The Real Cost of Fracking (28 page)

APPENDIX
A Primer on Gas Drilling

We have concentrated on the effects of drilling with hydraulic fracturing in unconventional tight shale formations, but have only hinted at the technical details. Here we will provide a short summary of the process and define some of the terms used throughout the book. The colloquial term that has permeated the media and web pages is
fracking
. In one sense, the choice of terms is unfortunate, because hydraulic, propane, or nitrogen fracturing (or “fracking”) is only one part of the multitude of steps that go into extracting gas and oil from shale deposits. Also, fracking is sometimes used on a much smaller scale in conventional oil and gas drilling and other types of drilling such as water wells and geothermal wells. Nevertheless, in the public mind, the term
fracking
is synonymous with the whole process. In order to understand not just the fracturing step but the entire life cycle, we need to know exactly what lies beneath our feet and to understand the chemistry and engineering that go into extracting hydrocarbons.

Turning the clock back a few billion years, we see that the continents were much different than they are today; the world is continually being reshaped by continental drift. The large area that encompasses Quebec, New York, Pennsylvania, West Virginia, and parts of Ohio and Maryland was once a shallow sea.
¹
The sea is long gone, but various types of sedimentary rock, including shale, remain. Because of the organic content of the shale layers, they became the source rock for oil and gas formation. What we mean by organic content is not what organic farmers grow, but rather what organic chemists study—molecules that contain carbon atoms. These range from methane (one carbon atom bonded to four hydrogen atoms) to longer-chain hydrocarbons (many carbon atoms linked to hydrogen atoms) found in gasoline and diesel fuel. As discussed in the epilogue, carbon atoms can make four bonds, so a linear string of carbon atoms (with single bonds) would have three hydrogen atoms attached on the ends (methyl groups) and two hydrogen atoms attached to the carbons in the middle (methylene groups). The smallest of this group, methane or natural gas, is a gas at room temperature and atmospheric pressure. Longer chains of carbon (butane, propane, etc.) can be stored as liquids under modest pressure, but will quickly evaporate if exposed to air at atmospheric pressure and room temperature. Methane requires very low temperatures (approximately –260 degrees Celsius) or high pressures to be stored as a liquid. The shale layers trap these compounds along with all the salt that was in the ocean. The layers also trap bacteria, archaea, more complex organic compounds such as benzene, heavy metals, and radioactive material.

Geologists have known about the presence of oil and gas in shale layers for a long time, but extraction of these hydrocarbons for use as fuels originally did not involve going to the source. Instead, the traditional method was to find a pocket of gas or oil that was trapped underground. Although the shale layers are the source of the hydrocarbons, the gas or oil can gradually migrate upward over millions of years into layers of more porous rock, where it can get trapped under a layer of impervious rock. By drilling down into this pocket of gas or oil, the hydrocarbon can be extracted, maybe even with a little stimulation by low-volume hydraulic fracturing. The overwhelming majority of gas and oil wells drilled worldwide have used this relatively simple idea, which the industry calls
conventional drilling
.

Despite the vast amount of oil and gas that has been extracted from the ground over the last 150 years, the pools of gas are limited. Consequently, drillers have, over the last 15 years or so, employed more extreme methods to extract fossil fuels. The two methods that are the most controversial are tar sands (also known as oil sands) extraction and horizontal drilling with high-volume hydraulic fracturing. The environmental impact of the tar sands method is beyond the scope of this book, but has been carefully covered by Andrew Nikiforuk in his book
Tar Sands.
²
We are concerned with the latter method, horizontal drilling and high-volume hydraulic fracturing (or propane or nitrogen fracturing).

