An operator requested Impact’s Technology Center perform comparative tests for two low weight drilling fluids (9.5 lb/gal water-based mud (WBM) and 9.5 lb/gal oil-based mud (OBM)). The drilling fluids incorporated STAR SHIELD 3000 and were tested on elongated slots alongside a conventional lost circulation material (LCM) to determine the most effective sealing product. These tests supported the use of STAR SHIELD 3000 in the active circulating system.
Wells drilled near Arnett, Oklahoma in Ellis County are known to have prolific drilling fluid losses in both the intermediate and production sections. While drilling the intermediate section through the Brown Dolomite, the operator consistently experienced lost circulation issues and would have to set intermediate casing near 6000-ft. When drilling the curve and horizontal section with OBM, the operator would experience seepage and total losses. The operator wanted to prevent lost circulation issues in both sections and eliminate the intermediate casing string, drilling from surface set, at 2000-ft, to total depth (TD) at 15,000-ft.
The operator approved the recommendation fromImpact’s Technology Center to drill the intermediate interval (Brown Dolomite section) with a light-weight WBM incorporating 6 lb/bbl STAR SHIELD 3000 and 6 lb/bbl conventional LCM. The operator then drilled the production section with an OBM incorporating 5 lb/bbl STAR SHIELD and mixed a standby pill treated with 15 lb/bbl STAR SHIELD 3000 and 15 lb/bbl LCM to be used in sweeps if losses were experienced.
The operator drilled to the intermediate interval (Brown Dolomite) with fresh water and displaced the well with a WBM system incorporating 6 lb/bbl STAR SHIELD 3000 and 6 lb/bbl conventional LCM. The operator drilled to the intermediate TD at 6040-ft without losing drilling fluid.
The operator wireline logged, ran intermediate casing, and cemented without losses.
The operator displaced the cement with OBM and 5 lb/bbl STAR SHIELD wellbore stability additive. An 80-bbl pill was mixed with 15 lb/bbl STAR SHIELD 3000 and 15 lb/bbl LCM and stored to be used in sweeps if lost circulation was encountered.
When drilling and sliding at 7282-ft the operator encountered 10 bbl/hr seepage losses. The operator pumped a pill consisting of 30 lb/bbl of the STAR SHIELD 3000 and LCM. Losses stopped after the pill cleared the bit.
At 12,213-ft after tripping for a new lateral assembly, the operator calculated a loss of 30 bbls during the trip and was experiencing seepage losses at 10 bbl/hr. The operator pumped another 30 bbl STAR SHIELD 3000 and LCM pill, which stopped the losses once the pill cleared the bit.
At 14,052-ft the operator encountered losses at 204 bbl/hr. It was decided to pump a 35 bbl STAR SHIELD 3000 and LCM pill and losses slowed to 140 bbl/hr. The operator pumped another 35 bbl STAR SHIELD 3000 and LCM pill and losses slowed to 10 bbl/hr. Once they were back in the rotation, losses stopped. The operator drilled to TD at 15,035-ft. ran 5½-in. production casing with no issues, and cemented with full returns.