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noted that corrosion rates were in the 22 lb / ftt -yr range, and should
be monitored with drill pipe corrosion coupons.
The contractors quickly realized that the fluids needed to be
tested for corrosion rates and treated immediately. The drill pipe
corrosion ring coupon was invented during the 1950s, and is still
used today.

Corrosion monitoring, testing

During the period discussed in this section, corrosion was
monitored with electronic corrosion rate meters, galvanic probes
and dissolved O 2 meters. Later, it was found that these were not
necessary in many cases, as down hole fluid may have a higher
corrosion rate than surface measurements would indicate. Some of
the factors causing the corrosion included О 2 in the fluid, pH and
salinity. In addition, dissolved acid gases such as CО 2 and H 2S
were influential in causing severe problems. It was generally found
that even a small concentration of sulfide could be less aggressive
if O 2 content were extremely low. With proper pretreatment, this
should mean that there would be fewer washouts and twist-offs to
contend with. And less tubular failure or downgrades, meant less
rig time.
While monitoring with coupons, any mineral scale deposit
that showed up could be important to the analyst, as it might hold
the key to the corrosion problem source. For instance, if rust were
noted, О 2 corrosion was suspected.

Problem / failure analysis

Accurate information on metallurgical failures should be
expected from the metallurgical labs. After necessary tests, one
could start to draw conclusions as to the cause, and cure (if any), of
failures being noted. Working with the contractor and the operator,
the nature of the problems, and chemicals or mechanical

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