Changes

The drilling levels increased significantly in 2007, with 153 wells completed during that year. Atlas Energy began its successful development of the Marcellus Shale in southwestern Pennsylvania. In 2007, the first significant horizontal completion was reported in Washington County, Pennsylvania, by Range Resources Corporation, with a reported initial potential (IP) of 3.9 mmcfepd. Also in 2007, Cabot Oil and Gas drilled its confirmation well, offsetting the 2006 discovery of the 5 Teel well in Susquehanna County. Several other key step-out and exploration wells were drilled in Butler, Elk, Greene, Clarion, and Lycoming counties of Pennsylvania. Significant drilling programs were initiated by Atlas Resources, Chief Oil and Gas, EOG Resources, Eastern American Energy, Pennsylvania General Energy, Range Resources Corporation, Rex Energy, Texas Keystone, and others. During 2007, the focus was still clearly on vertical well testing, and only a limited number of horizontal wells were drilled and completed.

The drilling levels increased significantly in 2007, with 153 wells completed during that year. Atlas Energy began its successful development of the Marcellus Shale in southwestern Pennsylvania. In 2007, the first significant horizontal completion was reported in Washington County, Pennsylvania, by Range Resources Corporation, with a reported initial potential (IP) of 3.9 mmcfepd. Also in 2007, Cabot Oil and Gas drilled its confirmation well, offsetting the 2006 discovery of the 5 Teel well in Susquehanna County. Several other key step-out and exploration wells were drilled in Butler, Elk, Greene, Clarion, and Lycoming counties of Pennsylvania. Significant drilling programs were initiated by Atlas Resources, Chief Oil and Gas, EOG Resources, Eastern American Energy, Pennsylvania General Energy, Range Resources Corporation, Rex Energy, Texas Keystone, and others. During 2007, the focus was still clearly on vertical well testing, and only a limited number of horizontal wells were drilled and completed.

The year 2008 was the breakout year for the Marcellus Shale play, with more than 360 completed wells reported for that year. Several key vertical and horizontal discoveries were established. These include discoveries reported by CNX Gas and EQT in Greene County, Pennsylvania, and Epsilon Resources in Susquehanna County, Pennsylvania. Encouraging vertical test results were reported by Atlas Energy in Fayette and Westmoreland counties of Pennsylvania after developing effective two-stage fracturing techniques for vertical wells, with average test rates after completion of 2 mmcfpd. Range Resources reported several strong horizontal wells with reported IPs ranging from 4 mmcfepd to more than 26.0 mmcfepd in Washington County, Pennsylvania.

The year 2008 was the breakout year for the Marcellus Shale play, with more than 360 completed wells reported for that year. Several key vertical and horizontal discoveries were established. These include discoveries reported by CNX Gas and EQT in Greene County, Pennsylvania, and Epsilon Resources in Susquehanna County, Pennsylvania. Encouraging vertical test results were reported by Atlas Energy in Fayette and Westmoreland counties of Pennsylvania after developing effective two-stage fracturing techniques for vertical wells, with average test rates after completion of 2 mmcfpd. Range Resources reported several strong horizontal wells with reported IPs ranging from 4 mmcfepd to more than 26.0 mmcfepd in Washington County, Pennsylvania.<ref>Range Resources Corporation, 2010, [http://b2icontent.irpass.cc/790%2F112383.pdf?AWSAccessKeyId=1Y51NDPSZK99KT3F8VG2&Expires=1282674243&Signature=T%2FrJ6ggrDsxTUsOJXDNyXkKvHbI%3D Range Resources Company Presentation, August 2010].</ref>

Current drilling for the Marcellus has been focused along a northeast–southwest-trending fairway extending more than 800 km (500 mi) in length and mainly targeting areas where the Marcellus Shale occurs at vertical depths of 1370 m (4500 ft) or greater. As of July 2010, more than 100 drilling rigs and 31 operators were reported active in the Marcellus Shale play across 26 separate counties in Pennsylvania and West Virginia. By midyear 2010, at least 800 Marcellus wells had been completed in the overpressured area of the play by 70 companies. New discoveries were reported in 2009 and 2010 by Chesapeake, Ultra Petroleum, East Resources, and Talisman Energy across broad areas of the play, including large discoveries in Bradford and Tioga counties, Pennsylvania. Cabot Oil and Gas reported some of the highest reported IP rates for its horizontal wells (6.0–18.0 mmcfpd) as it significantly expanded its Susquehanna County project area. Finally, in early 2010, the first reported successful horizontal tests of the Upper Devonian Genesee Group and Ordovician Utica Shale were reported by Range Resources, opening new opportunities to further expand shale-gas development in the Appalachian Basin.

