Research on the External Pressure Resistance of Non‐ <scp>API</scp> ‐Standard and High‐Toughness Oil Well Casings

ABSTRACT This study introduces a microstructure‐temperature coupled framework to analyze the collapse behavior of non‐API high‐toughness casings (BG110V/BG140V), addressing a 16%–18% prediction error in conventional API standards through experimental validation, 3D modeling, and a novel multifactor correction formula. Full‐scale collapse tests at 50°C and 85°C revealed temperature‐dependent elastoplastic behavior. BG140V showed higher‐pressure resistance (75.89 MPa at 50°C vs. 59.47 MPa for BG110V), attributed to its finer grain structure (ASTM 10.0 vs. BG110V's 6.5). Thermal softening reduced yield strength by 4.3% (BG110V) and 2.4% (BG140V) at 85°C, correlating with accelerated dislocation mobility (1.5 × 10 8 /cm 2 vs. 10 8 /cm 2 at 50°C). Finite element simulations (mesh size: 5 mm global/2 mm local) replicated collapse pressures with ≤ 3% error, validated against experimental data. Microstructural analysis identified dual failure mechanisms: axial collapse initiated at stress‐concentrated zones (100–150 mm from ends, 30% above average stress), while radial failure originated from surface defects (0.1 mm scratches amplifying strain by 40%). A novel multifactor correction formula integrating API standards with microstructure‐aware terms (grain size: n = 0.5 Hall–Petch exponent; defect tolerance: ovality ≤ 2%) reduced collapse pressure prediction errors from 16% to 18% (API) to ≤ 6.7%. The model quantifies temperature effects via Arrhenius‐type decay ( α T = 0.0032 for BG110V) and inclusion‐driven microcrack thresholds ( C inclusion ≤ 1.2 vol%). These findings establish a microstructure‐property‐performance framework for optimizing casing design in ultra‐deep reservoirs, balancing computational efficiency with industrial reliability. Recommendations include expanding validation to cyclic fatigue scenarios and hydrogen embrittlement environments to advance next‐generation well integrity protocols.