Mud filter cake is a layer formed by solid particles in drilling mud against porous zones due to differential pressure between hydrostatic pressure and formation pressure. For the drilling operation, it is preferred to have a filter cake that is impermeable and thin. Practically, the filter cake from API or HTHP fluid loss test should be less than or equal to 1/16 inch. If drilling fluid is not in a good shape, which results in a thick filter cake in the wellbore, it will lead to a stuck pipe situation and high torque/drag.
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