Apparent Viscosity Measurements in the Quantification of Gas Hydrate Slurry Transportability with Anti-Agglomerants in Multiphase Systems with and without Wax

Abstract

Gas hydrate management with the application of antiagglomerants to produce a transportable hydrate slurry is a strategy that requires well-defined knowledge of the fluid and suspension properties to ensure low/no risk for disruptions to the production of hydrocarbon fluids. One of the key properties in transportability is the apparent and relative viscosity of the hydrate slurry, which can be used to assess the flowability in flowlines. Here, experimental measurements of the apparent viscosity of well-defined hydrate slurries (homogeneous finely dispersed suspension of solids) were obtained from two independent testing setups (rheometer and rock-flow cell) covering a range of water cuts (10–60%) for systems without and with wax (2 and 5 wt %). Hydrates were formed from a gas mixture, mineral oil, water, and a commercial anti-agglomerant chemical. Apparent viscosities were measured before and after hydrate formation, yielding relative viscosities that exponentially increase with the solid content and precipitated wax having a significant impact on the slurry apparent viscosity. The measured relative viscosity data are consistent with well-known suspension models by using the water fraction (and wax) as the effective solid fraction, as opposed to the water conversion to hydrate or hydrate fraction, for systems using anti-agglomerants yielding homogeneous suspension of solids.