Gas hydrates are ice-like solids that form and block subsea gas pipelines, and represent the most significant flow assurance risk to operations. Current subsea operations use thermodynamic hydrate inhibitors (THI) to prevent the formation of gas hydrates in pipelines and subsea equipment. The operating cost of this prevention strategy increases geometrically with wellhead depth, and already limits the economic viability of some deep-water assets. Recent studies have qualitatively shown that reducing the amount of THI injected may not increase the risk of pipeline blockage, as the limited amount of gas hydrate can be effectively managed. This study will develop a quantitative understanding of how under-inhibited operations (where THI is injected below the full inhibition requirement) impact upon hydrate nucleation13, growth, and potential plug formation. Two PhD students will conduct laboratory experiments to quantifiably establish when and where THI costs may be reduced while maintaining low risk in the subsea pipeline. Results from autoclave experiments (PhD 1) will be up-scaled using a single-pass gas-dominant flowloop run by UWA and CSIRO in Perth, which will deploy world-first distributed fibre optic temperature and pressure measurements to validate high-precision predictive modelling for subsea pipelines (PhD 2). The outcome will be a quantitative relationship between the degree of under-inhibition and the risk of hydrate blockage, over a range of expected subsea conditions, impacting both existing and future developments by reducing the capital and operating costs associated with THI systems.
Reducing MEG Use Through Under-Inhibited Operations
