Deep hole core drilling technology and accident treatment in Chating copper polymetallic mining area

Abstract:

To address the problems of tight schedule and frequent accidents in deep-hole core drilling in the Chating copper polymetallic mining area， the mechanisms of downhole accidents such as out-of-tolerance borehole deviation， casing fall-off， drill pipe fracture， and bit burning were analyzed in combination with the formation conditions and engineering practice of the mining area. A total of 62 boreholes were designed， with depths of 1000~2000 m， a total drilling footage of 96240 m， and an exploration spacing of 50 m. Three-spud and four-spud borehole structures were adopted according to hole depth； impregnated diamond bits and bentonite/KCl polymer-sulfonate staged drilling fluid systems were used； and drilling parameters were optimized. The results show that spudding-in before foundation solidification， improper casing placement， and human operational errors were the main causes of accidents. After the application of treatment techniques such as directional deviation correction with a positive displacement motor， artificial bottom hole with a cement plug， hole reaming， casing isolation of chloritic rock， reverse-thread drill pipe fishing， milling and jointing， and wire rope fishing without an inner tube， the drift angle of borehole ZK4503 decreased from 4.82° at 700 m to 0.4° at 1000 m， and drilling in borehole ZK4714 was resumed after 46 days of treatment for multiple downhole accidents. Spudding-in quality directly determines the effectiveness of deep-hole drilling， and high-quality spudding-in can reduce non-drilling time by 15%~30%. This study provides an engineering reference for deep-hole core drilling in this mining area and mining areas with similar conditions.