The spill occurred Wednesday at the Houston-based independent's Erie saltwater disposal well in Mountrail County.
The cause was a tank overflow from a failed fitting, according to a release from the North Dakota Oil & Gas Division.
A state inspector has visited the site.
Oasis did not immediately respond to a request for comment.
Brine spills are an increasingly common occurrence in North Dakota, a state with both conventional and unconventional oil and gas production.
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