"Unconventional" Gas Plays

More information from the online "World Oil Magazine" on the "Shale Gas" plays in the United States. (source)

Peter

SPECIAL FOCUS: NORTH AMERICAN OUTLOOK- UNCONVENTIONAL RESOURCES
Unconventional plays grow in number after Barnett Shale blazed the way
The Haynesville and Marcellus are becoming exciting new gas plays, while activity in the Woodford and Fayetteville continues.
Katrina Boughal , Technical Editor

Unconventional gas plays in the US have been booming since technological advances increased production in the now-famous Barnett Shale. Horizontal drilling and fracture stimulation in the shale source rock, as opposed to the sandstone/limestone/dolomite reservoir rock, have proved to be successful not only in gas plays like the Barnett, Fayetteville and Woodford, but also in the Bakken-a primarily oil-rich formation.

Resources that were previously thought to be unrecoverable are now being reassessed and, in some cases, rediscovered. Many shale plays have been producing a small amount of gas for years (the Indiana and Kentucky New Albany Shale since the late 1880s), but with the Barnett example, they are becoming more successful. Hot plays in the industry include the Louisiana/Texas Haynesville and Bossier Shales, and the Marcellus of Pennsylvania/Appalachia. The Williston Basin Bakken Formation has also gained popularity after a recent reassessment by the USGS.

HAYNESVILLE
The fairly recent Haynesville gas play, having garnered attention over the past few months, is an Upper Jurassic formation overlain by the Cotton Valley Group, and lies over the Smackover Formation. The Haynesville is an ultra-low permeability shale, and is focused in northwest Louisiana and East Texas, particularly in Caddo, Bossier and DeSoto Parishes, but also to a lesser extent in Red River and Sabine Parishes, and Harrison and Panola Counties, Fig. 1. The Haynesville Shale underlies the Bossier Shale (part of the Cotton Valley Group), and they are sometimes referred to as the same unit or related units. 2 Deeper than most shale gas plays, the Haynesville is located at depths ranging between 11,000 and 13,000 ft. 3

Fig. 1 . Map of the Haynesville Shale play (shaded). 1
Chesapeake is a large participant in the Haynesville play, holding about 550,000 acres as of late June 2008, with plans to acquire more acreage. Chesapeake entered a joint venture with Plains Exploration and Production, and the companies plan to drill about 600 wells in the Haynesville in the next three years. Chesapeake is estimating a mid-point estimated ultimate reserve of 6.5 Bcf, and their initial horizontal production rates are encouraging for the play.
“The initial production rates on the eight horizontal wells we have completed have ranged from 5 to 15 MMcfd on restricted chokes at flowing casing pressures of up to 6,500 psi,” said Chesapeake CEO Aubrey K. McClendon. 4

Petrohawk is also an active participant with about 275,000 acres, and completed their first horizontal well in the Haynesville in late June 2008. The Elm Grove Plantation #63, drilled in Bossier Parish, encountered about 212 ft of Haynesville Shale, and produced at a rate of 16.8 MMcfd. Completion of Elm Grove Plantation #63 included 11 stages of fracture stimulation. Petrohawk is drilling three horizontal wells, and expects to be operating six rigs in the Haynesville by mid-September 2008. 5

Companies are scrambling to lease plots in the Haynesville, with Forest Oil announcing in late June 2008 a net holding of 90,000 acres in the area. 6 GMX Resources added 7,300 net acres in early July, bringing its total acreage to 27,500. 7 EnCana has about 325,000 acres in the Haynesville, and completed a horizontal well in February with an initial production rate of 8 MMcfd. 8

FAYETTEVILLE
A few years ago the Fayetteville Shale experienced an upswing in interest somewhat akin to what the Haynesville is experiencing now. The Fayetteville of Arkansas is a Mississippian formation on the eastern end of the Arkoma Basin, with thicknesses varying between 50 and 300 ft and drilled at depths ranging from 2,000 to 6,000 ft. Thickness in the Fayetteville differs from east to west, at about 50 to 75 ft thick in western Arkansas to about 300 ft at the eastern edge of the Arkoma Basin. The formation is productive from its middle to base because the lower section is rich in organic material, with chert and siliceous interbedding. 9 The unit is thermally mature, and is differentiated from surrounding units by high radioactivity and resistivity signatures. 10

The Fayetteville is found in multiple eastern and central Arkansas counties, including Cleburne, Conway, Faulkner, Franklin, Jackson, St. Francis, Pope, Prairie, Van Buren, White and Woodruff Counties. The Fayetteville is about the same age and is seen as a geologic equivalent to the Barnett Shale near Fort Worth.

The Fayetteville followed the Barnett in production technology. As with other shale gas plays, the Fayetteville was previously known to be a gas-bearing formation, but only produced when horizontal drilling and fracture stimulation were introduced. 8 Some 460 of the over 500 producing wells in the Fayetteville are horizontal, and total production from the shale has reached, and likely exceeded, 52 Bcf. 11

Rig counts in the Arkansas Arkoma Basin have increased dramatically in the past two years. In August 2006, the rig count hovered at slightly over 20. In early July 2008, the count was at 59 operating rigs, with most located in Van Buren, White and Conway Counties. Southwestern Energy was operating 18 of the 59 rigs (about 31%) in the Arkansas Arkoma Basin during the first week of July 2008. 12 Southwestern, one of the most dominant players in the region, owns about 851,100 acres in the Fayetteville area, and has completed 557 wells in the play as of March 2008, of which about 88% were horizontal. During the company’s first quarter 2008, estimated 2007 production from the Fayetteville was 53.5 Bcf. 13

