is the technology of removing any undesirable object from the wellbore.
The " fish " may include all or a part of the drill string, smaller pieces of equipment such as bit cones, pieces of tools, or any materials accidentally dropped into the wellbore.
There are many different types of fishing jobs and tools. Which tool to be used depends on the type of fish in the hole; whether the fish is stuck or free, whether it is in a cased hole or an open hole, the condition of the top of the fish and the condition of the hole at the top of the fish should be taken into considerations. At the beginning, we must show the fishing steps to get the junk:
We have 2 types of fishing :
Let’s dig in details to get more advanced information about open hole fishing.
This section discusses fishing in open hole environments. Open hole environments present unique challenges for successful fishing jobs. A free point and back-off must be made first; they will be illustrated later. After thefree point has been located, study the well plot carefully and check for true dog legs before deciding where to make the back-off. The back-off must be made at the depth that offers the best chance of connecting to the fish.
NOTE : Do not back-off just below a dogleg or in the hole curve if possible.
Develop a plan for the most effective bottom hole configuration and jar placement prior to the back-off.
Do not place the jars in the curve (Figur 1). Place them either in the vertical section or in the straight section below the curvature.
Now we discuss some specialized tools used in Open Hole Fishing.
Check to see if the magnet is charged properly by attaching a 20-lb. sledge hammer to the face of it. If the magnet will support the weight of a sledge hammer, it will likely hold any small pieces of junk in the wellbore. The lifting capacity is a function of size, area, and charge.The OD of the magnet should be 1/4- to 1/2-in. less than hole size.
Procedure run Magnet:
Free Point Indicator
A free point indicator is an electronic strain gauge running on a single conductor cable. It is used to measure the amount of torque or stretch in a string of stuck pipe. The tool is anchored to the pipe ID at two fixed points by either bow springs, dogs or magnets.
When stretch or torque is applied at the surface, the gauge electronically transmits this information to the surface via the wireline. Following are the five requirements for a successful back-off:
A string shot can be run in a combination with the free point tool and usually will not damage the connection. It can be run in a smaller ID than cutters.
A string shot can be used for an outside back-off as a jar shot, to jar a test plug out of a well head, to knock nozzles out of a bit, or to knock plastic and corrosion off the ID of pipe prior to making a chemical cut.
An inside-outside back-off collar is run above an overshot. The overshot is attached to a plugged fish. A 35-ft. long string shot is deflected to the outside of the fish and fired.
The plugged fish is retrieved. Avoid pulling pipe into the wall/free point with torque (Fig 7).
String Shot Back-off
A string shot back-off is the process of unscrewing a tool joint or coupling with explosives at a predetermined depth. The string shot the blasting cap that is used to perform the back-off. The string shot back-off method uses the following steps to loosen the stuck pipe.
Where to Back-off ?
It is important to figure out where to back-off. Performing a back-off in the wrong location can be a costly mistake.
- Do you intend to fish the well?
* No - Back-off as deep as possible.
* Yes – At least one free joint above stuck point. Two free joints above a key seat. 100 feet below a casing seat.
Now, it’s your turn to get specialized details about this subject, you just need to read more and more, then you will get technically-improved.
So, you have learnt:
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