Coalbed methane potential in the Appalachian states of Pennsylvania,West Virginia, Maryland, Ohio, Virginia, Kentucky, and Tennessee--An overview
Paul C. Lyons
Open-File Report 96-735
Appalachian CBM production data
CBM production from coal reservoirs is affected by gas content, sorption rate, saturation, pressure, permeability, and other factors. Hunt and Steele (1991b) suggested the following hypothetical minimum values
for economic development from multiple seams in CBM reservoirs:
1. Gas content 125-150 cf/ton
2. Permeability 0.1-0.5 md
3. Pressure 125-175 psi
The gas contents of coal beds in the central and northern Appalachian basin, as given in the section on desorption data, range from 6-660 cf/ton. In general, the central Appalachian basin has higher values (as much as 660 cf/ton), as compared with as much as 252 cf/ton for the bituminous coals in the northern Appalachian basin. Hunt and Steele (1991b) noted that the Pocahontas No. 3 coal bed has a high average permeability (5 to 27 md), which is probably related to its high CBM productivity. According to these authors, coal beds in both parts of the Appalachian basin are underpressured probably due to geological history, extensive coal mining, and many nearby conventional oil and gas wells. Kelafant and Boyer (1988) reported a minimum reservoir pressure of 215 psi in their study area in the central Appalachian basin.
In 1995, CBM production in the United States was 973 Bcf, of which the central and northern Appalachian basin accounted for an estimated 32 Bcf (see Table 1). CBM production data for the central and northern Appalachian basin are summarized by state in Table 1; the data for the Black Warrior basin and the Cahaba coal field (Alabama) in the southern Appalachian basin are shown for comparison.
Central Appalachian Basin
Historic production (1970-1988) for this part of the Appalachian basin is summarized in Hunt and Steele (1991b). The early wells were producing from the Pocahontas No. 3 coal bed, Beckley, and Jawbone coal beds. In 1992, about 272 new Virginia CBM wells were permitted and completed (Fig. 4; Jack Nolde, Virginia Division of Mineral Resources, personal commun., 1995) through casing perforations and fractures stimulation with sand, water, and nitrogen foam; production from invididual wells at depths to 2,680 ft was as much as 356 Mcf/day.
In 1994 in Virginia, 649 wells (see Fig. 4) produced about 28.33 Bcf of CBM (Fig. 5; Jack Nolde,Virginia Division of Mineral Resources, personal commun., 1995; see Fig. 1 and Table 1). This is an average of 119.6 Mcf/d (thousand cubic feet/day) for CBM wells in Virginia, which is about two to four times the average daily production rate for CBM wells in the northern Appalachian basin. In April 1996, there were 708 producing CBM wells in Virginia (Jack Nolde, Virginia Division of Mineral Resources, personal commun., April, 1996). The principal producers in Virginia are Equitable Resources Exploration (EREX), Pocahontas Gas Partnership, OXY USA, Consol, Inc., and Island Creek Coal Company. In Virginia, CBM has been produced in commercial quantities in the Southwest Virginia coalfield since 1988 (Nolde, 1995).
In southern West Virginia, there is no record of CBM production in 1992, 1993, and 1994 (K.L. Avary, West Virginia Geological and Economic Survey, personal commun., April, 1996). However, in southern West Virginia, 17 CBM wells were permitted in 1995 (K.L. Avery, West Virginia Geological and Economic Survey, personal commun., April, 1996). These include 15 wells in the Welch field--2 in McDowell County and 13 in Wyoming County-- and 2 wells in Raleigh County in the Slab Fork field (Fig. 1). The Raleigh and Wyoming Counties wells reportedly produce from the Pocahontas No. 3 and 4 coal beds at depths of 655 to 1,650 ft. Production data for these wells were not available in April, 1996. It is interesting to note in Cardwell and Avary (1982, p. A-43) a record of an inactive gas well in the Welch field, Browns Creek District, in McDowell County that was producing from an 80-ft-thick Pocahontas sandstone.
CBM information in Kentucky comes from B.C. Nuttall (Kentucky Geological Survey, personal commun., April, 1996). Three wells were completed in coals in Harlan County in 1957, and one of these remained as a domestic gas supply until 1980 or later. There was no public record of any CBM production in southeastern Kentucky for the period 1992-1994 . In Letcher County, Equitable Resources Exploration completed in 1990 a CBM test well (KF1300 Fee well), but production data for this well were not available at the time of this report. Also there is a report of another company that has drilled CBM test wells in eastern Kentucky, but further details were not available.
