REAMING STABILISERS
Use of reaming stabilisers provide the cleanest and straightest hole, as the reamer stabilisers or centralises the bit and the drill string in the hole. Parallel mis-alignment is caused by the use of small drill pipes and collars (in relation to the hole size) and NO stabilisation. The bit can move off centre until the drill string OD contacts the wall of the hole. Apart from the problems involved when attempting to log, run casing, cement, complete and test, bit life is drastically reduced and rate of penetration is slowed, as rings of uncut bottom develop due to drilling off centre. For best results, stabilisers should be between 3 mm and 6mm (1/8" and ¼") less in diameter than the drill bit.
The first stabiliser should be positioned as close as possible behind the drill bit with the next stabiliser following the first or second rigid drill collar.
