August 2015
Oilfield Technology
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envelope for a variety of high‑expansion applications. Inflatable
elements have been developed that can perform well in
applications where the required expansion is up to two or three
times the run‑in‑hole diameter. Nevertheless, high‑expansion
applications in deepwater or other extreme environments have
sometimes presented requirements that exceed the design
limits of the packer element, meaning job objectives could not
be met. Improvements in element design are also evolving and
setting a new standard for through‑tubing inflatable packer
performance.
In one new product line, dual anchoring elements have
been redesigned to improve their ability to perform effectively in
high‑expansion, high‑differential applications. The improvements
have led to new elements with higher differential ratings,
increasing anchoring ability. Elements such as this complement
the improved inflation pressure output from the latest slickline
setting tool.
Wireline interventionwith inflatabletechnology
During the life of a well, problems typically surface first in the
production tubing, the production liners, or the production
casing. A common indicator of these issues is sustained
casing pressure between the production casing and surface or
intermediate casing strings. Most of the older assets showing
such a casing pressure are on some form of secondary recovery,
such as gas lift or other artificial lift methods. A loss of gas
lift pressure will obviously impact that well’s production
performance negatively, and a workover will be required to
resolve the well integrity problems and restore production.
An operator in the deepwater Gulf of Mexico observed
sustained casing pressure on the primary annulus of an oil
producer. Gas lift needs and regulations dictated that the leak
be repaired. The tension leg platform did not have a rig, so a
retrievable inflatable packer was the primary option available
in this scenario. With further investigation, the operator
determined an isolation packer seal was leaking and believed
the leak could be isolated with a scab liner placed inside the
ported sub that the packer was isolating.
A slickline‑deployed, through‑tubing, inflatable scab liner
was utilised to set a scab packer below the ported sub. This
packer formed a base with a polished bore receptacle to receive
the seals on the scab liner, which was run separately. The
second (upper) scab packer and a section of 1.66 in. pipe were
also deployed on slickline. Once landed and set, they completed
the isolation of the ported sub. The well was put back online
and began again to produce up to 1500 bpd.
The sustained casing pressure was gone, and gas lift
performance was improved. The operator eventually plans to
pull the well for a fuller workover when a rig is mobilised for
other intervention work on the platform. But he noted that the
rigless intervention enabled him to keep the well online and
to maintain production when he would have had to shut it in
otherwise. Not only is the scab liner system retrievable, but
also this intervention cost a fraction of what a conventional
workover would have cost even before taking account of
potential lost production.
Interventiononsubseawellheads
In another recent example, a subsea well required wellhead
repairs due to leaking seals. A secondary barrier was needed
in addition to the tubing‑mounted safety valve. Since no
profile was available to set a mechanical plug in this area of
the well, an inflatable bridge plug was chosen. A lightweight,
multifunctional supply vessel, equipped with a remotely
operated vehicle (ROV), was brought in to run and set the
inflatable bridge plug assembly on wireline.
The job consisted of running the plug through a 2.99 in.
restriction inside the subsea tree, then setting it inside the
3.958 in. ID of the 4 ½ in. chrome production string. Once
the plug was set and tested, the operator wanted to remove
and replace the defective wellhead stack. A 2.50 in. diameter
inflatable bridge plug was selected for the job. This inflatable
bridge plug would have a working differential pressure rating of
4021 psi when set inside this tubing string.
The slickline setting system was used to deploy and set
the inflatable bridge plug. In this application, the bridge plug
included onboard fluid reservoirs to ensure clean fluid was
available to inflate the packer in case gas was present at setting
depth. The tool string was picked up and lowered from the
lightweight intervention vessel via a wireline unit. At the mud
line, the ROV removed the tree cap and guided the tools inside
the well.
Once inside the well, the plug was run to a setting depth
of 4352 ft. After it reached setting depth, slack‑off and pick‑up
weights were recorded before the setting sequence started.
The onboard computer was designed to recognise setting
conditions when the string remained stationary at setting
depth for a predetermined amount of time. In this case,
after 30 min of no motion, the computer initiated a signal
to start the inflation process. The setting system completed
the inflation cycle by locking in the inflation pressure and
disconnecting from the bridge plug. At that point, tension was
pulled to confirm the slickline was free from the bridge plug,
then weight was slacked off to tag the bridge plug to verify
plug anchoring.
After setting the inflatable bridge plug, the setting system’s
timer and transducer data files were retrieved from the tool
string for post‑job analysis. The acquired data confirmed
that the setting system had functioned properly throughout
the job, progressing through each of its pre‑programmed
phases after reaching setting depth. The wellhead stack was
released and pulled to surface, and then the new wellhead
was lowered, installed, and pressure tested against the bridge
plug.
Conclusion
Lower‑cost intervention options continue to evolve that
provide better, more economical means for addressing well
problems in a deepwater setting. Inflatable packer technology
has long been a viable option to address challenging well
conditions like these, but this technology is also adapting in
response to the needs of the industry to maximise the value
of ageing assets. In these cases, workover operations are
an integral part of maintaining well integrity, and creative
solutions with inflatable packer technology can often
extend the producing life of the wells in a given field. The
case histories presented here illustrate the types of creative
approaches to deepwater interventions that the deployment
of inflatable packers on slickline or wireline can offer
operators.
