Case Study: SILDRIL Gives Top Performance in High-Angle Well


After setting 13⅜” casing at 1,490’, the operator wanted to drill directionally to 85º to prepare drilling horizontally into a narrow sand reservoir. The target was crucial. The operator wanted to install a submersible pump and run a pre-packed screen completion. There was no room for error.

The formation to be drilled was highly reactive Tertiary shales interbedded with unconsolidated sands. To drill this interval successfully would require a high degree of inhibition and optimal hole cleaning. The correct rheology profile was required to avoid washing out the unconsolidated sands at angles ± 60º.


Based on tests performed in Aberdeen and extensive computer modelling from offset data, a SILDRIL water-base mud, containing 5.0% by volume SILDRIL L, was recommended as the preferred system. It was to be the first time that the SILDRIL system would be used to drill to an extreme high angle well.


  • Fast Drilling: The interval was drilled and cased off in five days.
  • All Objectives Met: All targets were achieved. The reservoir was drilled, as planned, through 2,500’ of sand. Completion and testing were successful.
  • Excellent Lubricity - Additions of up to 3.5 % by volume of silicate lubricant reduced the average coefficient of friction from 0.39 to 0.25.

Well Information
Location Central North Sea
Spud / Completion June 16 1998 / Oct 15 1998
Interval Drilled 12¼” hole section: total length, 2,613’
Interval Max Density 9.7 lb / gal
Deviation Vertical to 85º

Benefits of the SILDRIL system

  • Resulted in Fast Drilling
  • Achieved Objectives
  • Provided Excellent Lubricity
  • Reduced Costs

Download: SILDRIL Gives Top Performance in High-Angle Well (0.24 MB PDF)

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