STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

928 Drilling and Well Completions
housing stops abruptly. Compute the maximum deceleration x in g's
and the deceleration time t. All calculations can be made in English or
metric units.
2. Taking into account the spring only compute the distance traveled x and
the maximum deceleration a in g's when the housing stops abruptly.
3. Now if both the spring and the shock absorber are acting together, what
will be the distance traveled x and the maximum deceleration a in g's when
the housing stops abruptly?
4. What is the advantage in adding a shock absorber to the spring in such a
system?
Solution
1. Neglect the effect of gravity. Energy balance: Fx = 4 mv2 (v = 3.048 m/s)
x = mv2/2F = 0.209 m
a = F/m = 22.24 m/s2 = 2.26 g
x = +at2 + t = (2~/a)'/~ = 0.137 s
x = 0.209 m = 0.685 ft = 8.23 in. = 20.9 cm
a = 2.26 g
t = 0.137 s = 137 ms
2. Before the tool hits, going down at a constant velocity, the spring is already
compressed by the weight of the instrument package, so the effect of
gravity can be neglected. Energy balance:
;Smv2 = +kx2
x = (mv2/k)'/' = 0.043 m = 0.141 ft = 1.69 in.
Fma = kx = 430 N
a = F/m = 215 m/s2 = 705.38 ft/s2 = 21.9 g
x = 0.043 m = 0.141 ft = 4.3 cm = 1.69 in.
a = 21.9 g
3. Still neglecting gravity. Energy balance: Fx + +kx2 = +mv2
kx2 + 2Fx - mv2 = 0
x = [-F + (F2 + kmv2)1/21/k = 0.0388 m = 0.127 ft = 1.53 in. = 3.88 cm
F, = FS + 1/2 kx = 432.5 N
a = F/m = 216.2 m/s2 = 709.5 ft/s2 = 22.03 g
x = 3.88 cm = 1.53 in.
a = 22.03 g
4. Oscillations will be dampened; x slightly decreased: 3.88 cm versus 4.3 cm.
Teledrift and Teleorienter
The first transmission of data during drilling using mud pulses was commercialized
by B.J. Hughes Inc. in 1965 under the name of teledrift and
teleorienter. Both tools are purely mechanical. A general sketch of principle is
given in Figure 4-239. The tool is now operated by Teledrift Inc.
The tool generates at bottom positive pulses by restricting momentarily the
flow of mud each time that the mud flow (pumps) is started. The pulses are
detected at surface on the stand pipe and recorded as a function of time.
Figure 4-240 shows the sketch of principle of the teledrift unit which is
measuring inclination.
A pendulum hangs in a conical grooved bore. A spring tends to move the
pendulum and the poppet valve upwards when the circulation stops. If the tool