Fishing operations object which has been lost or stuck in a borehole, and has a serious negative impact on well operations. Fishes can be anything, whether that is a drill string that has come away, a bit cone, or even a hand tool that has been inadvertently dropped into the well. To solve this issue, fishing involves the use of special tools and procedures to recover the fish and allow drilling to continue. While this article will deal solely with regular fishing, there is also an alternative method, which involves using through-tubing processes that make use of tools on a wireline or coiled tubing.

Virtually any object that is dropped into a well, or even run into it, may need to be fished out at some point. Furthermore, the need for fishing may arise at any given point during operations, and there are therefore a wide range of different tools and methods. There are three main technologies that these solutions are built around, though: pulling, milling, or cutting the pipe itself, and other downhole parts.

There are several types of fatigue failure, and they may occur simultaneously:

Twist-off : Twist-off occurs when applied torque exceeds a pipe body or tool joint’s torsional strength limits. This failure usually causes a sudden loss of hook load, as well as a sharp drop in pump pressure. Twist-offs may occur when trying to rotate stuck pipe.

Washout: Washout is when a hole is worn in the pipe, and becomes increasingly larger due to circulating drilling fluid. This can eventually sever or twist off the pipe entirely. Washouts usually occur at rotary connections, due to improper make-up, cracks or defective materials.

Cyclic Stress Failure: Drill pipes can experience cyclic stress if they wear out after a great deal of use. Furthermore, corrosion or mishandling may lead to fatigue failure.

Junk: can consist of all manner of things, from bit cones and tong dies, to hand tools or other objects that have been accidentally dropped into the hole. Junk can cause irregular torque, or prevent drilling ahead after a new bit is run.