Chesapeake holds the largest land area in the play with 1.1 million acres, and in March 2008, had a net production of 130 MMcfd from the Fayetteville. Chesapeake had 12 rigs operating in March 2008, and plans to escalate drilling activity to 25 rigs in the play by early 2009. 14

MARCELLUS
In 2002, the USGS released an assessment of the undiscovered oil and gas in the Appalachian Basin Province. The Marcellus Shale was characterized as an individual assessment unit in the Appalachian Basin region that contained gas resources of about 1.9 Tcf. 15

The Marcellus had been fairly quiet until recently, when in late 2007 Range Resources announced horizontal well test rates from 1.4 MMcfd to 4.7 MMcfd. Shortly after, in January 2008, Pennsylvania State University and the University of New York at Fredonia released a report estimating recoverable reserves at 50 Tcf. Since then, The New York Times and USA Today have run stories on the Marcellus and the formation’s producing potential.

The Marcellus Shale is part of a large suite of rocks known as the Devonian shales, and stretches NE-SW about 600 mi across several Appalachian states, including New York, Pennsylvania and West Virginia, Fig. 2. 16 The naturally fractured, dry gas-producing Marcellus covers an area of about 54,000 square mi, 17 and ranges in thickness from 50 to 200 ft. Like the Fayetteville, the Marcellus thins from east to west, with 200-ft sections in northeastern Pennsylvania and 50-ft sections in northern West Virginia, Ohio, Pennsylvania and western New York. The formation depth ranges from 5,000 to 8,000 ft below sea level. 18

Fig. 2 . Map of the Marcellus and Devonian Shales. 16
The organic richness of the Marcellus, however, decreases generally from north in New York to south in West Virginia. The thermal maturity of the shale is an estimated 1.5 to 3% vitrinite reflectance (Ro). 18

As of April 2008, Range Resources held about 1.15 million acres of the Marcellus play, and had drilled 10 successful horizontal wells with initial production rates ranging from 2.6 to 5.8 MMcfd. 19 Other players in the Marcellus include Atlas Energy Resources and Chesapeake (largest lease holder with 1.2 million acres). Atlas, whose drilling plan is focused primarily in southwestern Pennsylvania, announced in February that it had 21 producing vertical wells, with 6 more due to be completed and producing shortly. 20

Marcellus players face the problem of minimal public information on the area, and have to resort to academic papers and regional geologic information due to the lack of log data. Oilfield services and equipment in the area are also somewhat scarce, with only four or six Appalachian rigs capable of drilling horizontal wells. 16

WOODFORD
Activity in the Woodford Shale began in 2003-2004 as a vertical play, but quickly transitioned to horizontal wells after the Barnett became horizontally driven. 21
The Woodford Shale is located in Oklahoma on the western end of the Arkoma Basin, and ranges in age from Middle Devonian to Early Mississippian. The stratigraphic equivalent to the Bakken and Antrim Shales, the Woodford shows a wide range of thermal maturities from 0.7 to 4.89% Ro?. Although known to be a gas-producing formation, the Woodford may have the potential to produce oil as well, 22 and the silica-rich shale has provided a good environment for fracturing due to its brittle nature. 21

The Woodford has seen many players in the area including Newfield Exploration, Devon, Chesapeake and XTO Energy. Newfield has about 165,000 net acres in the Woodford, is looking to drill about 100 horizontal wells this year and had a gross production of 165 MMcfd as of February 2008.23 Drilling depths for Newfield have ranged from 6,000 to 13,000 ft, with lateral lengths to about 5,000 ft. 21 For a more in-depth discussion on the characteristics and production potential of the Woodford Shale, please see page 83.

BARNETT
No unconventional play article would be complete without a mention of the Barnett. The very well-known Barnett Shale is the gas play that introduced horizontal drilling and fracture stimulation techniques to the unconventional shale gas field, allowing other plays’ production potential to be realized. Indeed, every time a new shale gas play is discovered, it is compared to the Barnett, or is called the “next Barnett” or a “baby Barnett.”

The Mississippian Barnett in the Fort Worth Basin of Texas is about 6,500 to 8,000 ft deep, and thickens toward the northeast-from about 30 to 50 ft thick in the south to about 1,000 ft thick in the northeast. 24

At the end of 2007, the total number of Barnett producing wells over time was at about 8,960, with cumulative production of 3.69 Tcf and 11.6 million bbl of oil. The rate of production from 8,435 active Barnett wells in December 2007 was 3.524 Bcfd plus 7,477 bpd. From 2003 to 2007, horizontal wells have become the dominant well orientation. In 2003, about 21% of wells completed in the Barnett were horizontal; in 2007, about 94% were horizontal. 25

The Barnett continues as the giant that it has become in the past five years. The players list in the Barnett is exhaustive, with Devon, Chesapeake, XTO, Encana, EOG and others. Devon has drilled more than 1,300 wells in the Barnett since 2002, and produces nearly 600 MMcfd. 26

BAKKEN
The April 2008 USGS assessment of the Bakken Formation in the Williston Basin has caused a flurry of activity in the area, particularly because of the undiscovered, technically recoverable oil resource estimation-between 3.0 and 4.3 billion bbl. The large increase in the Bakken’s recoverable resources (formerly estimated by the USGS at 151 million bbl in 1995) is due to the same factor that has lead to expanding shale gas plays: advances in horizontal drilling and hydraulic fracturing.

