Difficulties and countermeasures of core drilling in complex strata in high altitude working area of Xizang

Abstract:

Xizang Luobusha working area is located at a high altitude with complex geological conditions， featuring fractured rock layers and significant fissure development， resulting in poor formation stability and drilling challenges such as strata fragmentation， leakage， and shrinkage. This paper focuses on the construction practice of medium-deep holes designed to a depth of 800 m in this working area， summarizing the construction process in extremely complex formations dominated by fractured chlorite petrified olivine， which suffer from severe leakage and frequent shrinkage. To address core challenges such as personnel shortages， special equipment assembly requirements， hole wall instability caused by severe leakage， flushing fluid contamination and failure， and frequent shrinkage leading to stuck bits， the key technologies were systematically summarized， including innovative combination technologies of drilling rigs and drill towers， optimization of flushing fluid systems based on dynamic plugging and anti-contamination formulations， casing protection combined with periodic drilling and hole sweeping to prevent shrinkage， and phased dynamic personnel adjustment and rapid training models. Through practical verification， this drilling operation successfully overcame various difficulties and completed the hole smoothly. The case study provides technical reference and management experience for core drilling under similar conditions of high altitude and complex strata.