Fishing Tools

NExTNExT

Introduction To Fishing

Ricky J. BohannonSchlumberger IPMWellsite Training Supervisor

2 Initials04/18/23 NExTNExT

Fishing Tools and their Uses

• At the end of this lecture, YOU will be able to;

1. State and be able to Identify different types of fishing tools.

2. Understand the components of the fishing tools and how they work.

3. Be able to select the right tools for the job


Defining the Fishing Job

• When faced with a fishing job, there is certain information about the fish and the wellbore that is crucial to succeed.

• A good wellsite supervisor will know at all times all down hole tool information and have it recorded.


• This would include the lengths,OD’s, ID’s, and fishing necks of all down hole equipment.

• The string and tools limitations as well as hours each tool would have accumulated at the time of the fishing problem

• These things should be kept on the well site by the WSS and the toolpusher and the driller should always know what is in the hole and where.


• How ever sometimes this isn’t always the case and some things might not be known and it may be necessary to take a bit of time to discover the missing data


Information about The Fish


Lead Impression Block


If you find after the impression block has been pulled that the fish is not smooth enough to work with, then the possibilty of running a mill in the hole to clean off the fish would be the next course of action.

• Total weight of fish• Is the fish clean and will you be able to

circulate through it• Last casing details• Last recorded Depth• Any wash outs that are known or possible


• Drilling fluids in the wellbore• Formation Litho logy at the point of the fish• Is there a possibility the fish could be

stuck, differentially or by other means.• The possibility of being packed off by

cuttings or cavings

You should always make a diagram of the well bore and the fish to give a visual mental picture. Below is a diagram of a fish from a well in Lithuania


Taper Tap diagram

.67

Genciu Nafta G8H Re- entry

.46

O.D. 4.6875

O.D. 3.92”

O.D. 1.85”

O.D. 3.03”

O.D. 3.43”

O.D. 2.16”O.D. 2.63”


Designing A Fishing Strategy• You can only use those tools that you have

available. In some areas tools can be sent to the wellsite pretty quickly, in other areas you will be limited to those tools already on the rig (or that you can build on the rig). Generally, a rig contract stipulates that the Drilling Contractor (the owner of the rig) shall provide sufficient fishing tools and consumables to latch on to the outside of all tubulars.


• It may also stipulate that other tools are kept available, such as fishing jars, mills, etc.

• Listed below are five classifications of fishing tools. All currently available tools can be put in to one of these categories. The type of fish and it's situation in the hole will dictate which can be used and will also determine which of those has the greatest chance of success.


• It is important that all the people on the rig who have knowledge of the well, the fish and of fishing operations be consulted for advice.

• This means that you should talk to the Drillers, Toolpusher and Fishing Tool Supervisor. By using their knowledge you might be presented with an idea which you wouldn't otherwise have thought of.

• Note all the possible approaches and rank them in order of preference.


If a fishing supervisor is on the rig then generally he will run the fishing operation, after consulting with (and while reporting to) the Drilling Supervisor. On some operations, no fishing supervisor will be present and a simple fishing job might just be done by the Well site Supervisor, Toolpusher, or Driller.

• A good competent Driller is quite capable of carrying out a straightforward fishing job. While fishing, keep a complete record of everything that is run in to the hole and a detailed record of exactly what happens .


• Fishing decisions, like most rig decisions, have an economic impact. In other words, you have to ask yourself when it will cost less to stop fishing and take alternative actions. Generally your alternative actions are limited to;

• 1.Put cement on top of the fish and sidetrack around it.

• 2.Abandon the well.• 3.Occasionally you might have the option

to complete the well on a higher zone or to convert the use of the well.


Chapter summary• This chapter covered the following topics.

• Information required about the fish

• Information required about the well

• Determining a fishing strategy


Classifications of fishing tool• There are five classifications given below, each

tool is put in to a category depending on it's primary mode of operation.

• Examples of each tool classification will be given. Each classification will be covered in detail in separate slides.