The Upper Devonian-Early Mississippian Bakken is a continuous, 200,000-sq mi formation composed of sandstone, siltstone and dolomite bounded by two shale layers. Average porosity in the Bakken is between 8% and 12%, and permeability ranges from 0.05 mD to 0.5 mD. The Bakken is about 2-mi deep, and has a net thickness of about 6 ft to 15 ft. Key players in the region include EOG Resources, Whiting Petroleum, Brigham Exploration, Hess, Newfield Exploration, XTO and Marathon. 27 For a more comprehensive view on the Bakken assessment, please see World Oil June 2008, page 83.

OTHER PLAYS
There are a multitude of unconventional shale plays being assessed, and the following are a few from various parts of the US.
Utica. Located in New York, northern Pennsylvania, Quebec and Ontario, the Utica Shale is an Upper Ordovician reservoir with typical low permeability, high organic content and varying thickness-the formation ranges from 150 to 1,000 ft across New York. The Utica’s close proximity to the Marcellus makes it interesting, but recently drilled Utica wells have “not responded well to the normal shale fracturing practices.” 28 Forest Oil has acquired 269,000 net acres of the Quebec Utica, and in April 2008, reported 1 MMcfd production rates from two 4,800-ft vertical wells. 29

Chattanooga.

This Devonian shale formation extends across a large part of the US, although the gas play is centered in southern Kentucky, eastern Tennessee and northern Alabama, Fig. 3. Sources cite the Chattanooga as being an equivalent to both the Marcellus and the Woodford Shales, all of which are Devonian formations. 30,31

Fig. 3 . Map of the Chattanooga Shale play (shaded). 30
The USGS reported in 2007 on the petroleum system of the Black Warrior Basin in Alabama and Mississippi that encompasses part of the Chattanooga Shale. The USGS report focused on the carbonates and sandstones, and discussed the Floyd and Chattanooga Shales as source rocks alone-no unconventional shale gas assessment was released. The Chattanooga is a Devonian-age shale that is separated from the Mississippian-age Floyd Shale by a thin layer of chert and limestone, and they are often referred in relation to each other. The Alabama Chattanooga play lies in the eastern Black Warrior Basin, and is a thin unit with a Total Organic Carbon (TOC) weight percent range of 2.4-12.7. 32 The Tennessee Chattanooga play is relatively shallow compared to other gas plays with depths ranging from 1,500 to 2,000 ft. 33

In 2007, CNX Gas Corp. drilled a horizontal well in Tennessee with an initial production rate of 3.9 MMcfd. 34 Atlas Energy Resources announced in June 2008 the successful drilling of four horizontal wells in the formation. 35

Floyd. In close contact with the Chattanooga Shale, the Floyd play is situated in the Black Warrior Basin of Mississippi and Alabama. The formation is primarily shale, but also contains clay, sandstone and limestone beds, with chert and large siderite modules. 32 Found at depths from about 4,000 ft to 9,000 ft below surface level, 36 the Floyd thickens toward the northeast, with a maximum thickness of about 600 ft, and has a TOC percent weight of about 1.8. The Floyd is believed to be the source rock for the conventional reservoirs in the area. 32 Carrizo Oil and Gas drilled a horizontal well in the Floyd in July 2007,37 and Murphy Oil drilled several wells in 2006. 38 With minimal news concerning the Floyd in 2008, play activity seems to have slowed down.

New Albany.

Found in the Illinois Basin, the New Albany Shale is a mostly Devonian-aged formation (the top few feet of the unit are Mississippian) that spans Kentucky, Indiana and, to a smaller extent, Illinois. The New Albany can be correlated with the Antrim Shale of Michigan and Indiana, and the Chattanooga Shale of Tennessee. 39 The New Albany gas play has been focused in Kentucky and southeastern Indiana. Formation thickness varies-the shale is about 100 to 140 ft thick in southeastern Indiana and almost 340 ft thick farther southwest in the Illinois Basin. 40 The USGS released a report in 2007 on the Illinois Basin that assessed the undiscovered, technically recoverable gas resources of the New Albany Shale at 3.79 Tcf. 41 Aurora Oil and Gas reported an average production of 424 Mcfd from their New Albany holdings in the first quarter 2008. 42 CNX Gas drilled six wells in the New Albany in 2007 to determine reservoir information and future drilling locations. 34

As the Barnett proves to be continually successful, shale plays, oil and gas, are looking to be important in the future.
There are already whispers of the Haynesville being the next Barnett, and although those rumors have been heard before about other plays, expect to hear about the Haynesville, and the Bakken and Marcellus, in the months to come.

LITERATURE CITED
1 “Core leasing area: Haynesville Shale map,” Haynesville Shale Map, http://haynesvilleshalemap.com/, accessed July 7, 2008.

2 Welborn, V., “What is the Haynesville Shale?” Shreveport Times , July 7, 2008.

3 “Shale gas fever drives land drilling in US,” Platts Oilgram News , July 4, 2008, pg. 6.

4 “Chesapeake and PXP announce Haynesville Shale joint venture,” Yahoo Financial News, July 1, 2008, http://bix.yahoo.com/bw/080701/20080701006524.html, accessed July 8, 2007.

