Down-hole incident treatment and prevention for the 3000m scientific deep borehole in southern Hunan

Abstract:

The 3000m scientific deep borehole in southern Hunan is the first 3000m geological core drilling extra-deep hole in Hunan province. It is located in the transition zone of complex folds， and many complex formations， such as borehole shrinkage in clay， total hole leakage， water-sensitive collapse shrinkage and vertical joint development collapse， have been drilled， resulting in many down-hole incidents. In view of the main down-hole incidents such as bit sticking and hole collapse， the drilling structure， drilling fluid system and drill assembly were optimized， and various technical measures were adopted to effectively deal with various difficulties in drilling， such as sidetracking， circulating sand bailing， wall protection with film forming drilling fluid and wall protection with cement slurry. The final hole depth is 3008.93m， and the average core recovery rate is 98.16%， which has achieved the expected goal. Qualified geological boreholes and physical core data are provided for the theoretical study of deep mineral mineralization and resource exploration in this area.

Key words:complex formation;scientific drilling;deep drilling;vertical joints;low solid film-forming drilling fluid;incident treatment