Simulation of Hydrate formation In the Subsea Pipeline and its Mitigation by Inhibitor

This thesis investigates gas hydrate formation in subsea pipelines and evaluates mitigation strategies using numerical simulation. Gas hydrates are crystalline compounds formed under conditions of high pressure and low temperature, which commonly occur in offshore hydrocarbon transportation systems. Their formation can lead to pipeline blockage and major flow assurance problems. The study uses OLGA transient multiphase flow simulation combined with thermodynamic data generated in MULTIFLASH to analyze hydrate formation behaviour in a 5.78 km subsea pipeline. Two operating scenarios with different mass flow rates (55.7 kg/s and 12.7 kg/s) are investigated to evaluate the influence of flow conditions on temperature, pressure, and hydrate volume fraction along the pipeline. Results show that at high flow rates the fluid temperature remains above the hydrate equilibrium temperature, preventing hydrate formation. At lower flow rates, increased cooling and residence time allow the system to enter the hydrate stability region, leading to hydrate formation and accumulation in downstream sections of the pipeline. Methanol injection is analyzed as a thermodynamic inhibition strategy. Increasing methanol concentration significantly shifts the hydrate equilibrium conditions and reduces hydrate formation risk.