Analysis of CO2 Hydrates in Crude Oils from a Rheological Point of View

Abstract

Gas hydrates are crystalline solids formed by water and light molecules when a specific thermodynamic condition of high pressure and low temperature is attained. The formation of such structures can plug the production line, causing a shutdown with expensive consequences. In fact, besides waxy deposition, gas hydrate formation is among the hugest problems in flow assurance faced by oil companies. High concentrations of CO2 have been reported in the Brazilian presalt oil wells, with large potential to form hydrates, but to our knowledge, this kind of scenario has not been the subject of a deep rheological study. Here, we conduct a sequence of tests, using a high-pressure rheometer system, to take into account the effects of the water fraction and shear rate on the hydrate formation. We also investigate the ability of reconstruction of the hydrates and its memory effect. The main tests are displayed in terms of viscosity over time. By doing so, the hydrate formation is indicated by a viscosity jump.