STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

954 Drilling and Well Completions
6. The mud flow rate is 500 gal/min and the fluidic pulser has 4 x 24/32
in. diameter nozzles in parallel. Compute the pressure loss in the fluidic
pulser in the minimum loss mode (C = 1).
7. What is the equivalent diameter of each nozzle in the maximum loss mode
to produce the peak to peak wave value computed in question 2 (C = l)?
Solution
1. 5 bit/s x 4 cycles = 20 Hz (cycles/s).
2. P(x) = P(0) e-JD
P(x)/P(O) = 0.0544, x = 4572 m
P(0) = 91.9 psi
3. Yes, by filtering only the wave amplitude corresponding to 20 Hz can be
measured, thus eliminating the noise.
4. P(x)/P(O) = 0.1049
P(0) = 47.6 psi
5. Yes, each detector will "see" only the wave amplitudes corresponding to
20 and 12 Hz. They will be sensitive to "their" signal only.
6. 78.8 psi
7. 0.619 in.
Dlrectional Drilling Parameters
With the modern accelerometers and solid-state magnetometers, a complete
set of data is available for inclination, tool face and azimuth calculation.
Magnetic corrections can be done. Inclination can be calculated with Equations
4-174 and 4-175. The gravity tool face angle can be calculated with Equation
4-176.
Azimuth calculation can be done by using vector analysis. In Figure 4-258 the
vector 2 represents the borehole axis, vector H the earth magnetic field and
vector G the vertical or gravity vector. The azimuth is the angle between the
vertical planes V, and V, counted clockwise starting at V,. This angle is the
same as the angle between vectors A and B, respectively, perpendicular to V,
and V,. We know that
A = G x H (vector product) (4-190)
B=GxZ
The components of H and G are measured in the referential of the MWD
tool, and Z is the vector (0, 0, 1) in the same referential. Now the azimuth a of
the borehole can be computed with the scalar product B A thus
(4- 191)
Some precautions must be taken to be sure that the correct angle is computed
since cos(a) = cos(-a).
The MWD sensors are located in a nonmagnetic part of the drill collars. The
magnetic collars located several meters away still have an effect by creating a
perturbation in the direction of the borehole axis. This introduces an error that is