courtesy of WesternGeco
The deepwater OBC 4-C Bluefin, a floating example of technological
advances designed to meet exploration demands.
Deeper targets? Deeper water? Maturing
Whatever the challenge, the oil and gas folks keep
coming up with the technology needed to meet the most complex and
demanding scenarios head-on.
Much of the tech know-how originates within the seismic
industry, which currently is laboring to regain at least some semblance
of its former robust health.
Yet, ongoing R&D efforts belie this struggle
-- at least for now.
WesternGeco alone spends $50 to $60 million a year
on R&D, according to Jim White, vice president multi-client
They have plenty to show for it.
The company's new Multi-Vision™ regional program
in the Gulf of Mexico (GOM) incorporates both the old stand-by technology,
2-D, and the new 4-C, or multicomponent technology -- a survey concept
developed by project partner AIM Geophysical, according to Robert
Hubbard, manager North and South America new ventures for multi-client
"From a regional understanding, the 2-D with 10,000
meter offsets we have is important to tie key fields throughout
the shelf into the deepwater," Hubbard said.
"Doing this with OBC technology, we know exactly
where the cable is versus a 2-D streamer boat," he said, "and we
feel this is a great advantage for looking at the deeper potential
targets on the shelf that people are starting to chase.
"We're pleased with the data we're getting, both
pressure and shear," Hubbard added, "and we think the images we'll
get will be excellent with the cable on the bottom."
He noted the shear wave data will enable them to
see through some of the shallow gas clouds that have plagued the
industry on the GOM shelf for years.
The plan is to come up with a contiguous grid shot
in phases with an average of two crews working over the life of
Besides this long-term undertaking, the company is
busy with projects using its new "Q-Marine*" technology. This fully
calibrated single-sensor marine seismic acquisition and processing
system provides high-resolution, and low noise data for enhanced
It's part of the Q-technology package for both land
and water, designed to afford improved reservoir images as well
as reliable pictures of subsurface areas that previously could not
The repeatability levels of Q-Marine technology mean
the data are 4-D ready, i.e., every survey can be a baseline time
lapse survey -- a plus for the oil finders who increasingly are
wanting 4-D surveys to get a better handle on what's happening in
the reservoir over time.
When used on land, Q-technology has a 30,000-channel
capacity. Q-Marine, however, boasts 4,000 channels per streamer,
up to a maximum 20 streamers. The system uses point-receiver recording
with a 3.125m interval between individual hydrophones, and the output
from each hydrophone is digitized and recorded separately on tape.
'Q' Case Study
Q-Marine was the topic of a case study paper presented
by Jeff G.S. Pan, senior advisor at Kerr-McGee Oil & Gas, in
the Convention Theater at the recent AAPG Annual Meeting in Houston.
Nick Moldoveanu, geophysical support manager at WesternGeco, co-authored
Kerr-McGee acquired and processed a data set provided
via five 2-D single sensor (Q) lines from a multi-client Q-2D program
conducted over a recent field discovery in the deepwater GOM. The
initial discovery occurred via conventional 3-D multi-client seismic
The objective, according to Pan, was to determine
the benefit of single sensor data for reservoir characterization
and field development.
He noted the project results showed the Q data enabled:
- Effective coherent noise attenuation.
- Preservation of broader frequency bandwidth.
- Proper spatial sampling of the seismic wavefield.
- Preservation of accurate amplitude.
- Applicability to AVO analysis.
Kerr-McGee is conducting a 3-D Q survey in the North
Sea as part of its ongoing evaluation of the single sensor technology.
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The GOM is a prime example of the challenges facing
operators in the quest to create value. The shelf area is dotted
with highly mature fields that demand evermore sophisticated technology
to detect remaining reserves.
Then there's the "frontier" deepwater region with
its tantalizing potential for big finds, at the same time calling
for the newest technology available to key in on reservoir detail
and avoid a super-pricey dry hole in this complex arena.
One of the techniques being used to depict the intricacies
of the reservoir is spectral decomposition, which affords unique
high resolution seismic images of both stratigraphic and structural
reservoir traps (see Geophysical
Corner). Resolution of reservoir boundaries, heterogeneities
and thickness is much greater than what is possible with traditional
broadband seismic displays.
