B"C = 



PROBLEMS 253 



B"E AB" sin 5 



sin (180 - b - a) sin (5 + a) 



L = J^+ AB" 



sin a cot 8 sin a + cos a 

 L = h(J-+ ;f ?--">*. ) (28) 



\Sin a cot 5 Sm a + COS Q!/ •^ 



Compare with Eq. (23) above where similar remarks 

 apply respecting the altitudes of the derrick floor and the 

 outcrop. 



When the surface is flat AB" = AB' = AB and then 



i = BC = ^^HLL (29) 



sm (5 + a) 



Compare with Eq. (24) above. 



26. The Displacement of the Borehole. 

 DC = B'B" + FC 



AB" 



H cot a + 



tan a cot 5 + 1 



2c. The Total Depth of the Borehole. 

 BD = H + h 



BD = H+ ,/5 , =h(i + '''1]-'''1^ ) (31) 



cot 5 + cot a \ cot 5 + cot a/ ^ ^ 



The reason for choosing the persistent term AB" is 

 because it is the dimension most likely to give the least 

 trouble in obtaining in practice. 



C. HORIZONTAL BOREHOLES 



Here the inclination of the borehole is nil, so that in 

 Eq. (20) a = deg., making the expression for the displace- 

 ment X (Fig. 170). 



H — AB' sin 02 tan 8 AB' sin 9-, — H cot 5 ,„^, 



^ ^ . = . (32; 



— sin di tan 8 sin di ^ ^ 



