Preparation Of Reversible Invert Emulsion And Its Transition Mechanism

Due to the massive increase in natural gas and oil demand all over the world,several technologies have been utilized in drilling and completion processes.The natural gas and oil production have been improved by drilling with environmentally friendly fluids,such as invert emulsion.In this work,the preparation of reversible invert emulsion and the performance of acid and base in the reversibility of the emulsion obtained using amine surfactant(C₁₈H₃₉N),oilfield emulsifier,and SKALN 5#white oil are reported.Several properties of the prepared emulsion,such as electrical stability,conductivity,viscosity and droplet size distribution are studied to understand the transition mechanism.The influence of several factors,including emulsifier concentration,stirring time,intensity,temperature,and acid and base fraction volume have been investigated.The results indicates that the stability of the prepared emulsion depends much on various factors such as emulsifier concentration,stirring time,intensity and temperature.The optimum emulsifier concentration for the preparation of the w/o emulsion using amine surfactant and an oilfield emulsifier were found to be 0.33%and 0.44%while stirring time are 20 min and 40 min,respectively.Different acids,hydrochloric（HCl）,formic（HCOOH）,acetic（CH₃COOH）,acrylic（CH₂CHCOOH）and sulfuric（H₂SO₄）acids,were used for phase inversion.All acids converted w/o into o/w emulsion,except for sulfuric acid in the emulsion stabilized by amine surfactant.Reversibility from invert to the regular emulsion is achieved with a low amount of acid such as 0.1%of 5 wt%.In the presence of an excess base such as（5 wt%of NaOH,Ca（OH）₂ or Na₂CO₃）solution,an invert emulsion can be obtained.The protonation and deprotonation mechanism of the emulsifiers were monitored through changes of pH,and microstructure of the emulsion.