Guest Editorial: Rising Pressures and Legacy Wells: The Permian Basin’s Next Challenge

_ For most of the past decade, injection-induced seismicity has posed the greatest challenge to the management of produced water in regions of the US midcontinent with active unconventional oil and gas production. In the Permian Basin, high rates of seismicity have been mitigated in parts of the basin by local curtailments to deep injection volumes. However, an increasing percentage of the more than 20 million B/D of produced water in the Permian is injected into shallow reservoirs, creating new challenges for operators and regulators. Pressure increases are now encroaching on hundreds of thousands of legacy wellbores in the basin; these wells are aging, have been cased to varying standards, and are sometimes unplugged or orphaned. Impacts of this interaction include subsurface crossflow resulting in loss of containment, with potential threats to groundwater and releases of brine at the surface through vertical migration, depending on localized permeability structure including faults and legacy wellbores. How operators, regulators, and researchers work together to respond to this emerging risk will define the next chapter of produced-water management in the Permian. The Seismicity Challenge as Addressed by Industry and Regulators Earthquake rates rose sharply throughout oil- and gas-producing basins of the US midcontinent from the 2010s onward (Zoback and Hennings 2025). Most of these earthquakes are associated with deep injection of produced water into carbonate reservoirs below producing shales and above seismogenic basement (Smye et al. 2024, Hennings et al. 2024), and in nearly all cases, the injection reservoirs are in direct hydrogeologic connectivity with the earthquake domain through basement-rooted faults (Horne et al. 2024). In recent years, voluntary or mandatory curtailments of injection into deep reservoirs in areas of concentrated seismic activity, called “seismic response areas” (SRAs), have proven successful in mitigating the rates and magnitudes of earthquakes (Fig. 1). Specifically, in the North Culberson-Reeves SRA in the Texas Delaware Basin, the shut-in of 20 deep injection wells led to earthquake rates declining by two-thirds from 2022 to 2025. While earthquake rates are likely to stay elevated above background levels for several years (Langenbruch and Zoback 2016 for analog system), the successful mitigation of the most problematic seismicity is a collective success of industry, regulators, and academia.