• The examples below do not constitute a complete list of all tools available for Fishing.

• Different tools and the knowledge of such will depend on the experience and help of your fishing tool supervisor.


Classification 1- Outside catch(Overshots)

• When fishing for tubulars which have an outside diameter which is significantly less than the hole diameter, such as drillpipe, drill collars or tubing, an outside catch tool will be the most common choice.

• Outside catch tools are very strong, normally you will be limited by the strength of the drillpipe and not the strength of the tool. If the top of the fish is straight and not badly damaged, outside catch tools can easily move over and grip the fish.


There are two tools in this category, the Overshot and the

Die Collar.


Overshot• An overshot consists of a barrel, inside is a

special helical profile which is shaped like a wedge. Into this profile fits a grapple with teeth on the inside. The teeth catch on the fish and as tension is applied is applied, the wedge shaped helical profile causes the grapple to grip tighter --- just like a set of slips in the rotary table. The more you pull, the tighter the grapple grips the fish.


• An overshot also gets tighter if you rotate it to the left, so it is possible with an overshot to apply left hand torque and back off a connection lower down in the fish. Conversely, rotating to the right causes the overshot to release the fish so it can be easily released downhole.


• An overshot is generally the tool of choice because;

• It is tremendously strong and will allow very high pulls on the fish, even if a jar is used to hammer on the fish. It can be released downhole by right hand torque.

• It can be used to apply left hand torque to the fish to potentially back off down hole.


• Latching on with an overshot does not cause serious damage to the fish and so other tools could be attempted after an overshot.

• The overshot can include a packoff element to seal around the outside of the fish to allow circulation through the fish (unless the fish itself is plugged).


Bowen series 70 circulating overshot, cutaway drawing with

Spiral Grapple


Overshot With Spiral Grapple


Die collar

• A die collar is like an inverted cone with threads on the inside. It is lowered on top of the fish and turned

• to the right; the inside threads cut in to the top of the fish. Compared to an overshot, a die collar has some significant disadvantages;


• It does not increase it's grip with higher pulls.• The older model with grooves cut in the

threads (see photo below) does not seal around the fish.


Cut away drawing of Die collars, with straight

guide shoe (middle) and spiral

guide shoe (right)


• Modern die collars do not have these grooves and so can allow circulation through the fish.

• It cannot be released from the fish downhole, so a safety joint must be run above the die collar..


Classification 2 - Inside catch


• Inside catch tools pass through the inside diameter of a tubular fish and latch on by one of several mechanisms.

• Inside catch tools have one big disadvantage when compared to Overshots, they tend to be weaker (they have to be small to get inside the fish).

• Inside catch tools are generally only used when it is not possible to run an outside catch tool; if the clearance between the fish and the hole is too small, for example.

• Three tools are included in this category; the Releasing Spear, Taper Tap and Packer Picker.


• The Releasing Spear is just an overshot in reverse.

• A steel mandrel supports a slip cone which has a wedge shaped helical profile on the outside. Positioned around this mandrel is a set of slip elements, with teeth on the outside. When run inside the fish, the slips press against the fish inside diameter with some friction.

• When the drillstring is picked up, this friction will try to keep the gripping elements still while the mandrel moves up. As it moves up, the wedge shapes of the matching profiles (outside of slip cone & inside of elements) will push the slip elements outwards.


Releasing Spear


• The more pull is applied, the harder the slips get pushed against the ID of the fish.

• The spear is usually released by right hand rotation of the drillstring.

• Releasing spears are usually used for fishing casing out of the hole.


Taper Tap

• A Taper Tap is a die collar in reverse. It has similar disadvantages to a die collar; cannot be released downhole (except by breaking the tool or stripping the threads) and is weaker than a releasing spear.

• Modern taper taps do not have the longitudinal grooves that old style taps had and so it can be used to circulate through the fish.


Old fashioned type Taper Tap with

longitudinal grooves


Packer Picker

• Also known as a "Packer Milling and Retrieval Tool"' the Packer Picker can mill and retrieve a downhole permanent packer in a single run, once the tubing above the packer is fished. The packer has a hole through the centre (to allow fluids to flow through it) and a special spear first goes through this hole.

