Abstract
Earthquakes occurring naturally or induced by human activities can damage surface and subsurface infrastructure. Oil and gas wells represent a category of subsurface infrastructure that can act as leakage pathways connecting oil and gas reservoirs, groundwater aquifers, and the atmosphere. The integrity of these wells can be compromised through a wide range of processes and contribute to groundwater contamination, greenhouse gas emissions, and air quality degradation. We estimate the increase in such subsurface leakage potential due to seismic activity through geospatial analysis of 579,378 oil and gas well and 196,315 earthquake (magnitudes greater than 1.0) locations in Oklahoma, California, and British Columbia. We perform density-based clustering analysis and point density mapping using ArcGIS. We combine the well and earthquake point density maps to identify hot spots of joint high well and earthquake densities. We find that oil and gas wells and earthquakes are clustered in space, with densities reaching ∼60 wells per km2 and ∼40 earthquakes per km2 in California. There are at least two hot spots where these clusters overlap in each state/province. In Oklahoma and British Columbia, the hot spots are more correlated with earthquake densities; while, in California, the hot spots are more correlated with well densities. Our findings indicate the need to investigate the role of earthquakes on wellbore leakage through additional analysis of earthquake characteristics, wellbore attributes, improved data collection, and empirical field studies for all oil and gas wells, including those that are abandoned. In particular, large scale geospatial analysis establishing the scope of the problem and empirical field studies focusing on identified hot spots are needed to understand potential environmental impacts of earthquakes, especially those induced by oil and gas activities.
Highlights
Oil and gas wells can act as pathways for fluid leakage leading to groundwater contamination and emissions of greenhouse gases and air pollutants, thereby impacting climate, air quality, and water resources
We find that oil and gas wells and earthquakes are clustered in space, with densities reaching ∼60 wells per km2 and ∼40 earthquakes per km2 in California
In Oklahoma and British Columbia, the hot spots are more correlated with earthquake densities; while, in California, the hot spots are more correlated with well densities
Summary
Oil and gas wells can act as pathways for fluid leakage leading to groundwater contamination and emissions of greenhouse gases and air pollutants, thereby impacting climate, air quality, and water resources. Failure in barriers to well leakage, or wellbore integrity issues, can occur due to thermal, chemical, and/or mechanical stresses during oil and gas production and other activities and create or enhance fluid leakage in and around wellbores [2–5]. Database analysis are used to estimate rates of wellbore integrity failures such as cement and casing impairment and to link these issues to well characteristics, spud date, well type and construction, production history, well location, geology, operator, abandonment method, oil price, and regulatory changes [6–11]. A salient process that is yet to be studied in linkage with oil and gas well leakage is earthquakes
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