岩层物性对自锁式取心工具岩心抓卡心的影响

自锁式取心工具是一种适应于硬地层的常规取心工具,使用的岩心抓形式为摩擦式,卡心功能主要靠岩心抓与岩心之间的摩擦力来实现的,通过对自锁式卡心机构力学分析及实践表明,当岩心抓与岩心之间的摩擦系数小于岩心抓卡紧岩心所需的最小摩擦系数时容易掉心; 当钻具上提力所产生的最大拉应力先达到岩心抗拉强度,而最大剪应力尚未达到岩心抗剪强度时,岩心被正常割断,反之,则岩心发生剪切破坏——撸心,当岩心比较细,岩心直径小于或接近岩心抓闭合尺寸时,岩心滑脱。

INFLUENCE OF ROCK PERFORMANCE ON SELF-LOCKING CORE CATCHER WORKING

Self-locking coring tool is a kind of conventional hard formation coring tool.The core catcher employed belongs to friction type.Its core grip function is mainly achieved by the friction force produced between the core and the core catcher during pick up the whole drill strings.The mechanical analysis on the core grip structure and the coring practice indicated that:If the friction coefficient between the core and the core catcher is less than the minimum level needed by the core cutting operation,the core is likely to be lost into the hole;If the string pull force reaches the core’s tensile strength firstly and the maximum shearing strain has not reached the core’s shearing strength yet at the same time,the core will be cut normally,whereas,the core will be damaged.If the core becomes thin and the core diameter is close to the full closure size of the core catcher,the core will be lost into the hole too.