If you work in the drilling or completion sector of the oil and gas industry, you probably heard about something called fishing.
Not all drilling and intervention operations go as planned and sometimes pieces of equipment or tools might end up falling into the well.
In addition, sometimes downhole tools break apart or get stuck in the well.
In most cases, before the well can be put on production, these pieces of equipment and tools have to be retrieved from the well.
The process of retrieving things from the well is called fishing and the tools left downhole are called fish.
Types of Fish
Common types of fish are parts of the drilling and milling motorhead assemblies, parts of the drill string or wireline, and tools that were unintentionally dropped into the well.
Retrieval of the coiled tubing or drilling strings after it was cut at the surface due to stuck-in-hole situations or string failures is also called fishing.
Read next: What is Wireline in Oil and Gas?
How Fishing is Performed?
Often coiled tubing is used for fishing operations.
The coiled tubing rig uses a long flexible metal pipe that is spooled on a reel to retrieve the tools left downhole.
The type of downhole tools used to retrieve the fish highly depends on the shape and size of the fish.
Some examples of the downhole fishing tools are:
Overshoot – this tool grabs the outside surface of the fish
Spear – this tool grips the inside of the fish
Magnet – can be used to retrieve small metal pieces from the well
Washover – a circular mill that is used to clean the top of the fish
Mill – can be used to change the shape of the fish to make it easier to retrieve it
Often before the fish is retrieved, its top is washed and an impression block or even camera is used to get a better understanding of what fishing tool should be used.
Usually, it takes more than one try to retrieve the fish from the well.
What makes things even more challenging is that you don’t always know whether you got the fish or not until you pulled the pipe to the surface.
In some cases, downhole sensors can be added to the fishing bottom hole assembly to make the fishing job easier.
This is usually done in combination with an e-coil which is a coiled tubing string that has an electrical cable inside.
This way the data from the downhole sensors can be sent to the surface and used to make real-time decisions during the fishing operation.
Read next: What is Coiled Tubing?