Overview of Woodford Gas-Shale Play of Oklahoma, U.S.A. Brian J. Cardott Abstract a b c d e The Woodford Shale (Late Devonian-Early Quartz 63-68% 29-87% 30-60% 9-61% 27-53% Mississippian), an important hydrocarbon source rock in K-Feldspar 4% 0-2% 2-10% 2-42% 0-2% Oklahoma (south-central United States), is age-equivalent Plagioclase 3% 1-4% to Late Devonian gas shales in the United States (e.g., Calcite 10% 5-25% 0-7% 0-11% New Albany, Antrim, Ohio). It exceeds the minimum non- Dolomite 6-9% 0-56% 0-5% 0-10% 0-6% negotiable parameters necessary for an economic gas Pyrite 5-7% 0-1% 0-5% 2-30% 1-13% shale: gas source rock and fracture-able. Abundant oil- Total Clays 12-14% generative organic matter (e.g.., Type II kerogen; 2-14% Illite 8-35% 2-5% 7-53% 13-40% total organic carbon) in the Woodford Shale is the source Illite/Smectite 2-20% of thermogenic methane and a bitumen network, Kaolinite 1-7% 2-5% 0-2% 0-5% beginning in the late oil window, that are sites for gas storage and migration. Abundant natural fractures in Chlorinite 2-5% 0-40% 0-5% silica-rich (30-87% quartz) lithologies of the Woodford Woodford Shale Mineralogy (a, O’Brien and Slatt, 1990; Shale in southern Oklahoma exposures illustrate b, Kirkland et al., 1992; c, Greiser, 2006; d, Branch, lithologies that develop induced fractures, required to Isopach map of Woodford Shale (from Comer, 1992) 2007; e, Abousleiman et al., 2008) produce gas from shales in the subsurface. Since 2004, more than 200 Woodford Shale gas wells have been completed in eastern and southern Oklahoma by using advanced completion techniques (e.g., frac technology, horizontal drilling). Most interest is where the Woodford Shale is in the condensate or dry-gas window (>1.15% vitrinite reflectance, VRo), greater than 50 ft thick, and at relatively shallow depth (<12,000 ft) in the western part of the Arkoma Basin where initial 1 potential gas rates up to 11 million cubic ft per day have been realized. Thermal maturity of the Woodford Shale in 0.56 MISSISSIPPIAN the Arkoma Basin covers a range of issues from possibly 0.72 & OLDER lower gas rates and oil handling in the oil window 1.03 1 OUTCROP (<1.15% VRo) to gas composition changes at high 0.6 0.56 AREA thermal maturity (>3% VRo). An additional Woodford 0.57 0.94 0.64 1 Shale gas play in south-central Oklahoma is primarily in 0.82 0.56 the oil window at relatively shallow depth (<7,000 ft). 0.59 0.64 1 0.54 0.74 1.87 0.57 2.25 1 2.26 2 0.49 1.73 1.98 0.86 2.81 3.47 1.05 1.79 0.5 1.37 1.88 1.23 0.77 2.4 3 3.46 0.83 0.5 2.48 3.36 2.09 2 2 1.14 2.44 3.44 1.69 1 0.5 0.58 4.85 4.76 4 1.66 1.23 0.79 2.31 3.32 3 1.62 1.88 3.41 3.4 3.6 2.94 2.85 6.36 0.57 0.62 2.51 CHOCTAW FAULT 0.51 1.89 2.69 0.63 0.58 0.64 2.52 1.15 2.53 0.57 2.01 0.55 0.79 2 0.52 0.59 0.52 1 0.5 0.78 1.58 2.19 1.31 0.56 0.49 1.61 PETRA 8/10/2007 11:30:29 AM Vitrinite isoreflectance map of Woodford Shale in eastern Generalized structure map of Woodford Shale in eastern Oklahoma (contoured by R. Vance Hall from data by B.J. Oklahoma (prepared by R. Vance Hall). Cardott)
553 ft (IP 122 Mcf) 15,310 ft (IP 234 Mcf; 7BO 42° API; GOR 33,429) Oklahoma gas shale well completions, 1939-2008 Woodford Shale gas well completions, 1939-2008 (471 wells; 70 Caney wells; 401 Woodford wells) (405 wells) Woodford Shale gas well completions by year, 2004-2008 Woodford Shale gas well completions by major operator on (overlay of 2007 & 2008 wells; 389 wells) isoreflectance map, 2004-2008 (321 wells) 200 200 200 250 Horizontal 180 Discovery 180 180 Caney 160 Vertical 160 Wells Number of Wells 160 Number of Wells 200 Number of Wells Woodford 140 140 Number of Wells 140 120 120 120 100 150 100 100 80 80 60 80 60 100 40 60 40 20 20 40 50 0 0 20 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 0 0 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year Year Year Woodford Shale Well-Type History Woodford Gas Shale Completion History (1939-2007) Woodford Shale Gas Field Discovery History Oklahoma Gas Shale Completion History (1939-2007)
