310 



L. A. Galkin 



of productive strata of the coal bearing sequence of the Tournaisian stage, 

 of the Naryshevskian Beds and of the Upper Givetian substage of the Bash- 

 kiriyan strata (Shkapov and Stakhanov areas). It can be seen that the pene- 

 tration rate varies within wide hmits. 



Table 2. Rates of boring in productive beds in certain wells 



7 

 9 



10 

 13 

 15 

 18 

 29 

 31 



3 



4 



11 



15 



0.8 



Shkapovka area 



Stakhanovka area 



Average of Shkapovka and Stakhanovka areas 

 8.2 I 1 , I 5.2 I 10.7 I 0.6 I 3.6 I 7.8 I 0.5 



3.1 



2.8 

 11.6 

 11.2 



5 



2.8 



2.4 



15 

 1 



4.5 

 9.4 



6.8 



It follows from formula (2) that the gas saturation of the drilling fluid is 

 inversely proportional to the duration of boring and is therefore directly 

 proportional to the rate of boring. In correspendence with the wide range 

 of variation of the boring rate, the gas saturation of the drilling fluid can 

 also vary within very wide limits — by ten times or more. It varies within 

 narrower limits with pump output, which varies from 20 to 60 1/sec during 

 the boring of productive beds. 



Table 3 gives calculated valvies of gas saturation of the drilling fluid for 

 some values of the rate of boring and pump output, illustrating the consider- 

 able variation of the gas saturation of the drilling fluid with rate of boring. 



It should be noted that, as experience of gas logging shows, actual values 

 for the gas saturation of the drilling fluid often lie below the calculated 



