Impression block Definition
A block with lead or another relatively soft material on its bottom. it is made up of drill pipe or tubing at the surface, run into a well, and set down on the object that has been lost in the well. the block is retrieved and the impression is examined. the impression is a mirror image of the top of the fish and indicates the fish’s position in the hole, i.e., whether it is centered or off to one side. from this information, the correct fishing tool can be selected.
Related Oil & Gas Terms
Safety joint
An accessory to a fishing tool, placed above it. if the tool cannot be disengaged from the fish, the safety joint permits easy disengagement of the string of pipe above the safety joint. thus, part of the safety joint and the tool attached to the fish remain in the hole and become part of the...
Mechanical jar
A percussion tool operated mechanically to give an upward thrust to a fish by the sudden release of a tripping device inside the tool. if the fish can e freed by an upward blow, the mechanical jar can be very effective. also called a hydraulic jar....
Overshot
A fishing tool that is attached to tubing or drill pipe and lowered over the outside wall of pipe or sucker rods lost or stuck in the wellbore. a friction device in the overshot, usually either a basket or as spiral grapple, firmly grips the pipe, allowing the fish to be pulled from the hole....
Bumper sub
A percussion tool run on a fishing string to jar downward or upward on a stuck fish to knock it free. the bumper sub body moves up and down on a mandrel....
Taper tap
A tap with a gradually decreasing diameter from the top. it is used to retrieve a hollow fish such as a drill collar and is the male counterpart of a die collar. the taper tap is run into a hollow fish and rotated to cut enough threads to provide a finn grip and permit the...
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