During the drill , compress air goes into the annular through the air box, then the debris go up in the inner hole under the effect of waterhead.It is the air lift reverse circulation.
Compared with the direct circulation,it is more fast because the debris goes up from the inner hole under the low friction.The well will be more cleaned,so the drill efficiency will be improved.
It is widely used in the waterwell drilling of complex stratum with big diameter hole, such as the gas let well, coal rescue well, coal bed gas well and shale gas well.
It is unfit for the dry and loss stratum drilling.
