Thursday, August 11, 2011

Natural Gas, Energy and the Environment

It is a dream of some for the United States to become “energy independent.” For others the dream is to convert our nation to renewable energy sources. These two ideas or dreams are related, but we are not about to jump from oil dependence to solar and wind, and the resurgence of atomic power plants in the United States may not come to fruition after the post Tsunami reactor disaster in Japan. Many think that the way to progress is to move from oil and coal fired electrical generating plants to cleaner natural gas plants and from there to more renewable sources of power. Clearly, all your eggs in one basket mega power plant strategy is not the optimal plan.

Our ability to recover natural gas buried a mile or more beneath the earth has increased. Advances in horizontal drilling which allows a vertically drilled well to turn and run thousands of feet laterally through the earth combined with advances in hydraulic fracking, the pumping of millions of gallons of chemicals and water into shale at high pressure have increased our ability to recover natural gas from shale. Hydraulic fracking is a technology that was unknown 60 years ago. In the past decade the advances in drilling and fracking technology have been adapted to exploit gas in the Barnett shale in the Fort Worth Basin in Texas and applied to a series of major shale gas deposits that could not have been viable without the advances in drilling and fracking. The Fayetteville shale, the Haynesville shale, the Marcellus shale reserves all in the United States and the Horn River shales in Canada are now accessible. At the current rate of natural gas consumption North America is reported to have a 100-year supply of proven, producible reserves and even with expanded use of natural gas, there is more than a generation of currently accessible reserves.

A large swath of Pennsylvania, New York and West Virginia sit atop the Marcellus Shale, which is the third-largest natural gas field currently known in the world. The Marcellus Shale alone is estimated to be 500-trillion-cubic-feet of gas reserve. This resource could heat our homes for a generation or more, and power our electrical generating plants, even fuel cars either directly or through plug in hybrids. The possible impacts to our economy and environment are far reaching. The potential risks are also far reaching.

In hydraulic fracking on average 2-3 million gallons of chemicals and water is pumped into the shale formation at 9,000 pounds per square inch and literally cracks the shale or breaks open existing cracks and allows the trapped natural gas to flow. While geologists and engineers believe that there is little risk that the fracking “water,” a mix chemicals and water, will somehow infiltrate groundwater reserves though a fissure created by the fracking there are other routes of contamination and impact. It is believed that the intervening layers of rock would prevent a fissure from extending thousands of feet to the water table, there are other risks in how we build wells and fracture the shale. There have been documented cases of seepage into drinking water wells through improperly sealed or abandoned drilling wells. There are also places where groundwater is only several hundred feet above the gas reserves as they are in Wyoming and groundwater is more easily directly impacted by fracking.

Though it is unlikely that the strontium and barium and radioactive materials that occur naturally in the brine in the Marcellus shale, will flow from the shale through a crack or fissure up thousands of feet to the groundwater supplies, there are still other routes of contamination a portion of the fracking water is recovered and reused, disposed or stored. In fact, there have already been several high-profile cases of groundwater contamination. According to the PA Department of the Environment surface spills and shoddy construction practices (by Cabot Oil) allowed natural gas from a shallow deposit above the Marcellus to drift into the drinking-water wells of 14 Pennsylvania residents. The state is currently investigating traces of toluene, ethylbenzene and xylene chemicals that are sometimes used in fracking and are common in fuel found in some of the drinking water wells in the area. These could easily be long present contaminants from leaking underground storage tanks, but the residents did not regularly test and document their water quality historically.

According to the US Geological Survey in 2000 the United States used about 323 billion gallons per day of surface water and about 84.5 billion gallons per day of ground water. Although surface water is used more to supply drinking water and to irrigate crops, ground water is vital in that it not only helps to keep rivers and lakes full, it also provides water for people in places where visible water is scarce and rural areas. To survive over time, a population must live within the carrying capacity of its ecosystem, which represents a form of natural capital. One of the most important elements is potable water. Without water there can be no life. As populations grow water is needed for drinking, bathing, to support irrigated agriculture and industry. In the quest for fuel and wealth we can not forget our need for water.

The recharge of groundwater and the possibilities for its abstraction vary greatly from place to place, owing to rainfall conditions and the distribution of aquifers (rock and sand layers in whose pore spaces the groundwater sits). Generally, groundwater is renewed only during a part of each year through precipitation, but can be abstracted year-round. Provided that there is adequate replenishment, and that the source is protected from pollution, groundwater can be abstracted indefinitely.

Groundwater forms the invisible, subsurface part of the natural water cycle. Any attempt to accurately model the groundwater component of the water cycle requires adequate measurements and observations over decades. The computer models in common use in the United States only address the shallower groundwater and surface water interactions; GSFLOW (USGS) and ArcHydro (ESRI) are two commonly used models. Proper study and modeling of groundwater has not yet been done, rules of thumb and common knowledge assumptions are utilized instead of facts to assess the risks to water. This is irresponsible when pumping 2-3 million gallons of chemically laced water a mile into the earth. In hydraulic fracking water is pumped into the shale formation at 9,000 pounds per square inch and literally cracks the shale or breaks open existing cracks and allows the trapped natural gas to flow. To reach the gas deposits requires drilling though a couple of miles of earth and rock using “common knowledge” that our groundwater will not be impacted. In addition, natural gas which is methane and a significant greenhouse gas, escapes from the well heads due to imperfect operations, grouting and sealing. It is estimated that between 1% and 8% (depending on who is doing the estimating)of the natural gas escapes in this way.

This past spring, the Shale Gas Subcommittee of the Secretary of Energy Advisory Board was created to identify the measures that can be taken to reduce the environmental impact and improve the safety of shale gas production utilizing fracking. Their report was issued today after 90 days. The report had a rational approach to regulation recommending disclosure, testing, evaluation and modification of regulation and practices based on the information and data obtained. The report is to some extent a collection of the best regulatory framework among the states and covers little new ground overlooking some of the significant questions. This is a work product of a subcommittee at the Department of Energy that reports to the Secretary of Energy. EPA will be the regulatory agency and is currently engaged in a multi-year study of hydraulic fracturing.

No comments:

Post a Comment