Oil and gas development in the Williston Basin of North Dakota and Montana has not impacted shallow water resources, according to a new study. However, the age of the groundwater sampled and the sample locations indicate additional research should be conducted to fully evaluate energy production impact on regional water resources. The study was published in the latest issue of the journal Groundwater.
“These results are good news for water users, and the data provide a valuable baseline against which future water-quality data can be compared,” Peter McMahon, a USGS hydrologist and lead author of the study said in a statement. “However, it is important to consider these results in the context of groundwater age.”
Oil production in the Bakken region has increased dramatically, with total oil output now surpassing 1 million barrels per day.
A majority of these wells are stimulated and completed using hydraulic fracturing technology, a technique that is under the microscope regarding its potential to contaminate water resources. This study appears to corroborate evidence that fracturing itself – which typically occurs thousands of feet below drinking water acquifers – is not a primary contamination vector. Improperly cemented well casings that pass through sensitive aquifers and/or surface spills pose greater risk to local water resources.
The study relied on data collected from domestic wells and additional research based on wells targeting shallower water resources in closer proximity to producing wells is recommended.
“It is important, however, to consider these results in the context of groundwater age. Most samples were recharged before the early 1950s and had 14C ages ranging from <1000 to >30,000 years. Thus, domestic wells may not be as well suited for detecting contamination associated with recent surface spills as shallower wells screened near the water table,” according to the study’s abstract.
“The groundwater age results indicate that a long-term commitment to monitoring is needed to assess the effects of energy development on groundwater quality in the Williston Basin production area,” said McMahon.
