•Foaming occurs due to high interfacial surface tension phenomena or mechanical air entrapment.
•Most foaming occurs on the surface and normally does not adversely affect the mud.
•If the foam or air bubbles become dispersed throughout the mud, the pump may stroke in an erratic manner, which could cause serious mechanical damages
•Air leak in mud pump
•The discharges of the desilter/desanderor mud hopper can whip air into the mud.
•High chloride content in mud.
–Salt water muds have an inherent tendency to foam.
•Lignosulfonateshave a tendency to foam, especially in high concentrations.
Causes •Over treatment of mud detergents. •Air entrapped in drill pipe after tripping. •High pressure-low volume formations or swabbing when tripping may cause the mud to become gas cut. •Thick mud containing a large amount of drilled solids are particularly susceptible to foaming. •Bacteria fermentation of the mud.
•The mud has to be thinned in order to permit effective removal and prevent a build-up of foam.
–Lower the viscosity, YP and in particular the Gel Strengths with dispersants (Desco) or Lignite as required to allow the foam to dissipate.
•Alcohol base defoamersor Aluminum Sterate(oil soluble only; mix with diesel oil) may be added directly into the suction tank.
•Avoid air leaks in pumps and suctions.
Prevent whipping air into mud.
–Submerge all surface guns, hopper and solids control equipment discharges.
•"Roll" the tanks with the submerged guns to allow the air or gas bubbles to escape into the atmosphere.
•If a wash gun is available, spray the surface of the mud with a fine spray of diesel or water.