of different oil based drilling fluids were then investigated with the epoxy cell method in which a voltage of 200 v was applied for a duration of 25 minutes these fluids were two different field samples of versaclean versaclean 1 and versaclean 2 and a further sample of versaclean 2 which has been centrifuged at 3000 rpm for 20 nm to remove barite measurements of the electrical stability and density of the untreated muds and of pv and yp before and after treatment are shown in table 1 fig4 shows a graph of the mass of the electrodeposit against voltage for each of the obms including the versaport obm this shows that the electrodeposit mass depends on the density of the mud suggesting that the fine particles attracted to the negative electrode tend to trap the barite the graph also shows that high voltages do not necessarily provide a greater electrodeposit for all the field muds the electrodeposit mass reached a maximum between 450 to 500 v the collection process becomes less efficient as the applied voltage approached the breakdown voltage of the api electrical stability test api 1988 possibly owing to a drop in the electric field experienced by the oil phase as chains of emulsion droplets begin to form prior.