Understanding Pathways of Unconventional Oil and Gas Produced Water Spills in the Environment Completed

Sources/Usage: Public Domain.

Increasing demand for fossil fuels, depletion of traditional oil and gas reservoirs, and decades of public- and private-sector investment in methods to extract oil and gas from low-permeability formations have accelerated the development of UOG resources using technologies such as directional drilling and hydraulic fracturing. With the increase in production of UOG resources, the amount of produced wastewaters has also increased.

Sources/Usage: Public Domain.

U.S. Geological Survey (USGS) and University of Missouri researchers are studying the pathways of UOG wastewaters into the environment. Previous work was done to understand stream chemistry changes downstream from a UOG injection disposal facility in Wolf Creek, West Virginia. In this current study, the research team is working to understand movement of chemicals from a UOG-produced water pipeline leak in northwestern North Dakota that flowed into Blacktail Creek, a small tributary of the Little Muddy River, which flows into the Missouri River. An estimated 11.4 million liters of produced wastewater was spilled into Blacktail Creek.

Scientists measured a broad range of chemicals and isotopic markers associated with UOG-produced waters following the report of a pipeline leak (January 2015). Samples of sediment and water were collected during February and June 2015 at seven sites along Blacktail Creek and the Little Muddy River to represent the full range of upstream and downstream environments. Caged-fish survival and assays to measure endocrine-disrupting activity in water samples were used to understand potential exposures and adverse health effects, if any, on organisms.

Concentrations of sodium, chloride, bromide, strontium, boron, lithium, ammonia, and hydrocarbons in the stream water downstream from the spill were greater than upstream concentrations, particularly in February, and some chemicals persisted in water samples from Blacktail Creek for several months (June) after remediation efforts started. Stream-sediment samples collected downstream from the spill during the same periods contained boron, strontium, and radium at concentrations as much as 15 times greater than concentrations in sediment at upstream locations. Caged-fish mortality was observed downstream from the spill, and similar to findings in West Virginia study, endocrine-disrupting activity was present in water samples located downstream from the spill.

The results from this collaborative study provide data that can be used to understand pathways of chemicals that may be associated with UOG produced waters where wastewater is accidentally spilled in or near steams. Research at the study site is ongoing and several key questions regarding the contamination are being pursued. Both organic and inorganic chemicals were elevated downstream from the spill; however, the extent to which these chemicals are derived from the wastewater spill as compared to other anthropogenic (for example, agriculture) and natural sources is an ongoing topic of research. Studies are underway to understand the role of contaminated sediments and their transport and storage within the channel as a potential long-term source of chemicals to the stream. Scientists are also working to understand the factors associated with the observed caged-fish mortality and endocrine-disrupting activity to put the chemical results into a health context.

USGS Environmental Health Program (Toxic Substances Hydrology and Contaminant Biology), Energy Resources Program, and Fisheries: Aquatic and Endangered Resources Program funded this study.