What is Hydrofracking?

Slick water hydraulic fracturing, also known as hydrofracking, is a new development in natural gas extraction. The process was created by Halliburton Inc. (well known for its work in Iraq and elsewhere), Schlumberger Inc., and Messina Inc. This process makes mining for natural gas in dense shale more economically possible, where before it was not. 

Slick water hydrofracking is different from conventional natural gas drilling in a couple of ways. First, slick water hydrofracking uses significantly more water than conventional drilling, as well as a “slick water” mixture that is pumped into the shale to fracture the rock and release the gas. Second, there is an increased potential for toxicity and its long-term impacts. Finally, there is the environmental impacts of the drilling: surface and subterranean damage including forestland loss, multiple well sites, groundwater and surface water contamination, habitat and species disturbance, and likely an increased number of access roads to the well sites.

Figure1. Conceptual sketch to illustrate the concept of horizontal
drilling and hydrofracing. (By permission of Geology.com)

Actual fracking site

Unfortunately, slick water hydrofracking is being used in the largest deposit of Marcellus shale in the United States, as well as other areas of the country. This deposit’s approximate area is 48,000 square miles, stretching from eastern Ohio to the Catskills and south through northern and western Pennsylvania and West Virginia. It was formed 48 million of years ago when North America was still covered by an ocean. The Marcellus basin deposit is estimated to hold as much as 500 trillion cubic feet of natural gas, or the equivalent of 80 billion barrels of oil.

The Process, Specifically

To begin, the drilling company sets up the dill site by cutting down any surrounding trees and groundcover, most likely build an access road and rig, set up their necessary equipment, and truck in water, proppant, and chemicals.

After the drill site has been set up and prepared, the drill bores a well downward and then horizontally for up to 8,000 feet in each direction. While the drill bears downward, it will drill through the natural aquifer, or water table.

So what’s the problem?

Slick water hydrofracking involves a process that utilizes 6-8 million gallons of freshwater per fracking (though this varies with the depth of the shale and the gas deposits), and sand or other lighweight “proppants” (substances used to prop open the fissures caused by the well bore to allow the gas to seep through the pores in the shale). Following the injection of both the water and the proppant, several chemical-based additives are used to create a more timely, efficient, and overall more economic process. Some of the chemical additives frequently used include: diesel fuel, biocides, benzene (an additive to gasoline and industrial solvent), and hydrochloric acid.

Companies employing this method of natural gas extraction have resisted efforts to require disclosure of what chemicals and in what amounts they use, only assuring us they these chemicals are used in “small amounts”. However, “small amount” is generally unspecific, and some of these chemicals (especially benzene) are harmful at any level of exposure, even toxic at an exposure level of only parts per trillion. This matters because if any of these chemicals were to mingle with the water table, under which lies the shale with a layer of bedrock in between, it is possible that people’s drinking water could be affected.

Additionally, how companies are containing the slick water post-fracking varies from company to company, sometimes with a great potential for soil and groundwater contamination.

fracking effluent pit.