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The tiny particles are extremely hard and jagged. When
accelerated to the velocities
inside gas pipelines, they act like an abrasive used in
sandblasting, affecting pipes and
parts never intended to endure such punishment.
The Pipelines Departments collection of a large number of black
powder samples,which it submitted to R&DC for analysis, was
crucial in identifying the composition and
properties of the black powder.
Many industry experts at the National Oil Companies 2007
Symposium in Stavanger,
Norway, were surprised at the findings reported by senior lab
scientist Abdelmounam
Sherik of the companys R&D Upstream Program.
The comprehensive study noted that although mill scale and
hydrotesting of pipelines
may have a minor and short-lived contribution to the problem,
the source of the blackpowder is much different.
When I approached this project, I approached it to resolve this
question. When we got
into it, we discovered that mill scale could not be the cause
because within a year or so,
it would be all finished, Sherik said.
It couldnt be hydrotesting, either, because we do hydrotesting
during commissioning.
Some of the pipelines from which we collected black powder had
been in operation for
30 years.
Sherik enlisted the help of Southern Area Labs, which conducted
extensive testing of
the gas itself. The test results were unexpected.
We analyzed the gas for the first time from a corrosion point of
view by looking at the
gas components on a parts-per-million level, Sherik said.
To our surprise, and to everyones surprise at Saudi Aramco, we
found oxygen, he
said. Everybody thought there was no way our gas would have
oxygen. We didntestablish this in one test but by eight different
tests.
We also were very surprised to find the gas had moisture in it.
So we have moisture,
and we have oxygen, which are what you need to have a corrosion
problem in the
pipeline.
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The effects werent obvious because they were happening on a
small scale and they
werent affecting the pipeline, but the control valves. When you
have a long pipeline
hundreds of kilometers you get a lot of black powder, Sherik
said.
Another finding of the study was that about 20 percent of the
weight of the black powderactually was tiny particles of metal,
sand, dirt, hydrocarbons and elemental sulfur.
The Pipelines Department and the Consulting Services Department
are acting on the
results of that study, and revisions have been made to company
hydrotesting
procedures and control-valve specifications. Improvements to the
gas drying process
also are being implemented by gas plants and the Process and
Control Systems
Department to ensure no moisture enters the pipelines.
Now the world will be watching as another study led by Saudi
Aramcos Research andDevelopment Center seeks to predict the speed
at which the powder will form and what
preventive measures to take to stop it from generating in the
first place.
Sherik credits his colleagues for his research success.
The Pipelines Department was very active in this, he said. They
are the people we
collected the samples with, and we had a lot of interaction with
them. Without the
Pipelines Department, this work would have been very difficult
to do. The Southern Area
Labs did all the gas analysis, and that was a big help, too.
Now Saudi Aramco is spearheading an industry-wide initiative,
with NOCs of China,
Norway, Brazil, Malaysia and Algeria taking part. The scope of
the latest project will be
presented by Sherik in November when the NOC Natural Gas Working
Group meets in
Brazil.
