Yanbin Wang

Summary: Carbon dioxide (CO2) corrosion remains a critical threat to production tubing integrity in high-temperature, high-pressure (HTHP) gas wells, where accurate service life prediction continues to challenge the industry. This study establishes an improved corrosion rate model through laboratory experiments under coupled temperature-pressure conditions. The model employs a polynomial representation that achieves higher predictive accuracy than conventional methods under varied operational conditions. Furthermore, a service life prediction framework has been developed that incorporates triaxial stress distribution and temperature-dependent material degradation, providing a more realistic assessment of production tubing performance under actual service conditions. Validation with field measurements confirms a strong agreement between predictions and observed data. Sensitivity analysis reveals complex nonlinear relationships between key parameters and corrosion behavior, with the most vulnerable sections identified at a 200–900-m depth. This work provides both methodological advances and practical guidance for tubing design and integrity management in HTHP environments.

Summary: Vortex-induced vibration (VIV) poses a significant threat to the structural integrity of deepwater drilling risers operating in complex ocean environments. In this study, we propose a novel VIV prediction framework based on the discrete vortex method (DVM), which, for the first time, incorporates time-varying axial tension resulting from riser bending deformation into the hydrodynamic simulation. A key methodological advancement is the coupling of 2D vortex shedding with the actual lateral displacement of the riser, enabling simultaneous prediction of both in-line and crossflow VIV responses along the entire riser span. Unlike conventional models that assume constant axial tension or ignore bending-induced tension variation, the proposed approach captures the dynamic interaction between structural deformation and flow-induced forces. Validation is performed through comparison with existing numerical studies, confirming that the model can accurately reproduce the overall VIV response trends of the riser system. Comparative analysis demonstrates that the proposed model predicts a distinct lock-in region between 0.40 m/s and 0.75 m/s, with a critical transition at 0.75 m/s separating the upper and lower response branches. Moreover, a significant reduction in in-line vibration amplitude, up to 25%, is observed when time-varying axial tension is considered. In contrast, its impact on crossflow response remains limited. These findings underscore the importance of tension variation in realistic riser VIV prediction and provide a more robust basis for riser fatigue assessment in practical offshore applications.

Summary: How to effectively control the recoil response after an emergency disconnection is one of the core technical problems in ensuring the safe and reliable operation of a deepwater drilling riser. Currently, the theoretical analysis is based on a discretization model or numerical simulation, which ignores the continuity of the riser system and the coupling effects of load acting on the riser. To address this problem further, in this paper, we establish a mechanical model and control equation with infinite degree of freedom for riser recoil response, where the heave motion of the floating drilling platform, seawater damping, and the viscous resistance of drilling fluid discharge were taken into account. In addition, the correctness of the model and solving approach are verified against the Orcaflex software. On this basis, the influence of wave period, wave height, initial phase angle, and tension coefficient on the recoil characteristics are discussed. The success of riser emergency disconnection is related to the clearance between the lower marine riser package (LMRP) and the blowout preventer (BOP) and the axial force distribution of the riser. The influence of the above-mentioned factors on the riser recoil response is also complicated. On the basis of the assumptions put forward and the model established, some quantitative conclusions are drawn. This study is of reference significance for safety control of riser emergency disconnection operation.

Hybrid nanofluids have many real-world applications. Research has shown that mixed nanofluids facilitate heat transfer better than nanofluids with one type of nanoparticle. New applications for this type of material include microfluidics, dynamic sealing, and heat dissipation. In this study, we began by placing copper into H₂O to prepare a Cu-H₂O nanofluid. Next, Cu-H₂O was combined with Al₂O₃ to create a Cu-Al₂O₃-H₂O hybrid nanofluid. In this article, we present an analytical study of the estimated flows and heat transfer of incompressible three-dimensional magnetohydrodynamic hybrid nanofluids in the boundary layer. The application of similarity transformations converts the interconnected governing partial differential equations of the problem into a set of ordinary differential equations. Utilizing the homotopy analysis method (HAM), a uniformly effective series solution was obtained for the entire spatial region of 0 < η < ∞. The errors in the HAM calculation are smaller than 1 × 10⁻⁹ when compared to the results from the references. The volume fractions of the hybrid nanofluid and magnetic fields have significant impacts on the velocity and temperature profiles. The appearance of magnetic fields can alter the properties of hybrid nanofluids, thereby altering the local reduced friction coefficient and Nusselt numbers. As the volume fractions of nanoparticles increase, the effective viscosity of the hybrid nanofluid typically increases, resulting in an increase in the local skin friction coefficient. The increased interaction between the nanoparticles in the hybrid nanofluid leads to a decrease in the Nusselt number distribution.

During deepwater drilling, the subsea wellhead will be subjected to dynamic loads transmitted from the marine environment, floating drilling platform, riser, and blowout preventer (BOP). Therefore, complex dynamic responses will be induced, which will seriously affect the safety of the subsea wellhead. In this paper, considering the effect of auxiliary pipelines on the riser, a novel entire mechanical model of the floating platform–riser–BOP–subsea wellhead is established. By using the finite-difference method, the governing equations are solved. Finally, the dynamic bending moment and stress distribution of the subsea wellhead are obtained. Moreover, the model is verified by numerical simulation in Orcaflex. On this basis, the influence of the wave height, wave period, sludge height of the subsea wellhead, rotational stiffness of the lower flexible joint, and wall thickness of the conductor on the dynamic characteristics of the subsea wellhead is discussed. Analysis results show that the theoretical analysis results are in good agreement with the numerical simulation. The auxiliary pipelines have important influence on the dynamic characteristics of the subsea wellhead. Wave period is the most important factor affecting the mechanical behavior of the subsea wellhead. Wave height, wall thickness of the conductor, and sludge height are secondary factors affecting the mechanical behavior of the subsea wellhead. The rotational stiffness of the lower flexible joint has little influence on the mechanical behavior of the subsea wellhead. By solving the optimized mechanical model proposed in this paper, the dynamic characteristic of the subsea wellhead conforms more to the actual deepwater drilling conditions. This study has reference significance for the design and mechanical control of the subsea wellhead in deepwater drilling.