Natural gas drilling activity has declined in parts of the Marcellus Shale formation under Pennsylvania and other eastern states, largely as a result of low gas prices. These prices in turn are largely the result of significant increases in the available supply of recoverable natural gas made possible by horizontal drilling techniques and hydraulic fracturing or fracking. As a consequence, many natural gas producers are focusing on areas of shale rich in both gas and natural gas liquids.
The Marcellus Shale, a layer of ancient marine sediment rich in organic material and extending beneath Pennsylvania, Ohio, West Virginia, New York, and Maryland, is believed to be one of the world's largest natural gas fields. In 2008, drilling activity in the Marcellus Shale began to increase significantly, as these newer drilling techniques and increases in the price of other fuels like oil made the shale gas economically feasible to recover. (Compare this map of Marcellus shale drilling activity in Pennsylvania from 7/25/2008 to this map of permits issued as of March 9, 2012.) As of this spring, Pennsylvania alone had issued 11,772 permits for vertical and horizontal gas wells in the Marcellus formation.
One result of the expansion of shale gas production is a significant decrease in the price of natural gas. Since 2008, natural gas prices at the Henry Hub in Louisiana (where gas as a commodity is typically priced) have fallen from over $12 per million British thermal units (MMBtu) to as low as $2 per MMBtu. Other factors have played a role in this price decline, such as a mild winter with lower-than-expected heating demand and the overall economic slowdown, but the increase in supply due to shale gas production is viewed as a major cause of the price decline.
Now, one of the effects of the price decline is a decrease in natural gas drilling activity. This decrease is particularly marked in areas where the shale produces "dry gas", or natural gas that is primarily methane and is low in so-called natural gas liquids. Natural gas liquids -- hydrocarbons other than methane that are extracted when natural gas is
processed in a natural gas treatment facility -- include ethane, propane,
and butanes. These natural gas liquids are important feedstocks for the production of many chemicals and plastics, and add value to the natural gas produced from "wet" shales.
Where shale gas contains significant amounts of natural gas liquids, production appears steady or increasing, while gas producers in areas with lower amounts of natural gas liquids are now saying that they are having a hard time making money off gas alone. If this trend continues, areas of dry gas like much of the known portions of the Marcellus Shale may continue to see a slowdown in drilling activity while producers focus on areas rich in natural gas liquids.