Drilling technology for massive overburden at high altitude in Luobusa Chromite Mine， Tibet

Abstract:

The Luobusa Chromite Mine in Tibet is characterized by high altitude， thick overburden， complex geological conditions， broken rock strata， developed fractures， local water dissolution， water erosion and water sensitivity， leading to some drilling problems such as formation leakage and borehole shrinkage. This paper summarizes the drilling experiences from 28 medium and deep boreholes in this area in respect of drilling structure， drilling technology， drilling fluid， wall protection and plugging technology， technical measures taken in complex situations， etc. Good results have been achieved with all index meeting the design requirements. The core recovery rate is more than 90%， the rig-month efficiency is 555m， and all quality indicators meet the design requirements.

Key words:deep prospecting;core drilling;massive overburden;complex formation;wall protection and plugging