drilling term â€“ the wall cake that forms from the platelets in bentonite-based drilling mud. Filter cake is the barrier between the borehole and the formation, limiting the amount of drilling mud needed to complete the borehole.
A filter cake is formed by the substances that are retained in or on a filter (depending on whether a depth or a surface filter is used). The filter cake grows in the course of filtration, becomes "thicker" as particulate matter is being retained. With increasing layer thickness the flow resistance of the filter cake increases.