(107c) CFD Modeling of Electrically-Enhanced Oil-Gas Separators

Oil and gas production is often accompanied by water and the separation of these phases becomes a necessity.  Chemical de-emulsification and heat treatment have been widely applied methods to address this separation issue and these processes are time consuming, require injection of chemicals and the output could still have a water content of 5 – 10%. This separation limit is further overcome by using other techniques like coalescers where small water droplets are forced to coalesce with each other to form larger fast settling droplets. If the average droplet size is doubled, separation time decreases by a factor of four. An electrocoalescer takes advantage of the conducting nature of the water droplets and can reduce the water content to under 0.5%. In the presence of an electric field, these conducting water droplets become dipoles whose electric charges, in sufficiently high field strength, can overcome the repulsive surface-surface interactions, resulting in oil film drainage and consecutive coalescence. It follows that a fundamental quantitative understanding of water droplets’ dynamics in electric field is very crucial in understanding and improving the operational envelope of this technology. In this work, the behavior of an isolated uncharged conducting drop in external electric field is simulated using CFD. The Navier-Stokes system augmented with Maxwell’s stress and Maxwell’s equations constitute the governing equations, which are solved using Galerkin finite element analysis. Drop dynamics, deformation, total charge & dipole-dipole interaction of water droplets as a function of applied field strength are discussed.