OPTICAL METHODS OF BORE-HOLE INVESTIGATION 345 



(dark grey dolomite, light grey limestone) constituting the breccia are 

 easily visible; the dimensions, shape and mutual disposition of these fragments 

 can easily be discerned (Fig. 10, 1-3). 



In the photographs the stratification, presence of veins and seams in the 

 rock, and the fissuring of the rock can be easily seen. Here it is possible to 

 distinguish the cracks filled with some cementing material, in the given 

 case white calcite (Fig. 10, 6-8), from those not filled with cement (gaping) 

 (Fig. 10, 4-5). 



In well 2589 in the Kamenskaia region, having a diameter of 90 mm, 

 forty-five photographs were taken at depths from 42 to 90 m. In these 

 photographs it is also possible to establish the lithological character of 

 the bed. 



Sandstones are distinguished by their clearly visible individual grains 

 (Fig. 11, 4); coarse-grained sandstones being distinguishable from fine- 

 grained sandstones. The greater the grain size, then, naturally, the more 

 accurately is the grain structure of the sandstone recorded and the more 

 distinctly can the individual grains be distinguished. 



Clayey rocks are marked by irregularities in the wall, which are due to 

 erosion of the rock (Fig. 11, 3), and by stratification. 



Coals (in the given region close to anthracites) are well distinguished by 

 alternation of dark and light regions which are due to the presence of sharp 

 boundaries at the fracture of specimens; often these regions are extended 

 in one direction, corresponding to the stratification of the rock (Fig. 

 11, 1 and 2). 



On the basis of an analysis of the photographs the following conclusions 

 can be reached. 



1. From the photographs of the rock it is possible to form an idea — al- 

 though not always unambiguous — of the lithological character of the rock. 



2. Photography of the rock permits the petrographic character of the 

 rock — structure, grain, presence of cementation, etc. — to be defiiaed more 

 accurately. 



As a result of photography of the rocks along the walls of wells, problems 

 of elucidating the structural features of the rock (the presence of inclusions, 

 stratifications, fissures) are solved most successfully. 



It should be noted that geophysical methods at present employed for 

 well surveying do not permit detection of the degree of fissuring of rock, 

 while such fissuring is a very important property of the rock. In a series 

 of reservoirs the reservoir properties of the beds are connected with the 

 fissuring. 



