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Downhole Well Applications Using RFID Technology
During the drilling and
completion of oil and gas wells, it is necessary to actuate a very wide variety
of downhole tools and equipment. Methodology has generally been direct hydraulic
pressure (sometimes with ball drops), hydraulic pulses, pipe rotation and/or
reciprocation, wireline intervention and very limited attempts to use more
advanced systems, such as acoustic telemetry. Marathon Oil Company recognised
the significant benefits of adapting key elements of radio frequency
identification (RFID) and has been championing its use for downhole
applications. RFID has become commonplace in many areas, such as package and
asset tracking, identifying cars on toll roads and even keeping track of pets
and livestock. In the oil and gas sector, field tests have proven successful and
more widespread use is becoming a reality as two service companies, very much
focused on this technology, assist Marathon in RFID development.
Use of RFID in surface oilfield applications is not new. Companies in the past
utilised RFID tags with mixed results for asset tracking as well as work history
on drill pipe. These surface applications of RFID appear to be gaining momentum,
with efforts to now track premium tubular inventory, packers, completion
hardware and other expensive equipment. Better methods to permanently attach the
tags are partially responsible for growth in the industry. What is new, and the
subject of this article, is using the technology for the downhole well
operations environment.
To actuate wellbore equipment, the downhole tool is configured with a reader,
and it actuates when the correct chip or unique identification code is noted.
The RFID tags can be pumped past the reader, flowed past the reader or otherwise
conveyed past the reader when attached to other tool strings. The RFID tag can
be programmed to not only ‘tell’ the downhole tool to fully actuate, but in many
instances it may be desirable for downhole tools to only partially actuate.
Usually, the operator may desire to partially actuate downhole tools during the
drilling phase, while most completion operations usually desire the tools to
fully actuate. Some specific applications for completion operations are
described below.
Zonal Isolation Tools
Zonal isolation valves generally are used to prevent fluid loss to a gravel
packed zone, as a barrier to set packers, and to prevent flow from the well when
changing fluid systems over to lighter weight completion brines. These zonal
isolation valves are typically cycled closed when the work string is pulled from
below the tool, and a shifting tool actuates the device. Later in the well
completion, a series of hydraulic pressure cycles re-opens the valve. RFID
allows new approaches to be employed. The appropriate RFID tag is passed by the
valve to either open or close it. This adds tremendous flexibility to the
operations and reduces the fear of the valve accidentally being opened with
pressure cycles. It is also possible to place the reader at a remote distance
from the valve itself, increasing the level of confidence with which the tools
can be actuated, even if debris exists on top of the barrier.
Wellbore Clean-up Tools
The key to many well completions is actually having a clean fluid system and all
of the drilling mud and other solids removed from the well. One of the first
tools developed by the
North Sea
service companies working with
Marathon (Petrowell and
IIItec) was a downhole circulating sub, utilised for well clean-up. A downhole
circulating sub is run as part of the drill string and activated by passing
small pre-programmed RFID tags through the RFID circulation sub. The signal
received by the reader in the circulation tool opens or closes the sub depending
on the coding of the RFID tag. The RFID tags can be easily programmed on
location. From a completion standpoint, being able to not only circulate the
liner clean but to also have higher circulation rates above the liner top
increases the chances of successfully getting the hole clean. As other operators
have become aware of these tools and their capabilities, the desire to perform
other operations which could not otherwise be considered are being discussed.
The circulating tools can be designed to partially actuate, thereby allowing
what would broadly be described as variable flow rates. As one example, the
feature of the downhole wellbore clean-up tool or circulating sub may take 100
‘strokes’ to fully actuate. RFID tags can be pumped past the tool, which contain
electronic commands telling the tool to only actuate 50 ‘strokes’. In this
manner, flow rate to one or more downhole devices can be adjusted as many times
as desired. Not only can tools be opened, closed or retracted, but it will allow
finite control of desired assembly changes.
Marathon is currently contemplating using this tool for a completely different
reason. When drilling long horizontal wells onshore US in underbalanced
conditions, it is desired to spot heavy weight kill fluid prior to tripping.
This well clean-up tool can be used to spot fluids, and then be re-closed. This
approach has a lot of merit versus having to first trip out of the horizontal
portion of the well to then spot kill weight fluids.
