Release Date: November 7, 2005

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 (EOR) program.

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.