VERTICAL AND INCLINED SURFACES OF SEPARATION 297 



I — Distortions of Qj^ are lacking for any directions of the DQP branches. 



II — For one direction of the DQP branches a deviation of Qf^ on the side 

 of increase is observed; values of Qf^ on the opposite branches of the DQP 

 are not distorted. 



III — For one direction of the DQP branches a deviation of Qi^ on the side 

 of increase is observed; values of ^^ on the opposite branches of the DQP 

 are not distorted: 



IV— A deviation of Qj^ on the side of decrease is observed for any directions 

 of the DQP branches; deviations from the opposite DQP branches are 

 equal in the central part of the region: 



V— A deviation of Qj^ on the side of decrease is observed for one direction 

 of the DQP branches and on the side of increase for the other direction 

 (in the central part of the region the deviations are of equal magnitude but 

 of opposed sign). In addition, there is a very shght decrease in Qi^ in this 

 region due to the other non-horizontal contact which can clearly be ignored. 



If we take a graphic mean of ^^ and allow for the possible level of its 

 deviation from (^j j^)j^, we obtain the behaviour of the isolines in the lower 

 part of the cross-section which describes the relative variation in the value 

 of Qi^ along the profile. It is not possible to obtain more or less reliable 

 values of Qf^ in region IVowing to the fact that the directions of the deviations 

 of Qi^ here coincide on the opposite DQP branches because of the presence 

 of two non-horizontal contacts. The isohnes of Qj^ are therefore given as 

 a dashed hne (two variants) in region IV. 



These variants do not, however, significantly alter our general view of 

 the qualitative features of the change in the electric cross -section along 

 the line of the profile. 



The method for calculating distortions in DQP therefore enables us 

 to establish the position of the buried contacts and to obtain values for the 

 total conductivity which are closer to the true values from the distorted 

 curves and thus to improve the quantitative interpretation of DQP curves. 



REFERENCES 



1. V. N. Dakhnov, Electric Prospecting for Oil and Gas Deposits. Gostoptekhizdat (1953). 



2. ''Elkageer,'' 1/2, 1938. Articles on materials from the firm SPE. CV-IS, CV-2S and 



CV-3S reference graphs. GSGT, 1938. 



3. E. N. Kalenov, The C-l-S reference graph. ''Elkageer," 3/4, GSGT, 1938. 



4. A. M. Pylaev, a Guide to the Interpretation of VEP. Gosgeolizdat (1948). 



