4 DEEP BOREHOLE SURVEYS AND PROBLEMS 



grouped his results graphically about the same vertical, 

 giving the remarkable suite of horizontal displacements 

 shown in Fig. la and the accompanying angular deviations 

 shown in plan in Fig. lb. 



All other influences considered equal, the amount of 

 deviation depends a great deal on the method of boring. 

 Many are of the opinion that the greatest deviation is 

 obtained in the rotary system yielding cores as in the shot, 

 calyx or diamond processes, and the least in the percussion 

 systems particularly the free-fall systems. In a recent^ 

 statistical survey of results which appear to support this 

 contention the data yielded from 21 boreholes was as 

 follows : 



Table III. — Summary of Some Rumanian and Russian Boreholes 

 Using Different Methods 



Method of boring 



Number 



of 

 boreholes 



Depth, 

 meters 



Most 



favorable 



case 



Worst 

 case 



Remarks 



Turbine borer 



(Kapeljuschnikov) 



Rotary system 



Rod percussive 



Rope percussive 



American rotary 



American-Chield rotary 



4 

 4 



1 



1 



10 



580 

 578 

 840 

 822 

 480 

 606 

 580 

 700 

 595 



5° 10' 



In the 

 same 

 strata 



In the 

 same 

 strata 



However, this point is very debatable. The diamond- 

 drillers claim that diamond-drilled holes can not drift as 

 much as holes drilled by other methods because the core 

 barrel nearly fills the hole. In hard rock the core barrel 

 normally occupies all but Ke in- of the diameter of the 

 hole. 



The rotary drill prevents the hole from drifting as much 

 as would occur by other methods by using at the bottom 

 a long steel drill collar of a diameter nearly equal to that 



. ^A. L. Schachnazarov, Engineer "Asnef" Oil Trust, Baku, in Petroleum, 

 No. 23, p. 772. 