A large part of the CBM production in the central Appalachian basin comes from Consol and Equitable Resources with a combined production of 12 to 16 Bcf annually (Ayers, 1996). Consolís Oakwood field in Buchanan County, Virginia, is the largest field and had 209 fractured wells in 1995 (Stevens et al., 1996). Cumulative CBM production in southwestern Virginia for the period 1988 through 1994 was 97,844,896 Mcf (Jack Nolde,Virginia Division of Mineral Resources, personal commun., April, 1996). The 85 early CBM wells operating in Virginia in 1991 and early 1992 had an average production of 100 Mcf/d (Quarterly Report of Methane from Coal Seams Technology, 1992).
In 1995, Virginia had the following CBM production by county: County Annual Production (Mcf) Buchanan County 24,300,209 Dickenson County 5,227,176 Russell County 569,549 Wise County 258,936 Total: 30,355,870
The Virginia production statistics for 1995 (Fig. 5, Table 1) indicate that CBM production is 61% of the stateís gas production (Jack Nolde, Virginia Department of Mines, Minerals and Energy, written commun., June, 1996). In 1995, Buchanan County accounted for 80% of the production in Virginia and for most of the CBM production in the northern and central Appalachian basin. For 1994 there were 52 new CBM gas wells in Virginia, which averaged 2,240 ft in depth and cost $79.06/ft to drill and complete (Oil and Gas Journal, March 11, 1996).
There is scarcely any public record of CBM production in southeastern West Virginia for the period 1992-1994 (K.L. Avary, West Virginia Geological and Economic Survey, personal commun., April, 1996). One well (Permit 912) produced 2,592 and 5,308 Mcf in 1992 and 1994, respectively. However, 12 new CBM wells were permitted in this area in 1995. These wells, except for one in the Beckley (War Creek in Virginia) coal bed (Fig. 3), will be producing from the Pocahontas No. 3 (9 wells) and from both the No. 3 and No. 4 coal beds (2 wells). For 1996 (as of May 24), four new CBM wells were permitted (3 in Wyoming County and 1 in McDowell County), all to be drilled by U.S. Steel Mining (K.L. Avary, West Virginia Geological and Economic Survey, written commun., June, 1996). These four wells are expected to be producing from the Pocahontas No. 3, 4, and 6 coal beds.
Northern Appalachian Basin
CBM production from eight historic projects (1932-1980), from the Pittsburgh and Clarion/Kittanning coal beds, and from mutiple coal beds in the northern Appalachian basin, is summarized in Hunt and Steele (1991b). The Pine Grove and Big Run fields in northern West Virginia were producing CBM from shallow depths along the axes of anticlines in the Pittsburgh-Huntington Synclinorium (Dunkard Basin) along what has been called ìstructurally high and dryî features (Patchen et al., 1991). The cumulative unstimulated gas production (1932 to1982) from about 52 wells in the Big Run field (Wetzel County, West Virginia; Fig. 2), mainly from the Pittsburgh coal bed 2-10 ft thick, was about 2.0 Bcf. The production rates ranged from 8-121 Mcf/d with a mean of about 38.5 Mcf/d (Hunt and Steele, 1991a; Patchen et al., 1991; Rogers, 1994). The Pittsburgh wells in the Big Run field have now been abandoned.
In 1994, CBM production in northern West Virginia was from 8 wells in three different fields in Monongalia County (K.L. Avary, West Virginia Geological and Economic Survey, personal commun. April, 1996). All of these wells are producing from the Pittsburgh coal bed. Total production from the 8 wells in 1994 was 97,372 Mcf (average about 33.4 Mcf/d)(see Table 1). In the Pine Grove field, 16 wells have had production from 8-60 (average 28) Mcf/d from Pittsburgh coal 1 to 7 ft thick. For these fields, the total CBM production, all from the Pittsburgh coal bed, for 1992, 1993, and 1994 are 198,428; 223,554; and 97,372 Mcf, respectively (K.L. Avary, West Virginia Geological and Economic Survey, personal commun., April, 1996). In northern West Virginia, there is a record of production from seven CBM wells, all producing from the Pittsburgh coal bed, for the period 1992-1994 (K.L. Avary, West Virginia Geological and Economic Survey, personal commun., April, 1996). In 1995 in northern West Virginia, 8 new coalbed methane ventilation wells in Monongalia County (CNG Development, operator) were permitted for Pittsburgh coal bed at depths of 750 to 1,090 ft (K.L. Avary, personal commun., April, 1996). Production data for these 8 wells are not available at the time of this report; however, it is estimated here that they are producing at an average of about 40 Mcf/day. According to Rod Biggs (CNG Producing, personal commun., May, 1996), initial production on all these CNG ventilation wells was about 100± Mcf/d declining to 20 or less Mcf/day. There is an unknown amount of CBM coming from overlying coal beds, including the the Redstone, Sewickley, and Waynesburg coal beds. For 1996 (as of May 24), three new CBM wells in Monongalia County, which are planned by CNG Producing, have been permitted (K.L. Avary, June, 1996).
