A simplified calculation procedure has been developed in order to predict hydrate plug formation location and growth rate in a gas-condensate line discharging to a burn-pit, downstream a restriction orifice where as an effect of condensate flashing and cooling the fluid enters the hydrate stability region, and gas is flowing at high velocity.
This method uses a combination of OLGA2000 simulations (to determine pressure, liquid holdup and temperature profiles), reference correlation for estimation of gas and water consumption rates related to hydrate monomers formation, as well as agglomerates of hydrates, and evaluation of flow regime of the slurry of hydrate particles in the condensate phase.
Experimental evidence suggests that, in condensate pipelines hydrates may deposit on the pipe wall, where a strong adhesion may develop, and the deposit can progressively grow by jamming of upstream incoming hydrate particles up to complete blockage. Wall deposition is more probable to occur in low elevation points and bends, especially at low flow velocity. Based on this, hydrate particles potential settling risk as dependent on carrier fluid velocity is evaluated along the line profile, thus identifying points of accumulation and the relevant hydrate plug growth rate.
The method has been applied to a design case, by evaluating possible hydrate and ice plugs formation time, erosion rate caused by hydrate particles in case of prolonged operation, and solutions for hydrate risk prevention.
