Add some chemical components in oil based drilling fluid could optimize the performance of oil muds. The order of addition as listed below is the most common procedure for preparation of oil base muds, though each mud system may require some modification of this procedure.
Fluids with oil as the continuous phase and less than 10% water by volume, with any water forming an emulsion of water within the oil -- Oil Muds
The mixing time may vary depending upon the amount of shear either at the rig or at the liquid mud plant. Organophilic viscosifiers require considerable quantity of shear to fully develop their viscosity; therefore, more of this additive may be required on initial mixing. As the oil mud is used over the first couple of days, improvement in the emulsion stability and fluid loss control will vastly improve compared to what the mud was when it was initially mixed.
- Add the required quantity of base oil to the mixing mud tank.
- Add the primary emulsifier and secondary emulsifier as required.
- Add filtration control additives if required.
- Add lime as required.
- Add required amount of water to the above mixture. If brine is to be used, then add brine after the lime additions.
- Add organophilic viscosifier as required.
- Add calcium chloride powder if brine is not used. If calcium chloride powder is not available, then mix the calcium chloride flakes into the water and add as a brine.
- Mix above for several hours to ensure a good emulsion is formed.
- Add weighting material as required for the desired density.
The viscosity contributed by the organophilic gellant will be higher if it is added to the mud after the water is added and before the calcium chloride is added. If brine is used, then the is added after the brine and the viscosity will generally be lower. The electrical stability of the mud after mixing will be lower initially if brine is used instead of adding calcium chloride to the mud after the water is added.
The electrical stability and fluid loss control will improve after use due to the shear generated during circulation. The above mixing procedure will be suitable for most mud systems. The supplier’s mixing procedure should first be reviewed to determine if any variations in the above are to be employed.