EOG Resources' Baseline Groundwater Monitoring Program for the Bakken

EOG Resources (EOG) conducts baseline groundwater monitoring at privately-owned water wells within a 1-mile radius of newly proposed oil and gas wells in North Dakota’s Bakken Region. The baseline program is a voluntary risk management tool that establishes baseline groundwater conditions before drilling. The baseline program is modeled after Wyoming Oil and Gas Conservation Commission (WOGCC) rules and it involves available water source identification, preparing a site specific groundwater sampling plan, collection of groundwater samples, laboratory analysis, data quality assurance, and reporting.

Groundwater samples collected from private well owners are analyzed for most of the parameters specified in the WOGCC rules, which include inorganic compounds, hydrocarbons, and dissolved gases such as methane, ethane, and propane.

Many private water wells in the Bakken are in or near shallow lignite beds. Methane is common in lignite and is often present in shallow groundwater wells where it can be mistaken to be a result of local oil and gas production. EOG completes additional gas analysis if the dissolved methane concentrations are found to exceed 5 mg/L to “fingerprint” or further define the origin/diagenesis of the gas. Fingerprinting includes analyzing for fixed C1-C6 hydrocarbons and stable isotope concentrations of carbon (¹²C and ¹³C) and hydrogen (¹H and ²H) in the methane.

Barr Engineering performs the sampling for EOG in North Dakota and coordinates with the contract laboratories. The program strengthens landowner relations by demonstrating a commitment to environmentally responsible operations and provides transparency by sharing the data with the landowner if they agree to be part of the program. Some of the logistical challenges in implementing the program include garnering the attention of the landowner, the often remote nature of the work, and making decisions regarding which wells are most appropriate for inclusion in the program.