Geometrical Calculation Technique
The drift angle TEY can alternatively be calculated as follows (Figure 4).
In the example:
3000 — 2866.24
tanx= ^ x = 0.96o
8000
2866.24cos0.96 _ ,,nmo
siny = ^ y = 20.99
8000
a=21.950
Note : It is possible for angle x to be negative if d < R, but these equations are still valid.
Once the drift angle is known the other points on the wellpath can be calculated as follows:
AE (measured depth at end of build section)
AE = AB + BE (curved length)
be a
BE can be calculated from =———————— ^——— BE = 1097.50′
2nR 360
AE = 2000 + 1097.50 = 3097.50’
AX (TVD at end of build)
AX = AB + PE
where PE = R sin a = 1071.39′
AX = 2000 + 1071.39 = 3071.39’
XE (horizontal deviation at end of build)
XE = OB — OP
where OB = R OP = R cos a = 2658.47′
XE = 2866.24 — 2658.47 = 207.77’
AT (total measured depth)
AT = AE + ET
ET can be calculated from;
ET = 8000 — 107 09 = 7470.12′ Cos 21.95°
AT = 3097.50 + 7470.12 = 10567.62’
Exercise 1 Designing a Deviated Well
It has been decided to sidetrack a well from 1500 ft. The sidetrack will be a build and hold profile with the following specifications:
Target Depth : 10000 ft.
Horizontal departure : 3500 ft.
Build up Rate : 1.5o per 100 ft.
Calculate the following :
a. the drift angle of the well.
b. the TVD and horizontal deviation at the end of the build up section.
c. the total measured depth to the target.