(484f) Benefits of Injecting Carbon Dioxide into Coal Seams

This paper will share advances in sequestering carbon dioxide into underground coal seams. To date, approximately 375,000 metric tons of CO₂ have been injected into coal seams across the world. Over the past 30 years, the underlying science of CO₂ sequestration in coal has been investigated extensively, including several studies funded by NETL, and the technology has been performed repeatedly and successfully by many groups. CGC has advanced the technique to address issues around coal swelling and other formation damage that can sometimes accompany the process.

By using downhole Raman spectroscopy in CCS wells located in the US and Australia, the authors have been able to observe CO₂ gas and solution gas flowing through coal seams in a sustainable manner with no apparent damage to that coal. By mimicking the conditions under which those events were observed, the authors have been able to repeatedly and reproducibly sequester CO₂ into coal.

Those sequestration experiments have included:

• Sequestering CO₂ into one cubic centimeter chunks of coal charged with methane and water in high pressure laboratory cells while monitoring solution gas and head space gas using Raman spectroscopy;
• Sequestering CO₂ into a one meter long, 10 centimeter diameter tube filled with coal and water; and
• Sequestering CO₂ into a 30 meter thick coal located in a 160-acre field in the Powder River Basin of Wyoming.

It is well-known that coal preferentially absorbs CO₂ over methane and nitrogen. This characteristic of coal can be used to filter CO₂ from mixed gas streams including nitrogen. As a result, gas streams containing relatively low concentrations of CO₂ can be injected directly into coal seams and only the CO₂ is retained.

Technoeconomic analysis of the approach indicates that as a result, a CCS project using a coal sink vs. a traditional sink can reduce its capture and cleanup costs by 50% to 80%.

The paper will describe experimental design and results as well as the implications for global CCS.