American Oil and Gas Reporter - September 2023 - 87

SpecialReport: CCS Feasibility Studies
Long-Term Considerations
Once sites are operating, they will
need to be monitored for any possible
leakage through the cap rocks. " CO2
shows up well on time-lapse seismic, "
Karr assures. " If a company takes a snapshot
of the earth, pumps a bunch of CO2
in the ground and takes a second snapshot
six months later, it can deduce where the
CO2 has moved.
" As a gas or liquid, CO2 contrasts
well with the solid rock matrix, " he explains.
" A liquid is harder to see than a
gas, and most CCS projects aim to keep
the CO2 in a liquid state. However, even
liquid CO2 causes changes in the local
pressure signature that are quite clear in
seismic. "
Using seismic to monitor CO2 is a
proven technique, Karr says. " We have
injected CO2 underground as part of EOR
projects for decades, " he notes. " We may
be changing where we put CO2 in CCS
applications, but we have a long history
of transporting and managing it. If CCS
is something people will pay for, we
have the tools to do it. "
The greatest challenge is political,
Karr assesses. " CO2 is a nasty substance.
It's highly corrosive, so many people will
not want a pipeline near their neighborhoods, "
he acknowledges.
The regulatory framework will need
to support surveys, Karr continues. " As a
general rule, getting a detailed look at
the subsurface requires at least twice as
much space on the surface, " he says.
" Some of the CCS surveys will involve
investigating 20-50 square miles of the
subsurface. "
An area that is accessible initially may
become difficult to survey as cities and
their accompanying infrastructure expand,
Karr muses. " Right now, we are asking
companies to monitor CO2 for at least 50
years. A lot of companies do not even
exist that long, " he adds.
And what happens if the CO2 moves
in unexpected ways? " If we build a storage
site in an area that looks fantastic only to
discover that it leaks, it could create an
opportunity for lawyers to go after companies
that were involved in the project, "
Karr speculates. " That could be the operator
who put the CO2 in the ground,
the plant that created the CO2 or a service
company that helped design, build or
monitor the site. "
EOR projects suggest that although
such situations should be extremely rare,
they are possible. " We have seen cases
where CO2 injected into the ground has
leaked to the surface, " Karr allows. " Usually,
this occurs because of inadequate
analysis at the start of the project. But if
there is one truth about the subsurface, it
is that every time we learn something,
we open a whole new set of questions.
As CCS matures, we may discover that a
few sites we once considered promising
are poor storage candidates. "
Fortunately, he suggests, there are legions
of experts at companies and universities
that are doing everything they
can to ensure CCS is safe and profitable.
" At the end of the day, if you give people
a bunch of money to do something, they
will figure it out, " Karr says.
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FG Available 3D Data
FG Available 2D Span
Tier 1 Priority Depleted Reservoir (BOEM)
TX GLO Carbon Sequestration Leases
Bayou Bend CCS Project
Emission Sources by Quantity
Existing seismic data will be key to assessing potential carbon storage sites, Fairfield Geotechnologies suggests. The Gulf of Mexico offers
a case in point. This map shows some of Fairfield Geotechnologies' Gulf seismic to highlight coverage of Texas General Land Office lease
sites and depleted reservoirs that the Bureau of Ocean Energy Management identified as strong candidates for CCS.
SEPTEMBER 2023 87

American Oil and Gas Reporter - September 2023

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