RELEASING MECHANICAL SPEAR Russian patent published in 2002 - IPC

FIELD: drilling and repairs of wells, particularly, fishing tools designed for catching and withdrawal from well of broken-off part of pipe string. SUBSTANCE: spear body is telescopic, its internal and external parts are spring-loaded and have splined joint. Internal surface of body external part has bore and stop end face. Spear has two expanding rings installed on spring-loaded collet and on external surface of body internal part with possibility of stop of collet in position of expansion of the first ring, and the second, into bore, respectively. Collet is installed to thrust into body internal part. Operation of spear releasing mechanism is possible only after lowering, fishing and unsuccessful lifting of emergency string. Use of the given releasing mechanical spear allows reduction of expenditures for its manufacture due to its simple design and avoidance of unproductive round-trip operations associated with false operation of spear releasing mechanism in its lowering into well and in process of fishing of emergency string. EFFECT: simple design, higher efficiency of offered releasing mechanical spear. 4 dwg