Dynamic Viscosity of Methane and Carbon Dioxide Hydrate Systems from Pure Water at High-Pressure Driving Forces

TL;DR

This study measures the viscosity of methane and carbon dioxide hydrate systems at high pressure, revealing the effects of temperature and pressure, and introduces rheological phase diagrams to better understand hydrate formation conditions.

Contribution

It provides new high-pressure viscosity data and develops rheological phase diagrams, highlighting conditions where hydrate formation is kinetically or thermodynamically hindered.

Findings

Viscosity increases with temperature more than pressure in most cases.

Carbon dioxide systems show higher pressure sensitivity due to greater solubility.

High driving forces do not always lead to hydrate formation due to kinetic and diffusion limitations.

Abstract

The viscosity of methane and carbon dioxide hydrate systems were measured using a high-pressure rheometer up to 30 MPag. Where hydrate formation was not detected, the effect of temperature on the viscosity was one order of magnitude higher than the pressure effect on viscosity in most of the experimental pressure range (-0.048 mPa s/C at 1 MPag and 0.009 mPa s/MPag at 2C). The pressure effect on the viscosity of carbon dioxide systems where no hydrate formation was observed was up to one order of magnitude higher than that of the methane systems, due to carbon dioxide's higher solubility in water. Novel rheological phases diagrams were developed to further characterize the gas hydrate systems. Several systems with high driving forces for hydrate formation (2.07 MPag to 4.1 MPag) did not form gas hydrates. System limitations to the formation of hydrates were categorized as kinetic, mass diffusion, and/or heat of crystallization effects.