• A milling shoe contacts the top of the packer and it mills down the outside of the packer, until the slips are released or destroyed. Once the packer slips no longer grip the casing, the packer will fall but will be caught by the spear.


Packer Picker Diagram


Classification 3 - Washover and basket tools

• The first two classifications dealt with tubular fish, such as drillpipe or drillcollars. Washover and basket tools are used to fish miscellaneous pieces of junk out of the hole. These pieces range in size from pretty small (tungsten carbide teeth from a TCI bit, or tong dies, for instance) to large enough to cover a large part of the bottom of the hole (cones from a drillbit).

• Many of these tools use the movement of drilling fluid to "wash" pieces in to a container.


• Or a barrel may be run over the fish and the bottom of the barrel closed beneath the junk to trap the pieces inside.

• Also included in this classification is the Fishing Magnet, which can be run on wireline or drillpipe, to recover ferrous metal junk.


Magnet


Tools using movement of fluid to trap junk

• Several tools fall into this category under Classification 3. The Jet Junk Retriever is run in and a ball is dropped. This ball diverts flow down the string to outside the tool and diverts flow coming up the inside of the tool back to the annulus. In this way, reverse circulation outside the tool can wash junk up past spring-loaded fingers which close behind the junk. This will catch larger pieces of junk such as drill bit cones (see the diagram below).


Jet Junk Basket or Reverse circulating Basket


• Another tool in this category is the Boot Basket. This is run in on a drilling assembly and can catch small bits of junk, such as insert bit teeth. If a PDC bit run is anticipated, a Boot Basket might be run above the previous bit so that the bottom of the hole should be free of any small bits of junk which can damage PDC cutters.


Tools using a barrel to go over pieces of junk

• There are several tools that aim to trap junk inside a barrel. A "poorboy" finger basket tool may be made on the rig with a piece of tubing or casing of a suitable size. The bottom end has slots cut in it and the resulting "fingers" of metal are bent slightly in and rounded off. This is run in the hole and, when on bottom, is carefully rotated and weight sat down on it. The fingers bend in and close up, trapping junk inside. See the picture below.


Poorboy Finger Basket


• A hydraulic tool which works on a similar principle is available. When on bottom, a ball is dropped on to a seat and pressure is applied on the drillstring. This moves a piston down which forces a set of fingers to move over a ramp, which closes the fingers together. In soft formations, it is possible to cut a small core off the bottom with this tool.

• There is also a basket with a mill shoe on the bottom and spring loaded fingers inside, which is designed to cut a small core on bottom and recover a bit of core and the junk in one go. This would not work in hard formations.


Reverse Circulating basket with Mill Shoe Guide


Fishing Magnet

• If run on pipe, circulation below the magnet is possible through holes. This allows settled cuttings to be

• blown off the junk. To work, the magnet must be able to touch, or get within an inch or so, of the junk.

• You can run this on wireline if your well bore is in good shape and a wireline unit is easily available at shallow depths.


Fishing Magnet Diagram


Classification 4 - Fishing for Wireline

• Fishing for wireline is a painful and tedious job at best. If a wireline tool is stuck in the hole and the wire is still intact, it is possible to hold the wire at surface and strip over it with drillpipe, guiding a special overshot to the wireline tool.

• When pulling back out of the hole, the wire has to be cut every stand so it's a long, slow job and creates lots of mess on the rig.


• In wireline fishing you need a good wireline supervisor and good communication skills, as well as a good unit operator.

• You could possibly loose the well in this operation depending on the experience of the wireline group.

• If the wireline is broken and down the hole, a rope spear is used which has barbs sticking out of the side.


• This is run on drillcollars to below the top of the wireline and rotated a few times. This winds the wireline on to the spear around the barbs. When pulling back out of the hole, the wireline tool is often recovered too.


