OIL PRODUCTION
Pressure release
Oil companies may save thousands of pounds in lost production with a pressure
pulse method of clearing blocked deep-sea pipes. Siobhan Wagner reports
A NEW method that uses a pressure pulse
to locate blockages inside pipelines could
help oil extraction on the ocean floor.
34
The technology from researchers at
the Norwegian University of Science and
Technology (NTNU) promises to speed up
the oil production processes and reduce
costs.
Based on the ‘water hammer’ effect,
the principle is the same as the bang one
can hear in a washing machine or
dishwasher when the flow of water to the
machine is shut off quickly.
The researchers create a similar
‘bang’ by closing a pressure valve on the
pipeline flow-line. The valve is closed for
a few seconds and then reopened. The
resulting pressure pulse is recorded at
two locations upstream of the valve with
transducers.
The information gathered is then fed
into a data acquisition system and put
through complex analytical methods. The
measurements are used to create a map of
the inside of the pipeline.
‘We’re able to see where the blockage
is and how much it is,’ said Jon Steinar
Gudmundsson, who developed the
method.
Operators are able to see on a
computer screen where the next pressure
vent is located. The information helps
them choose the best possible method for
clearing the pipe.
Gudmundsson said the ocean floor is a
difficult environment on which to
maintain and repair pipelines. There are
few ways to do it that aren’t costly or time
consuming.
One major cause of pipeline blockages
is wax build-up. As oil passes through
pipelines on the seabed it cools, leaving a
wax layer along the inside of the pipe.
The pipeline is then shut down and a
robot has to be sent through to find the
cause of the problem. In cases where
robots gets stuck, operators have to close
off the pipeline and reverse the pressure
to eject the robot.
At other times, the robot has to travel
through a long stretch of pipeline before
it comes across a blockage. In either
Much oil
extraction
takes place on
the ocean floor,
a difficult
environment in
which to maintain
and repair pipes
When a well is closed with a pressure valve, a
pressure wave is constructed. Gudmundsson
realised that this pulse could be used
situation, blockage detection and
removal can take a long time.
Lost production time can quickly
become a costly affair. The Norwegian
researchers estimated that if pipeline
problems caused a platform to be closed
for longer than several months, the lost
revenue could be up to £10m.
The new blockage location method
was developed after Gudmundsson
observed the shutdown of a geothermal
well in Iceland. He noticed that the well
was closed with a pressure valve and
this created a pressure wave. He
realised that this pulse could be used
for constructive means.
One of the advantages of using
the pressure pulse method is it is
inexpensive and requires very
little installation. The hardware
requirements are limited to the
pipeline’s existing pressure valve and
two transducers.
Gudmundsson said NTNU’s spin-off
company Markland Technology, set up
to commercialise the method, is
looking to sell maintenance services to
oil companies rather than equipment.
So far, Gudmundsson said Markland
Technology has achieved success in
offshore oil companies operating in
Norway and Africa.
the EnGIneeR 29 SEPTEMBER–12 OCTOBER 2008
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