| Case Studies
TRACERCO Diagnostics™ Pipeline Assurance
Flow Assurance
Tracerco had been requested by a North Sea major to determine
the total amount of deposit within a 22km long, 16”
diameter subsea pipeline running between two platforms,
by the use of the TRACERCO Diagnostics™ Flow
Assurance Study. Measurement of the accurate velocity of
a pulse of tracer between the platforms would be compared
to the flow rate through the line and used to determine
the effective average internal diameter of the pipe and
therefore highlight the extent of deposit within the line.
The 16” oil line had not been pigged for a number
of years, therefore the amount of deposit in the line needed
to be measured to enable a cleaning program to be devised,
and confirm the amount of expected deposits that would have
to be disposed.
A sharp pulse of suitable radiotracer was injected into
the pipeline at the sending platform, and a Tracerco data
logger mounted externally on the pipework measured the exact
time that it passed the known position on the riser. A second
Tracerco data logger measured the exact timing of the eventual
arrival of the pulse of tracer on the receiving platform,
and a simple measurement of flow velocity obtained by dividing
the time of flight of the pulse by the total distance travelled.
The accuracy of the transit time was +/- 0.05%, derived
from the error produced in the measuring of the centroid
of the tracer pulse at the receiving platform.
The fiscally metered flow rate during the tracer test was
then compared to the measured velocity, allowing the effective
average internal diameter of the pipe to be calculated.
Any reduction from the internal diameter schedule of the
pipe will be due to deposit within the pipe, as long as
the flow is full bore and turbulent during the measurement
period.
An average deposit throughout the full 22km of 10mm was
detected within the line, which equated to a total measured
deposit volume of approximately 140 cubic metres. The accuracy
of this measurement depends on the accuracy of the fiscal
flow meter.
Unfortunately, it was not possible to arrange for the deployment
of subsea detectors, which would have provided further intermediate
velocity measurements, which would give further information
on the location of the deposit within the line.
Detector responses on each platform:
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