Gas Hydrate Formation and Dissociation: Effect of Salinity of Formation Water in Subsea Flowline

The total dissolved solid (TDS) of formation water has an impact on its tendency to form or dissociate Gas Hydrate in gas production, handling and subsea transportation systems. The effect of salinity of formation water on hydrate formation and dissociation was studied in this paper. Two seawater samples (SW1 and SW2) of different salinities: 35.4g/L and 34.8g/L respectively, and synthetic seawater sample (SSW) were used. Afresh water sample was used for comparison. The SSW sample with a salinity of 36.0g/L experienced a longer onset time for hydrate to form, and dissociated quickly in this sample than the rest samples. The onset time for hydrate formation increased as formation water salt content increases and vice versa for dissociation. The 0.04 wt% concentration of the commercial kinetic hydrate inhibitor (PVCap) used, performed better for the hydrate inhibition experiment involving the SW1 by reducing pressure to 120 psi. This attained pressure at the end of the experiment was lesser than the values obtained with the rest concentrations. The 0.01 wt% concentration of PVCap reduced pressure to a lesser value when compared to the values obtained using other concentrations for the experiment conducted with SSW.