T Marcellus Shale is a sedimentary rock formation deposited over 350 million years ago in a shallow inland sea located in the eastern United States where the present-day Appalachian Mountains now stand (de Witt and others, 1993). This shale contains significant quantities of natural gas. New developments in drilling technology, along with higher wellhead prices, have made the Marcellus Shale an important natural gas resource. The Marcellus Shale extends from southern New York across Pennsylvania, and into western Maryland, West Virginia, and eastern Ohio (fig. 1). The production of commercial quantities of gas from this shale requires large volumes of water to drill and hydraulically fracture the rock. This water must be recovered from the well and disposed of before the gas can flow. Concerns about the availability of water supplies needed for gas production, and questions about wastewater disposal have been raised by water-resource agencies and citizens throughout the Marcellus Shale gas development region. This Fact Sheet explains the basics of Marcellus Shale gas production, with the intent of helping the reader better understand the framework of the water-resource questions and concerns. What is the Marcellus Shale?

Water Resources and Natural Gas Production from the Marcellus Shale

The successful development of gas and oil resources from shales in North America

An approach for assessing engineering risk from shale gas wells in the United States

Structural changes in coal at elevated temperature pertinent to underground coal gasification: A review

Although natural gas has been obtained from organic-rich shales in the United States since the first commercial gas well was produced in 1821 to provide gas light to four commercial establishments and a mill in the small town of Fredonia, New York, large-scale shale gas production is a recent phenomenon. Assessments of the geological and engineering challenges of shale gas resources were performed in the 1970s and 1980s, as new domestic energy sources were sought in response to an oil embargo imposed upon the United States, and the resulting “energy crisis” that followed. The amount of natural gas present in the shales was found to be significant, but commercial production had to await advances in drilling and completion technology that came about in the 1990s. The new technology allowed for the economic development of this resource in the 21st Century.

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Shale Gas Development in the United States

Natural gas continues to be one of the major sources of energy produced and used in the U.S. Declining gas reserves and curtailment of supplies have reemphasized the major influence this energy source has on the U.S. economy. The U.S. DOE is investigating several options for increasing the supply, including a program for unconventional gas recovery (UGR). Four UGR projects currently are being assessed: western tight gas sands, geopressured reservoirs, Devonian shales, and methane from coalbeds. Both the Devonian shale and methane-fromcoalbeds projects are paramount in this assessment, since they underlie a large section of the U.S. The eastern (Devonian) shales contain a vast, essentially tmexplored volume of natural gas. This area could represent new gas recovery from approximately 250,000 sq miles throughout the U.S. Studies by the government and industry have been focused on shale characterization to determine the magnitude of potential gas reserves and technology development needed to improve current state-of-theart stimulation techniques. The initial R&D results have shown promise and point out the technology needed for successful development. The goal of the methane-from-coalbeds project is

Potential New Sources of Natural Gas

In the fall of 1972, the U.S. Bureau of Mines began an experiment to investigate the technologic, economic, and environmental considerations of underground gasification of a W. subbituminous coal. The gasification site is near the town of Hanna, Wyo., approx. 70 miles northwest of Laramie. The test results indicate that gas volumes and gas heating values have fluctuated over a wide range depending on operating conditions. The ranges have been from 50,000 to over 3 MMscfd of produced gas with a composite heating value from 30 to 465 btu per scf. Even though these fluctuations have occurred, a semisteady state condition existed for a 6-mo. period. From Sept. 1973 through Feb. 1974, a low btu gas averaging about 130 btu per scf was produced at an average rate of 1.6 MMscfd. A material balance made during this period indicated: (1) there was little or no underground gas leakage from the site; (2) about 80 bbl of formation water were consumed each day; (3) between 13 and 46 tons of dry coal were affected each day depending on the assumptions made; and (4) from 23 to 65% of the energy of the coal being subjected to carbonization and/or gasification is beingmore » recovered.« less

An underground coal gasification experiment, Hanna, Wyoming

Geophysical well logs, petrographic thin-section core analyses, and production- and pressure-decline curve analyses were used to characterize the geology and to estimate the reserves, recovery, and well life of the East Canton oilfield, northeastern Ohio. Clean sand sections of the Clinton were found to contain an average of 95 percent quartz and less than 4 percent clay. These sections correlated with the 80-percent-sand line determined by gamma ray logs and witg core permeabilities averaging more than 0.1 millidarcy. Production was found to be more closely related to thickness of 80 percent sand than any other reservoir characteristic. Economic life and output of the wells studied are predicted to be approximately 10 years and about 30,000 to 40,000 barrels per well. A primary recovery factor of 9 to 12 percent is indicated. Primary reserves of the 60,000-acre field are a minimum of 51 million barrels. Approximately 500 additional wells will have to be drilled to complete development of the field. With such a low primary oil-recovery factor, much oil will remain for secondary recovery possibilities.

Reservoir and production characteristics of the Clinton Sand, East Canton oilfield

Unique approach to oil-production decline curve analysis with applications

In this reservoir study of the Clinton sand, East Canton oil field, Ohio, results indicate that a properly engineered waterflood may be feasible for secondary oil recovery. Waterflood forecasts that account for a wide range of reservoir conditions are included and can be used for preliminary waterflood performance estimates.

Leo A. Schrider

Papers

Potential New Sources of Natural Gas

An underground coal gasification experiment, Hanna, Wyoming

Reservoir and production characteristics of the Clinton Sand, East Canton oilfield

Unique approach to oil-production decline curve analysis with applications

An Evaluation of the East Canton Oil Field Waterflood