Retrievable gravel packer and retrieving tool

A retrievable gravel packer and retrieving tool therefor. The gravel packer includes an inner mandrel assembly attached to an operating tool by a left-hand threaded connection. The packer is set without rotation by the operating tool to move a pusher sleeve downwardly with respect to the mandrel, compressing a packer element and setting slips into engagement with a well bore. A ratchet prevents the pusher sleeve assembly from moving upwardly with respect to the mandrel. The packer may be retrieved by the retrieving tool which has a lower collet engagable with a releasing mandrel in the packer. After releasing collets held by the releasing mandrel, the inner mandrel of the packer is released so that the packer element and slips engaged by the mandrel are disengaged from the well bore. An upper collet in the retrieving tool engages the left-hand thread in the packer mandrel so that the packer and retrieving tool may be raised out of the well bore. If the packer becomes jammed and cannot be retrieved in this manner, the retrieving tool may be further raised so that the lower collet in the retrieving tool is released from the releasing mandrel in the packer. The packer includes antirotation pins so that is can be easily milled out of the well bore.