Current drilling for the Marcellus has been focused along a northeast–southwest-trending fairway extending more than 800 km (500 mi) in length and mainly targeting areas where the Marcellus Shale occurs at vertical depths of 1370 m (4500 ft) or greater. As of July 2010, more than 100 drilling rigs and 31 operators were reported active in the Marcellus Shale play across 26 separate counties in Pennsylvania and West Virginia. By midyear 2010, at least 800 Marcellus wells had been completed in the overpressured area of the play by 70 companies. New discoveries were reported in 2009 and 2010 by Chesapeake, Ultra Petroleum, East Resources, and Talisman Energy across broad areas of the play, including large discoveries in Bradford and Tioga counties, Pennsylvania. Cabot Oil and Gas reported some of the highest reported IP rates for its horizontal wells (6.0–18.0 mmcfpd) as it significantly expanded its Susquehanna County project area. Finally, in early 2010, the first reported successful horizontal tests of the Upper Devonian Genesee Group and Ordovician Utica Shale were reported by Range Resources, opening new opportunities to further expand shale-gas development in the Appalachian Basin.

[[:File:M97Ch4FG14.jpg|Figure 14]] shows the major part of the northeastern core area of the Marcellus Shale with key wells, test rates, and thermal maturity. In the northeastern core area, vertical well performance has ranged from 0.100 to more than 7.0 mmcfpd, and horizontal well performance has ranged from 1.0 to more than 18.0 mmcfpd. In the northeast core area, the Marcellus Shale attains a gross play interval of 60 to 105 m (200–350 ft), has a Btu content of 1000 to 1050 because of the elevated thermal maturity levels, and is generally more structurally complicated than the southwestern play area. Both areas appear to be consistently overpressured and have relatively comparable reserve potential based on reported flow rates and estimated ultimate recovery estimates.

[[:File:M97Ch4FG14.jpg|Figure 14]] shows the major part of the northeastern core area of the Marcellus Shale with key wells, test rates, and thermal maturity. In the northeastern core area, vertical well performance has ranged from 0.100 to more than 7.0 mmcfpd, and horizontal well performance has ranged from 1.0 to more than 18.0 mmcfpd. In the northeast core area, the Marcellus Shale attains a gross play interval of 60 to 105 m (200–350 ft), has a Btu content of 1000 to 1050 because of the elevated thermal maturity levels, and is generally more structurally complicated than the southwestern play area. Both areas appear to be consistently overpressured and have relatively comparable reserve potential based on reported flow rates and estimated ultimate recovery estimates.

The July 27, 2009, issue of the Gene Powell Newsletter identifying the top 868 Barnett Shale wells out of a database of 8266 wells indicated that the average peak 30-day actual production tests for these top tier wells range from 3.0 to more than 10.0 mmcfepd (Powell and Brackett, 2009). Although the Marcellus Shale play is in its infancy compared with the maturing Barnett Shale play, reported IP rates (commonly actual 30-day production tests) for the Marcellus range from 1.0 to more than 26.0 mmcfepd. This suggests that the extent of sweet spots in the Marcellus Shale play are considerably larger than the Barnett Shale play and that well performance on an average or playwide basis is at least equal if not superior to that of the Barnett Shale.

The July 27, 2009, issue of the Gene Powell Newsletter identifying the top 868 Barnett Shale wells out of a database of 8266 wells indicated that the average peak 30-day actual production tests for these top tier wells range from 3.0 to more than 10.0 mmcfepd.<ref>Powell, M. E., and W. Brackett, 2009, Best Barnett Shale wells based on peak month daily average: Powell Barnett Shale Newsletter, July 2009, p. 9.</ref> Although the Marcellus Shale play is in its infancy compared with the maturing Barnett Shale play, reported IP rates (commonly actual 30-day production tests) for the Marcellus range from 1.0 to more than 26.0 mmcfepd. This suggests that the extent of sweet spots in the Marcellus Shale play are considerably larger than the Barnett Shale play and that well performance on an average or playwide basis is at least equal if not superior to that of the Barnett Shale.

==Reserve potential==

==Reserve potential==

# Powell, M. E., and W. Brackett, 2009, Best Barnett Shale wells based on peak month daily average: Powell Barnett Shale Newsletter, July 2009, p. 9.

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# Range Resources Corporation, 2010, Range Resources Company Presentation, August 2010: http://b2icontent.irpass.cc/790%2F112383.pdf?AWSAccessKeyId=1Y51NDPSZK99KT3F8VG2&Expires=1282674243&Signature=T%2FrJ6ggrDsxTUsOJXDNyXkKvHbI%3D (accessed August 1, 2010).

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# Reed, J. R., and D. Dunbar, 2008, Using ArcGIS to estimate thermogenic gas generation volumes by Upper and Middle Devonian shales in the Appalachian Basin (abs.): AAPG Eastern Section meeting: http://www.papgrocks.org/reed_p.pdf (accessed October 15, 2009).

# Reed, J. R., and D. Dunbar, 2008, Using ArcGIS to estimate thermogenic gas generation volumes by Upper and Middle Devonian shales in the Appalachian Basin (abs.): AAPG Eastern Section meeting: http://www.papgrocks.org/reed_p.pdf (accessed October 15, 2009).

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