Multiphysics Simulation of Hydrate Risk During Restart of Deepwater Gas Wells After Shut-in and the Associated Model-Based Screening Window

The restart risk in a deepwater gas well is governed by the thermal and phase history established during shut-in. This study develops a multiphysics workflow that continuously transfers temperature, pressure, water availability and residual hydrate from shut-in into restart. The workflow couples transient thermal and hydrate evolution with pressure reconstruction and deposition–erosion–restriction feedback. The quality-gated computational path completed every requested time point in the 24 h simulations, and grid and time-step tests gave well-wide peak differences of 0.0195% and 0.0020%, respectively. Across 17 LS36-1 cases, well-wide peaks increased from 0.07268 after 12 h shut-in to 0.15837 after 24 h and 0.18858 after 48 h. Five additional cases placed the model-based 0.10 crossing between 14 and 16 h (linear interpolation: 14.87 h). Ramp increment controlled the duration of exceedance rather than the initial peak, whereas MEG concentration and pre-injection modified the shut-in end state. The results identify shut-in duration as the leading restart constraint and provide a two-scale screening framework for mudline and target interval risk.