Determining the Frequency and Risks of Unconventional Oil and Gas Spills

Rapid growth in unconventional oil and gas (UOG) has produced jobs, revenue, and energy, but has also raised concerns over spills and environmental risks. Since the demand for unconventional oil and gas is likely to rise, the SNAPP Hydraulic Fracturing Working Group examined the frequency and causes of oil spills related to UOG activity, as well as their associated environmental risks. Their findings were published in two recent papers. The first paper, published in Environmental Science and Technology, determined the causes and frequencies of spills. The second paper, published in Science of the Total Environment, focused on understanding the characteristics of spills and their associated environmental risk. Along with the journal articles, the working group also created a data visualization tool that brings together all of the spills data analyzed in an interactive format.

A fracking rig and operation stands among forests and fields in Bradford County, PA. Photo Credit: Bob Warhover


UOG, especially hydraulic fracturing within shale reservoirs, will be a key component of future energy development. However, these UOG activities have raised concerns about their potential environmental impacts. One of the public’s greatest concerns with fracking is the impact of surface spills.

To learn more about the occurrence of spills, the working group created an interactive spills data visualization tool to allow for the exploration of the following factors:

  1. When spills are most likely to occur
  2. Where spills are most likely to occur
  3. Underlying cause of the spill

This tool not only allows for visualization of spills, but also enables users to examine how spill frequency, volume and pathways vary with the age of the well in addition to the underlying cause of the spill.

Sample of the spills data visualization tool. Photo Credit: Hydraulic Fracturing Working Group


Since every state had different reporting requirements, extensive time and effort was put into data wrangling, cleaning and standardizing to create a useable dataset for analysis. This standardized dataset allows for comparisons within and across states, in a user-friendly, interactive format.

The SNAPP Working Group analyzed over 30,000 wells in Colorado, New Mexico, North Dakota and Pennsylvania between 2005 and 2014 to determine the causes and frequencies of spills. Overall, 15% of all wells reported a spill, with more than 75% occurring within the first three years of well life. The most common reported pathways, or location of the spills, were tanks, flowlines, and unknown. While tanks and flowlines can be targeted for improvements to decrease the chance of spills moving forward, it is impossible to target efforts when the data are not collected.

“Each state has different requirements for when a spill is reported, what is reported, and how it is reported. Those requirements influence the data collected and all subsequent findings,” said lead author Lauren Patterson.

Determining the ecological impacts of UOG development, especially related to spills, is a top priority to inform energy policy and the conservation of natural systems. The frequency of spills, type of material spilled, volume of material spilled, and proximity of the spill to surface waters and other ecologically sensitive systems were used to assess the environmental risk of UOG. The Working Group found that wastewater and crude oil were two of the most frequently spilled materials across all states. Additionally, a large subset of spills occurred within current setback regulation distances. Spills also occurred in very close proximity to streams and in watersheds of high importance to drinking water. Therefore, these freshwater resources may be at risk from UOG development. As UOG activity continues, the researcher’s findings can be used to better understand the risk of spills from UOG development and help inform management decisions, policy, and regulations.

Assembling spill data from multiple states within a centralized database allows state regulators and other stakeholders to identify trends in common pathways and causes, and pinpoint wells associated with unusually high spill rates. Better insight into the where, when and why spills occur will provide all decision makers with important information on where to target efforts for locating and preventing future spills.

More information about SNAPP Hydraulic Fracturing

To view the data tool: Interactive Spills Data Visualization Tool

For access to the full reports:

Unconventional Oil and Gas Spills: Risks, Mitigation Priorities, and State Reporting Requirements

Unconventional oil and gas spills: Materials, volumes, and risks to surface waters in four states of the U.S.

This research was conducted by the SNAPP Hydraulic Fracturing expert working group supported by Science for Nature and People Partnership (SNAPP), a partnership of The Nature Conservancy, the Wildlife Conservation Society, and the National Center for Ecological Analysis and Synthesis (NCEAS) at the University of California, Santa Barbara. SNAPP is generously supported by Shirley and Harry Hagey, Steve and Roberta Denning, Angela Nomellini and Ken Olivier, Seth Neiman, the Gordon and Betty Moore Foundation, Ward W. and Priscilla B. Woods, the David and Lucile Packard Foundation, and the blue moon fund.


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