Fishing Assemblies and tools


fishingFishing Assemblies and tools.Fishing is the general term used to describe the special techniques that are employed to recover items or equipment from downhole. Details of tools, equipment, and procedures are included in this section.

1. Standard fishing assembly:

Overshot - Fishing bumper sub - DC - fishing jar - DC's - Accelerator - HWDP.

This configuration may be modified to suit particular conditions.

The number of drill collars depends on what is available and what may be already downhole. To achieve the maximum jarring effect, the amount of drill collars in the fishing assembly should equal the amount of those already downhole.

With an accelerator in the fishing assembly the number of drill collars may be substantially reduced. An accelerator is recommended for all fishing. Additional information can be found in the manufacturers literature (e.g. Bowen).

A safety joint shall not be run while fishing, because safety joints are likely to freeze when jarred. However, a full opening safety joint (drive joint made for jarring) may be used when a wash-over string is run. This full opening safety joint is run below the standard fishing assembly so that internal cutters may be run when the wash-over string sticks and has to be backed off.

Detailed drawings of the fishing assembly shall be made and kept, before the assembly is run. Tools with restricted ID's shall not be run.

If penetration rates were high when a twist-off occurred, circulate the hole clean before pulling out. Also circulate as required before latching on to the fish and avoid tagging the top of the fish        prematurely.

A spiral grapple should be used whenever possible in preference to a basket grapple.

If an overshot is run after the fish has been milled over, then always run an extension so that the          grapple can catch onto unmilled pipe.

In a washed out hole if a standard fishing assembly fails to locate the top of the fish, then attempts     should be made using either a bent single or a wall hook.

2  Fishing Tools and Equipment

2.1 Reverse Circulating Junk Basket

When using a reverse circulating junk basket it is important to tag the bottom gently and then rotate slowly with the pump on to get junk into the centre of the hole. Gradually increase weight to 2 - 3 MT rotating with 45 rpm and circulating 1000 l/min (250 gpm). Core approximately 0.1 m (4 in) then pick up off bottom and circulate at a high rate back to the bottom before pulling out.

It is essential that a high circulation rate is maintained to ensure sufficient jetting action is generated at the tool to maintain the reverse circulation mode. Do not add an extension below the jets of a reverse circulating junk basket.

Before running the tool, carefully measure the distance from the bottom to the lower fingers to ensure that there is sufficient distance so that when coring, the top of the core does not come into contact with the fingers.

Check that the ball used to divert the flow through the nozzles will pass through the drill string, (i.e.: circulating sub, etc.).

2.2 Core Basket

If a core basket is run then make sure that after it is made up the catcher fingers can rotate freely. Check that the correct size of basket is used for the junk in the hole.

2.3 Hydraulic Junk Retriever

The (A.D.T.) hydraulic junk retriever is another tool that uses fingers to catch junk. It is capable of retrieving both large (bit cones) and very small (ball bearings) items of junk, and it can even be run on wireline.

The concept of the tool is that hydraulically operated interlocking finger sleeves completely close off the bottom of the tool, and literally scoop up the junk being fished. The normal method of cutting a small core can also be performed.

2.4 Spears

a) The standard spear assembly comprises:

Spear - Spear stop - Fishing bumper sub - DC's - HWDP.

Note: The spear must be equipped with a pack-off rubber when circulation is required.

If the first attempt did not succeed, include a fishing jar above the bumper sub, and an accelerator.

To prevent stabbing in too deep and to make release easier while also allowing resetting of the jars, a stop-ring or spear-stop must be spaced into the assembly. The distance from the stop-ring to both the 7" and 9 5/8" spears is 1 - 2 m.

Check the spear-stop OD when it is run in open hole and use the stop only if hole conditions permit.

b) When engaging the spear, always make sure that a tool joint is at a workable distance above the rotary table. This may require using pup joints.

c) If the spear has to be released and knocking down on it does not free it, then install the surface jar (with a 1.25 m stroke) below the kelly and jar down on the spear. The 1.25 m surface jar and 1 m fishing bumper sub are recommended, as this combination enables the bumper sub to close completely before the surface jar has reached the end of its stroke.

2.5 Standard Fishing Tools

The following standard tools shall always be available on the rig:

  • Overshots and oversized guides with grapples, baskets and extension subs to catch all size of tools in the hole.
  • Hydraulic jars to match the drill collar string in use.
  • Fishing bumper subs (with 1 m stroke) to match the drill collar string in use.
  • Bowen surface jar to match the drill pipe in use.
  • Accelerator to match the hydraulic jar in use.
  • Reverse and straight circulating baskets for hole sizes required.
  • Junk subs for hole sizes required.
  • Magnets to be able to fish in 18 3/4" (476 mm) BOP stack and in subsequent casing strings (i.e. 1 x 12", 1 x 10", 1 x 8" and 1 x 5" magnet).
  • Casing spears (when running casing) complete with stop-rings and pack-off assemblies for each casing weight used.
  • Fishing tools to catch electric wireline tools; to be supplied by the Logging Contractor.
  • 5 7/8" junk mill when drilling 6" holes, and 8" (203 mm) junk mill when drilling 8 1/2" holes.
  • Die-collar, taper tap, and tubing spear, when using tubing.

2.6 Wash Over String

The standard wash-over string comprises:

Washover shoe - wash over pipe - drive sub - safety joint- bumper sub - fishing jar - DC's - Accelerator - HWDP

E.g. the following equipment is required for a wash-over string for 8 1/2" hole:

  • 2 pcs 8 1/8" x 6 5/8"" wash-over shoe with 7 5/8" extra line box.
  • x joints 7 5/8" extra line pin x 4 1/2" IF box drive sub.
  • 1 pc full bore 4 1/2" pin x box safety joint.
  • x pcs lifting plugs for wash-over pipe.
  • x pcs hardfacing to redress wash-over shoes.
  • Handling tools for 7 5/8" extra line pipe; e.g. elevators, pick up elevator, slips, tongs, safety-clamp, etc.

Note: The above equipment is suitable for washing over gravel-pack assemblies used inside 8 1/2" hole or 9 5/8" casing. The number of wash-over joints required depends on the length of the  gravel pack assembly. This equipment is not normally kept on board as routine.



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