During the August 2005 drilling and completion of CNR’s N46z well (approximately
15,000ft on the Ninian North platform in the UK sector of the North Sea, an RFID
circulating sub was run during the clean-up operation prior to running the
completion string. This was the first application of such technology in the oil
and gas industry and the operation was performed flawlessly. The RFID tag used
in CNR’s application looks like a small glass pill about 3mm in diameter and 3cm
in length. The tag and a scale are shown in
Figure 1.
Packer Setting
During completion operations, a task as simple as setting a packer can contain
its own share of problems and risk. Current technology generally uses hydraulic
set packers in many instances. This requires some type of downhole barrier so
differential or absolute hydraulic pressure can be applied to actuate the packer
setting devices. There have been many instances over the years, all quite
expensive, where the barrier device that is used to set the packer is difficult
or impossible to retrieve due to debris or mechanical issues. In this case, RFID
actuation allows an economic alternative. The dropped RFID tag is read by the
packer setting tool, and well hydrostatic pressure actuates the packer after a
port is exposed. This approach is not only more economical, but in many cases,
it eliminates the risk of having to run and subsequently retrieve the barrier.
Zonal Isolation and Water Gas
Injection
The RFID technology allows a much simpler alternative than smart well technology
to regulate flow from or to downhole intervals. Operators are now considering
the option of being able to pump down the small RFID tags to actuate downhole
readers, which in turn will turn on, turn off or regulate the amount of water or
gas being injected into individual reservoir intervals. There is considerable
interest in being able to perform such well work without having to install
external lines and only having to pump down the small glass tags or chips, which
are coded with the appropriate information to actuate the specific completion
tool.
Cementing Operations
RFID systems can easily be adapted to open and close cementing stage collars and
eliminate the need to subsequently drill out the stage collar, as no plug
blocking the interior of the casing need exist. In many aspects, the RFID
portion of these tools is similar to the wellbore cleanup tools already
developed, which greatly reduces the engineering design time requirements to
meet the needs the operators are bringing forward as they become aware of the
RFID technology.
Perforating Operations
Four years ago,
Marathon fired a
downhole external perforating gun using RFID technology in its Excape®
Completion Process on an 8,000-foot deviated gas well near
Kenai, Alaska. This is
believed to be the first overall commercial use of the technology in the oil
industry. This RFID application was not progressed to any great extent at the
time, due to the conventional hydraulic control line firing methodology working
well and being economically more viable. As other RFID applications and
development companies make additional resources and technical input available,
this perforating application is again being re-visited. It appears that RFID may
be a preferred firing system in wells where the use of control lines is not an
option the operator wants to consider.
Future RFID Actuated Applications
A great number of opportunities exist and are being progressed to utilise RFID
in the wells with downhole readers and the RFID chips subsequently run or pumped
past the tool:
RFID chips small enough to survive being pumped through a drilling motor are
feasible. This will allow tools below the motor to be fully or partially
actuated. Both drilling angle and direction can be changed. A key area of
interest is in air-and-foam drilling applications, where conventional fluid
pulse or pressure activated systems are ineffective. RFID systems will still
operate effectively in this environment.
Drilling disconnects, expandable and contracting stabilisers, expanding and
contracting under-reamers and similar tools where either full or partial
actuation would be desirable are already under development.
There are many more applications such as coiled tubing tools, indexing fishing
tools, changing fishing grapple sizes, retracting casing scrapers near nipple
profiles, actuating hydrostatic bailers and a host of other ideas.
Although Marathon holds a significant, worldwide RFID intellectual property
portfolio and has licensed aspects of patents and know-how included in this
portfolio to others, the company’s primary driver is ensuring that this
technology is available to industry. The company chose to become involved
because of the potential for this technology to improve well operations by
reducing costs and rig time for not only themselves but for other oil and gas
operators as a whole. Their Technology Services organisation estimated that a
major oil and gas operator could realise at least US$17,000,000 annual savings,
as well as improved operational safety benefits, with even limited acceptance
and use. Many of the RFID tools can displace existing infrastructure and
Marathon
did not want to see the technology shelved or to otherwise be slow coming to
market.
Marathon joined with
prior investors in a company called In Depth Systems Inc. to progress RFID for
the downhole well environment. This stirred interest and additional research and
development. Two North Sea service companies are now licensed to apply
additional engineering expertise for the applications described in this article.
Petrowell, primarily a well completions company, is developing RFID uses in the
completion arena. IIITec is a new company with significant funding, and its sole
business is developing RFID applications for drilling and coiled tubing
operations.