Carbon dioxide/calcium oxide responsive behavior and application potential of amine emulsion

Green and low cost CO2 and CaO were used to stimulate amine emulsions to reveal the responsive behavior of amine emulsions. On this basis, oil-based drilling fluids responsive to CO2 and CaO were formulated and their properties were evaluated. The results showed that the amine emulsions inversed from water-in-oil state to oil-in-water state readily and their rheological behavior underwent transitions of decreasing, rising again and decreasing again via induction by CO2. These CO2 responsive behaviors could be reversed by CaO. Oil-based drilling fluids prepared based on the amine emulsions with oil-water volume ratios of 50:50 to 70:30, densities of 1.4–2.0 g/cm3 had good rheological and filtration properties at 160 °C; and be readily cleaned up using CO2 bubbling. The useless solid phase with low density could be removed efficiently via reducing the viscosity of emulsion by CO2 and the residual liquid phase could be restored to the original state by CaO and reused to prepare drilling fluid. The mechanisms analysis indicated that CO2/CaO induced the reversible conversion between amine emulsifiers and their salts, which enabled the reversible regulation of both the hydrophilic-lipophilic balance of amine emulsifiers and the emulsion particles' size and finally caused the controllable-reversion of the form and rheology of amine emulsion.