Session: 11-02-02 Well Drilling Fluids & Hydraulics

Submission Number: 156972

CO2 Hydrate Inhibition in Drilling Fluids Using Mono-Ethylene Glycol 

Carbon capture and storage (CCS) has been identified as a part of the solution to the climate crisis, but to play a major role, a massive scale-up is required. This will inevitably lead to a need to drill wells into existing CO2 storage formations, and consequently, the risk of well control incidents where the influx from the formation into the well is dominated by CO2.

One of the main concerns associated with these incidents is the potential formation of CO2-hydrates caused by Joule-Thomson cooling when the CO2-loaded drilling fluid is subject to pressure drop as it is circulated out of the wellbore or when flowing through topside valves. In order to prevent the formation of hydrates, inhibitors such as mono-ethylene glycol (MEG) are added to the drilling fluid. 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 characterise 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 order to shed light on these aspects, 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 a selected WBDF.

Lab results on drilling fluid- MEG mixtures loaded with CO2 are presented along with considerations on rheology modelling aspects. Further, it is discussed how a software tool including impact from MEG in the drilling fluid may contribute to reduce the risks related to primary barrier integrity related to drilling of CO2 infill wells.

Presenting Author: Elie Ngouamba SINTEF

Presenting Author Biography: Dr. Elie Ngouamba is a researcher in the Drilling and Well Group at SINTEF in Norway. He holds a PhD in fluid mechanics and his current research area is drilling and well materials. He is involved in several research projects on the use of materials as well barriers for P&A and CCS.