Geothermal Well Drilling
Drilling Through Rock
Once the drill hits rock it's time for a different bit. The rock bit relies more on compressed air to bang it into the rock. At the same time the bit turns, removing some rock. Some water is pumped in at the same time to clear out the hole.
For our two wells they would be drilling 300 feet down. That's the length of a football field.
Once the special rock bit is attached the drilling process is pretty redundant. The pipes are continually attached as they go deeper and deeper. The drill grinds and bangs away the rock, which is then forced to the surface.
At about 100 feet the drillers hit water, which made the whole process much wetter and messier. On the second day they brought a special truck to deal with the water.
To drill, they connect the bit to one of the long pipes and slowly drill through the ground. When they reach the end of one pipe, another piece of pipe is connected. They keep adding pipes until the desired depth is reached.
In the image above, the drillers are adding sections of pipe to the drill so they can go deeper. Eventually they will have 300 feet of pipe in the well with the drill bit on the end.
During drilling, a balance between bit pressure, water, and air pressure must be maintained to get an efficient and stable well cut.