CO2 Hydrate Inhibition in Drilling Fluids Using Mono-Ethylene Glycol

Abstract Mono-ethylene glycol (MEG) is added to drilling fluid as an inhibitor, to prevent the formation of hydrates. While most studies of MEG as hydrate inhibitor have considered natural gas hydrates, MEG is also a natural candidate for CCS infill wells alleviating risk for CO2 hydrates. In addition to the CO2 inhibition performance it is of crucial importance to characterize how MEG may affect the drilling fluid important properties. This especially concerns rheology and drilling fluid robustness towards degradation, which is crucial in maintaining the fluid column as a barrier against influx from the formation, as well as in keeping the desired flow properties. In this paper, MEG effectiveness as an inhibitor of CO2 hydrate formation is first demonstrated for a reference fluid (NaCl brine) and then studied for different concentrations of MEG with measurements of rheology and studies of robustness for selected water-based drilling fluid.