Underground Coal Gasification (UCG) with CO 2 Enhanced Oil Recovery (EOR) in Western North Dakota Zhengwen Zeng and Peng Pei Department of Geology and Geologic Engineering University of North Dakota

Outline Concept of UCG-EOR  Underground coal gasification (UCG) coupled with CO 2 enhanced oil recovery (EOR) Introduction to the selected site  Lignite resources, oil production, topography and aquifers Site modeling work  Procedure, current results

Concept of UCG-EOR

Our Goals Generate power and/or syngas products via underground coal gasification to recover the huge, unmineable lignite resources in North Dakota Enhance oil recovery in nearby mature petroleum reservoirs using CO 2 from the underground coal gasification plants Sequester the CO 2 eventually in the deep oil reservoirs to reduce greenhouse gas emission

Site Screening for UCG-CO 2 EOR

Selected Site – Dunn County, ND (Fischer et al, 2005) 4 townships, 144 square miles Lignite in Fort Union Formation

Oil Production in the Selected Area Little Knife and many other fields are under the lignite resources in the selected area. Many fields are in water flooding phase (secondary production). There is big demand on CO 2 for tertiary EOR.

Oil fieldPool OOIP 10 6 bbl Cum. prod bbl Water inj. Start date Little KnifeMadison /7/1994 Blue ButteMadison /1/1968 Big StickMadison /9/1988 KnutsonMadison /6/2001 Rough RiderMadison /13/1997 T.R.Madison /19/2004 Candidate Oil Fields for UCG-CO 2 EOR

Aquifers in the Selected Area The lignite bearing formation (Fort Union) coincidences with the Lower Tertiary Aquifer. The aquifer consists of sandstone interbedded with shale, mudstone, siltstone, lignite and limestone. Aquifer is not highly permeable, but is an important source of water supply. This is a complex dual system. (Whitehead et al, 1996) (Fischer et al, 2005)

Aquifers in the Selected Area Contaminants transport mechanisms are advection, molecular diffusion and mechanical dispersion. Contaminants can be adsorbed on the coal and strata. Low-permeability sandwich layers can function as a filter and a seal to reduce spread of contaminants induced by UCG. Target: locations with high clay content. (Liu et al, 2007)

Modeling the Coal Seam and Adjacent Layers Harmon coal sub- zones in Fort Union Formation Lithological interpretation logs from US Geological Survey Oil & gas well logs from North Dakota Geological Survey (Flore et al, 1999)

Modeling the Coal Seam Screen oil wells with logs penetrating the coal seams (Fort Union) Find 38 wells with GR logs (144 sq. mile) Identify the formations: Lignite GR=5~10; Mudstone GR  20. Create model: –digitize  interpret  correlate  build model

Model result: Coal Seam and Topography

The Harmon Coal Seam Depth, ft Isopach, ft

Clay Content Clay content at 10 ft below the coal seam Coal seam

Clay Content Clay content at 30 ft above the coal seam Clay content at 10 ft above the coal seam

Summary Integrated lignite UCG-CCS-CO 2 EOR in Williston Basin, North Dakota is proposed. Candidate lignite and oil fields are screened. Hydrological and petroleum reservoir production conditions of the candidate fields are studied. Geology of the lignite and the clay seals above and beneath the coal seams are modeled.

Acknowledgements This research is funded by: US DOE through contracts of DE-FC26-05NT42592 (CO 2 Sequestration) and DE-FC26-08NT (Bakken Geomechanics); North Dakota Industry Commission with five industrial sponsors (Encore Acquisition Company, Hess Corporation, Marathon Oil Company, St. Mary Land & Exploration Company, and Whiting Petroleum Corporation) under contract NDIC-G ; North Dakota Department of Commerce together with Schlumberger, IHS and American Petroleum Institute through Petroleum Research, Education and Entrepreneurship Center of Excellence (PREEC) program. We greatly appreciate all the sponsors for their support!

Underground Coal Gasification (UCG) with CO 2 Enhanced Oil Recovery (EOR) in Western North Dakota Thanks Contact Info: