was a long time coming, but the disconnect between soaring commodity
prices and languishing oil company stocks appears to be history
-- at least for now.
it's a pressure cooker out there, and companies are producing all
out and scurrying to find the hydrocarbons to replace what's being
produced -- a more daunting mission than ever before with the bulk
of the "easy" finds already claimed.
challenges for many oil finders lie deep below the waters of the
Gulf of Mexico, where numerous massive salt bodies wreak havoc on
the travel path of seismic waves as they propagate through the earth
during the seismic data collection stage. Indeed, these salt features
taunt the most knowledgeable geoscientists as they seek to acquire
the ultimate image of the reservoir in the complex subsalt environment.
increasing interest in the subsalt among the companies, and without
decent imaging techniques, it's basically impossible to see anything
there," said Colin Murdoch, senior vice president of data processing
at Veritas DGC.
Gulf of Mexico is the driving force behind some of the imaging techniques
currently used," Murdoch said. "Also, the drastic decrease in the
cost of computing -- not just clusters, but all the surrounding
technology -- is letting us do things people have wanted to do for
a long time but couldn't."
of oil companies to farmout most of the research work to the contractors
plays a key role in advancing seismic imaging, according to Jerry
Young, vice president of imaging technology at Veritas.
is a lot more revenue from the oil company to the vendor that's
driving the whole market forward," Young said, "especially in the
deepwater Gulf of Mexico subsalt imaging."
forefront of the imaging technologies in vogue today is wave equation
migration (WEM), which has been around for close to 30 years but
without the computing power necessary to use it until the past five
years or so, Young noted.
algorithm does a better job of imaging beneath the salt as opposed
to Kirchhoff migration, which is quite good above salt, according
to Pete Bennion, vice president at TGS Imaging.
to do wave equation 3-D depth migration where we can output pre-stack
gathers as well has been a tremendous step forward for the industry,"
Bennion said. "It's where the market is headed.
our big data sets will go through wave equation 3-D depth migration,"
he continued. "In fact, the industry is heading toward doing time
and depth processing together on new data sets."
the big issues in subsalt imaging is how well velocity models can
industry, our ability to image far exceeds our ability to derive
velocity models from the data," said Nick Bernitsas, senior vice
president at GX Technology. "Going forward, the emphasis should
be on improving our tools for velocity model building so they're
more accurate and have higher resolution."
migration requires high resolution velocities," Murdoch noted. "It
requires you to know the answer before you run the migration."
technical issues specific to subsalt noted by Young and others:
How well multiples can be removed -- Veritas is pushing the use
of 3-D SRME (surface related multiple elimination).
is a need for various flavors of WEM having differing strengths
impact of the acquisition scheme, particularly regarding illumination
issues that might exist, i.e., the seismic energy didn't hit the
target or, if it did, it wasn't able to get back to the surface
to be recorded by the array of receivers deployed at the time.
who think this might be a problem are considering the potential
for wide azimuth surveys to provide the answer, Murdoch noted.
the widespread use of WEM technology, it's not without flaws. In
fact, there's much work yet to be done.
the problems with wave equation migrations is they are dip-limited
in general -- a big downside in salt territory, where events such
as near-vertical salt flanks are commonplace. Advances in technology
are needed to handle steep dips, particularly those that exceed
companies working to address this issue is Applied Geophysical Services,
which has developed a proprietary 3-D prestack depth migration algorithm
akin to the beam method.
handle steep dips beautifully where wave equation doesn't," said
Kevin Sherwood, vice president processing. "It's different from
all others -- we have the best parts of Kirchhoff and wave equation
in the algorithm to image steep dip and overturned dip and also
get very good subsalt response."
the consensus among the experts is there's no panacea at the moment.
you just can't define the shape of the salt body in the Gulf of
Mexico very well," Bernitsas said. "Salt distorts the signal, and
sometimes you can get it unraveled very well and sometimes not at
think anyone thinks the problem will be solved 100 percent of the
time, because there are limitations imposed by Mother Nature," he
noted. "But there are things on the horizon that suggest we'll do
a better job going forward."
to overcome the complicated subsalt imaging problems in the Gulf
must encompass much more than migration algorithms.
the right mix of a number of different technologies working all
at once, from angle gathers to visualization systems," Murdoch noted.
"There's a whole series of bits and pieces to have in place and
give the impression wave equation appears, and all problems are
solved," he said, "but it's just a stage in the technology."
be a whole big bag of tools, but companies better have the people
to use them, Murdoch cautioned.
huge issue, having the interpreters who can do a decent job on doing
salt," he said. "If the model you build is no good, the imaging
algorithm won't put the seismic data together to give a clear picture
of what's going on.
limiting factor for imaging is having enough highly skilled qualified
people to perform the difficult, complex work to get a good result."
the technology, the know-how, the work-flows are all important,"
Bernitsas noted. "The demands on the data and the processing have
to go hand in hand; you can't have sloppy processing and extract
amplitude attributes that make sense."
a whole series of processing techniques that go into the data prior
to the migration and algorithm stage. If the data are not prepared
correctly or sampled correctly the migration techniques won't provide
a good result.
gets missed by people these days because it's nicer to talk about
the more glamorous components," Murdoch said. "To work those other
algorithms that come before the migration stuff is critical to providing
a good image."