Fracking to extract gas and oil from shale rock remains among the most controversial practices in the new energy landscape. It’s also among the least well-understood … by pundits and perhaps also by many proponents and opponents.

Curiosity about fracking, more formally known as “hydraulic fracturing,” and its costs and benefits is widespread, informed insights much less so.

Let’s here revisit pro-con perspectives examined at this site’s article of two years ago, May 27, 2015, surveying recent trends and updates in the research literature.

Key recent research findings

Two broad, peer-reviewed research papers that synthesize the vast related literature – one published in Annual Review of Environment and Resources (2014) and the other in Annual Review of Earth and Planetary Sciences (2016) – provide the basis for some of the findings synthesized below.

Those two papers draw on hundreds of studies and are authored by leading researchers; both are useful for those diving deep into the pros and cons of this set of energy extraction techniques.

Yale Climate Connections asked the principal authors of both of those papers to weigh in on the state of fracking research. Each pointed to notable trends, and each agreed that uncertainties still plague key areas.

Robert Jackson of Stanford University, lead author of the 2014 paper, says that we now know a lot more about issues such as methane leakage and earthquakes, but it’s the larger patterns of energy use that are important in terms of understanding the role of fracking in society.

“Absolutely the biggest trend is the decline in coal use,” Jackson says. “Coal use dropped a further 20 percent from 2014 to 2016, to be overtaken by natural gas in 2016. Natural gas is now the number one fuel for electricity generation in the U.S.”

J. Quinn Norris of University of California, Davis, lead author of the 2016 paper, says that a lot more could be learned – and fast – but such knowledge remains elusive because of the lack of cooperation from the energy industry.

“Many of the questions being asked by the research community have already been answered by proprietary research, but that research is not being shared,” Norris says. “It is not that we need more exploration, we need more openness and sharing of what is known.”

Overall, most of the points made in the earlier pros-and-cons article still apply, and many of its conclusions still stand – especially around questions relating to local air quality and community infrastructure impacts. But particularly in the areas of drinking water contamination, earthquake risks, and emissions leaks, there are some relevant updates:

Fracking and drinking water issues

Issue: There are concerns that fracking may contaminate drinking water supplies with harmful chemicals, raising public health issues.

Updates: This issue has attracted the most intensive attention to findings from the research world over the past 12 months, largely because the Obama administration’s Environmental Protection Agency (EPA) finished up its six-year study of the issue in somewhat dramatic fashion. There had been heated controversy over final drafts of the report in the final months of that review, and EPA’s draft study in early 2016 had cast doubt on whether there were “widespread, systemic impacts” on drinking water supplies.

However, an EPA science advisory board in August 2016 criticized that “no harm” conclusion, saying the data do not support it.

So can fracking degrade drinking water sources? When the final report was issued in December 2016, toward the end of the Obama EPA but prior to the inauguration of Donald Trump, researchers partially reversed that original conclusion. EPA concluded at that point that there are indeed risks throughout the “hydraulic fracturing water cycle” – from “water withdrawals to make hydraulic fracturing fluids, through the mixing and injection of hydraulic fracturing fluids in oil and gas production wells, to the collection and disposal or reuse of produced water.”

The overall peer-reviewed, final verdict was: “These activities can impact drinking water resources under some circumstances. Impacts can range in frequency and severity, depending on the combination of hydraulic fracturing water cycle activities and local- or regional-scale factors.”

There is a lot of nuance in the lame-duck EPA report, and plenty of acknowledgment of uncertainties and areas where insufficient data precludes reaching hard conclusions.

In a critical review of the literature published in Environmental Science & Technology, academic researchers explored four possible pathways for contamination of water resources:

• “(1) shallow aquifers contaminated by fugitive natural gas (i.e., stray gas contamination) from leaking shale gas and conventional oil and gas wells, potentially followed by water contamination from hydraulic fracturing fluids and/or formation waters from the deep formations;
• (2) surface water contamination from spills, leaks, and the disposal of inadequately treated wastewater or hydraulic fracturing fluids;
• (3) accumulation of toxic and radioactive elements in soil and the sediments of rivers and lakes exposed to wastewater or fluids used in hydraulic fracturing; and
• (4) the overuse of water resources, which can compete with other water uses such as agriculture in water-limited environments.”

In Pennsylvania, there continue to be complaints and documented small incidents, researchers say, but concerns over surface activities and well integrity remain more common than those involving deep fracking; problems arise, for example, when companies leave thousands of feet of uncemented wells. Adhering to industry best practices’ and guidelines appears to eliminate most issues with deep fracking itself.

However, research does suggest that shallower fracking, which comes closer to water resources, may require more precautions. Authors of a 2015 paper, for instance, provide one of the most comprehensive looks at the issue: “Because hydraulic fractures can propagate 2,000 feet upward, shallow wells may warrant special safeguards, including a mandatory registry of locations, full chemical disclosure, and, where horizontal drilling is used, predrilling water testing to a radius 1,000 feet beyond the greatest lateral extent.”

Fracking and earthquakes and tremors

Issue: There have been well-publicized concerns that fracking wells, drilled thousands of feet down, may change geology in a substantial way, leading to earthquakes.

