Beneath the surface: Dakota Gas uses seismic surveys to monitor carbon capture and storage project

The loud whine of engines reverberated across the open fields at Dakota Gasification Company (Dakota Gas) as three vibroseis trucks sent seismic waves deep into the earth. A gray sky foretold that the seasons were changing, and the trucks were there to conduct seismic surveys at the company’s Broom Creek carbon dioxide (CO2) injection field near Beulah, North Dakota, before Old Man Winter arrived.

Kurt Dutchuk, pipeline superintendent at Dakota Gas, a subsidiary of Basin Electric, says winter months can present significant challenges for surveys, making it crucial to complete them before the snow flies.

“When deep snow or mud is present, access to the survey lines can be difficult,” he explains, “as the weight and size of vibroseis trucks can cause them to get stuck or make it impossible to travel through the terrain.”

Dakota Gas began injecting carbon dioxide into the Broom Creek formation last February, where it stores captured CO2 about 5,900 feet underground. The carbon dioxide, once captured and treated for transportation and storage, moves via pipeline to an onsite injection well and is sent to the underground storage site. Partnering with Denver, Colorado-based Carbon Vault, the seismic surveys—part of the permitting process for Dakota Gas to store CO2 underground—are required to monitor the captured carbon dioxide and ensure it stays within its confined geological storage site.

Rhonda Gathers, vice president of engineering and operations at Carbon Vault, was on site for the project in early November and explained the survey process.

The specially designed vibroseis trucks use hydraulic systems to generate seismic waves. “These seismic waves are reflected back to the surface when they encounter different rock layers,” Gathers says. “They are captured by sensors placed at the surface. The data collected is interpreted by the measured time it takes for the waves to return to the surface and results in a subsurface image.”

Data collected from these surveys helps confirm that the injected CO2 is staying within the geologic confines of the Broom Creek formation. She said the seismic survey is only a part of the storage facility testing and monitoring plan. This plan is in place to target early detection of any abnormalities and ensure that the geologic storage project is operating safely and protecting all underground sources of drinking water.

Dakota Gas is permitted to store roughly 26 million metric tons of carbon dioxide over 12 years at the Broom Creek formation. Since operations started in February, the company has sent about 1.3 million metric tons of it underground. Seismic surveys are required for this site during years one, three, five, and 10.

Dutchuk says data obtained from the November survey is still being analyzed. Once verified, it is then sent to a processing facility, with results available anywhere from four to eight weeks.

As the cool November breeze whipped across the dry prairie, the snow still weeks away, the reverberating sounds of the vibroseis trucks were carried with it as they continued to survey the storage field. As of this writing, Dakota Gas is still awaiting the results of the survey.