What Scientists Still Need to Learn About Oil and Gas Development in the Williston Basin

Unconventional oil and gas (UOG) development — horizontal drilling with hydraulic fracturing — has transformed the landscape of the Williston Basin, especially in North Dakota and eastern Montana, and exponentially increased its oil production.

The Williston Basin Province and the Bakken and Three Forks assessment units in the United States. Map: U.S. Geological Survey.

UOG activity touches the environment in many ways: roads and well pads, leaking pits or tanks, chemical spills, wastewater discharge, drilling before casing is installed, leaks during or after fracturing, failed casing seals, pipeline breaks, abandoned wells, deep-well disposal of wastewater, and new underground migration pathways.

Conventional and unconventional oil and gas activities in the Williston Basin. Diagram: U.S. Geological Survey.

Why this matters

Research on UOG's environmental effects in the basin has so far been limited and piecemeal. Managers need unbiased, integrated science on water quality, water availability, ecological effects and ecological and human health.

Federal agencies in the basin coordinate energy issues on federal lands through the Bakken Federal Executive Group, which includes the Department of the Interior, the USGS, the Bureau of Land Management, the Bureau of Indian Affairs, the Forest Service, the National Park Service, the Fish and Wildlife Service, the Bureau of Reclamation, the Army Corps of Engineers, the Environmental Protection Agency and the Department of Agriculture. For this group, the USGS and the Bureau of Land Management completed in 2022 the four-chapter Bakken Environmental Status and Trends report — an executive summary; physiography, climate, land use and people; water resources; and species of conservation concern — to inform decisions on compliance, permitting, leasing and work with other agencies. This fact sheet sets out the research needs that report and several USGS workshops identified. They fall into three areas, which must be studied together.

1. Water quality

Water is most likely to be degraded by accidental surface releases of produced water and chemicals, or by leaks through the casing or annular space of poorly sealed wells. Drilling and fracturing chemicals, hydrocarbons and formation water hold many chemicals that could harm groundwater and surface water, yet few have been studied there, and public data on the chemical and isotopic makeup of produced and flowback water — needed to recognize when oil field fluids mix with natural waters — are scarce. Needs include:

• deciding which UOG chemicals to monitor, developing methods for those that can't yet be measured well, and characterizing produced and flowback water;
• choosing sampling sites and frequency systematically, along a gradient of development intensity, with methods consistent with other oil and gas plays;
• starting with shallow groundwater, which is more easily affected and may feed important wetlands, and with the most important and vulnerable rivers, streams and reservoirs;
• a basinwide airborne electromagnetic survey of electrical conductivity, and other geophysics, to map salinization from produced-water releases and find vulnerable areas;
• continuous water-quality monitors that could detect spills in real time.

Water-quality sampling in a wetland. Photo: Tara Chesley-Preston, U.S. Geological Survey.

2. Water availability

Long-term energy development needs sustainable, high-quality water and current water-use data. Large volumes go to drilling and maintaining wells and to uses such as dust suppression, drawn from the same sources other users rely on, so an accurate, complete water budget is needed.

Collecting a produced-water sample, with a truck injecting fresh water into a well for routine maintenance behind. Photo: Joanna Thamke, U.S. Geological Survey.

Two completed USGS studies laid groundwork: a groundwater availability assessment — a 3D hydrogeologic framework, a conceptual model of the three uppermost principal aquifer systems, and a numerical groundwater-flow model of how human activity and climate might change them — and an estimate of the direct, indirect and ancillary water use of oil and gas development in North Dakota and Montana, which also improved the USGS's national water-use estimates. Further needs:

• a gravity station network to monitor long-term groundwater storage;
• better potentiometric-surface maps of glacial units;
• uniform digital stream network coverage;
• better information on ice-jam flooding;
• the combined effects of stock and diversion dams.

3. Ecological effects and decision tools

A central question is how the effects of individual projects add up amid ongoing landscape change. Answering it takes large-scale, replicated studies — including before-after control-effect designs — and species distribution models, prioritized for the species and endpoints that would benefit most, to test management scenarios and guide long-term, multispecies monitoring. Needs include:

• more data on species distributions and species-specific effects of UOG;
• other stressors, such as agriculture, to place UOG in a multistressor context;
• landscape-scale datasets to predict where species of concern live, at a scale useful to managers;
• baseline inventories of plants and animals, and monitoring of selected species;
• how light, dust, roads and noise affect ecosystems. Birds and mammals are the best studied, with large gaps; insect pollinators, reptiles and amphibians were almost entirely unstudied as of 2022.

An oil production pad in open pasture. Effects on ecosystems need consistent, long-term, integrated monitoring. Photo: Max Post van der Burg, U.S. Geological Survey.

4. Aquatic species and human health

Conventional and UOG development pose unknown risks to air, groundwater, surface water, soil and other resources, and the fast pace of UOG has put health in the national spotlight. Public concerns center on water contamination from drilling, injecting chemicals underground and wastewater spills. Species of prairie pothole wetlands and small headwater streams are of particular concern. Needs include:

• the fate and reactivity of substances released by UOG;
• site-based and process-based studies of how UOG wastewater changes water, soil, wetland and sediment chemistry;
• the occurrence of contaminants of aquatic and human-health concern, and of those that could serve as tracers of waste releases;
• toxicity studies of produced water and oil spills on native aquatic invertebrates, fish and mussels — field-based, multispecies toxicity assessments were almost entirely lacking as of 2022.

High-quality water is critical for ecological and human health. Photo: Gregory Delzer, U.S. Geological Survey.

Sources

Based on "Research needs identified for potential effects of energy development activities on environmental resources of the Williston Basin," U.S. Geological Survey Fact Sheet 2022–3088, U.S. Geological Survey; a work of the United States government in the public domain.