Technical Improvements and Application of Air-lift Reverse Circulation Drilling Technology to Ultra-deep Geothermal Well

Air-lift reverse circulation drilling technology is often used in geothermal well drilling, but there are many problems along with drilling depth increasing, such as double-wall drill pipe leaking, air-water mixer blocked, water way of bit blocked, Kelly bearing capacity insufficient, small ratio of tail pipe length and double-wall drilling pipe. These problems were thoroughly solved based on continuous technical innovation during geothermal well drilling practices. Using advanced air-lift reverse circulation drilling technology, the depth of drilled borehole was up to 4,200 meters, the deepest record in China.