The Marcellus Shale

Approximately 400 million years ago, organic, mud-like matter collected at the bottom of a vast, prehistoric sea. As the earth changed, the continents shifted, and the sea that once covered parts of the Eastern United States subsided. The massive collection that held the simple plants and organisms from well before the dinosaur ages hardened, trapping incredible amounts of natural gas left by decomposing organic matter. Today, this formation is an organic-rich black shale – known as the Marcellus Shale – could increase U.S. natural gas reserves by 20 percent.

The Marcellus Shale underlies large parts of Pennsylvania, Ohio, West Virginia, and New York, with small areas extending into Tennessee, Virginia, Maryland, and Kentucky. Geologists have known about the Marcellus Shale’s large natural gas deposits for quite some time, estimating them to be as high as 516 trillion cubic feet; however, standard vertical drilling technology could not fully access the resource potential within the shale, that is, until very recently.

Vertical fractures within the Marcellus Shale hold natural gas deposits; therefore, drilling a standard vertical well vastly limits the frequency of intersection with a large number of the fractures, decreasing the chance and volume of gas that is able to be retrieved. A change came with the advent of horizontal drilling and hydraulic fracturing techniques within the Marcellus Shale, techniques that have allowed natural gas companies to access the resource with impressive, yet currently limited, success.

Horizontal drilling, simply put, is a method wherein a well may be drilled to a certain depth, then turned at a 90-degree angle and drilled further into the medium. Drilling perpendicular to the shale, then making the right-angle turn to drill parallel, intersects a maximum number of gas-storing vertical fractures, enabling the establishment of gas wells that consistently produce higher yields.

Coupled with horizontal drilling, hydraulic fracturing is utilized to access the trapped natural gas through the introduction of high-pressure water or other liquids/gels into the formation to increase the number of fractures within the rock, accessing even more gas. Though the techniques are new to the Marcellus Shale, and the resource being retrieved is both economically helpful and environmentally safe, concerns have arisen regarding impacts upon our environment, cultural resources and public health due to drilling and the use of substantial amounts of non-allocated water via the hydraulic fracturing process. These concerns and activities are currently being addressed through permitting processes instituted to regulate harmful activity within the 600-mile expanse of the Marcellus Shale region.

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