5 “Petrohawk Energy Corporation reports Haynesville Shale result and leasehold update,” Fox Business, June 30, 2008, http://www.foxbusiness.com/story/markets/industries/energy/petrohawk-energy-corporation-reports-haynesville-shale-result-leasehold-update/, accessed July 8, 2008.

6 “Forest Oil increases holdings in E. Texas, N. La,” Forbes.com, June 30, 2008, http://www.forbes.com/feeds/ap/2008/06/30/ap5169765.html, accessed July 10, 2008.

7 “GMX Resources Inc. announces Haynesville/Bossier Shale drilling to begin 3Q08,” Prime Newswire, July 7, 2008, http://www.primenewswire.com/newsroom/news.html?d=145868, accessed July 10, 2008.

8 Fuquay, J., “Chesapeake, EnCana, boost activity in Louisiana gas shale,” Star-Telegram , June 16, 2008.

9 Brown, D., “Barnett may have Arkansas cousin,” AAPG Explorer , Feb. 2006.

10 “The Fayetteville Shale play: A geologic overview,” Arkansas Business.com, Aug. 27, 2007, http://www.arkansasbusiness.com/article.aspx?aID=99154, accessed July 8, 2008.

11 Shelby, P., “Fayetteville Shale play of North-Central Arkansas: A project update,” presented at the AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008.

12 “Baker Hughes US rig count- Summary report,” Baker Hughes- Investor relations- Rig counts, http://164.109.37.157/Reports/StandardReport.aspx, accessed July 11, 2008.

13 “Fayetteville Shale play,” Southwestern Energy Company, http://www.swn.com/operations/fayetteville.shale.asp, accessed July 8, 2008.

14 “Chesapeake reports Haynesville Shale discovery in Louisiana and announces CapEx increase,” OilVoice, March 24, 2008, http://www.oilvoice.com/n/Chesapeake_Reports_Haynesville_Shale_Discovery_in_Louisiana_and_Announces_CapEx_Increase/92f01da5.aspx, accessed July 11, 2008.

15 US Department of the Interior, US Geological Society, “Assessment of undiscovered oil and gas resources of the Appalachian Basin Province, 2002,” USGS Fact Sheet FS-009-03, February 2003.

16 Durham, L. S., “Another shale making seismic waves,” AAPG Explorer, March 2008.

17 Mayhood, K., “Low down, rich and stingy,” The Columbus Dispatch , March 11, 2008.

18 Milici, R. C. and C. S. Swezey, “Assessment of Appalachian Basin oil and gas resources: Devonian Shale- Middle and Upper Paleozoic total petroleum system,” Open file report series 2006-1237, USGS Reston, Virginia, 2006, pp.38-39.

19 “Range announces record first quarter results,” OilVoice, April 24, 2008, http://www.oilvoice.com/n/Range_Announces_Record_First_Quarter_Results/4c59a7ac.aspx, accessed July 11, 2008.

20 “Atlas Energy Resources, LLC increases estimated reserve potential from Marcellus Shale to between 4 and 6 Tcf,” Reuters, Feb. 21, 2008, http://www.reuters.com/article/pressRelease/idUS127932+21-Feb-2008+MW20080221, accessed July 14, 2008.

21 Brown, D., “Big potential boost the Woodford,” AAPG Explorer , July 2008.

22 Comer, J. B., “Reservoir characteristics and production potential of the Woodford Shale,” World Oil , August 2008, pp. 83.

23 “Newfield Exploration announces 2008 capital program,” Reuters, Feb. 4, 2008, http://www.reuters.com/article/pressRelease/idUS139442+04-Feb-2008+PRN20080204, accessed July 11, 2008.

24 Hayden, J. and D. Pursell, “The Barnett Shale: Visitors guide to the hottest gas play in the US,” Tudor Pickering, Oct. 2005, http://www.tudorpickering.com/pdfs/TheBarnettShaleReport.pdf, accessed July 10, 2008.

25 “Number of vertical and horizontal producer wells in the Barnett Shale as of Jan. 1, 2008,” Powell Barnett Shale Newsletter , March 27, 2008, http://www.barnetshalenews.com/documents/VHchart%201-1-08.pdf, accessed July 10, 2008.

26 “Operations- Barnett Shale,” Devon Energy, http://www.devonenergy.com/Operation/FeatuerStories/Pages/barnett_shale.aspx, accessed July 10, 2008.

27 Cohen, D. M., “USGS names Bakken play the largest oil accumulation in the Lower 48,” World Oil , June 2008, pp. 83-84.

28 Paktinat, J., Pinkhouse, J., Fontaine, J., Lash, G. and G. Penny, “Investigation of methods to improve Utica Shale hydraulic fracturing in the Appalachian Basin,” presented at the AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008.

29 “Forest Oil announces significant gas discovery in Utica Shale…” Reuters, April 1, 2008, http://www.reuters.com/article/pressRelease/idUS134787+01-Apr-2008+BW20080401, accessed July 11, 2008.

30 “Chattanooga Shale natural gas field,” Oil Shale Gas, http://www.oilshalegas.com/chattanoogashale.com, accessed July 9, 2008.

31 “AMI Project,” Irvine Energy PLC, http://www.irvineenergy.com/projects/index.htm, accessed July 9, 2008.

32 USGS Black Warrior Basin Province assessment team, “Geologic assessment of undiscovered oil and gas resources of the Black Warrior Basin Province, Alabama and Mississippi,” Hatch, J. R. and M. J. Pawlewicz, compilers, USGS Digital Data Series DDS-69-I, 2007, 76 p.

