Peh: Drilling Problems and Solutions Publication Information Petroleum Engineering Handbook

Drilled Cuttings. Excessive drilled-cuttings accumulation in the annular space caused by
improper cleaning of the hole can cause mechanical pipe sticking, particularly in directional-
well drilling. The settling of a large amount of suspended cuttings to the bottom when the pump
is shut down or the downward sliding of a stationary-formed cuttings bed on the low side of a
directional well can pack a bottomhole assembly (BHA), which causes pipe sticking. In
directional-well drilling, a stationary cuttings bed may form on the low side of the borehole (see
Fig. 10.2). If this condition exists while tripping out, it is very likely that pipe sticking will occur.
This is why it is a common field practice to circulate bottom up several times with the drill bit off
bottom to flush out any cuttings bed that may be present before making a trip. Increases in
torque/drag and sometimes in circulating drillpipe pressure are indications of large
accumulations of cuttings in the annulus and of potential pipe-sticking problems. 
Fig. 10.2—Mechanical pipe sticking caused
by drilled cuttings: (a) cuttings bed during
drilling, and (b) cuttings jamming the drill bit
during tripping out.
Borehole Instability. This topic is addressed in Sec. 10.6; however, it is important to mention
briefly the pipe-sticking issues associated with the borehole-instability problems. The most
troublesome issue is that of drilling shale. Depending on mud composition and mud weight,
shale can slough in or plastically flow inward, which causes mechanical pipe sticking. In all
formation types, the use of a mud that is too low in weight can lead to the collapse of the hole,
which can cause mechanical pipe sticking. Also, when drilling through salt that exhibits plastic
behavior under overburden pressure, if mud weight is not high enough, the salt has the
tendency of flowing inward, which causes mechanical pipe sticking. Indications of a potential
pipe-sticking problem caused by borehole instability are a rise in circulating drillpipe pressure,