Schlumberger

Performance Report: SILDRIL – Solution to Bit Balling in the GLYDRIL System

Challenge:

The 8½“ directional assembly, drilling in the Buzzard Field, encountered low rates of penetration upon entry into the Rodby Claystone Formation. Rates dropped to below 10ft/hr, despite efforts to alter the drilling parameters. The assembly was pulled on two occasions where the bit found to be balled with compacted claystone.

Different Pills of KCL brine, Nutplug, GLYDRILL and caustic proved ineffective in improving penetration rates. Following a further trip to replace a failed mud motor and a continued rate of penetration of only 15ft/hr, it was decided to introduce silicate to the circulating GLYDRIL system.

Solution:

Additional inhibition of the system may slow down the accretion process by slowing down the rate at which the shales hydrate hence remain in a plastic state longer. M-I provided an addition of 2% by volume of SILDRIL into the GLYDRIL System.

A pilot test with 5% by volume of sodium silicate liquor showed an unacceptable increase in the system rheology.

Result:

  • When SILDRIL treated GLYDRIL mud reached the bit, the penetration increased from +/-15ft/hr to +/-40ft/hr.
  • As drilling continued into the Kimmeridge Clay, silicate concentration had depleted to around 1.0%, but penetration rates remained at +/-50ft/hr.

Well Information
Location Buzzard Field, 19/10 - 1z, North Sea
Mud System GLYDRIL (KCl/ Glycol WBM)
Completion Date January 2002
Section Hole Size 8½“ Sidetrack
Section Length 6987 ft tangent
Hole Angle 43º maximum

Silicate Benefits

  • Cost effective solution to bit-balling with a GLYDRIL system. 
  • Successful concentrations have only minor influence on GLYDRIL system properties. 
  • Category E rating, environmentally friendly.

About SILDRIL

SILDRIL (M-I’s Sodium Silicate Liquor) is the primary constituent of MI’s highly effective water based SILDRIL system, but has proved effective as a simple addition to MI’s GLYDRIL system to cure bit-balling.

Sodium Silicate Liquor can be used in a range of concentrations and has a HOCNS category E, so is therefore environmentally friendly, and facilitates full discharge to the sea.


Download: SILDRIL – Solution to Bit Balling in the GLYDRIL System (0.30 MB PDF)

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