| 摘要 |
A downhole lock contains a housing 4 and a burst or rupture disc 5. A moveable mandrel 15 is held in place by a shear screw 17, locating in a groove on an inner sleeve 8. The mandrel 15, fishing neck 1 and housing 4 form an upper hydrostatic chamber 18 of a piston assembly. A lower hydrostatic chamber 19 is formed by the housing 4, rupture disc 5 and mandrel 15. Spring 9 biases the inner mandrel 12 upwards, with shear screw 17 preventing the mandrel 15 moving and inadvertently activating the keys 11 of the locking mechanism. A predetermined well pressure is defined to activate the lock via the rupture disc. A thread 20 is used to connect the lock to accessories and hence to the central conduit, by which means the lock assembly is conveyed to the appropriate point in the well tubing string. The lock does not require the use of a dedicated running tool. |