33 “Domestic Energy announces Appalachian Shale plan,” Reuters, April 28, 2008, http://www.reuters.com/article/preeRelease/idUS139048+28-Apr-2008+MW20080428, accessed July 9, 2008.

34 “CNX Gas reports fourth quarter and full year 2007 results,” Reuters, Jan. 29, 2008, http://www.reuters.com/article/pressRelease/idUS140410+29-Jan-2008+PRN20080129, accessed July 11, 2008.

35 “Atlas Energy announces four successful horizontal wells in Tennessee’s Chattanooga Shale, and a net acreage position of 105,000 acres in the play,” OilVoice, June 21, 2008, http://www.oilvoice.com/n/Atlas_Energy_Announces_Four_Successful_Horizontal_Wells_in_Tennessees_Chattanooga_Shale/9fc6bbe0.aspx, accessed July 9, 2008.

36 “Floyd Shale potential of the Black Warrior Basin: Executive summary,” Mississippi Geological Society eBulletin , Vol. 55, No. 7, March 2007.

37 “Carrizo Oil & Gas, Inc. announces record production and third quarter 2007 financial results,” Carrizo Oil & Gas, Nov. 8, 2007, http://carrizo.mediaroom.com/index.php?s=43&iten=154, accessed July 10, 2008.

38 Edmonds, C., “New shales may be ready to deliver,” The Street, Feb. 22, 2007, http://www.thestreet.com/story/10340267/1/new-shales-may-be-ready-to-deliver.html, accessed July 10, 2008.

39 “New Albany Shale,” Indiana Geological Survey, http://igs.indiana.edu/Geology/structure/compendium/html/comp82hw.cfm, accessed July 9, 2008.

40 Comer, J. B., Hasenmueller, N. R., Mastalerz, M. D., Rupp, J. A., Shaffer, N. R. and C. W. Zuppann, “The New Albany Shale gas play in southern Indiana,” presented at AAPG Eastern Section Meeting, Buffalo, N.Y., Oct. 8-11, 2006.

41 US Department of the Interior, US Geological Survey, “Assessment of undiscovered oil and gas resources of the Illinois Basin, 2007,” USGS Fact Sheet 2007-3058, August 2007.

42 “Aurora Oil & Gas Corp. announces first quarter 2008 results,” Reuters, May 9, 2008, http://www.reuters.com/article/pressRelease/idUS248894+09-May-2008+PRN20080509, accessed July 11, 2008.

Marcellus Shale And Natural Gas Production In The NE United States

The successful production of large volumes of natural gas from shale rocks has enormously positive economic consequences for America, and indeed, the world. This is a relatively recent development of extreme importance. For an idea of how important natural gas is, consider exactly what it is and its many uses:

Natural gas is a gaseous fossil fuel consisting primarily of methane but including significant quantities of ethane, propane, butane, and pentane—heavier hydrocarbons removed prior to use as a consumer fuel —as well as carbon dioxide, nitrogen, helium and hydrogen sulfide.[1] It is found in oil fields (associated) either dissolved or isolated in natural gas fields (non-associated), and in coal beds (as coalbed methane).

This so-called "Shale Gas" and the Marcellus Shale development warrants close attention.
Peter
(source)

Marcellus Shale - Appalachian Basin Natural Gas Play
New research results surprise everyone on the potential of this well-known Devonian black shale.
Super Giant Field in the Appalachians?A few years ago every geologist involved in Appalachian Basin oil and gas knew about the Devonian black shale called the Marcellus. Its black color made it easy to spot in the field and its slightly radioactive signature made it a very easy pick on a geophysical well log. However, very few of these geologists were excited about the Marcellus Shale as a major source of natural gas. Wells drilled through it produced some gas but rarely in enormous quantity. Few if any in the natural gas industry suspected that the Marcellus might soon be a major contributor to the natural gas supply of the United States - large enough to be spoken of as a "super giant" gas field.

Early Marcellus Estimates by USGSAs recently as 2002 the United States Geological Survey in its Assessment of Undiscovered Oil and Gas Resources of the Appalachian Basin Province, calculated that the Marcellus Shale contained an estimated undiscovered resource of about 1.9 trillion cubic feet of gas. [1] That's a lot of gas but spread over the enormous geographic extent of the Marcellus it was not that much per acre.

The First Hints of Big Production

Range Resources - Appalachia, LLC may have started the Marcellus Shale gas play. In 2003 they drilled a Marcellus well in Washington County, Pennsylvania and found a promising flow of natural gas [2]. They experimented with drilling and hydraulic fracturing methods that worked in the Barnett Shale of Texas. Their first Marcellus gas production from the well began in 2005. Between then and the end of 2007 more than 375 gas wells with suspected Marcellus intent had been permitted in Pennsylvania [2].

Recent Surprise EstimatesIn early 2008, Terry Englander, a geoscience professor at Pennsylvania State University, and Gary Lash, a geology professor at the State University of New York at Fredonia, surprised everyone with estimates that the Marcellus might contain more than 500 trillion cubic feet of natural gas. Using some of the same horizontal drilling and hydraulic fracturing methods that had previously been applied in the Barnett Shale of Texas, perhaps 10% of that gas (50 trillion cubic feet) might be recoverable. That volume of natural gas would be enough to supply the entire United States for about two years and have a wellhead value of about one trillion dollars! [5]

What is the Marcellus Shale?
Marcellus Shale: Videos, News, Maps, Lease & Royalty Information

The Marcellus Shale, also referred to as the Marcellus Formation, is a Middle Devonian-age black, low density, carbonaceous (organic rich) shale that occurs in the subsurface beneath much of Ohio, West Virginia, Pennsylvania and New York. Small areas of Maryland, Kentucky, Tennessee, and Virginia are also underlain by the Marcellus Shale. See the map of the Marcellus Shale above.