Classification 5 Milling, drilling and smashing

junk• In softer formations and larger hole sizes,

miscellaneous junk (even as large as drill bit cones) can be pushed in to the side of the hole by a mill tooth bit and never seen again! Of all drill bit types, only a mill tooth bit is capable of drilling on loose junk without getting badly damaged though even a mill tooth bit can be damaged if used on junk with high bit weights or rotary speeds.


• There are two different types of mill available for milling away junk. In cased hole, a mill with stabilizer pads and a smooth OD is used so as not to damage the casing. In open hole, no stabilizer pads are used and the mill OD should be rough (capable of cutting) and in size should be equal to or slightly smaller than the drift diameter of the casing in the hole.

• It is very important not to run too much weight on a mill (most people run too much weight) and a good rule of thumb is 1,000 lbs per inch of mill diameter.


• A 12" mill should be run with about 12,000 lbs, though of course conditions and therefore milling parameters will vary. If loose junk is in the hole, use a flat bottomed mill. For junk that will not roll around (e.g. stuck pipe) then use a concave profile on bottom.


• If junk on bottom is large or oddly shaped so that it cannot be recovered with washover or basket tools, it can be broken up with a Jet Bottom hole Cutter. The cutter can be run on wireline or pipe.

• This is a shaped explosive charge which focuses the explosive energy downwards. Once the large junk is broken up, it may then be possible to recover it using conventional fishing tools, or drill on it with a mill tooth bit (use a boot basket above the bit), or mill it up.


Chapter summary

• If junk on bottom is large or oddly shaped so that it cannot be recovered with washover or basket tools, it can be broken up with a Jet Bottom hole Cutter. The cutter can be run on wireline or pipe.

• This is a shaped explosive charge which focuses the explosive energy downwards. Once the large junk is broken up, it may then be possible to recover it using conventional fishing tools, or drill on it with a mill tooth bit (use a boot basket above the bit), or mill it up.


Fishing economics• Fishing economics are probally the most

important part of a fishing job and the most over looked as well.

• Almost all drilling operational decisions ultimately have an economic basis; "what is the most cost effective way to proceed?".

• However when we talk of cost effectiveness, we need to look at the whole equation. We might make a decision to change the mud properties for drilling the reservoir and save a few thousand (or a few hundred thousand) dollars in mud costs but if that decision reduces the well productivity.


• Then overall, that decision will have been a very bad one because the well will earn millions of dollars less than it could have done. So it is with fishing; you have available several courses of action.

• Which one will ultimately be the most cost effective?

• When faced with a fishing job, there are some high-level choices possible. These will most likely come down to:


• 1.Try to fish the junk.• 2.Set cement on top of the fish and sidetrack

around it. This may not be an option if the fish contains a radioactive source; in many areas, Government regulations forbid or make it very difficult to abandon radioactive sources.

• 3.Finish the well higher than originally planned for. This will rarely be possible; perhaps if the well is at TD and the top of the fish does not prevent the well from reaching it's primary objectives.

• 4.Abandon the well (either to start drilling a replacement well or to abandon the well without spudding another).


• Now except in rare cases, the available options will be either to fish (or to continue fishing) or to sidetrack the well.

• Therefore the decision comes down to whether the cost of fishing is likely to be less than the cost of sidetracking. We have to introduce probability into the decision making process.


• The probability of a fishing job succeeding decreases with time. The best chance to get the fish lies on the first attempt. With time, wellbore conditions deteriorate (making the fish harder to remove), the condition of the fish will deteriorate (as you try to latch it with different tools) and the remaining alternative fishing strategies reduce as you try different methods. In general, fishing should be abandoned if the first attempt to latch on to it does not succeed, UNLESS you gain information during this first attempt which leads you to believe that the chances will be better on a second attempt.


• The decision on whether to fish and if so for how long can be calculated by using probabilities multiplied by costs to give the Effective Monetary Value of the various decisions. This can be done using an IPM designed spreadsheet.

• Most Operators have a spread sheet but the field hands don’t use them.

Fishing Tools

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