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sometimes utilized starches for filtration control. During this
period, carboxymethyl cellulose (CMC) was popular for filtration
control in gyps and seawater fluids. The lignosulfonates were used
with desirable improvements in stability.
There were many problems with tubular corrosion during
this period. Many investigators started to question the
lignosulfonate, based on lab testing. The pH values were low, and
unsuspecting drillers were plagued with bacterial attack and loss of
filtration control, along with corrosion problems. Bacteria can
attack the sulfate ion, and also the cellulosics, etc. H 2O could be
formed with this attack to further -.aggravate corrosion problems.
Biocides were initiated again to reduce the attack. And makeup
water was treated to minimize these detrimental bacterial effects.
A modern, effective biocide treatment is the addition of 25%
glutaraldehyde.

Oil muds

These systems were advertised as the muds of choice, as they
showed no corrosion, compared to water-based fluids. The
protective oil film that formed on the pipe lowered the corrosion
rate and the systems were generally considered to be protective.
These fluids contained organic chemicals that emulsify the brine
phase into the oil-exterior phase with a desirable film on the pipe.
Such muds need to be conditioned for high electrical stability (ES)
and a high mud alkalinity (Pom) to keep the internal phase
alkaline.

Some earlier treating techniques

Recognizing potential problems and using proper fluid
treatment early during the operation can help avoid corrosion
problems. The gypsum muds did not have a high pH necessary for
reducing overall corrosion rate and controlling some bacteria.

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