STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

MWD and LWD 921
Using the drawing Figure 4-234 find the algorithm to compute these
angles. Write a short computer program and use the data of Example 3
for a numerical application with a 2" sub.
2. If we change the tool face angle to -30" (turning left), what will be the
probable borehole deviation and azimuth after drilling another motor
length? Use the same computer program.
Note: We will assume that the borehole axis is the same as the drill collar axis
at the steering tool depth and also that the borehole axis is the same as the
mud motor axis at the mud motor depth.
Solution
The same algorithms are used as in Example 3. The vector Z (0, 0, 1) is
replaced by vector Z (sin 2' cos TF, sin 2" sin TF, cos 2"). This new vector
Z should be used to compute the new inclination, using the scalar product
Figure 4-234. Vector diagram showing the mud motor axis as well as the
steering tool axis.