Geology Reference
In-Depth Information
“Nothing, but I've watched Jed Clampett shoot it out of the ground,” I confessed
(Clampett was the hillbilly in the television sitcom who blasted his rifle into the
ground, struck oil and moved to Los Angeles to live in his new mansion in “The
Beverly Hillbillies”). Buchholz broke out in uncontrolled laughter. That type of
honesty he appreciated. I got the job. And with that, I became Schlumberger's
Supervisor, MWD Telemetry, for 2
nd
generation mud siren and turbine design.
The company's Analysts division, at the time responsible for an ambitious
next-generation, high-data-rate MWD design program, had built ultra-modern
office and flow loop facilities in southwest Houston. The metal pipe test section
was housed in an air-conditioned room where engineers could work in a clean
and comfortable environment away from the pulsations of the indoor mudpump
that supplied our flow. A small section of the flow loop was accessible in this
laboratory with the main plumbing carefully hidden behind a wall - details no
self-respecting, white-collar Ph.D. cared for nor admitted an interest to.
My charter was simple. We were transmitting at 3 bits/sec in holes
shallow by today's standards with a 12 Hz carrier frequency. Our objective was
N bits/sec, where N >> 3 (the value of N is proprietary). The solution seemed
straightforward, as company managers and university experts would have it.
Simply “crank up the carrier to (N/3) u 12 Hz and run.” I did that. But my
transducers would measure only confusion, with new pressure oscillations
randomly adding to old ones and results depending on mud type, pump speed
and time of day. What happened “behind the wall” controlled what we observed
but we were too naïve to know. Anecdotal stories told by different field hands
about new prototypes were confusing and contradictory. One simply did not
know what to believe. Thirty years later, the data rate is still comparable, a bit
better under ideal conditions, as it was then. Clearly, there were physical
principles that we did not, or perhaps were never meant to, fully comprehend.
Fast-forward to 1992 at Halliburton Energy Services, an eternity later,
where I had been hired as Manager,
FasTalk
MWD. Again, mass confusion
prevailed. Some field engineers had reported excellent telemetry results in
certain holes, while others had reported poor performance under seemingly
identical conditions. The company had acquired several small companies during
that reign of corporate acquisitions in the oil service industry. It would turn out
that “good versus bad” depended, with all other variables constant, on whether
the signal valve was a “positive” or a “negative” pulser. No one really
distinguished between the two: because the MWD valve was simply viewed as a
piston located at the end of the drillpipe, exciting the drilling fluid column
residing immediately above, it didn't matter if it was pushing or pulling. Sirens
were a different animal; no one, except Schlumberger, it seemed, understood
them. But nobody really did.
Additional dependencies on drilling conditions only added to the
confusion. Industry consensus at the time held that MWD telemetry
characteristics depended on drillbit type and nozzle size and, perhaps, rock
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