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On a four-well pad, an operator drilled the intermediate section of the first well and experienced significant non-productive time (NPT) due to large mud losses in the depleted Mission Canyon Sand. Drilling fluid losses occurred while setting intermediate casing and during cementing, leading to two-stage cement jobs. Also, the cement bond log (CBL) indicated cement did not cover the Dakota Sand. This issue required operator spend time and additional costs in remedial work to satisfy North Dakota’s requirement to place sufficient cement to cover the Dakota Sand.
To prevent mud losses and reduce NPT, STAR SHIELD was initiated at 6 lb/bbl in the active system 500-ft. above the depleted Mission Canyon in the second well on the pad. Hourly treatments were initiated while drilling the depleted Mission Canyon and STAR SHIELD concentration was increased to 8 lb/bbl throughout the interval with no losses to the formation. CBL logs indicated sufficient cement across the Dakota Sands satisfying the state’s requirements.
The operator drilled the intermediate section, through the depleted Mission Canyon with no losses and no wellbore instability issues. The intermediate casing was set with full returns. Also, a single-stage cement job was performed with full returns and the operator achieved a successful CBL across the Dakota Sand.
STAR SHIELD was adopted on the next two wells on the same pad with positive results.