Application of hollow-through DTH to completed strata and improvement of reverse-circulation drilling bit

Some problems in the process of drilling complicated stratum with hollow-through DHT,the improvement of reverse-circulation drilling bit was completed.Jet orifice had been added for air entry,only little air was got into the hole bottom,the most of air entered into internal pipe through the jet orifice,then was carried out from the hole bottom.The test shows that the improved bit is beneficial to reverse-circulation,and efficiency is satisfied.