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Oilfield Technology
August
2015
the onboard electronics. The electronics responsible for
determining proper location of perforation, or initiating
the perforation sequence, were subject to high failure rates
requiring replacement and/or repair of components and
downtime for the tool. Company engineers were able to
significantly increase the reliability and decrease the failure
rate of the customer’s tools by using Micro-Mounts as opposed
to hard-mounting the electronics.
In addition to providing shock and vibration solutions to
downhole applications, an increasing need for solutions across
a variety of other oil and gas operations has been encountered.
Similar to the downhole tool-working atmosphere, subsea
electronics also operate in a severe environment. As more and
more subsea electronics are being applied to monitor variables
at the sea floor, shock and vibration problems due to transport,
production and drilling operations are a concern.
While these subsea components have a service life
of approximately 20 years, the mounting and isolation
devices that protect these components must also survive
the transportation and life of the part. In such applications,
these mounts offer reliable performance, while mitigating the
effects of shock and vibration found in the subsea equipment
environment.
Snubber/Isolators forMWDs
Through collaborative discussions with clients in the oil and gas
industry, LORD discovered the need for longer-lasting downhole
tool isolators that can protect against shock and vibration.
Here, once again, the company applied its aerospace experience
to address the needs of the downhole community. The
company’s snubber/isolators offer the reliability, durability and
performance needed to isolate MWD batteries and electronics
from shock and vibration. They reduce the total cost of repair
and maintenance over the life of the snubber.
In accelerated endurance testing, LORD snubbers have
been proven to outlast competitive versions, and have
demonstrated more than 1800 hours service life downhole
without maintenance. Laboratory testing has shown the ability
to reduce a 245 g half-sine shock input of a 0.5 millisecond pulse
width to less than 50 g, over an 80% decrease. LORD snubbers
are designed to meet the unique needs of downhole conditions,
such as extreme environments, high-shock loads, and low
frequency harmonic disturbances.
Customisedsolution
A manufacturer of measurement-while-drilling (MWD) tools
approached Lord with the following challenge: shock and
vibration were destroying key components in the customer’s
downhole measurement system. The shock and vibration
were affecting the tool’s reliability and the accuracy of the
measurements was often compromised.
Over the years, the customer attempted to design and build
a more rugged tool, by ‘beefing up’ structural components,
making connections more rigid, and using exotic materials.
Due to the size constraints, temperature, and high shock
environment experienced in the wellbore, the customer’s
attempts to solve the shock and vibration problems were
unsuccessful.
The challenge was to design an elastomer mount that
would fit in a diameter of less than 4 cm, could isolate shocks
up to 5 g, withstand temperatures up to 392˚F, and last a
minimum of one year, reliably, in normal field use. There
was nothing available off the shelf that would meet these
requirements.
After evaluating the situation, engineers came up with
a solution that fit the limitations. They custom designed
a passive mount that isolated the sensitive electronic
components from the shock and vibration experienced by the
tool-body downhole.
A pair of isolators, mounted at the top and bottom of
the tool’s electronics package, isolates the electronics from
the tool-body shocks. The isolators are made with a silicone
formulation that balances temperature stability with dynamic
and fatigue properties. The mount is rigid enough to provide
full mechanical support of the electronics package’s weight
under normal shipping and operating conditions, but acts like
a spring under high shock inputs to isolate the assembly.
When the isolators were installed, the customer stated
that the isolators had increased the reliability of their MWD
tools in a high-shock environment “by an order of magnitude.”
Generally, the mounts last longer than their one-year fatigue
life expectancy. The customer has been able to attract new
business due to an overall increase in the reliability and
accuracy of the tools.
Futuredevelopments
As the oil and gas industry accelerates its operations to keep
up with demand and reduce operating costs, drilling tools are
driven harder, deeper and faster into more difficult formations,
and for longer runs. To help the oil and gas industry protect
its sensitive equipment in various applications including
downhole equipment and subsea products, the engineers at
LORD have adapted its aerospace technology in the areas of
high temperature, shock and vibration.
LORD is continuing its development of MWD tool-string-level
isolation for probe style tools. Mitigating shock and vibration,
while supporting a nearly 30 ft long, 200+ lb MWD tool string
exposed to drilling mud, raises a unique set of challenges.
Realising that a single solution may not be practical or feasible,
LORD engineers have split the functionality into two separate
isolator designs intended to be used in tandem. The result is two
devices, each with a dedicated function, to either attenuate high
frequency shock or isolate low frequency harmonic vibrations.
First, a SoftShoe™ is designed to be installed onto the
mule shoe to mitigate shock transmitted up through the BHA.
Second, an axial isolator is installed in-line with the pulser,
providing protection from low-frequency vibration, such as
that produced by axial excitation tools. The remaining dynamic
loads, particularly the low-frequency vibrations, are further
reduced by the second-stage axial isolator. Separate devices
provide the benefit of a multi-stage isolation system, where the
net reduction of both shock and vibration is additive.
Individual tools segments are further protected by the
third stage of isolation, LORD snubbers. Finally, any remaining
dynamic loading is additionally mitigated at a board level with
Micro-Mounts. The MWD tool string-level tools provide the first
and second stage of protection, while the snubbers and mounts
provide a third and fourth stage of isolation. This four-stage
system offers a solution for MWD isolation that can achieve
optimum performance.
