The blind box is used when heavy downward jarring is required to dislodge a fish or push something down the hole. It is flat on the bottom and hardened to reduce wear and damage.
Blind boxes are available in a range of sizes to suit the application and dimensions of the completion through which it is to be run.
When used as a cutter bar, it is made up below some stem and a rope socket then dropped in the well bore to cut wire down hole
The
impression block or lead impression block (LIB) is similar in appearance to the
blind box, but it is filled with lead. The lead is keyed in position by a roll
pin or a hex headed bolt that is installed prior to pouring molten lead inside
the housing. The impression block is used to obtain a picture (impression) of
the component creating the down hole blockage or obstruction. The information
gained is used in selecting an appropriate fishing tool assembly. To prepare
the impression block, roughly flatten the lead face with a hammer, then smooth
with a course rasp. Finish with a smooth file and a piece of steel shear stock
rubbed across the face to give a polished surface. There should be no
indentations in the surface prior to running and a check should be made to
ensure there are no overlapping edges that may hang up in the collars when
pulling out and dislodge or distort the lead. When refilling the impression
block, always melt the previous lead out and replace in a continuous pour.
Stopping and restarting will create a weak flaw, which could separate down hole.
In operation, the impression block should be positioned on the obstruction and
one jar down only applied to obtain one clear image. Subsequent jarring may
cause multiple impressions that will confuse the image.
The
tubing end locator is used to locate the end of the tubing string to provide a
cross-reference or correlation check of the tool string depth against known
tubing depth references. The end locator is also used to correlate the tag sand
depth accurately from the bottom of the tubing (depth known from completion
records). The tool may be fitted with more than one shear pin position to
enable the same tool to be run in different size tubing strings. Since the tool
operates on a one-shot basis, care should be taken to ensure the pin is not
accidentally sheared, e.g., take care pulling the tubing end locator up into
the lubricator. After the tubing end locator is started in the hole, it must be
run out the bottom of the tubing string, so that the loaded finger trips to the
horizontal position. Pick-up to tag the tubing end and obtain the tubing end
depth reference. A subsequent jar-up action shears the 3/16 in. brass pin below
the finger and allows the tool to be removed from the well bore.
The rope socket is used to make the connection between the slickline and tool string. Several types are commonly found, selection generally being dependent
on slickline size and type:
0.092 in. slickline – Disc & Spring type.
0.092 in., 0.108 in., 0.125 in. slickline - Pear drop (brass & wedge) type.
Sometimes referred to as sinker
bar, stem is used to provide additional weight to the tool string which may be required to run into the well bore against high-pressure and stuffing box friction.
Increasing the stem weight
increases the impact force delivered by a jar.
Flats for wrenches are provided
and should be used, never grip on the fishing neck or this will damage the sharp edges.
All connections should be clean
and dry. Do not lubricate down hole threads since they may unscrew down hole during extended jarring.
The stem is available in standard
lengths of 2 ft, 3 ft and 5 ft.
A
swaging tool is used to restore lightly collapsed or distorted damage to the
tubing string. The OD of the swage should be equal to the tubing drift. To
operate the swage, down- jars are required to force the swage through the
tubing damage. To ensure recovery of the tool string, up-jars should also be
included in the event the swage becomes jammed. The fluid bypass hole permits
the passage of fluid when the OD of the swage fills the tubing ID.
