What Does Filter Cake Mean?
A filter cake is a layer of drilling fluid that lines a borehole to prevent fluids from entering the surrounding soil. The drilling fluid creates a thin layer that cakes the borehole so that permeation of the native soil is reduced or eliminated.
A good filter cake is important for successful drilling in the trenchless construction industry.
Trenchlesspedia Explains Filter Cake
Drilling fluid, or slurry, is usually made of bentonite clay. The qualities of bentonite are ideal for inclusion in the semi-liquid slurry. One of the functions of drilling fluid is to coat the walls of a borehole. This serves to create a thin barrier between the drilling operation and the ground outside the borehole.
A 1999 post on Trenchless Technology Magazine’s website discusses the properties of drilling fluid. Under a section called “filtration control,” the writer describes how a good filter cake is an essential part of filtration control. Filter cakes are measured in 32nd’s of an inch.