"It's analogous to what you do with remote sensing
or satellite data on the surface," said Greg Partyka, staff geophysicist
at BP. "There you use frequency bands of infrared and visible wavelengths
to get subtle details.
"With seismic data, you have a seismic bandwidth
with much lower frequencies than used in remote sensing," he said,
"but you can leverage this by looking at the information provided
by discrete frequencies just like you do with satellite imaging
Using spectral decomposition, a suite of amplitude
maps is acquired from a range of frequency slices in the reservoir
zone. Images from certain frequencies are combined selectively to
depict the unique geologic relationships within the zone. The amplitude
maps can be animated to aid in the interpretation process.
When tied in with all other information, spectral
decomposition is an effective risk reduction tool, according to
Craig Cooper, manager of imaging technology at BP.
It's a novel -- but relatively inexpensive -- way
to use seismic data to try to extract details about a particular
zone in a seismic volume, according to Partyka.
"All you need is a seismic data set plus some kind
of guide horizon to help you identify the zone of interest," he
said. "Once you have that, for a fairly large 3-D survey it's a
matter of running over a few hours and looking at the results.
"You have nothing to lose and everything to gain,"
Partyka noted. "It lets you squeeze out that added bit of information
from the seismic."
He offered one note of caution: If there's no contrast
in the rock properties or fluid properties in the zone of interest,
spectral decomposition won't be a magic bullet. It only reveals
what's in the seismic, so if there's a bunch of noise, it will display
Although spectral decomposition deservedly carries
the "cutting edge" label, it is not a new application.
Partykya has been working on it since 1991 at Amoco,
and BP, which has established a track record for successful use
of the technique, acquired the patent in 1996. Apache also has had
a version of the technology for some time.
Now, however it appears to be on the cusp of widespread
Besides the role it plays in the demand for more
advanced reservoir interpretation processes, the ever-increasing
activity in the deepwater GOM is helping to hasten the development/commercialization
of a number of exciting tools to operate in this often-hostile environment.
Perhaps one of the most intriguing gizmos is the
autonomous underwater vehicle (AUV), which already has proven its
merits in the research milieu.
The AUV is a far more sophisticated tool for acquiring
remote data than its predecessor, the remotely operated vehicle
(ROV). The ROV requires a skilled surface pilot for operation, and
it has a tendency to veer off course and depth configuration during
a deep tow survey because of the extreme length of the tether. Turning
is difficult, sometimes requiring a second towing vessel.
In contrast, because it is autonomous, the AUV is
agile. It can be programmed to avoid obstacles and to maintain a
constant distance from the seabed and only needs a crew and vessel
for the launch and recovery process.
Needless to say, the AUV requires some ultra-sophisticated
programming technology. Boeing has been developing this kind of
software for a number of years, and the company recently formed
a partnership with Oceaneering and Fugro to provide an AUV for commercial
The machine, which is rated to 3,000 meters, currently
is being tested off the California coast and will be available commercially
the second quarter of this year, according to Carl Sonnier, AUV
program manager, Fugro Geoservices.
"The purpose of the tool is mainly deepwater construction
planning, like big offshore platforms, pipelines and such," Sonnier
said, "so the initial payload is designed as a survey tool and targeted
at that specific market."
Initially, the machine will collect side scan data
-- basically conducting acoustic mapping of the seafloor -- and
will be used for bathymetry to develop terrain contours. Sonnier
said it's also equipped with a shallow seismic system called a sub-bottom
profiler used to map the top 100 feet or so beneath the mudline.
"The vehicle is designed to handle multiple payloads,"
he said, "so we intend to do other types of things, like gravity
for instance. There's a variety of other oceanographic sensors we
can carry, and I view the vehicle as a sort of truck where we can
slap on different payloads."
The analogy is apt, given that once the cage containing
the AUV is lowered into the water, the vehicle backs out much like
a car out of a garage. It dives to the seafloor, goes through a
calibration process and begins its work.
Once the mission is complete, the machine returns
to the surface, is pulled back into the cage and brought onto the
boat -- an offshore work-class vessel will suffice.
The cost of the equipment tallies several million
dollars, but the overall throughput is much higher compared to alternative
deepwater techniques, according to Sonnier.
"The net effect," he said, "is you can reduce the
cost of these type surveys by 25 percent over previous tools to
collect deepwater data."