Definition - What does Fluid Assisted mean?
Fluid-assisted drilling can be defined as the use of bentonite-based lubricant for the purpose of drilling through the soil. The entire drilling operation is fluid-assisted and is crucial for the operation. Aside from lubricating and transporting cuttings back to the surface, the drilling fluid also provides stability to the borehole.
Trenchless methods of drilling such as horizontal directional drilling (HDD) make use of lubricants for the entire process of drilling.
Trenchlesspedia explains Fluid Assisted
Bentonite mixed with soil is made into slurry and introduced into the drilling process. As the drilling progresses, the slurry assists the drill bit by softening the surrounding soil while also acting as a coolant to the drill bit.
The circulation allows for drill cuttings to be transported back to the surface. A slurry collection chamber allows the cuttings to settle and recirculates the lubricant back into the system. The circulating fluid also acts as a support to the wall of the borehole so that it doesn't collapse.
In soft soil, fluid-assisted drilling works well, but in difficult soil conditions, fluid-assisted drilling may not be sufficient and may require the use of percussive impacting to assist the drilling process.