(174c) Rheological Characterisation of Hydrate-in-Oil Slurries

Gas hydrates are ice-like solids that readily form in oil and gas flowlines under high pressure and at low temperature. In oil-dominant systems, the formation of a viscous hydrate-in-oil slurry has been identified as a primary mechanism contributing to hydrate blockage, but there is a dearth of data available to inform hydrate slurry viscosity models. This work deploys a temperature-controlled, high-pressure rheometer with a vane blade rotor to study the rheological properties of methane hydrate-in-crude oil slurries, which are reacted from water-in-oil emulsions. The work represents one of the first applications of a high-pressure vane blade controlled-stress rheometer, which has enabled quantitative comparison of slurry viscosity as a function of the hydrate volume fraction. After the hydrate reaction in each experiment, flow curves are captured for the steady-state hydrate-in-oil slurries and the slurry yield stress is measured after a prolonged shut-in period. The results demonstrate that hydrate-in-oil slurries are typically shear thinning, and the apparent viscosity of the system decreases as temperature increases. The flow curves are compared with current industry-leading models for the hydrate slurry, which deviate up to 50% from the measured values.