The shale layers primarily discussed in this book are the Marcellus and Utica Shales in the Northeastern United States. The Marcellus is the better known and younger of the two—on the order of 380 million years old. It underlies much of the Appalachian basin, extending from New Jersey and Virginia through parts of Maryland, West Virginia, Ohio, Pennsylvania, and New York. It reaches the surface near the top of the Finger Lakes in upstate New York and is named after the town of Marcellus, just west of Syracuse, where it outcrops at the surface.
³
Although the formation is large, the area that is considered the best to develop is somewhat smaller, encompassing parts of West Virginia, about half of Pennsylvania, and the southernmost part of upstate New York. This is the “fairway,” where the portions of the shale may be sufficiently deep and thick to make extraction of large quantities of hydrocarbons possible.
⁴
The Utica Shale (named after the outcropping in Utica, New York) extends over a somewhat larger area, under the Great Lakes, and into Canada.
⁵
It is older (more than 400 million years old) and deeper, but has not been explored as well as the Marcellus.

In both the Utica and the Marcellus Shales, the composition of the hydrocarbons differs in different locations.
⁶
For example, in northeastern Pennsylvania, largely “dry gas” is extracted from the Marcellus Shale. Dry gas is mostly methane, which as we have noted is a gas at room temperature and atmospheric pressure. As you move to southwestern Pennsylvania, more “wet gas” is extracted. Wet gas includes the longer-chain molecules, such as propane and butane, which are volatile liquids at moderate pressures. The wet gases are more valuable because they can be converted to other useful compounds in chemical plants or in petroleum refineries. These plants can convert, for example, ethane into ethylene (two carbon atoms bound by a double bond, with two hydrogen atoms on each carbon atom) and subsequently into plastics and other chemicals. The western part of the Utica Shale, particularly in Ohio, has become of great interest to the industry because it has begun to yield even longer-chain hydrocarbons, in the form of crude oil (“tight oil”). Oil is a more valuable commodity than natural gas.
⁷
Typically, methane is also present with the oil and is often just discarded as a by-product. That is, the gas can either be vented to the atmosphere or be burned in a dramatic manner known as flaring. A good example of this is the oil boom in North Dakota (Bakken Shale), where large quantities of natural gas are extracted with the oil, but because few pipelines are present, the gas is largely wasted by flaring.
⁸
This practice, of course, wastes the resources owned by private landowners, and a lawsuit seeking to recover lost royalties has recently been filed against several large fossil fuel companies.
⁹

The Northeastern United States is no stranger to oil and gas extraction, as we mentioned in a previous chapter. In fact, one could argue that the oil and gas industries were born in Pennsylvania and New York. However, by going to the source, that is, to the shale layers themselves, the whole strategy used by the industry changes along with an increased impact on the landscape. In the past, small wells were drilled wherever pockets of gas or oil were detected. For example, driving around the countryside near the home of the famous Pennsylvania groundhog, Punxsutawney Phil, you can see older gas wells everywhere, and they are still in production. These wells were drilled into pockets of natural gas, which were common in the area.

Targeting the source rock means that huge areas of West Virginia, Pennsylvania, and New York can be exhaustively drilled with horizontal drilling and hydraulic fracturing. Proponents of such unconventional extraction will note that for a single installation, much larger areas can be drained because multiple wells can be placed on a single pad and drilled in all directions (or, more precisely, in a rectangular pattern). But the fact remains that much larger areas are now being targeted for production than would ever be considered by traditional methods. Given that even in intensively drilled parts of Pennsylvania and West Virginia, only a small fraction of the planned wells are in place, the environmental and societal consequences that we see now are only the beginning.

Let’s narrow our focus and look at an individual well pad. The whole process starts with leasing land. A company comes into an area, and the landsman convinces landowners to sign a lease. The lease can contain surface rights, in which case the drilling pad can be placed on the property, or the lease might include only mineral rights, in which case the oil or gas can be taken from under the surface of the property. In some cases, the owner of the surface rights may not be the same person as the owner of the mineral rights. This might happen if the owner of a parcel of land leases mineral rights to a company and then sells the property (the surface) without transferring the lease to the new owner. Once signed, the lease can be bought and sold many times by different companies.

