From Reagent to Control: The SPVA Framework for Precision Remediation of Deep Groundwater Contamination at Retired Oil and Gas Well Sites

Retired oil and gas well environments pose profoundly complex groundwater remediation challenges due to contaminant architectures that are characteristically deep, stratified, and severely heterogeneous. Historical remediation strategies frequently underperform because they disproportionately emphasize nominal reagent reactivity while neglecting critical dependencies on precise amendment delivery and strict treatment zone control. To resolve these systemic limitations, this comprehensive review introduces the Source architecture, Precision delivery, Verification, and Adaptive control (SPVA) framework to reassess in situ remediation of petroleum related groundwater contamination. Our analysis begins by synthesizing the mechanisms through which wellbore legacy effects, multiphase contaminant behavior, and aquifer compartmentalization inherently restrict amendment access and effective physical contact. Recognizing these physical constraints, we critically evaluate advanced delivery architectures such as discrete depth injection, and integrated chemical biological strategies. This evaluation deliberately pivots the disciplinary focus toward the structural construction of robust subsurface treatment zones. Furthermore, we investigate the persistent disconnect between localized injection achievements and overall remediation efficacy. Bridging this operational gap necessitates adopting emerging methodologies capable of verifying amendment distribution and identifying untreated zones, which seamlessly enables monitoring informed adaptive control systems. The proposed framework extensively explores the strategic opportunities provided by process modeling, machine learning algorithms, digital twins, and sustainable optimization to enhance full scale field operations. Ultimately, SPVA formalizes and extends established adaptive-remediation principles for the specific constraints of deep, stratified, legacy-infrastructure-affected aquifers. By defining remediation success around verifiable treatment-zone completeness, this structured workflow provides an evidence-based roadmap for addressing the global environmental legacy of retired wells.