Computational fluid dynamics simulation of natural gas hydrate sloughing and pipewall shedding temperature profile: Implications for CO2 transportation in subsea pipeline

Abstract

The continuous flow assurance in subsea gas pipelines heavily relies on the assessment of temperature profile during hydrate sloughing and pipewall shedding caused by hydrates, with similar implications for carbon dioxide (CO2) transportation under hydrate-forming conditions. Hydrate sloughing is the peeling off of some hydrate deposits from the pipeline inner surface. Similarly, pipewall shedding by hydrates involves the direct interaction of hydrates with the pipeline inner surface, resulting in the detachment or removal of hydrate deposits from the pipewall. While sloughing occur within the deposit of hydrates, pipewall shedding is related to direct interaction of the gas phase with the thin layer of hydrates on the pipewall. In this study, a computational fluid dynamics (CFD) simulation approach is employed, using a validated CFD model from the literature for predicting hydrate deposition rates (Umuteme et al., 2022), by applying a subcooling temperature to the pipe wall at hydrates forming condition. We have deduced the presence of hydrates based on the stable temperature profile of natural gas hydrates along the pipeline model. The study shows that the simulated temperature contours align well with the reported hydrate deposition profile in gas pipelines (Di Lorenzo et al., 2018). The conversion of the consumption rate of natural gas to hydrates was achieved using the equation proposed in the literature (Umuteme et al., 2022). Two shear stress regimes have been identified for hydrate sloughing and pipewall shedding in this study, with the latter resulting in higher shear stress on the pipewall. Presently, there is a growing concern regarding the potential leakage of CO2 in pipelines (Lu et al., 2020; Wang et al., 2022; Wareing et al., 2016), which may escalate due to pipewall corrosion caused by hydrates (Obanijesu, 2012). The findings in this research can provide further knowledge that can enhance the safe transportation of CO2 in pipelines under stable hydrate forming conditions.