The addition of components in their proper sequence when initial mixing an oil mud will optimize the performance of each product. 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. 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.
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 gellant 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.
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