Abstract:Circulation lost is a difficult problem in drilling construction, especially in wire-line core drilling. Severe circulation lost may lead low drilling efficiency and high construction cost, directly threaten the drilling safety and even result in drill hole abandoned. Aus-Plug was an effective delay expansion drilling plugging agent introduced in 2006, by which the circulation lost was well controlled. Since 2003, according to the different formations and lost situations encountered in the tests and construction in a number of mines and through years of practice, the hazards of circulation lost and some plugging methods were explored and summed up; and the practical and effective methods to deal with circulation lost in different geological conditions by Aus-Plug plugging agent also were summarized.