A challenging and costly situation to overcome in modern day directional drilling applications is stuck pipe in open hole due to differential and/or mechanical sticking forces. Chances of recovery decay with time and conventional fishing with a bottomhole assembly (BHA) is frequently unsuccessful. By incorporating downhole axial-oscillation technology, the fishing reliability and effectiveness improve exponentially. The Fishing Agitation Tool (FAT) is an excitation component of the fishing BHA used to deliver low impact, high energy oscillation to the engaged fish. The FAT keeps the string in motion, breaking static sticking friction.
The FAT was used in Saudi Arabia for the first time to recover differentially stuck BHAs from a 6 1/8 in. hole in deep, high angle wells. The initial application involved pipe that was stuck in hole for more than 12 days without any movement, during which several conventional fishing BHAs failed. FAT was run in the final fishing BHA, getting the fish free after an hour of axially agitating and stroking the fish. After the pilot field trials in Saudi Arabia, and several successes in recovering mechanical and differential stuck BHAs, downhole vibration analysis proved the FAT effectiveness in assisting fishing BHAs in recovering stuck pipe more efficiently.
The FAT offers a new level of fishing technology that maximizes the effect and reliability of fishing BHAs in challenging wellbore environments, where conventional fishing techniques are deemed insufficient. This increased efficiency offers substantial reduction in fishing lost time, and an increased potential for fish and well recovery.
This paper investigates the effectiveness of the Fishing Agitation Tool through a study of the impact forces, impulse and drag forces generated by the FAT compared to conventional jarring operations, utilizing drag modeling as well as jarring analysis software.
Successful cases histories are reviewed to highlight the benefit of this technology.