In Pennsylvania, CBM production data are summarized in Bruner et al., (1995). Three tests wells were staked in Greene County (PRI, 1991). A total of 22 new wells are expected to be drilled in 1996 by BTI Energy, Canton Oil & Gas Company, Belden and Blake, Equitable Resources, LAHD Energy, and the M.L. Minter Family (Toni Markowski, personal commun., 1996). CBM production is known from the Pittsburgh coal bed in the Gump and Waynesburg fields and from the Lower Freeport, Kittanning, Mercer, Quakertown, and Sharon coal beds (Fig. 3) in the Oakford field (WVGES and PTGS, 1993; Bruner et al., 1995). Also, gob gas (gas from underground mine waste) from the Pittsburgh coal bed is being produced in Pennsylvania and West Virginia through converted pre-mine ventilation wells (Bruner et al., 1995). The Sewickley and Waynesburg coal beds (Fig. 3) also have been reported to be CBM producers (Bruner et al., 1995). Permit numbers 30614, 30615, 30618, 30620, and 30622 in Blairsville, Indiana County, completed by OíBrien Methane Production in the Blairsville field (Fig. 2) in 1992 and 1994, have commingled gas production from Allegheny Formation coal beds (± Mahoning coal bed) (Petroleum Information Appalachian Basin Report, Section II, May 18, 1995 and August 10, 1995): Clarion (888-891 ft, fractured), L. Kittannning (802-805 ft), and U. Freeport (598-603 ft, fractured). The Mahoning coal bed in this well (546-549 ft) is not a CBM producer. In Fayette County, two CBM wells are producing CBM from the Kittanning coal zone at depths from 800 to 1,200 ft and 30 new wells are planned (Bruner et al., 1995). In Greene County, there are six CBM wells producing from the Kittanning, Freeport, Pittsburgh, and Waynesburg coal beds at depths from 750 to 1,865 ft and also two other wells producing from the Clarion and Kittanning interval and Clarion-Pittsburgh interval. One test well in Greene County penetrated a total of 28 ft of coal (Hunt, 1991). The Pottsville coal beds (Fig. 3), which are known to have CBM production in Westmoreland County (Bruner et al., 1995), have limited CBM potential because of their thinness and lack of continuity. The Brush Creek and Bakerstown coal beds in the lower part of the Conemaugh Formation (Fig. 3) may also have limited CBM production potential in local areas where they are thick and underlie a thick sedimentary cover.
In Ohio, there is no record of CBM production for 1992-1995 (Ron Rea, Ohio Department of Natural Resources, personal commun. April, 1996). In Guernsey County, there were some old wells (pre-regulation days) that produced CBM. In November 1995, two CBM wells (permits nos. 936 and 937, Land Energy Inc.) were permitted in Harrison County (Cadiz quadrangle, Section 23, 1.1 mi WNW of Unionvale) and, once drilled in 1996, they will produce from the Freeport coal zone.
In Maryland and Tennessee, there is no CBM production at the present time (April, 1996).
The CBM production in Pennsylvania is mostly from Indiana County, in southwestern Pennsylvania. Twenty CBM wells (average production of 40 Mcf/day) producing from Allegheny coals (Brookville, Clarion, Kittanning, Lower Freeport and Upper Freeport) were in production in 1995 and 1996, and eight more new CBM wells were planned in 1996 (Jim Mills, Belden and Blake, personal commun., April, 1996).
The annual CBM production for the Appalachian basin is shown in Figure 6. For 1994, the estimated total of 29.5 Bcf of CBM, which is about 1 percent of the 2,492 Bcf for Appalachian tight gas sands production (Kuuskraa et al., 1996) A comparison of CBM production between and Appalachian basin and with the Black Warrior basin is shown in Figure 7.
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