Before drilling starts, the site is often mapped using seismic testing. This is done either with large thumper trucks or helicopters and explosive charges. The idea is to provide a three-dimensional map of the geology of the area and to identify faults or other problems that might affect the efficiency of hydrocarbon extraction or cause environmental problems.

The drilling starts with the choice of a site and the construction of access roads. The site is usually five to seven acres of leveled land, typically on a plateau, the location of which is chosen mainly by the drilling company. Large ponds may be constructed nearby to hold millions of gallons of water (either water that will be used to hydraulically fracture the well or wastewater that returns to the surface). We have seen pads very close to barns and access roads that were within a few feet of homes.

Once the drilling pad is built, things can but do not always proceed rapidly, depending on the economic climate. As one strategy, companies establish wells throughout an area, perhaps drilling only one well per pad. Most leases are written such that once activity related to drilling begins, the lease cannot be canceled, so that establishing a well locks in the lease indefinitely. In any event, the next step is to drill one or more wells. This is when the iconic drilling rig is set up, and drilling begins. This is not your common, everyday well-drilling operation but rather an impressive industrial operation with very high-tech engineering.

The drilling company often uses three different drilling rigs in sequence. The first rig drills down below the water table, then a second rig that can handle high pressure if pockets of gas are encountered is put into action. Finally, a third rig drills the horizontal part of the well. The first stage of drilling is typically lubricated largely with air to help avoid contaminating an aquifer with drilling fluids. However, surfactants, some of which contain 2-butoxyethanol, are used in this stage and can be introduced into an aquifer. The drill bits for the second and third stages of drilling are lubricated with drilling fluids and muds.

It is this feat of horizontal drilling that really opened up the source rock for exploitation. Drilling vertically into a shale formation only allows the driller to contact a region equal to the thickness of the formation (perhaps fifty to two hundred feet). That is, since the formation is only fifty to two hundred feet thick, a vertical well can only make contact with the relatively small surface area surrounding the well. By turning the bit horizontally, the horizontal part of the well is in continual contact with the formation, and these
laterals
run long distances, typically about a mile and sometimes up to two miles, all within the shale formation. Thus, horizontal drilling allows a much larger area to be drained from a single well. By running multiple wells in a pitchfork pattern in two directions, a driller can drain a large rectangle.

But at this point, we have just described drilling a hole in the ground—a high-tech hole, but just a hole. The next issue to consider is the attempt to protect the aquifer with a steel and cement casing so that fluid can be injected into the well and so that gas and liquid can exit the well without contaminating the water supply. Several layers of casing are put into place surrounding the well bore to a depth well below the aquifers in the region. This is typically done after drilling the first stage. Failure of the cement around the steel casing pipe is one of the most common causes of aquifer contamination. Also, the cement does not necessarily make a complete seal with the surrounding rock and soil, leaving potential migration paths for methane that is released from the shale layers or more superficial layers.

The next step is to fracture the rock to release methane. The most common method is hydraulic fracturing, a process by which approximately five million gallons of fluid and large quantities of silica sand are injected into the well under high pressure (thousands of pounds per square inch, depending on the depth and pressure in the shale). (The alternatives to hydraulic fracturing are currently high-pressure propane and nitrogen fracturing. These are less well tested and may or may not be used extensively in the future. Propane fracturing carries with it the danger of explosion from accidents on the surface.) The high pressure fractures the rock, and the silica props open the fractures so that they don’t reseal. In this way, gas can flow out of the formation. The fluid is mainly water, but contains many chemicals, including biocides (to kill bacteria), friction reducers, oxygen scavengers, acids, chemical crosslinkers, and scale and corrosion inhibitors. It is this hydraulic fracturing fluid that has probably sparked the most controversy and alarm. The major points of contention include the composition of the fluid, its toxicity, interactions between the components, how the components change due to chemical reactions within the well, and whether the fluid can contaminate the water or air.