17/05/2026
A thorough borehole survey leads to a successful borehole….
*Loose, unconsolidated formations* can’t support themselves, so they need extra stabilization to prevent caving.
*Key requirements:*
*Stabilize the hole*
Use bentonite mud, polymer mud, or foam to create a filter cake and hydrostatic pressure. Control viscosity to suspend cuttings without causing lost circulation.
*Manage casing*
Advance casing immediately behind the bit, use temporary casing if needed, and grout the annulus once casing is set to seal the zone.
*Adjust drilling methods*
Drill slower, use low pump pressure, and avoid air drilling. Switch to air-foam or use casing if air is required.
*Adapt sampling & logging*
Expect disturbed samples and use split spoon, Shelby tube, or triple tube core barrels. Run geophysical logs after casing is set since open holes often cave.
*Follow safety practices*
Watch for bridging and stuck pipe, control pressure to prevent blowouts, and never leave the hole unsupported.
*Rule of thumb:* If the formation can’t stand unsupported for 30 seconds, treat it as loose and stabilize it immediately.
