resistance, are compared with the average 

 value for the permeability K^^, obtained from cores for different ranges 

 of permeability values; 0-200, 200-400, 400-600 and above 600 millidarcies. 

 The comparison was carried out for the Dj and Z)jj strata of the Tuimazinskian 

 deposit and the Dj^, and Dj^ strata of the Romashkinskian deposit ; the original 

 data are the same as those from which the mean values of permeability 

 were calculated in Table 1. 



Evidently only for a permeability close to the average value for the stratum 

 does the method for determining permeabihty by the specific resistance, 

 based on the use of the above curves Q =f{K), give favourable results. 

 For large and sm.all permeabihties, a large systematic error is observed — 

 increasing for the small permeabilities, and decreasing for the large 

 permeabihties. There is a sort of levelHng out of the readings. This error 

 is very dangerous, since in an individual well it can lead to a distortion of 

 even the qualitative idea of the permeability of the strata. 



The possibility of the method for determining permeability by the specific 

 resistance can be shown by comparing directly the coefficient of increase 

 in resistance with the actual value of the permeability. 



Fig. 5 gives the results of these comparisons for the Dj stratum of the 

 Tuimazinskian deposit. On the graph they are points, the abscissae of which 

 are the values of the permeability Kpgr-> determined from the core, and the 

 ordinates — the corresponding values for the coefficient of increase in 

 resistance Q. For the values of Q were taken those values wliich were used 

 in calculating the errors given in Table 1. The points are divided into two 

 groups; one group (marked on the graphs with circles) includes points for 

 which the values of the permeability were not very accurate (small number 

 of cores, for which the permeability was measured; a large difference in the 

 results) ; the other group (black) includes points for which the values of the 

 permeabihty were determined with a sufficiently high degree of reliability. 

 On each of the graphs an "empirical" curve for the dependence of 

 the coefficient of increase in resistance Q on the permeability Kp^^ was 

 drawn through the points. This is done in the following way: the abscissa 

 is divided into a number of separate intervals and for each of them 



