STANDARD HANDBOOK OF PETROLEUM & NATURAL GAS ...

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WRIIATIONS PROBLEMS
Caving-
CSCOXSOLIDATED
S.L.DS ILKD GRAVELS
€Lm ROCK
Lost circulation.
Table 4-59
Drilling Fluids: Problems in Surface Drilling
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Retention of sand In mud. (Weight build UP. Sand retained
in mud will increase density, which may aggravate
tendency towards lost circulation).
E.asaive viscosity and gels, tight hole. sloughing. hydrous
disintegration.
Removal of cuttings from hole.
Pmum control.
Cement contamination.
CONTROL
Adequate gel strcnnth to consolidate loose and.
Maintain filtration rate below 15-cc API to prevent hydrous dislntesation
of shales.
Prevent erosion by adequate vidty and pel strength
Maintain sufficient viscosity for lifting cuttines d caving&
Maintain colloidal content to provide good tiltrafion prapertk.. low
density. and thick mud. Viscosity wll and lost circulation materials.
Care in usc of meehmlcal tauipment.
Low enouah viscosity and gels to allow sad to drop out in ditch and
{,its by reducinp viscosity and gels with water dilution and chemical
treatinent.
Ditch and pit arrangement may be improved to promote and settling.
Mechaiiical sand and shale separators or centrifugation may aid.
Reduce vivcosity and r*ls: reduce filtration rate to pmvent hydrous
disiutegration or slougliiny.
Maintain colloidal content high enough to pmyide gela md vidtfes
adeqiiate to remove cuttings or prevent settling.
Maintain sufficient annular velocity.
Weight mud to pive hydrostatic pressure above formation RrraUrC.
Maintain low visco.4ty and gels for gar removal.
Keep hole full at all times.
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If saving mud. thin with water and chemicals.
If not saving mud. discard contaminated mud and mix fresh mud.
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