Updates: There is no longer serious doubt that activities associated with energy extraction can trigger earthquakes. Leading researchers have stated in a 2015 policy article published in Science that “[t]o a large extent, the increasing rate of earthquakes in the mid-continent is due to fluid-injection activities used in modern energy production.”

Evidence on that point involving the mechanics of these impacts has become clearer and more specific: Wastewater disposal, rather than the hydraulic fracturing itself per se, clearly causes most of the earthquakes.

The U.S. Geological Survey has sought to clear up “myths” and “misconceptions” in this regard: “Wastewater disposal wells typically operate for longer durations and inject much more fluid than hydraulic fracturing, making them more likely to induce earthquakes.”

That does not rule out the possibility that, given certain specific conditions, fracking procedures themselves can cause earthquakes; but it is worth noting that the majority of wastewater disposed in places such as Oklahoma (ground zero for the fracking-earthquakes controversy) comes from traditional oil recovery, not from fracking.

With more understanding of the mechanics of triggered earthquakes, researchers also are calling on energy companies to do more comprehensive assessments in advance of operations. Most such planning has been somewhat ad hoc. In a 2015 paper, researchers from Stanford University called for a comprehensive initial risk assessment that would focus on “site characteristics, seismic hazard, operational factors, exposure, and tolerance for risk.”

Fracking and leaky wells, methane, and climate risk

Issue: The extraction process results in leakage of some greenhouse gas emissions.

Updates: One of the chief arguments in favor of natural gas extracted through fracking is that it results in fewer greenhouse gas emissions when compared to coal. At the power plant level, natural gas emits about half the GHG emissions that coal does. However, critics point to problems of leaking methane at fracking wellpads. Methane is a highly potent greenhouse gas that, if leaked in sufficient quantities, undermines at least some and potentially much of the purported emissions benefits of natural gas.

Researchers have been debating this issue back-and-forth for years. Where does the controversy stand? For one thing, more datasets clearly show that emissions/leakage are higher than had been projected in previous EPA estimates.

New, more comprehensive research has brought a more empirical lens to the problem: A 2016 study based on an aerial survey of 8,000 fracking sites strongly suggests that oil-producing wellpads are more likely to leak than dry-gas pads. The research also shows a huge range (10-fold or more) in how likely leaks are across sites. Factors that can explain leaks may include geological, operator, regulatory, or other variables. In the vast majority of cases, tank vents and hatches were the culprit for leakage.

Authors of another new study, published in the Proceedings of the National Academy of Sciences, PNAS, find that a “small proportion of high-emitting wells,” most of them no longer in active use, can account for most of the problem. Monitoring old wells, then, is a crucial aspect of the solution to stopping leaks, but it’s no easy task. As the PNAS study notes, the “number of abandoned wells may be as high as 750,000 in Pennsylvania alone.”

Problems and ongoing controversy on the scope of this methane leakage, or so-called “fugitive emissions,” will persist, as new research continues to uncover problems in specific regions. For example, authors of a 2017 study found that methane leaks were incredibly high across fracking operations in northwestern Canada. There is sure to be more debate over the need for further government regulations. The so-called “methane rule,” passed under the Obama administration to address the leakage problem on a more systematic basis, has thus far survived attempts by the Trump administration and some in Congress to repeal it.

More questions begging answers going forward

So researchers continue to answer some fundamental questions on issues of great concern to the public. But where are the emerging areas of knowledge, and where are the blind spots and holes in the literature?

It is clear that, with new and better insights into the issues of earthquakes and methane leakage, regulations and/or higher-quality industrial practices could make a difference. But potential problems will need to be continuously studied as new practices are adopted or new rules adopted and enforced. It is hard to remember, but the contemporary fracking industry as currently understood is just more than a decade old as a large-scale enterprise (its roots go back further), and practices continue to evolve.

Numerous questions relating to these topics remain unanswered, and each deserves further research:

• How many fracking efforts are done improperly? How many well failures have there have been, and what were, and are, the consequences?
• How do geological fractures propagate in highly varying reservoirs? How do the induced fractures interact with naturally occurring fractures in the rock? Can small earthquakes during a fracking treatment trigger a large earthquake on a large fault?
• What are the sources of the water used in fracking operations? What are the implications in various parts of the country for maintaining adequate water supplies? What happens to wastewater? What is the best way to process that wastewater?
• With shallow wells, how acute are the dangers to water resources? Is it even possible to eliminate these risks, or to at least reduce the likelihood to an “acceptable” level? And what are the economics of such efforts?

The answers to these questions and more doubtless will be the focus of research for years to come. Hanging in the balance will be everything from the climate change future to issues involving human health in local communities across North America, as well as U.S. energy “independence” from unstable foreign supplies.

Many have seen fracking and the natural gas that the process produces as at best a “bridge,” a practice that is slightly less carbon-intensive compared to coal, but merely an imperfect step toward getting to an energy market based on renewables such as wind and solar. What has become clear in the policy world recently is that there may be no inevitable timeline to such a “bridge,” and while political fights continue, the practice of fracking must be better understood more quickly from a research perspective and regulation strongly tailored to the best evidence.

We may, after all, be living with active fracking operations for a long while hence, and the scale of operations already completed will be something to grapple with for a generation to come.