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Oilfield Technology
September 2016
performance of drilling operations, is therefore needed in cementing
and completions operations to drive structural cost changes. A fit for
purpose data telemetry platform that enhances drilling operations
but also assists completions and cementing in even the most extreme
environments will enable operators to reduce such costs.
Newhorizons
XACT’s acoustic telemetry network is designed to deliver real time
data in these previously unavailable environments with no change
to the string, downhole components or surface equipment; it is
not restricted by depth, fluid flow or formation constraints.
The system is based on the installation of acoustically linked
downhole measurement and telemetry tools to form a robust
telemetry data and sensor network.
The tools are typically placed about 5000 ft apart in the vertical
sections of the well and 3000 - 4000 ft apart in horizontal sections to
provide optimum signal strength and transmission range depending
on the deviation of the hole. All tools are fully through-bore,
which enables use in both cementing and completion installation
environments and allows for the deployment of wireline conveyed
tools as well as wiper darts, third-party activation balls or large
amounts of lost circulation material.
The collar-based design of the tools provides sufficient
space for lithium batteries, sensors, electronic boards and the
piezoelectric stack that allows for the acoustic transmission of
data back to surface. In addition, mechanical parameters such as
pressure, weight, torque, bending and temperature are recorded
downhole and transmitted acoustically in real time via the steel
body of what has now become essentially a smart string.
A benefit over the common mud pulse systems, which can only
take measurements at the bottom of the string, is the ability to
gather measurements from a range of locations via the multiple
spaced nodes, offering a real time snapshot of the conditions
along the entire wellbore. Distributed measurements coupled
with the integrated strain and pressure measurement capabilities
offer a new understanding of weight and torque transfer and
segmented equivalent circulating density (ECD), or annular
frictional pressure regardless of circulation rate.
These along-string measurements can greatly enhance the
understanding of effective weight or mechanic specific energy
(MSE) transfer, hole cleaning, and early kick detection. With this
higher resolution data, gathered in real time from intervals along
the string, ever more challenging wells can be completed with the
right information at the right time and from the right places.
As the system picks up like drill pipe, it enables an easy and
rapid rig up and rig down with minimal time added to existing
processes. Data is sent to a wireless receiver at surface and from
there travels wirelessly onto a laptop for integration with other rig
data to enable better and more accurate decision making.
Casestudy:deepwater completion installation
BP has actively been pursuing a solution that satisfies all the
criteria to provide real time downhole data during completion
installation in the deepwater Gulf of Mexico. The XACT acoustic
telemetry network was deployed to monitor the downhole
conditions and weights applied during screen installation and
packer setting. Additionally, it helped to maintain and accurately
monitor weights on packers and the crossover tool during critical
operations such as the acid wash, minifrac, step rate tests, and
during the actual fracturing operation. Knowing the weight
on these and the position of the setting tool has been a major
concern in deepwater, leading to several costly incidents.
Results
BP successfully engineered and safely executed the completion
installation. Real time telemetry operations were conducted with
minimal impact to normal rig activity and provided excellent insight
into the actual downhole situation at the crossover tool during the
critical phases of the installation. During operations it was observed
that more than 70 000 lb came off the setting tool, informing a
decision to put more weight down to continue safe operations.
Telemetry was provided throughout the entire completion
installation for the first time in the deepwater Gulf of Mexico. As
a result of this test, BP qualified the technology for use in the
demanding deepwater completion environment and is committed
to further developing and expanding the applications of the
technology into all aspects of well construction.
Casestudy:deepwater riserless formation integrity
test toenableslot recovery
Shell needed to re-evaluate a previously abandoned well in the
deepwater Gulf of Mexico. The slot had been abandoned at the
20 in. casing shoe due to an extremely narrow pore pressure
frack gradient window and the associated risks of weakening
the integrity of adjacent wells. The area has a history of shallow
hazards and shallow water flow conditions that have caused
significant problems in the past. To examine the feasibility of
recovering the slot required undertaking a formation integrity
test. The time and cost of purchasing a riser, installing a blowout
preventer (BOP) and the relevant rig time made this uneconomic
with conventional technology, particularly in the current economic
conditions. To undertake the operation without installing a riser
required real time measurement below and above a packer,
with the ability to transmit data through a packer without hard
wiring, and back to surface in low and no flow conditions. Full
through-bore capability was also required for wireline evaluation;
the potential to cement through the string and the ability to
mechanically activate circulation subs by dropping balls and bars.
The primary gauge of the success of the operation was
transmitting downhole data in real time through a fully inflated
downhole packer activated inside the 20 in. casing. The formation
integrity test could then be monitored at the downhole conditions,
and completed safely and to the limits required for recovery of the
slot without damaging the formation.
Shell engineered and safely completed the operation, which
may never have been attempted without the expanded envelope
provided by the telemetry network. Large cost savings were
achieved in both the evaluation and efficiency of the project. The
subsequent significant value was created in the knowledge that
the previously abandoned well could be recovered. Shell and
XACT together achieved several industry firsts, including wireless
transmission through a regular drill pipe and across a packer in
real time with no modification required of downhole or surface
equipment.
Thewayahead
Many of today’s obstacles in completions and cementing are the
result of attempting to tackle issues that operators have thus
far been unable to see. Improved downhole visibility, delivered
in real time, will have an increasingly important role to play in
reducing well costs. A versatile, easy-to-install acoustic telemetry
system, which can replace the practice of having to work with
limited or no real time downhole data, has the potential to save
the industry millions of dollars in reducing flat time, avoiding well
remediation or even coping with a well loss.