How Deep is the Marcellus Shale?

Throughout most of its extent, the Marcellus is nearly a mile or more below the surface. The map at right shows the depth of the Marcellus Shale. These great depths make the Marcellus Formation a very expensive target. Successful wells must yield large volumes of gas to pay for the drilling costs that can easily exceed a million dollars for a traditional vertical well and much more for a horizontal well with hydraulic fracturing. Using the two maps together, some especially interesting areas can be seen. These are where thick Marcellus Shale can be drilled at minimum depths. Although this is a great oversimplification, it correlates with the heavy leasing activity that has occurred in parts of northern Pennsylvania and western New York.

Where is the Highest Production Potential?

Rock units are not homogeneous. The gas in the Marcellus Shale is a result of its contained organic content. Logic therefore suggests that the more organic material there is contained in the rock the greater its ability to yield gas. John Harper of the Pennsylvania Geological Survey suggests that the areas with the greatest production potential are those areas where the net thickness of organic-rich shale within the Marcellus Formation is the greatest. A map showing this distribution for the state of Pennsylvania is shown at right. Northeastern Pennsylvania is where the thick organic-rich shale intervals are located.

Low Yield, Long-Lasting Production

Before 2000, many successful natural gas wells had been completed in the Marcellus. The yields of these wells were often unimpressive upon completion. However, many of these older wells in the Marcellus have a sustained production that decreases slowly over time. Many of them continued to produce gas for several decades. A patient investor might make a profit from these low yield wells with slowly declining production rates. For new wells drilled with the new horizontal drilling and hydraulic fracturing technologies the inital production can be much higher than what was seen in the old wells. Then as production rates decline a well might receive new hydraulic fracturing treatments to boost production. The wells will eventually deplete but the fracturing treatments help to produce a more complete recovery of the natural gas. Because this method has not been applied long-term to wells in the Marcellus there is little production history data.

How Does the Gas Occur in the Rock?

Natural gas occurs within the Marcellus Shale in three ways: 1) within the pore spaces of the shale; 2) within vertical fractures (joints) that break through the shale; and, 3) adsorbed on mineral grains. Most of the recoverable gas is contained in the pore spaces. However, the gas has difficulty escaping through the pore spaces because they are very tiny and poorly connected. Most historic wells in the Marcellus produced gas at a very slow rate because of the low permeability mentioned above. This is typical for a shale. However, the most successful historic wells in the Marcellus share a common characteristic: they intersect numerous fractures. These fractures allow the gas to flow through the rock unit and into the well bore. The fractures intersecting the well also intersect other fractures and those fractures intersect still more fractures. Thus, an extensive fracture network allows one well to drain gas from a very large volume of shale. A single well can recover gas from many acres of surrounding land.

Horizontal Drilling to Penetrate More Fractures

The fractures (also known as "joints") in the Marcellus Shale are vertical. So, a vertical borehole would be expected to intersect very few of them. However, a horizontal well, drilled perpendicular to the most common fracture orientation should intersect a maximum number of fractures. The diagram to the right illustrates the concept of a horizontal well. High yield wells in the Marcellus Shale have been built using the horizontal drilling technique. Some horizontal wells in the Marcellus Shale have initial flows that suggest that they are capable of yielding millions of cubic feet of gas per day, making them some of the most productive gas wells in the eastern United States. Although some experts are very optimistic on the long-term production rates of these wells, it is too early to determine their productive life or long-term yield.

Increase the Number of Fractures

A second method is used to increase the productivity of a well. That is to increase the number of fractures in a well using a technique known as "hydraulic fracturing" or "hydrofracing". This method uses high-pressure water or a gel to induce fractures in the rock surrounding the well bore. Hydrofracing is done by sealing off a portion of the well and injecting water or gel under very high pressure into the isolated portion of the hole. The high pressure fractures the rock and pushes the fractures open. To prevent the fractures from closing when the pressure is reduced several tons of sand or other "propant" is pumped down the well and into the pressurized portion of the hole. When the fracturing occurs millions of sand grains are forced into the fractures. If enough sand grains are trapped in the fracture it will be propped partially open when the pressure is reduced. This provides an improved permeability for the flow of gas to the well.

Economic Significance of the Marcellus Shale Gas Field

The presence of an enormous volume of potentially recoverable gas in the eastern United States has a great economic significance. This will be some of the closest natural gas to the high population areas of New Jersey, New York and New England. This transportation advantage will give Marcellus gas a distinct advantage in the marketplace. Gas produced from the shallower, western portion of the Marcellus extent (see map above) might be transported to cities in the central part of the United States. It should have a positive impact on the stability of natural gas supply of the surrounding region for at least several years if the resource estimate quoted above proves accurate.

