Page 148 - Geothermal Energy Systems Exploration, Development, and Utilization

124 3 Drilling into Geothermal Reservoirs

f 1
DL
2

DL
2

q 1

∆ MD
∆ Vertical

f 2
DL
∆ North
q 2

∆ East
Figure 3.10 Borehole trajectory with two measuring points.
(From Economides, Watters, and Dunn-Norman, 1998.)

a straight line which of course was not correct. Currently, a curve with a maximum
radius fitting into the measured points is assumed as shown in Figure 3.10.
For the calculation, the following formulae are used:
MD
North = [sin(
1 ) × cos( 1 ) + sin( 2 ) × cos(
2 )] × RF
2
MD
East = [sin( 1 ) × sin(
1 ) + sin( 2 ) × cos(
2 )] × RF
2
MD
Vert = [sin(
1 ) + cos( 2 ) × cos(
2 )] × RF
2
with
360 DL
RF = tan
πDL 2
cos DL = cos( 2 − 1 ) − sin 1 × sin 2 [1 − cos(
2 −
1 )]

With this technique, it is possible to steer a well’s trajectory with an accuracy in
the range of a meter. It is commonly used to drill several wells from one site into
different directions, for example, from offshore platforms. It also allows to drill
horizontal wells; the actual world record is held from the well BD-04A in Qatar