Spatial Redistribution of Gas Hydrates and Its Impact on Pressure-Limited Restart in Deepwater Subsea Flowlines
Year: 2026
Type: article
Abstract: Hydrates formed during a subsea flowline shutdown can persist as deposits that restrict the subsequent restart. Assessing restartability therefore requires both thermodynamic conditions and the pressure needed to recover flow. This study develops a one-dimensional screening model that couples transient heat transfer, suspended and deposited hydrate inventories, local area loss, and a source-pressure projection. A representative 30 km deepwater flowline in the South China Sea is examined over production, shutdown, staged restart, and recovery. In the case without monoethylene glycol (MEG), the maximum deposited fraction increases from 0.0173 at 24 h to 0.549 at 60 h, reducing the minimum open-area ratio to 0.451. The initial reference pressure drop is 1.51 MPa, below the available 4.54 MPa. The subsequent ramp first activates the pressure limit 2.06 h after restart, and the minimum available-flow fraction is 0.333 at 8.5 h. The 30.2 and 56.5 m3 d−1 MEG cases have maximum subcoolings of −0.00759 and −4.13 °C, respectively, and remain hydrate-free in the calculations. Parameter perturbations show that deposition and resuspension affect restriction severity, while the assumed bubble diameter can change the restart classification. Latin hypercube sampling and a proper orthogonal decomposition surrogate describe conditional threshold exceedance. The results support comparison of shutdown, restart, and inhibition strategies under the specified model assumptions.
Source: Processes
DOI: 10.3390/pr14203275
Authors: Haihong Chen, Xiang Zhou, Qiang Zheng, Junjie He
Language: English
Subfield: Ocean Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,896
Funder: Beijing Nova Program
Award: G464563206
OpenAlex ID: W7221509952
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