Initial Potential Gas vs Depth 100,000 Woodford Woodford Horizontal 10,000 Initial Potential (Mcfd) 1,000 100 10 1 0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000 Depth (feet) 352 Woodford wells (depth & IP pairs): depth 570-15,310 ft; IP 3-11,200 Mcfd. 253 Horizontal Woodford Wells (depth & IP pairs): depth 1,349-12,486 ft TVD; IP 3-11,200 Mcfd. Woodford Shale Wells with Initial Potential Gas Rates >1MMcfd (226 of 405 wells) 10,000,000 Gas 1,000,000 Average Monthly Production (Mcf) Oil 100,000 10,000 1,000 100 10 Apr-04 Apr-05 Apr-06 Apr-07 Jan-04 Jul-04 Oct-04 Jan-05 Jul-05 Oct-05 Jan-06 Jul-06 Oct-06 Jan-07 Jul-07 Oct-07 Date Woodford Shale Production (2004-2007) 41 Woodford Shale Oil/Condensate Producing Wells (2004-2007) Cumulative production from Woodford-only wells: 63,752,439 Mcf gas, 66,538 BBLS oil/condensate from 279 wells (excluding 23 OWWO; data from IHS Energy)
SOUTHERN OKLAHOMA Vitrinite Reflectance (%Ro) 0.50% Rm 0.50% Rm Tasmanites Tasmanites 0.00 0.50 1.00 1.50 2.00 2.50 3.00 green green fluorescence 0 fluorescence THERMAL MATURITY AND STRUCTURE 2,000 4,000 0.56% Rm 0.49-0.52% Rm Tasmanites 6,000 Tasmanites green Depth (feet) green fluorescence 8,000 fluorescence 10,000 12,000 14,000 Tasmanites green 16,000 fluorescence indicates immature thermal maturity “Loss of fluorescence of Tasmanites 18,000 alginites is reached at a stage 20,000 corresponding to 0.9-1.0% Rr (vitrinite)” Taylor et al., 1998, p. 137 Vitrinite reflectance of Woodford Shale in southern Oklahoma on Woodford Shale structure map (Woodford Shale structure map prepared by Carlyle Hinshaw in 1999; vitrinite-reflectance data by Cardott, in preparation). Portion of subsurface structure map of Marshall County, OK (modified from Huffman, 1987). Structure contours drawn on top of Viola Group (ft below mean sea level).
Cross section D- D’ of the North Madill field (from Huffman and others, 1987) GAS PRODUCTION IN OIL WINDOW Two examples of gas production from naturally-fractured Woodford Shale in the Madill and Aylesworth anticlines in the Ardmore Basin demonstrate gas production with little or no reported oil production at relatively shallow depths (e.g., @4,000 ft) where the Woodford Shale is in the oil window (@0.6% Ro). Even though Type II Kerogen is capable of generating about 75% of source-rock thermogenic methane by 3 Griffin-Olmstead well 1.1% Ro (Lewan, 2002), these examples may be special cases where thermogenic gas migrated into the Woodford Shale from deeper in the Ardmore Basin. Gas isotope data from these wells are not available. Principal subsurface structural features in Marshall County (from Huffman and others, 1987) 1,000,000 3 Griffin-Olmstead Structure contour map of the top of the Viola MADILL FIELD Group (Ordovician) in the North Madill field (from Average Monthly Production (Mcf) 100,000 Cimarex Energy of Colorado 3 Griffin-Olmstead well Huffman and others, 1987) Marshall Co.; NW¼ NW¼ NE¼ 16-5S-5E 10,000 Originally completed as oil well in McLlish (6,536- 6,544 ft) in 1955, oil workover well in McLish and Cross section C- C’ of the SE Bromide (5,664-5,696 ft) in 1956, and gas workover 1,000 Aylesworth District field (from well in Woodford Shale (4,052-4,135 ft) in 1992. Huffman and others, 1987) IP 747 Mcfd; Cumulative Woodford Shale gas 100 Jan-90 Jan-92 Jan-94 Jan-96 Jan-98 Jan-00 Jan-02 Jan-04 Jan-06 Jan-08 Jan-10 production of 1,792,734 Mcf from March 1992 to October 2007 (data from IHS Energy) Date 1,000,000 1 Mary Haynie SE AYLESWORTH DISTRICT FIELD 1 Mary Haynie well Verdad Oil & Gas Corp. 1 Mary Haynie well Average Annual 100,000 Production (Mcf) Bryan Co.; NW¼ SE¼ SW¼ SE¼ 22-6S-7E Originally completed as gas well in Misener sand 10,000 (4,192-4,227 ft) in 1956 and plugged back to Woodford Shale (3,710-4,054 ft) in 1974. 1,000 IP 962 Mcfd; Cumulative Woodford Shale gas production of 2,330,605 Mcf from November 1974 to August 2007. Produced 178 bbls oil in 1995 (data 100 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 from IHS Energy) Structure contour map of the top of the Viola Date Group (Ordovician) in the Aylesworth and SE Aylesworth District fields (from Huffman and others, 1987)
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