UNDERGROUND COAL GASIFICATION WITH CO2 ENHANCED OIL RECOVERY IN WESTERN NORTH DAKOTA

Studies have indicated that there is huge lignite resource in North Dakota, about 1.27 trillion tons. However, the economically recoverable reserve by surface mining is about 25 billion tons, only 2% of the total resource. Underground coal gasification (UCG) coupled with CO₂ capture process offers an important option to exploit the rest resource in a clean and efficient way. In such a process, CO₂ is separated from the produced syngas and used for enhanced oil recovery (EOR) in nearby oilfields, and the cleaned syngas can be upgraded to high-valuable energy or fuels.

The proposed investigation area is in western North Dakota, where the Harmon Coal Zone of the Fort Union Formation presents several deep and thick seams. The selected area also overlies with the Little Knife Anticline, and is close to the Nesson Anticline and Billings Anticline, where thousands of oil and gas wells have been drilled. Some oilfields are currently at the secondary or tertiary production phase, which means a potentially big demand for CO₂ in the purpose of EOR. We are using the information gathered from exploration activities of coals, petroleum, ground water, mineral resources and geological survey, in terms of electric logs, samples from drilling cores and samples from outcrops to construct 3-Dimensional model of the thick coal seam and associated overburden, and indicate related lithological and hydrogeological properties. We are also collecting the historical production data of the nearby oilfields, in the hope of investigating the possibility of applying CO₂ EOR process in these oilfields. With outcomes of the above works, we will finally screen out one or more suitable UCG project sites, and analysis the detailed issues associated with UCG- CO₂ EOR process.