In a recent article published in the journal AAPG Bulletin, researchers addressed the pressing issue of injection-induced earthquakes in the Midland Basin region, particularly focusing on the implications of wastewater disposal from the petroleum industry.
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As the industry coproduces an estimated 15 million barrels of wastewater daily, the disposal methods, primarily through subsurface injection, have raised significant concerns regarding reservoir pressurization, fault reactivation, and the resultant seismic activity. The authors emphasized the necessity of understanding the geological and geomechanical factors contributing to these phenomena and the importance of integrating various scientific disciplines to mitigate the risks associated with induced seismicity.
Background
The Permian Basin in west Texas and southeast New Mexico has become a focal point for unconventional oil and gas production, leading to substantial volumes of produced water. The article notes that since 1983, over 60 billion barrels of produced water have been injected into subsurface reservoirs, with projections indicating an additional 310 billion barrels may be produced in the coming decades.
This situation presents a significant challenge, as the subsurface capacity for injection is finite and has been exceeded in many areas. The authors highlight the need for a comprehensive understanding of the native in situ conditions before injection, including the flow characteristics of reservoirs, pore pressure conditions, stress states, and the potential for fault reactivation.
The Current Study
The research employs a multidisciplinary approach, integrating geoscience and reservoir engineering to analyze the impacts of wastewater injection. The authors review existing literature and data on the geological characteristics of the Midland Basin, focusing on the types of reservoirs used for injection and the associated risks.
They categorize the injection systems into four regional rock volumes: deep reservoirs in the Delaware and Midland basins and shallow reservoirs in those basins. The study also examines the geomechanical properties of these reservoirs, particularly the carbonate-dominated formations favorable for deep injection, allowing for high injection rates of up to 75,000 barrels per day.
To assess the impacts of large-scale injection, the authors utilize models to analyze the changes in pore pressure (ΔPp) resulting from wastewater disposal. They discuss the industry's technical capabilities to perform subsurface analysis, which includes understanding the dynamic interrelationships between pore pressure changes, stress alterations, and fault behavior.
The research also emphasizes the importance of monitoring seismic activity and understanding the characteristics of earthquakes that deviate from historical norms, as these anomalies can indicate the onset of induced seismicity.
Results and Discussion
The findings reveal a complex relationship between wastewater injection and induced seismicity in the Midland Basin. The authors report that the rate of problematic earthquakes has been significantly reduced in certain areas due to regulatory actions and improved operational practices. However, they also note that the rate of induced seismicity remains high in some regions, indicating that challenges persist. The study highlights the importance of understanding the geological context of injection sites, as variations in rock properties and reservoir characteristics can influence the likelihood of fault reactivation and seismic events.
The authors categorize the mechanisms of induced seismicity into seven distinct systems, each characterized by specific geological and operational factors. They synthesize earthquake causal mechanisms, emphasizing the role of reservoir pressurization and the reactivation of pre-existing faults. The research underscores the need for ongoing monitoring and analysis to predict and mitigate the risks associated with induced seismicity, particularly as injection practices evolve and the volume of wastewater increases.
The discussion also addresses the implications of these findings for future petroleum development in the region. The authors argue that a deeper understanding of the subsurface conditions and the potential for induced seismicity is essential for sustainable resource management. They advocate for a collaborative approach among industry stakeholders, regulators, and researchers to develop effective strategies for managing wastewater disposal and minimizing the risks of induced earthquakes.
Conclusion
In conclusion, the article provides a comprehensive overview of the challenges associated with injection-induced earthquakes in the Midland Basin region. The authors emphasize the critical need for a multidisciplinary approach to understanding the geological and geomechanical factors contributing to induced seismicity.
As the petroleum industry continues to produce significant volumes of wastewater, the risks associated with subsurface injection must be carefully managed to ensure the safety and stability of the region.
The findings highlight the importance of ongoing research, monitoring, and collaboration among stakeholders to address induced seismicity's complexities and develop effective strategies for sustainable resource management. The insights gained from this study are vital for informing future practices in wastewater disposal and mitigating the potential hazards associated with induced earthquakes in the Midland Basin and beyond.
Source:
Peter Hennings. (2024). The geology of injection-induced earthquakes in the Midland Basin region: Introduction. AAPG Bulletin 108 (12): 2195–2200. DOI: 10.1306/intro10012424106, https://pubs.geoscienceworld.org/aapg/aapgbull/article/108/12/2195/650125/The-geology-of-injection-induced-earthquakes-in