Gas Leases & Signing Bonuses

Many landowners are being approached with offers to lease their land. The size of the signing bonuses that have been paid in transactions between informed buyers and informed sellers is directly related to two factors: 1) the level of uncertainty in the mind of the buyer, and 2) the number of other buyers competing to make the purchase. These factors have changed significantly in a very short time. As recently as 2005 there was very little interest in leasing properties for Marcellus Shale gas production. The Marcellus was not considered to be an important gas resource and a technology for tapping it had not been demonstrated. At that time the level of uncertainty in the minds of the buyers was very high and the signing bonuses were a few dollars per acre. When the potential of the Marcellus was first suspected in 2006 a small number of speculators began leasing land - paying risky signing bonuses that were sometimes as high as $100 per acre.

In late 2007 signing bonuses of a few hundred dollars per acre were common. Then, as the technology was demonstrated and publicized signing bonuses began to rise rapidly. By early 2008 several wells with strong production rates were drilled, numerous investors began leasing and the signing bonuses rose from a few hundred dollars per acre up to over $2000 per acre for the most desirable properties. If the results of current and future drilling activity do not match the expectations of companies paying for leases the amounts that they are willing to pay could drop rapidly.

Gas Royalties

Although signing bonuses generate an enormous amount of interest because they are guaranteed income, royalties can be significantly higher. A royalty is a share of a well's income. The customary royalty rate is 12.5 percent of the value of gas produced by a well. Higher royalty rates are sometimes paid by aggressive buyers for highly desirable properties. The royalties paid to eligible property owners from a well yielding over one million cubic feet of natural gas per day can be hundreds of thousands of dollars per year. These royalties are divided by all eligible property owners within a production unit (an area of land that is thought to contribute gas to a producing well - typically 640 acres). The amount paid to each eligible property owner is based upon their ownership share. (Get a gas royalty estimate.) If the Marcellus Shale holds up to the optimistic expectations of some natural gas experts, Pennsylvania, Ohio, New York and West Virginia could temporarily have an enormous boost in income that might be sustained for a few decades.

Natural Gas Drilling Activity

Several companies are actively drilling, leasing or planning activity on Marcellus Shale properties. Range Resources, North Coast Energy Inc., Chesapeake Energy, Chief Oil & Gas LLC, East Resources Inc., Fortuna Energy Inc., Equitable Production Company, Cabot Oil & Gas Corporation, Southwestern Energy Production Company, and Atlas Energy Resources are all involved. Shares of most of these companies are up strongly over the past two years. The Pennsylvania Department of Environmental Protection says that drilling permits are up strongly since 2005 and much of the activity increase can be attributed to wells targeting the Marcellus shale. Some of the new wells appear capable of yielding millions of cubic feet per day and that has companies working hard to acquire leases on desirable properties and complete new wells.

Other Gas Shales in the United States

The events described above are not unique to the northeastern United States or the Marcellus Shale. The horizontal drilling and hydrofracing technologies were perfected for shale reservoirs about four years ago in the Barnett Shale of Texas. The technology was then applied to the nearby Fayetteville Shale of northcentral Arkansas. Then, shortly after the Marcellus activity began, drilling and leasing in the Haynesville Shale of northwestern Louisiana started. These are just two of several unconventional gas plays now happening in the United States.

Natural Gas, Marcellus Shale Play in Pennsylvania

The following article about a new natural gas exploration and production "play" in Pennsylvania and neighboring States, is a good example of how rising prices can increase the amount of oil and gas found and produced. Apparently there is a real boom going on. One of the reasons why producing gas from shale is economically attractive is because the layer of shale in the subsurface is often thick and widespread. This means it is easy to find. The rock also tends to be very impermeable and lacking in porosity (that is open space between rock particles).

Engineers have solved those problems primarily through the processes of "horizontal drilling" and "fracing" or fracturing the rock under ground by pumping fluid down the well bore and into the rock formation under high pressure. This is immediately followed with "sand" grains suspended in the fluid that goes into the induced fractures and keeps them open. This creates artificial porosity and permeability. It is an expensive and highly technical operation, but once perfected, as it seems to be, the results and the accompanying high value of the gas produced make it all worthwhile. This is a major development which can be very good for the area, and America's economy in general. It is a good time to be a working petroleum geologist and engineer.

Peter

source

April 8, 2008
There’s Gas in Those Hills
By CLIFFORD KRAUSS
HUGHESVILLE, Pa. — At first, Raymond Gregoire did not want to listen to the raspy voice on his answering machine offering him money for rights to drill on his land. They want to ruin my land, he thought. But he called back anyway a week later to hear more.
By the end of February, he had a contract in hand for $62,000, and he pulled together a group of 75 neighbors who signed $3 million in deals.

“It’s a modern-day gold rush in our own backyard,” Mr. Gregoire said.
Not just his backyard either — a frenzy unlike any seen in decades is unfolding here in rural Pennsylvania, and it eventually could encompass a huge chunk of the East, stretching from upstate New York to eastern Ohio and as far south as West Virginia. Companies are risking big money on a bet that this area could produce billions of dollars worth of natural gas.

A layer of rock here called the Marcellus Shale has been known for more than a century to contain gas, but it was generally not seen as economical to extract. Now, improved recovery technology, sharply higher natural gas prices and strong drilling results in a similar shale formation in north Texas are changing the calculus. A result is that a part of the country where energy supplies were long thought to be largely tapped out is suddenly ripe for gas prospecting.
Pennsylvania, where the Marcellus Shale appears to be thickest, is the heart of the action so far. Leasing agents from Texas and Oklahoma are knocking on doors, leaving voice mail messages and playing host at catered buffets to woo dairy farmers and retirees. They are rifling through stacks of dusty deeds in courthouse basements to see who has underground mineral rights to the deepest gas formations.

