Numerical Simulation of Multiphase Flow Erosion in the Gas Well Relief Line Elbow under Supercritical Conditions

Abstract

The erosion of a gas well relief line elbow under supercritical conditions must be investigated, because under these conditions, it may be pierced within a few minutes, which may significantly affect control safety and cause casualties and environmental pollution. Herein, the Eulerian-Lagrangian method was used to establish a numerical model to examine a gas well relief line elbow erosion under supercritical conditions. The numerical model was verified by combining the unit erosion experiments and field failure cases. On this basis, we conducted a simulation analysis of elbow erosion under supercritical conditions according to actual blowout conditions. Nine influencing factors, including the angle of the elbow and discharge volume, were considered. The erosion mechanisms and laws of the elbow under gas–solid two-phase flow, liquid–solid two-phase flow, and gas–liquid–solid three-phase flow were also determined. The erosion laws of the elbow under gas–solid and gas–liquid–solid flow conditions were similar, with severe erosion occurring in the extrados of the elbow. The maximum erosion rate increases with increasing sand content, particle shape coefficient, and temperature, and it decreases with increasing outlet length. Moreover, the maximum erosion rate first increases and then decreases with increasing particle size before finally stabilizing with increasing discharge amount. The erosion rate of the gas–solid flow first increases and then decreases with increasing elbow angle. In contrast, severe erosion occurs on the side wall of the bend for liquid–solid flow conditions. The maximum erosion rate increases with increasing velocity and sand content and decreases with increasing elbow angle and particle shape coefficient. Moreover, it first decreases and then increases with increasing particle size, and it is barely affected by the outlet length and temperature. This study provides key theoretical support for elbow selection and structural optimization.