It is significant especially for particles with a diameter of 5 �m and for particles which follow laminar flow conditions and slows down the process of filter cake formation, which prolongs the service life and the filtering stays permanently high.
22.
Bentonite is commonly used as an additive to control and maintain viscosity, and also has the additional benefit of forming a mud-cake ( also known as a filter cake ) on the bore-hole wall, preventing fluid invasion.
23.
Within industrial plants many substances with high proportion of solids-such as mechanically dewatered sewage sludges, filter cakes, bituminous coal sludges, waste and process sludges-have to be transported over relatively great distances to landfills or incineration plants.
24.
When the electrophoretic force " F E ", oppositely directed to flow, overruns the hydrodynamic resistance force " F W ", the charged particles migrate from the filter medium, thus reducing significantly the thickness of the filter cake on the membrane.
25.
For pre coat discharge, the solid output is approximately 2 to 40 gallons per hour per square foot . [ 5 ] Filtration efficiencies can also be improved in terms dryness of filter cake by significantly preventing filtrate liquid from getting stuck in the filter drum during filtration phase.
26.
A key difference is that perforating penetrates through the first 6-18 inches ( 15 45 cm ) of formation around the wellbore, whilst openhole completions require the reservoir fluids to flow through all of the filtrate-invaded zone around the wellbore and lift-off of the mud filter cake.
27.
Modifying the Darcy s basic equation, describing filter cake formation, with electro-kinetic effects by integration under assumption of using the constants of electro-osmotic pressure " P e ", the critical electric field " E " krit and the electric field " E " results:
