Electrochemical Protection and Gas Suppression Mechanisms under Reservoir Geological Conditions

Abstract

The intricate and extraordinarily harsh geological environments characteristic of deep oil and gas reservoirs—distinguished by exceptionally high temperatures that routinely exceed 120°C and frequently approach or surpass 180°C in high-pressure, high-temperature (HPHT) settings, intensely elevated formation pressures that commonly surpass 50 MPa and may escalate to values well beyond 100 MPa in overpressured compartments, remarkably high levels of mineralization in formation waters with total dissolved solids (TDS) typically exceeding 100,000 mg/L and often approaching full brine saturation at 250,000–300,000 mg/L, and the pervasive coexistence of highly aggressive acidic gases such as carbon dioxide (CO₂) with partial pressures ranging from 1 to 20 MPa and hydrogen sulfide (H₂S) at concentrations spanning tens to thousands of parts per million—are collectively responsible for imposing severe and multifaceted dual challenges upon the metallic infrastructure deployed in exploration, drilling, completion, and production operations. These dual challenges manifest as aggressive electrochemical corrosion processes that relentlessly degrade material integrity and pervasive gas-induced hazards that disrupt fluid dynamics and threaten operational safety. This comprehensive academic study systematically elucidates, from a rigorously mechanistic and theoretically grounded perspective, the fundamental principles governing polarization-induced blocking in electrochemical protection strategies, the sophisticated and multifaceted pathways of interfacial regulation that characterize gas suppression methodologies, and the complex, dynamic, and highly interactive coupling patterns that emerge between these two distinct yet complementary approaches within the heterogeneous, multiphase, and multi-field coupled media of subsurface reservoir systems. Key findings from this detailed mechanistic analysis convincingly demonstrate that the localized alkalization microenvironment deliberately generated through the precise application of cathodic currents substantially and significantly enhances the thermodynamic stability, kinetic persistence, and surface coverage density of chemical inhibitors adsorbed on metallic substrates. In a reciprocal and mutually reinforcing manner, the robust, continuous, and defect-minimized interfacial barrier meticulously constructed by these adsorbed inhibitor films effectively diminishes both the magnitude of corrosion current densities flowing through the metal-electrolyte interface and the disruptive hydrodynamic influence exerted by evolving gas bubble populations, thereby establishing a highly efficient, self-sustaining, and positive feedback synergistic loop that amplifies overall protective efficacy far beyond the additive contributions of individual mechanisms. These detailed, mechanism-based interpretations and profound insights—derived through careful consideration of electrochemical thermodynamics, interfacial physical chemistry, fluid dynamics, and reservoir geology—provide a solid, reliable, and operationally actionable theoretical foundation for the design, optimization, and field implementation of long-term, sustainable, and adaptive corrosion prevention measures, as well as for enabling precise, targeted, and proactive management of gas-related hazards throughout the lifecycle of oil and gas field development and production.