When oil wells are drilled through the producing formation in the customary manner, with the use of an aqueous mud fluid, it commonly occurs that a mud sheath is left on the wall of the hole. The drilling fluid adjacent porous formations is likely to lose water by absorption and thus to become densely packed and consolidated, forming a barrier to the subsequent flow of oil into the hole.
It is customary to remove as much of this barrier as possible before putting the well on production, as for example by simple washing through the perforationswith streams of water, by the use of acid (which tends to fiocculate the cake) and by the use of water softening agents.
The removal of the mud sheath from the walls of the hole on zones to be cemented is also desired so as to insure a good seal between the wall and the cement. The complete breaking up of the mud sheath by dehydrating agents, preceding cementing operations, will allow a successful seal between the wall and the cement.
A successful cementing operation is not possible without a clean mud removal process. The remained mud in the well bore can cause significant problems in the isolation process. Non proper mud removal has the following consequences: causing corrosion, underground blowouts, stimulation out of zone, production of unpredicted fluids and chemicals.