FLOWLINES AND PIPELINES
Assessing the working condition of aging off- shore pipelines is a challenging process made more complicated by their loca- tion on the seafoorand limited access points. An operator off the coast of
West Africa faced such challenges in its plans
to inspect 160 shallow-water offshore pipelines that had been in service for decades. These
pipelines possessed widely varying temperature,
pressure, and fowrate profles, and the operator had a limited local inspection infrastructure to draw from.
The operator needed an in-line inspection solution that could accurately assess the condition of these lines, which ranged in size
from 8 in. up to 24 in. (200 mm to 600 mm) in diameter and from 0.5
to 17. 3 mi (0.8 to 27.8 km) in length. Service of these lines varied
from oil and gas to water injection to multi-phase fow. The majority of lines were smaller in both length and internal diameter (ID),
while the largest and longest pipelines were devoted to transporting
product from the offshore feld to shore.
Baker Hughes had developed an in-line inspection solution,
which was both integrated and in country, that could address the
operator’s needs. The pipeline service company had a local workshop and associated facilities located in close proximity to the operator’s onshore operations base. This onshore facility would also house
any required spare parts and maintenance activities for the inspection
tools. Baker Hughes took advantage of an eastern hemisphere operations base as a coordination location, and assembled and mobilized
the tools from Aberdeen, UK, to the local facility.
The inspection strategy called for deploying two different tools to
accommodate the various pipe sizes. The frst, a multi-channel caliper
(MCC) tool, was deployed in line to detect and characterize changes
in the internal bore of the pipe, which could indicate integrity issues.
The MCC comprises a series of spring-loaded deformation sensor
arms positioned around a central tool body, which ensure constant
direct contact with the interior pipe surface. The close spacing of the
arms ensures circumferential coverage of the pipe wall.
The MCC also includes bend-radius sensors to detect and defne
pipe bends, thus providing more up-to-date pipeline data profles
ahead of deploying more expensive and sensitive in-line inspection
tools. The tool contains dual, independently recorded odometers,
onboard orientation sensors, and fash memory data storage to acquire high-quality pipe data and an accurate location of any pipeline
The second type of inspection tool deployed magnetic-fux leakage (MFL) technology, which can accurately and simultaneously
detect multiple corrosion-induced anomalies and morphologies in
the pipeline. Common anomalies detected include general, pitting
or complex corrosion; manufacturing defects; gouging or grinding;
and deformations with metal loss.
The large number of pipelines to be inspected, coupled with a lack
of knowledge of their condition, prompted a systematic inspection process. The MCC tools, in size ranges from 8 in. to 24 in., were deployed
frst to gauge the internal bore and determine the next steps for repair
or further inspection. This tool quickly and accurately determines the
extent and location of dents or other obstructions in the pipeline.
The operator ran MFL in all of their pipelines after MCC, including the larger ID pipelines (from 20
in. to 24 in.). The information from the caliper-based
inspection runs would be critical prior to deploying the MFL,
which is a more expensive and sensitive tool. The MCC indicated
whether the ID of the pipeline was large enough for the MFL to
pass through without getting stuck at bends or dents. The MCC also
provided valuable information on whether the pipeline was clean
enough to allow for an accurate MFL reading. And fnally, because
the MFL has to move through the line within a certain speed range
in order to collect meaningful data, the MCC tool confrmed whether or not the pigging speed was in the desired range.
The deployment strategy called for personnel on the platform from
where the inspection tools would be launched. To accommodate the
various pipe sizes, personnel had to adapt the tools on-site. New MCC
tools were manufactured specifcally for this operation in sizes that
included 8-in./10-in., 16-in./20-in., and 24-in./28-in.
Once the calipers had been deployed and information on the minimum bore of the pipeline was available, the operator had to decide on-site
whether to run the MFL tool. By having the same personnel at the site to
run both the MCC and the MFL, the inspection was quick and seamless,
allowing the operator to stay on inspection schedule.
The high-resolution MFL technology was deployed on those lines
that were deemed suitable by the MCC run. After each run, the gi-gabytes of data recorded by the tools were collected and transferred
through a cloud-based network from the West Africa location to an operations center in Europe for analysis.
The analysis reported back a comprehensive report of the defects
in each line, as well as its dimensions (depth, width, and length). The
analysis also assessed the degree to which the wall strength decreased
around the defect and compared that to the desired operating pressure
when fuids fowed through the line.
Armed with this information, the operator was able to make a more
informed decision on the next steps required to ensure the safe operation of the pipeline. For high-risk lines that show signifcant wall loss,
parts of or entire sections of the line may need to be replaced. Other
lines showing less severe wall loss may simply be kept in service, but
fagged for future mitigating action.
The high-resolution in-line inspection service, performed on lines
that did not have to be taken out of service during inspection, gave the
operator the information necessary to determine near-future pipeline
To date, Baker Hughes has inspected 58 of the feld’s 160 pipelines, through an effcient mobilization of personnel and tools. The
continued use of locally sourced Baker Hughes personnel and inspection equipment will create an ongoing reporting process that
allows the operator to track how fast corrosion is advancing in their
pipelines and optimize their long-term feld maintenance programs
In-line inspections guide offshore
field management decisions Barry Nicholson Baker Hughes
A 24-in. high-resolution MFL inspection tool was deployed
to detect multiple corrosion-induced anomalies and mor-
phologies in the operator’s pipeline system offshore
West Africa. (Courtesy Baker Hughes)