Thomas B. Murphy, a Pennsylvania State University educator who runs a program to instruct landowners on their rights, estimated that more than 20 oil and gas companies will invest $700 million this year developing the Marcellus Shale. Up to one half of that will be invested in Pennsylvania, he estimated.
The cost to companies for leasing mineral rights jumped from $300 an acre in mid-February to $2,100 now. “It shows you the pace this is going,” Mr. Murphy said. “I would call it breakneck.”
Dale A. Tice, a lawyer representing landowners in lease negotiations, said companies were on a “feeding frenzy.

A natural gas drilling site on a farm in Hickory, outside Pittsburgh, that seeks to extract gas from 600 feet below the surface.

Industry experts say in the last three years companies like Anadarko Petroleum, Chesapeake Energy and Cabot Oil and Gas have leased up to two million acres for drilling in the region, half of that in the last nine months.
Whether their bets will pay off is by no means a sure thing.
Researchers at Penn State and the State University of New York at Fredonia estimate that the Marcellus has 50 trillion cubic feet of recoverable natural gas, roughly twice the amount of natural gas consumed in the United States last year. But government estimates of the amount of gas recoverable from the Marcellus are relatively modest.
Early test results have encouraged companies to keep drilling, but most are holding details of their test wells close to the vest.

The company that has done the most work is Range Resources of Fort Worth, which says it plans to invest at least $426 million in the Appalachia region this year.
The company has reported promising results from the first 12 wells that it has drilled horizontally, the technique considered by most experts to be the most effective in the Marcellus. The most recent six have each produced more than three million cubic feet of production a day in recent months, and company executives say that is better than the average for wells recovering natural gas in the Barnett Shale in north Texas.

“The Marcellus is important to Range and it could be important to the country but it really is still early,” said Rodney L. Waller, a senior vice president at Range. “I can build you a scenario where it can be significantly better than the Barnett but it’s a function of economics.”
Energy experts say the Marcellus, along with other smaller shale formations being developed around the country, is coming under scrutiny at an opportune moment, just when conventional domestic natural gas production and imports from Canada are diminishing. With easy-to-find gas fields in decline, the country will need to explore in deeper waters in the Gulf of Mexico and penetrate deeper under the surface on land.

If all goes well, the Marcellus could help moderate the steep climb in natural gas prices and reduce possible future dependence on natural gas from the Middle East, which is beginning to arrive at coastal terminals in liquefied form.
Natural gas in the Marcellus and other shale formations is sometimes found as deep as 9,000 feet below the ground, a geological and engineering challenge not to be underestimated. The shales are sedimentary rock deposits formed from the mud of shallow seas several hundred million years ago. Gas can be found trapped within shale deposits, although it is too early to know exactly how much gas will be retrievable.

The gas from all the shales combined “is a game changer,” said Robert W. Esser, an oil and gas expert at Cambridge Energy Research Associates. He estimated that shale produced four billion cubic feet of gas a day on average last year, or about 7 percent of national production, and that shale gas production would increase to nine billion cubic feet a day by 2012, or about 15 percent of expected national production.
The New York State Energy Research and Development Authority estimates that developing New York’s portion of the Marcellus could roughly double the amount of natural gas now produced in New York. Currently that is about 55 billion cubic feet a year, providing for 5 percent of the state’s needs.

The Marcellus has suddenly become attractive in large part because natural gas prices have spiked in the last several years and the geologically similar Barnett Shale has been an industry sensation.
By using horizontal drilling techniques, oil and gas companies have been able to draw natural gas from underneath the city of Fort Worth, even from below schools, churches and airports. The companies have perfected hydraulic fracturing techniques, pumping water and sand into well bores to fracture shale and release gas from its pores.
Production in the Barnett has exploded from a trickle five years ago to over three billion cubic feet a day, and energy experts say that number could more than double by 2015. Shale gas development in other parts of Texas, Louisiana and Arkansas has also shown promise.
But no formation compares in size to the Marcellus. It is deeply entrenched in wooded and mountainous countryside and expensive to reach. But the reserve is also within short pipeline distance from some of the nation’s most energy-hungry cities.

Still, not everyone here is happy about all the leasing and drilling. At meetings with the companies, landowners have asked questions about potential hazards to water and woodlands.
Keith Eckel, 61, a grain farmer with 700 acres in northeastern Pennsylvania, said he had not decided whether to let the companies drill on his property. “Farmers have taken care of this land all their lives and don’t want to see it destroyed,” he said.
But many farmers and retirees in rural Pennsylvania appear excited that their lives are about to change.

“Now I can retire,” said Robert Deiseroth, a 63-year-old farmer and auctioneer from the town of Hickory, who recently received a $16,000 royalty check from Range Resources that he hopes will be repeated month after month. “This was a godsend for me. If it weren’t for this I would have to sell off some of my land to get some money for retirement.”
Mr. Deiseroth has put new windows in his house, bought a new fishing boat and plans to build a new garage. His 89-year-old father and 90-year-old mother, who live nearby, just got a $20,000 monthly check. His father has replaced the golf cart he drove around his farm with a Kubota utility vehicle, while his mother has bought a flat-screen television.
“When Range came in a lot of people didn’t like it,” Mr. Deiseroth said, “But things changed when they started getting their checks.”