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.