Performadril® high-performance, water-based mud system delivers superior shale inhibition in Nahr Umr and Laffan formationsDownload PDF
Enable effective hole cleaning in a large-bore interval
A major offshore operator faced continuous challenges drilling the 20-inch interval through troublesome shale formations. When using conventional water-based mud (WBM) and a competitor’s high-performance water-based mud (HPWBM), a low rate of penetration (ROP) and balling tendencies were experienced with these fluid systems. Excessive back-reaming was required on trips through the reactive and mechanically unstable shales that resulted in further destabilization of the wellbore and occasional pack-off events. The operator required an alternative fluid formulation to drill the Nahr Umr and Laffan shales without incurring non-productive time (NPT) and with optimal ROP.
The large hole size planned through unstable clay conditions posed several challenges to drilling engineers. A highly inhibitive, water-based mud would be needed to maintain wellbore stability, especially when navigating the anticipated 16-degree inclination. The large hole size would also cause low annular velocities and present hole-cleaning issues, impacting the overall well delivery results.
The Halliburton Baroid Technical Team initially performed an in-depth review of suitable fluid technologies. Extensive laboratory testing was performed to evaluate the swelling, dispersion, and accretion tendencies of the Nahr Umr and Laffan shales in candidate formulations. The customized PERFORMADRIL® fluid system with BaraSeal® W-1040 sealing agent exhibited optimal test results, with 2.1% dispersion and 2% accretion tendency. Before being deployed, the PERFORMADRIL fluid was also stress tested against London Clay and achieved <3% accretion. BaraSeal W-1040 was added to PERFORMADRIL to minimize filtrate invasion and further stabilize the Nahr Umr and Laffan formations. Detailed DFG® Drill Ahead hydraulics modeling was performed during the well planning and execution phases. Finally, BAROLIFT® sweeps were employed as a supplemental hole-cleaning strategy through the interval.
Increase in ROP
Estimated savings for 10 days of rig time
Reduction in pack-off events
Increase in tripping speeds
The 11.9 ppg PERFORMADRIL fluid system was successfully deployed, and the 20-inch section was drilled to target depth. The benefits of this innovative system compared to legacy applications can be summarized as follows:
The operator was satisfied with the outstanding performance of Baroid’s customized PERFORMADRIL plus BaraSeal W-1040 formulation, as efficiency improvements resulted in an estimated savings of 10 days of rig time, with a value of $1.5 million.
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