Bentonite vs Polymer for drilling 2

[pelelo]

Engineers,

I was wondering what are the advantages of using either of these materials for drilling.

In my geotechnical practice, all the drillers have used bentonite.

Please advise.

 

[GeoEnvGuy]

I have found that polymer is required for drilling in loose saturated tailings as the bentonite influences the soil sample and the lab actually characterizes a plasticity index between 4 and 7. Surface samples and augered holes that probably suffered from some heave indicate no plasticity.

 

[MTNClimber]

Specialized polymer can work better when drilling in salt water environments. I've seen drillers use bentonite drilling on the water but it still resulted in running sands. An expensive guar gum polymer was used in the same applications with considerably less or no sand blowing into the casing. It also required less drilling fluid maintenance while advancing each hole, resulting in saved drilling time (days) which offset the cost of the polymer (about $250 per bucket cost/$400 per bucket charged by the drilling co.). Each bucket would last about 1.5-2 holes with the holes being drilled down to 175' below mudline/200' below high tide.

As far as working on land, my experience has been that it just depends on the driller's preference. The best drillers I've seen use mud and know how to properly mix and maintain it resulting in great production. Sometimes its too good to the point where I can't keep up with them.