10 DEEP BOREHOLE SURVEYS AND PROBLEMS 



need. Unfortunately, apart from Rumania, there are no 

 actual master borers' schools in Europe. 



The Detection of Incipient Curvature in Boreholes. — 

 Suspected curvature of the rods may be checked by noting 

 the following surface indications of the deflection. It must 

 be noted that these indications may be entirely absent, 

 making the curvature untraceable without instrumental 

 means. 



a. The uneven wearing of the chisel or crown hit due to 

 encountering unequal resistances at the floor of the hole. 

 The contact surface of the tool tends to become inclined due 

 to excessive wear on one side. It also tends to snap off. 



6, Lateral abrasions of the rods and brushing of the rope 

 sides in rope boring. This is due to side wear and in the 

 case of rigid rods will usually show the side on which curva- 

 ture is occurring, i.e., the ''off" side. 



c. Difficulty in Inserting the Casing. — Frequently the 

 casing sticks fast as often does the boring tool owing to the 

 curvature. 



d. Scoring of the core and core box in rotary boring. This 

 will often provide fair information as to the cause of the 

 deflection. 



e. Laboring of the Rig Gear. — The surface engine labors 

 under the extra load, the bearings run hot and general signs 

 of lack of uniformity ensue. 



/. Study of the Progress Reports. — This often provides 

 clues which can be reduced to curvature as the cause of 

 variations in the progress graph. 



g. Throttling of the circulating water, the circuit being 

 accomplished in gusts and frequently hindering or loading 

 the plant. Lesser deflections may be corrected by second- 

 ary boring or partial reaming. The borehole will thus be 

 widened and the casing set without being influenced by 

 the previous borehole walls. This simple remedy only 

 applies to deflection which has been detected just after it 

 has begun. 



h. Instrumental Means. The Anschiltz-Kaempfe Acoustic 

 Device. — Nearly all of the many and varied devices for 



