I am on vacation this week, so we are running a “Best of Common Science.”
The NC Legislature’s overide of Governor Perdue’s fracking ban means that the process of designing the regulatory framework for fracking will begin in earnest. I am in the initial stages of what will be my fourth column on fracking to address the challenges of designing these regulations. The first challenge will be to define exactly what fracking is. This may be a bit more challenging than it sounds since nearly all forms of drilling involve the injection of fluids into ground. In addition, a fair portion of the risk to drinking water purity comes from the fact that you have to drill through the water table to reach the oil and gas whether you frack or not. To proivde you with the background you need to sort through this debate we are re-posting my first column on fracking, “To Frack or Not to Frack” which covers the basics of the technology and its inherent risks.
On July 19th, 2011, 400 people assembled in the Fearrington barn for an event called Fracking Bewareness to hear a cautionary message about the potential to drill for natural gas in North Carolina using a technique called hydraulic fracturing or “fracking.” Fracking has been prominent in the national news over the last few years both because of dramatic increases in natural gas supplies as well as out of concern for drinking water contamination.
In order to talk about fracking, we need to run through a quick review of how natural gas is formed and extracted. If you read “Petroleum: 300 Million Years of Sunlight
”, you will recall that both petroleum and natural gas were formed when algae and bacteria fell to the bottom of ancient seas, were buried in hot, high-pressure environments, then broken down into oil and gas over the course of millions of years. If the gas and oil formed in locations with porous rock, they began to migrate upward until either they reached the surface (think tar pit), or until they hit an impervious rock layer. Traditional wells tap into these pockets of oil and gas which have become trapped below the sections of impervious rock.
Natural gas in traditional wells is easy to recover since it flows up the well pipe on its own. (Ironically, until the 1970s, natural gas was considered to be primarily a waste product and was often burned in a flare.) The liquid petroleum, however, requires more effort to extract from the ground. When the well is first drilled, the pressure within the well is often high enough that some of the liquid petroleum will flow out on its own. Eventually the pressure drops, and the oil must be extracted using enhanced recovery techniques.
The most common technique is to drill an additional well into the oil field and pump water into the new well to push oil back out of the first one. In addition, the oil companies try to enhance the flow of oil through the rock formation by breaking up the rocks with a process called fracking.
Fracking was invented by Haliburton in 1947, and it is estimated that approximately 90% of all wells worldwide have been fracked. Fracking is a relatively simple technique. You make a mixture of 99% water, 1% sand and some trace chemicals (more on those later), then pump them down into the well at very, very high pressure. The high pressure water fractures the rock (hence the name) creating larger channels for the oil and gas to travel through the rock to reach the well. After the fracking process, most of the water is pumped back out of the well, leaving the sand in place, along with some of the chemicals, to keep the new fractures in the rock from collapsing.
So the question for me was, “If wells have been fracked since 1947, why all of the new concerns now?”
If you Google “fracking,”
you will get thousands of hits. 99% of these will be for fracking of shale gas wells, not the traditional oil/gas wells I described above. Recall that traditional wells extract natural gas that has already migrated a fair distance upward from the depth where it was originally formed and, rather accommodatingly, collected in a pocket underneath some impervious rock.
Shale gas is natural gas that was formed deep underground in little pockets within some imperious rock. So instead of migrating towards the surface and collecting together, it is still deep underground where it was formed and dispersed in small, unconnected pockets in the shale. The picture at the top of this blog shows a nice cartoon of the different types of underground natural gas locations and their relative depths.
We have known for a long time that this gas was there, but there was little interest in recovering it until recently. Recall that natural gas was flared off as a waste product until the 1970’s. In the 1990’s as impending shortages in fossil fuel sources began to loom, people started to look more seriously into shale gas. In 1995, improvements were made in fracking technology which allowed for recovery of the shale gas. I have not yet been able to determine the precise nature of those improvements, but, generally speaking, they had to involve supplying higher pressure water. Since the shale is deeper underground than traditional wells, it is under greater natural pressure. To fracture and underground rock formation, you need to use pressure which exceeds the natural pressure of the formation. Therefore, the pressure is higher for shale gas compared to traditional wells. Another key difference for fracking a shale gas well, compared to a traditional well, is that significantly more water is required, approximately 2 to 5 million gallons per well. For the well to be able to withstand these high pressures and high water flow rates, it is necessary to use steel and concrete casings. This well casing extends down from the surface with the intent of protecting underground aquifers from contamination. See the picture below.
