Abstract: During drilling process of Hemei-3 well,there were 8leakages in 360~1 030 m well interval and the total loss of drilling fluid was up to 100 m3.Through optimization of water slurry system,the low density and ultra low density cement slurry system containing toughened specialty fibers of leakproof and leakproof material have been matched for cementing,which can effectively prevent lost circulation and be of good cementing quality.The successful application of this ultra low density cement slurry in Hemei-3 well can provide a strong technical support for a large area of coalbed methane development in this block.