THE LOOP METHOD IN EXPLORING BURIED STRUCTURES 251 



nature of merging structures and the relationship between the tectonic 

 zones. 



This material should be used for a rational distribution of seismic profiles. 

 If this is not fully appreciated, errors can be introduced when planning 

 work and eventually errors can arise in the deductions about tlie structure 

 of the area, as was the case in the Vladislavov-Kharchenkovskaia tectonic 

 zone and in the zone of merging of the Moshkarevskaia and Shirokovskaia 

 structures. 



Seismical studies on these areas, which have no interesting petroleum-bea- 

 ring aspect (although complex in their structure), were carried out by a sparse 

 network of profiles ignoring the details <^^). As a result, the Frontovaia and 

 Kharchenkovskaia structures represented by data of the loop method, of 

 the geological survey and by the subsequent exploratory drilling, as t^vo 

 inde|)endent connected folds, were united by seismic exploration into one 

 wide structure (Fig. 4). A well drilled in the crest of the fold to the south 

 of Lake Parpach gave an oil gusher of several tens of tons. This fact demanded 

 final solution of the problem of the structural position of the well. For this 

 purpose, in the summer of 1956 detailed seismic profiles were made, con- 

 firming that at that section the two structures merged. The gusliing well 

 was situated at a deep western depression of the Kharchenkovskaia brachy- 

 anticline, in connection with which further exploratory drilling was tran- 

 sferred to the Kharchenkovka region. 



In the light of the preceding, it is necessary to reconsider the schematic 

 structural map of the Moshkarevka area, compiled for the arbitrary seismic 

 horizon M. Surveying by the loop method shows the complex merging 

 of the small, intensively dislocated, Moshkarevskaia fold into the relatively 

 large Shirokovskaia fold. Despite the fact that on the western depression 

 of the Shirokovskaia structure and on the Moshkarevskaia upfold more 

 than 100 wells were drilled, up to the present time opinions about 

 the structure of this region to A\hicli the location of petroleum is related 

 vary. 



From the seismic data on the arbitrary level M, the anticlinal upfold 

 is drawn on an area 8x4 km^ with an axis striking north-east course ^^^K On 

 comparing contours of structures for various data (Fig. 5) it becomes 

 apparent that the whole eastern periclinal part of the fold according to the 

 data of seismical survey is placed within the limits of the western crest 

 of the Shirokovskaia structiu'e. Confirmation of the fact that the structure 

 contours imited t-\vo different upfolds is provided by the data of the seismic 

 profiles XVIII, XX and XXI, intersecting the Moshkarevskaia anticline, 

 and the XXll profile, cutting the Shirokovskaia structure. The first of them 



