An operator drilling through the lower Bunter sands experienced extreme overbalance (greater than 6800 psi) severe cavings and excessive washout (11-15-in. hole diameter). In previous wells, the operator used conventional bridging materials (over 76 lb/bbl) creating a challenge of controlling drilling fluid rheology.
Impact worked with the operator to define the two KPI’s – sealing the depleted sands and improving drilling fluid properties. Impact suggested the use of 6 lb/bbl FLC 2000 to prevent hole washout, increase the mud density and drill through the problematic interval (5 7⁄8-in. section from 15,583 to 16,236 feet).
The 5 7⁄8-in. section was drilled with a gauge hole and the drilling fluids properties were improved by the use of 6 lb/bbl of FLC 2000, compared to the 76 lb/bbl conventional bridging material. Impact met the operator’s KPI’s by sealing the depleted sands and improving the drilling fluids solids loading. Five successful wells have been drilled to date.