西部侏罗系砂岩饱和-泥浆包裹磨蚀特性研究OA

To address the abnormal tool wear and low drilling efficiency in the construction of vertical wells in Jurassic coal mines in the western region,Cerchar abrasion tests were conducted on weakly cemented sandstone under three conditions:dry,saturated,and mud-saturated states.These experiments,alongside tests of the fundamental physical and mechanical properties of the rock,aimed to explore the correlations between changes in abrasion characteristics and tool wear,elucidating the reasons for abnormal tool wear and discussing abrasion efficiency under different conditions.The main findings are as follows:(1)Compared with the dry state,the internal cementitious materials of sandstone are compromised after water and mud saturation,resulting in varying degrees of strength and hardness reduction.The Cerchar Abrasivity Index(CAI)decreases by 9.62%in mud saturation and by 19.23%in saturation.(2)The penetration depth of the steel needle in sandstone under both saturated conditions ranges 1.05 mm,significantly higher than the 0.6 mm observed in the dry state.Due to internal structural damage,particles in contact with the needle are more prone to detachment,leading to lower wear than in the dry state.The wear in mud-saturated conditions exceeds that in saturated conditions.(3)The abrasion efficiency of sandstone in the dry state is only 1/10 that of the saturated state,while in mud-saturated conditions,it is approximately 1/5 of the saturated state.Based on these findings,it is recommended to optimize the mud-slurry properties and enhance the cleaning of the drill bit in practical engineering to mitigate abnormal tool wear.