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It is not only the potential size of this gigantic gas lode that will make a big difference in the U.S. energy supply, but also the Marcellus Shale’s location, within spitting distance of arguably the most avaricious gas consumers in the nation: New York City, Philadelphia, Washington, D.C., and the whole Northeastern region.

One reason for the lack of front-page attention to this enormous development is the slow recognition, even by the experts, of the immensity of Marcellus Shale gas resources.

As recently as 2002, the United States Geological Survey (USGS) severely underestimated the amount of gas the region could produce. While its Assessment of Undiscovered Oil and Gas Resources of the Appalachian Basin Province published that year reported that Marcellus Shale contained an estimated undiscovered resource of about 1.9 trillion cubic feet of gas, no one considered the deposit a game changer because the gas reserves were spread over such a large physical region. It seemed likely that the cost of extracting the gas might exceed the value.

It wasn’t until January 2008 when the Marcellus Shale potential became really interesting to gas explorers. Professor of Geosciences Terry Engelder at Penn State University and Professor of Geosciences Gary Lash at State University College, Fredonia, N.Y., published a paper contradicting the USGS lowball estimate and predicting that the Marcellus could produce 500 trillion cubic feet of natural gas.

Then, another important development sparked rising interest in tapping the Marcellus Shale: the introduction of a different drilling technology that had been proving its worth for almost a decade in Texas’s Barnett Shale. There, for the first time, horizontal drilling was used in a gas shale formation, instead of vertical drilling, to tap and collect the gas distributed in the shale. Productivity increased dramatically. As John Harper, chief of the mineral resources division of the Pennsylvania Geological Survey, was reported to have said in the Scranton (Pa.) Times in September, Marcellus wells that produced gas in the last fiscal year averaged almost 2 million cubic feet per day – “a lot better” than the earliest dozen or so Marcellus wells in the state that produced an average of only 89,000 cubic feet per day.

Thus, the Marcellus Shale has the potential to be the largest and most productive natural gas field in the United States. According to Engelder, who is considered the leading authority on the Marcellus Shale, natural gas production from the Pennsylvania Marcellus will likely average 1 billion cubic feet per day during 2010 and approach 2.5 billion cubic feet per day during 2011.

Fully developed, the Marcellus Shale has the potential to be the second largest natural gas field in the world, behind only the South Pars/Asalouyeh field shared between the nations of Iran and Qatar.

The natural gas found in the Marcellus could produce energy equal to 87 billion barrels of oil, enough to meet the demand of the entire world for nearly three years.

“At present consumption rates in the United States,” Engelder has said, “the Marcellus alone can meet the natural gas demands of our country for more than 20 years if the gas could be produced fast enough, which, of course, it can’t.”

Presently, there are about 800 producing wells in the Marcellus Shale; the majority are simple vertical wells. More than 60 new wells are being drilled there each month.

One obstacle to realizing the great potential of the Marcellus Shale gas bonanza, however, is the amount of water required for the horizontal drilling operations. Horizontal drilling uses a process called hydraulic fracturing to complete the wells, requiring 3.5 million to 12 million gallons of water for each well. The water is mixed with sand and chemicals and pumped under high pressure through the drill hole into the formation, breaking up the underground shale and releasing the gas.

When the gas emerges it is combined with approximately 25 to 50 percent of the injected water. Frac flowback – water that is contaminated with salt and minerals that have been dissolved out of the formation – requires disposal. Acquisition of clean water and disposal of contaminated water have raised environmental concerns and slowed the development of new wells in some areas.

Currently, Pennsylvania has limited the amount of water the drillers can take out of its lakes and rivers. To increase its water supply, the state is investigating the possibility of reclaiming acid mine drainage (AMD) water for reuse. More than 4,600 miles of waterways in Pennsylvania have been impaired by drainage from old abandoned coal mines, loaded with acids and insoluble metal oxides.

The AMD discharge from a single mine or coal tailing pile can range from 10 to more than 10,000 gallons per minute. The Lackawanna River in northeastern Pennsylvania, for example, is being contaminated from at least seven monitored AMD locations with estimated peak flow of 40 million gallons per day.

One way drillers are confronting the contaminated water issue is to reclaim the water that is recovered. By finding cost-effective, environmentally friendly water reclamation processes, the drillers can use the reclaimed water from drilling one well for the hydraulic fracturing of additional wells at the same site.

Although environmental concerns have deterred some land owners from permitting drilling on their property, the number of new wells in the Marcellus Shale continues to increase rapidly. Water is a precious commodity for which there is no known substitute. Seventy percent of the earth’s surface is covered with water, yet only 2.5 percent of all water is fresh. Of this 2.5 percent, only 40 percent is available for human, animal, agricultural and other requirements for fresh water.

Stanley Weiner is CEO of STW Resources Inc., a water reclamation company, based in Midland, Texas. For more information, visit www.stwresources.com.