The views expressed on the internet on fracking are, to put it lightly, widely divergent. If you read the material posted by the oil and gas industry, they almost uniformly point to the fact that fracking has been in use since 1947, implying that any risks involved would have become apparent long ago. I find this approach to be intentionally deceptive. The techniques used from 1947 through 1995 were not sufficient to frack a shale gas well, so that experience is completely irrelevant. Furthermore, fracking of shale gas wells has only really been used extensively since the spike in natural gas prices, which occurred in 2004. Therefore, our actual experience with fracking of shale gas wells is quite limited. Therefore, our assessment of the attendant risks is, necessarily, limited as well.
The anti-fracking info on the internet is similarly flawed. Motivated by concerns about risks and seeking an immediate ban on fracking, much of this information seems to rely on anecdotal evidence and suspect science. In particular, there are often pictures of cloudy drinking water and cartoons of underground cracks from the fracking process which extend thousands and thousands of feet creating a connection from the well to the water table. Neither of these two scenarios seems plausible to me.
Here is my evaluation of the potential environmental and health risks from fracking including:
· Contamination of underground aquifers with the fracking chemicals
· Contamination of underground aquifers with natural gas
· Contamination of surface waters with the fracking chemicals
· Release of natural gas into the atmosphere
Let’s start with potential contamination of aquifers. Shale gas wells range from 5,000 to 20,000 feet underground. Aquifers for drinking water tend to be less than 1,500 feet deep. The cracks made in the fracking process are, at most, a couple hundred feet long. This means that it is nearly impossible for either natural gas or fracking chemicals to migrate to an aquifer through one of the cracks. My conclusion is consistent with several credible university studies (including this one from Duke
) which have not been able to detect the presence of any of fracking chemicals in aquifers near to shale gas wells.
What has been found in the aquifers near shale gas wells is increased concentrations of methane, the primary component of natural gas. The authors of these studies conclude that the high pressures utilized in fracking shale gas wells is sufficient to create cracks in the well casing. Therefore, as the gas is being extracted, some of the gas is escaping through these cracks and entering the neighboring aquifers. This seems quite plausible to me. It would not surprise me if increases in the pressure supply from the fracking pumps, the part of the technology that is basically the money maker, outpaced improvements in the well casing, a part of the technology that is purely a cost to protect the environment.
Contamination of surface waters from the fracking process is a clear risk, but not one that requires much investigation to understand. Fracking a shale gas well requires the use of millions of gallons of water. After the well has been fracked, most of that water is pumped out and collected. The water contains some portion of the fracking chemicals, many of which are quite toxic, so it needs to be handled carefully like any other industrial waste. There have been many documented cases where drilling companies have spilled some of this water during handling and contaminating nearby surface waters.
No new technology is required to manage this water, just responsible waste handling and appropriate monitoring and inspection. (Of course, appropriate monitoring requires that the government have sufficient staff, which requires sufficient funding, which requires taxes, but that is another story.)
The release of methane into the atmosphere from fracking is a more interesting question. If you deciding whether to burn methane or coal to generate the same amount of heat, you’ll release about 25% less carbon dioxide into the air if you use methane (subject of a future blog). This difference is the basis of the ubiquitous use of the adjective “clean” in the phrase “clean-burning natural gas.”
There is a catch though. Methane is an even more efficient greenhouse gas than carbon dioxide. (For more on the greenhouse effect, read “Welcome to the Greenhouse”.) Therefore, it is important not to have any natural gas leak into the atmosphere during the collection of the natural gas.
Fracking of shale has a bit of an Achilles heel here. When you pump the high-pressure water into the shale formation the water becomes super saturated with natural gas. This water is then pumped out and collected in open pits. Since the pressure at the surface is much lower than in the underground well, much of the dissolved natural gas is released into the atmosphere. Recent calculations indicate that enough methane is released such that shale gas is actually disadvantageous compared to coal in terms of climate impact.
OK, so what should we do here in North Carolina? When natural gas prices spiked in 2004, the shale gas boom was ignited. Already 20% of our natural gas comes from shale gas. Some projections show this percentage growing to more than 40% by 2050. (In reviewing these projections, I sense a bit of irrational exuberance.)
Over the course of the next 50-100 years, we will need to transition away from fossil fuels. Unfortunately, as a society, we have not yet made meaningful steps to prepare for this. For example, Congress is spending time in trying to thwart legislation to move to more efficient light bulbs rather than trying to prepare for a resource-scarce future.
We also need to consider our own actions. In general, most of us are not living a lifestyle which would easily adapt to a significant drop in energy consumption. Preparing for this transition will take time. Using the shale gas can help provide this time, though there is no guarantee that we will use it wisely.
My conclusion is, therefore, that the shale gas which is in North Carolina will be, and needs to be, extracted. That being said, there is no rush. It appears that the three key risks are cracked well casings, improper waste water handling, and release of methane into the air. We should wait until the experience from other wells helps to determine how to extract it as safely as possible before we proceed.
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