Mechanical sand-control screens are core completion components for maintaining sand retention and flow conductivity in oil, gas, geothermal, hydrate, and underground gas storage wells. This review summarizes recent progress in the plugging mechanisms, diagnostic indicators, and plugging-removal technologies of mechanical sand-control screens. The reviewed studies show that screen plugging is a multi-mechanism process controlled by external sand bridging, internal fines invasion, drilling/completion fluid residues, chemical scaling, organic deposition, and their coupled cementation effects. External plugging is mainly associated with slot- or pore-entrance bridging and filter-cake compaction, whereas internal plugging is controlled by fines retention in mesh layers, prepacked gravel, or tortuous porous media. Pressure drop, permeability damage/recovery, produced-sand particle-size distribution, and microstructural characterization are key indicators for evaluating plugging severity and treatment effectiveness. Hydraulic jetting, mechanical vibration, ultrasonic treatment, acidizing, oxidizing systems, thermochemical treatment, and physical–chemical combined methods are compared in terms of mechanisms and applicability. The analysis indicates that single treatments are usually insufficient for strongly cemented multicomponent plugging; a sequential strategy of chemical weakening followed by physical stripping and flowback is more suitable for complex field conditions. Future work should focus on green and selective chemical systems, downhole diagnosis-guided treatment selection, and integrated sand-control designs combining plugging prevention, monitoring, and removal.

Driven by the extreme high temperatures (≥150 °C) and high salinities of deep wellbore environments, the corrosion failure of drill strings in water-based drilling fluids (WBDFs) is becoming increasingly severe. This study systematically investigates the corrosion behaviors and underlying mechanisms of N80 steel in simulated WBDFs under varying temperatures (80–180 °C), inorganic salts (NaCl, CaCl₂, KCl), dissolved oxygen (DO) levels, and hydrodynamic conditions, utilizing weight-loss tests, SEM, and XRD. Results reveal that the corrosion kinetics are synergistically governed by temperature and salt concentration, exhibiting a non-linear “increase-then-decrease” trend with a peak at 120–150 °C. The aggressiveness of the inorganic salts ranks as NaCl > CaCl₂ > KCl. Specifically, highly penetrative free Cl⁻ in the ultra-high-concentration NaCl system induces severe interconnected localized pitting. Conversely, high-concentration Ca²⁺ in weakly alkaline environments couples with carbonate to form a protective inorganic scale, serving as a physical barrier. Although the “salting-out effect” of high-concentration salts effectively reduces the DO level, the synergy between residual oxygen and active Cl⁻ in dynamic flow fields still triggers highly concealed deep under-deposit pitting. At the extreme high temperature of 180 °C, background salt ions dictate the competitive interfacial film formation: the NaCl system undergoes oxygen depolarization to generate a porous Fe₃O₄ layer, whereas K/Ca-containing systems promote CO₃²⁻ adsorption, forming a dense and thermodynamically stable FeCO₃ film. This study elucidates the fundamental mechanisms of uncontrolled pitting induced by extreme HTHP environments, providing vital theoretical guidance for the anti-corrosion design of deep-well drilling engineering.