TULSA, OK - — U.S. Department of Energy–funded
research has yielded a breakthrough in high-resolution subsurface imaging
with the first low-cost depiction of CO2 movement through a
thin, shallow oil reservoir.
The University of Kansas Center for Research project combines the time-lapse
approach of 4-D seismic, which is essentially a series of three-dimensional
images recorded over time, with a carefully selected application of the
higher-resolution imaging of other advanced seismic technologies.
The first-of-its-kind project is being implemented for a landmark CO2
flood pilot project underway in the Hall-Gurney oilfield, near Russell,
Kan. That pilot—itself the first CO2 flood in Kansas—also
is funded by DOE. Both projects are managed by the Office of Fossil Energy’s
National Energy Technology Laboratory as part of its Enhanced Oil Recovery
During a 6-year span ending in August 2009, a total of 12 3-D surveys,
making up the 4-D time lapse, will portray the movement of reservoir fluids
and CO2 injection in the Hall-Gurney field. At the same time,
the project will assess the best approaches to 4-D seismic monitoring
to determine the minimum requirements needed for it to emerge as a cost-effective
tool for routine monitoring of small, low-budget EOR projects.
CO2 injection has been underway in the Hall-Gurney field for
about a year. High-resolution 3-D data gathered to date have highlighted
changes consistent with expected CO2 movement, demonstrating
that it is possible to detect CO2 movement in thin, relatively
shallow, mature reservoirs. The data will enable the operator to adjust
injection and production schemes in an effort to improve the EOR scheme’s
efficiency and economics.
What marks the novelty of this project is its low-cost approach to implementing
a valuable imaging tool that is usually too expensive to justify in monitoring
the thin reservoirs prevalent in the U.S. Midcontinent.
The use of 4-D seismic surveying has grown in the past decade and promises
to be an effective tool to assess the effectiveness of conventional EOR
programs. It is the latest advance in the science of seismic imaging.
Scientists have long been able to “see” how fluids such as
crude oil or injected gases behave in underground formations by creating
high-resolution images of the subsurface derived by gathering and interpreting
seismic data. The seismic data are gathered from sound waves with unique
acoustic signatures that are bounced off those underground formations.
The capability to gather and process enough seismic data to render those
subsurface images in three dimensions (3-D seismic) has revolutionized
oil and gas exploration and production the past two decades.
4-D seismic, the latest innovation in seismic imaging, is essentially
a series of 3-D images recorded over time that presents a time-lapse approach
to monitoring the behavior of subsurface fluids. Taking a time-lapse approach
helps an oilfield operator adjust injection and production schemes in
order to improve an EOR program’s efficiency and economics.
For such time-lapse monitoring of reservoir injection and production behavior
to be effective, the operator must be able to secure consistent and repeatable
3-D data. That causes costs to mount rapidly and limits the use of 4-D
seismic monitoring to only the biggest and most prolific reservoirs.
Commercial CO2 floods in the United States to date have largely
been limited to the prolific oil reservoirs of the Permian Basin of Texas
and New Mexico, which are especially amenable to this EOR process. For
CO2 EOR to be commercialized on a broader scale requires the
U.S. oil industry to gain more knowledge of how CO2 acts in
a reservoir over time, especially through the use of high-resolution seismic
imaging. But costly 3-D seismic surveys, especially when implemented for
a CO2 flood in stages over time, are difficult to justify for
most of the reservoirs that predominate in the U.S. Midcontinent.
A priority for DOE funding of CO2 EOR research is to adapt
high-resolution seismic imaging in order for this advanced technology
to become a cost-effective tool for monitoring CO2 floods.
CO2 EOR also offers the potential for beneficial disposal of
the greenhouse gas.
Efficiently designing and implementing 4-D monitoring of EOR programs
could significantly increase oil recovery in fields with marginally economic
volumes of remaining oil. A clearer, real-time image of the subsurface
at a economically feasible cost could unlock billions of barrels of oil
for the Nations use.