Published: 09/26/2018
Published: 09/26/2018
An operator in the Norwegian sector of the North Sea planned a 2,383-ft [726-m] sidetrack through a narrow hydraulic window in an overburdened section of a mature field. Successfully drilling to the 7¾-in shoe required a cost-effective drilling fluid with enhanced sag stability and a sufficiently low rheological profile that would reduce the ECD in the tight operating conditions.
M-I SWACO, a Schlumberger company, suggested using the RheGuard system with MicroBar additive to drill the sidetrack and run the 7¾-in liner. The RheGuard system maintains low rheology and reduces the risk of barite sag for extended static periods during casing or liner runs, emergency disconnects, and planned long-term logging programs. Compared with conventional API barite, the uniquely engineered and cost-effective MicroBar additive optimizes rheologies and overall drilling performance.
The RheGuard system with MicroBar additive was used while drilling the 8½-in × 9½-in sidetrack to TD at 12,636-ft [3,851-m] MD and 10,061-ft [3,067-m] TVD. The 7¾-in liner was run and cemented without issues or losses. A programmed increase in the oil/water ratio (OWR) steadily decreased the rheological profile and ECD during drilling, and the RheGuard system maintained excellent hole cleaning. The system also generated sufficient viscosity to eliminate a sweep during the milling operation.
The system remained within the narrow hydraulic window throughout drilling and easily maintained optimized rheology while drilling the section to TD.
The fluid system field trial exceeded all KPIs, even when some contamination was discovered immediately after displacement.
The third-party MWD and directional services provider lauded the hole-cleaning performance and adaptability of the MicroBar additive. After completing the operation, the cementing engineer said the gels were easily broken, which made displacement optimal when performing the foam cement job.
Challenge: Enhance sag stability and reduce equivalent circulating density (ECD) while drilling a sidetrack in a mature offshore field.
Solution: Deploy RheGuard* flat rheology drilling fluid system formulated with MicroBar* micronized weighting additive.
Results: Exceeded KPIs by drilling to TD and successfully running and cementing liner without losses.
