SILDRIL System: Solution to Bit Balling in the GLYDRIL System

Published: 10/30/2012

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Well Information
Location Buzzard Field, 19/10 - 1z, North Sea
Mud System GLYDRIL (KCl/ Glycol WBM)
Completion Date January 2002
Section Hole Size 8 1/2-in Sidetrack
Section Length 6987 ft tangent
Hole Angle 43º maximum

The Situation

The 8 1/2-in 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.

The 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.

SILDRIL – Solution to Bit Balling in the GLYDRIL System
Figure 1: Accretion model. The time is minutes of hot rolling.

The Results

  • 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.

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.


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.

“ Recent drilling in the Buzzard Field, operated by EnCana (U.K.) Limited, has provided several cases of extended periods of low rate of penetration attributed to bit-balling. During a suspected case of bit-balling whilst drilling Well 19/10 -1z, MI’s GLYDRIL† water based system was treated with sodium silicate liquor, resulting in an immediate increase in rate of penetration.”

Simon Gibb, Senior Account Manager

Questions? We’ll be glad to answer them.

If you’d like to know more about GLYDRIL or SILDRIL, please call the M-I SWACO office nearest you.

North Sea, United Kingdom, Europe, Onshore

Challenge: The 8 1/2-in directional assembly, drilling in the Buzzard Field, encountered low rates of penetration.

Solution: M-I SWACO provided an addition of 2% by volume of SILDRIL system into the GLYDRIL system.

Results: Penetration increased from 15 ft/h to 40 ft/h.

Products Used