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An operator drilling through the Keathley Canyon, a field known for severe losses and highly-depleted sands, wanted to prevent wellbore instability issues, including lost circulation events. In this particular area in the Gulf of Mexico, offset wells experienced pore pressures as low as 8.0 lb/gal. The operator required a higher mud weight below the salt formation but wanted to avoid induced lost circulation due to these higher mud weights. High mud losses were anticipated when exiting the salt, due to a rubble zone below. The operators anticipated multiple loss zones throughout the production interval.
Effective concentrations of STAR SHIELD Wellbore Shielding additive was engineered into the drilling fluid system before entering the production interval. The concentration of STAR SHIELD was 8 lb/bbl without adverse effects on rheology and equivalent circulating density (ECD). The integration of STAR SHIELD allowed for the extension of the frac gradient window, to create a shield against the fluid-rock interface.
The adoption of STAR SHIELD helped enable the operator to drill their first infill well to total depth (TD) without utilizing a drilling liner/casing string to cover the base of the salt. The operator drilled through the depleted sand sections from 16,278-ft. measured depth (MD) and 15,690-ft. true vertical depth (TVD), to 17,661-ft. (MD) 16,939-ft. (TVD) with a mud weight of 12.3 lb/gal without fluid loss to the formation. STAR SHIELD helped to extend the mud weight as high as 0.5 lb/gal over the anticipated fracture gradient with zero losses. The operator drilled to TD, ran production casing to bottom, and cemented the well with full returns.