RELEASABLE SPEAR Russian patent published in 2006 - IPC E21B31/18 

FIELD: well drilling and repair, particularly fishing tools adapted to engage and remove broken pipe string section from well.

SUBSTANCE: spear comprises telescopic body with inner and outer parts connected one to another so that the parts may perform limited movement in axial direction. The outer part is provided with thrust end. The spear also has collet with expanding ring installed on the collet and performing limited downward movement along recess limited by conical surface from above so that expanding ring may abut the thrust end in released position. The collet is provided with through channel in which seat is arranged by means of shear member. The seat is adapted to receive ball dropped from well head. The collet is telescopically installed so that the collet may be axially moved into body. Outer body part is provided with hydraulic cylinder located from cylinder top. Inner body part has piston with a number of lower radial channels, which form hydraulic chamber along with hydraulic cylinder. The hydraulic chamber is hydraulically communicated with pipe string interior.

EFFECT: increased workability and reduced loads applied to equipment.

2 dwg