Methane hydrate phase behaviour in EMIM-Cl water based mud (WBM): An experimental and modelling study

摘要

Gas hydrate sediments are known as future energy source and potential technique for the storage CO2. However, the drilling of hydrate sediments are challenged with inappropriate drilling mud systems. Ionic liquids are introduced as novel drilling mud agents that can enhance the rheology of water-based mud and at the same time manage hydrate formation risk during hydrate sediments drilling. However, the disturbances of ionic liquid water-based mud filtrate on hydrate in-situ rocks is not well understood. To achieve this, the phase behaviour of methane hydrates in 1-Ethyl-3-methy-limidazolium chloride (EMIM-Cl) water-based mud at different EMIM-Cl concentrations were measured using the isochoric T-cycle technique in a high-pressure hydrate cell within the temperatures and pressures and ranges from 273.68 – 286.10 K and 3.60 – 9.70 MPa, respectively. The rheological properties of the EMIM-Cl mud systems were tested using a TA rheometer at 271.15 K – 313.15 K. The presence of EMIM-Cl had very minimal disturbances (less than 0.5 K shift) on methane hydrate at the studied concentrations. The disturbance of EMIM-Cl of methane hydrates in pure water system is reduced by 74% in drilling mud systems. The use of EMIM-Cl at 3 wt.% could reduce the methane hydrate disturbance effect 2 times as methanol. EMIM-Cl reduced the thermal degradation of the mud by 55% at 1 wt.% with very low viscosity. The viscosity reduction of the mud occurs at lower EMIM-Cl concentrations. Suggesting that, using ionic liquids water-based mud to drill hydrate sediments will reduce the risk of releasing compacted methane gas into the borehole while drilling. In addition, an attempt is made to predict the methane hydrate equilibrium curve in the presence of the EMIM-Cl using the Dickens and Quinby-Hunt, (1997) model.