Changes in Deep Groundwater Flow Patterns Related to Oil and Gas Activities

Area of Science:

• Hydrogeology
• Petroleum Engineering
• Environmental Science

Background:

• Oil and gas production generates substantial volumes of saline formation water, necessitating subsurface injection.
• The spatial distribution of production and injection wells and their impact on deep groundwater flow remain understudied at regional scales.
• Potential effects on shallow aquifers due to altered deep groundwater flow patterns are uncertain.

Purpose of the Study:

• To investigate the regional-scale distribution of oil and gas production and injection wells.
• To assess the impact of these activities on deep groundwater flow patterns and hydraulic head.
• To evaluate the potential for fluid migration towards shallow aquifers.

Main Methods:

• Analysis of production and injection well locations and volumes in the Canadian Williston Basin.
• Hydraulic head modeling to predict pressure changes in sedimentary strata.
• Assessment of cumulative fluid deficits and surpluses at various spatial scales.

Main Results:

• Over 4.6 × 10^9 m^3 of water produced and 5.5 × 10^9 m^3 injected in the Canadian Williston Basin.
• Localized fluid imbalances (deficits/surpluses) exceeding 100 mm are present over 100 km^2 scales.
• Fluid fluxes from oil and gas activities likely surpass background groundwater fluxes since 1950.
• Modeled upward hydraulic gradients predicted in the Midale Member and Mannville Group.

Conclusions:

• Despite basin-scale fluid balance, localized imbalances create potential for altered groundwater flow.
• Upward hydraulic gradients suggest potential for fluid leakage through permeable pathways like faulty wells.
• Oil and gas activities significantly impact deep groundwater systems, with implications for shallow aquifer integrity.