In inclined wellbores, the drillpipe when not in motion will lie on the low side of the hole and penetrate the mud filter cake. The pipe section embedded in the filter cake is exposed to the filter-cake internal pressure while the rest of the pipe surface is exposed to mud pressure. Because of filtration, the filter-cake pore pressure underneath the embedded pipe begins to decrease. Differential pressure caused by the filter-cake-pressure decrease causes the pipe to stick. The force necessary to unstick the pipe depends on differential pressure and filter-cake strength. Filter-cake-pressure decrease depends on filter-cake permeability when compacted.