Shale Gas Plays

Until recently, many oil and gas companies considered natural gas locked in tight, impermeable shale uneconomical to produce. Advanced drilling and reservoir stimulation methods have dramatically increased gas production from unconventional shales. The Barnett Shale formation in Texas has experienced the most rapid development. The Marcellus Shale formation of the Appalachian basin, in the northeastern United States, potentially represents the largest unconventional gas resource in the United States. Other shale formations, such as the Haynesville Shale, straddling Texas and Louisiana, have also attracted interest, as have some formations in Canada. The resource potential of these shales has significantly increased the natural gas reserve estimates in the United States (Andrews, 2009). 

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U.S. shale gas plays. (Adapted from U.S. Energy Information Administratioiv www.eia.gov/ oil gas/rpd/shaleusa2.pdf.)... 

A significant benefit of shale gas plays is that many exist in areas previously developed for natural gas production therefore, much of the necessary pipeline infrastructure is already in place. Many of these areas are also proximal to the nation s population centers, thus potentially facilitating transportation to consumers however, additional pipelines will have to be built to access development in areas that have not seen gas production before (Muhlfelder, 2009). 

As shown earlier in Figure 4.2 in Chapter 4, shale gas is present across much of the lower 48 states. Figure 4.2 shows the approximate locations of current producing gas shales and prospective shales. To date, the most active of these shales are the Barnett Shale, Haynesville/Bossier Shale, Antrim Shale, Fayetteville Shale, Marcellus Shale, and New Albany Shale. This chapter does not discuss all of the unconventional gas shales rather, discussion here is limited to these most active shale gas plays. Each of these shale gas plays or basins is different, and each has a unique set of exploration criteria and operational challenges. Because of these differences, the development of shale gas resources in each of these areas faces potentially unique challenges. The Antrim and New Albany Shales, for example, are shallower shales that produce significant volumes of formation water, unlike most of the other gas shales. Development of the Fayetteville Shale is occurring in rural areas of north-central Arkansas, while development of the Barnett Shale is focused in the area of Forth Worth, Texas, in an urban and suburban environment. 

The Barnett Shale formation is located in the Fort Worth Basin of north-central Texas. It is a Mississippian-age black shale occurring at a depth of 6500 to 8500 feet (Table 5.2) and is bounded by limestone formations above (Marble Falls Limestone) and below (Chappel Limestone) (Figure 5.2). With 15,306 wells drilled or pending, the Barnett Shale was the most prominent shale gas play in the United States, but the Flaynesville Shale gas play has surpassed Barnett in shale gas production (Railroad Commission of Texas, 2009 ... 

Note Information presented in this table, such as original gas-in-place and technically recoverable resources, is presented for general comparative purposes only. The numbers provided are based on the sources shown and this research did not include a resource evaluation. Rather, publicly available data was obtained from a variety of sources and is presented for general characterization and comparison with other shale gas plays. Resource estimates for any basin may vary greatly depending on individual company experience, data available at the time the estimate was performed, and other factors. Furthermore, these estimates are likely to change as production methods and technologies improve. 

The Marcellus Shale is the most expansive shale gas play, spanning six states in the northeastern United States. The estimated depth of production for the Marcellus is between 4000 and 8500 feet (Table 5.5). The Marcellus Shale is a Middle Devonian-age shale bounded by shale (Hamilton Group) above and limestone (Tristates Group) below (Figure 5.5). 

The Marcellus Shale covers an area of 95,000 square miles at an average thickness of 50 to 200 feet. Whereas the Marcellus is lower in relative gas content at 60 to 100 scf/ton, the much larger area of this play compared to the other shale gas plays results in a higher original gas-in-place estimate of... 

The New Albany Shale is an organic-rich geologic formations located in the Illinois Basin in portions of southern Illinois, southwestern Indiana, and northwestern Kentucky (IGS, 1986). Similar to the Antrim Shale, the New Albany Shale occurs at depths between 500 and 2000 feet (Table 5.8) and is a shallower, water-filled shale with a more CBNG-like character than the other gas shales discussed in this text. The New Albany formation is a Devonian- to Mississippian-age Shale bounded by limestone above (Rockford Limestone) and below (North Vernon Limestone) (Figure 5.8). The New Albany Shale is one of the largest shale gas plays, encompassing an area of approximately 43,500 square miles with approximately 80-acre spacing between wells. Similar to the Antrim Shale, the New Albany play has a... 

Harrison, W. (2006). Production History and Reservoir Characteristics of the Antrim Shale Gas Play, Michigan Basin. Western Michigan University, Kalamazoo. 

Estimated Water Needs for Drilling and Fracturing Wells in Select Shale Gas Plays... 

Shale Gas Play (gal) Volume of Drilling Water per Well (gal) Volume of Fracturing Water per Well (gal) Total Volumes of Water per Well (gal)... 

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