What is fishing in Oil and Gas Drilling and Completion Operations? 

Fishing is a term used to recover lost, damaged or stuck objects from the wellbore in oil and gas drilling and completion operations. The item lost down the well is generally referred to as a “fish”. The key elements of planning a successful fishing job include an understanding of the type and dimensions of the “fish”, the nature in which it became lost or stuck, and the borehole geometry and wellbore conditions. Fishing jobs can last anywhere from a few hours or can continue on for weeks. Generally when determining if it is worthwhile to fish rather than “sidetrack” around the fish or “abandon” the well things like “likelihood of success” and the rig daily operations costs must be compared to the cost to sidetrack or the cost of the equipment lost in hole.

What tools are used in fishing operations?

Different tools are required to “catch” various types of “fish”. The most common tools used to fish are overshots and spears which are run with grapples sized for the particular outside or inside diameters of the fish. The primary difference is the overshot goes outside of the fish whereas the spear goes inside the fish. (See pictures). When the overshot or spear engages the wicker profile on the grapple bites into the surface of the fish. The harder the fish is pulled the hard the grapple digs into the fish.

In certain cases simply pulling on the fish may not be enough to free the stuck item. In such cases Jars and even Accelerators are used to add additional force to free the stuck fish. When the Jar is activated it creates “impact” hammer action downhole. The energizer effectively magnifies this by increasing the duration the force (“impulse”) created by the jar applies. Jar placement programs can be run to simulate proper placement of the Jar and Accelerator in the tool string and give an indication of the magnitude of the anticipated “impact” and “impulse”.

In cases where the wellbore has collapsed or there is significant debris trapping the fish it may be required to “wash over” the outside of the fish to clear the debris. Examples include sanded up tubing anchors in cased hole situations and packed off bottom hole assemblies in drilling applications.

Other specialized tools can be used to recover other more exotic equipment lost downhole. Below is only a small example:

• Scrub grab or wireline spear is used to recover braided wire or slickline
• Reverse circulating junk baskets (RCJB) or magnets are often used to catch medium sized debris like tong dies, broken cutters or teeth off of drill bits or sometimes even entire drill bit cones. The tool are run on drill pipe to within a few meters of where the suspected junk is located. Circulation is established to wash on top of the junk.
  • The magnet as suggested by the name uses magnetism to pick up any metallic objects which then can be pulled from the well.
  • The RCJB works much differently trapping loose metal in a basket inside the tool. To “suck” metal inside the tool a ball is dropped while circulating. When this ball reaches the RCJB it lands in a ball seat redirecting the flow from through the tool into the annulus to into the annulus and back up the inside of the tool. This sudden change in flow direction can lift small metal objects up into the RCJB. The spring loaded fingers in the basket at the bottom of the RCJB then prevent the object from falling back down the well. (See picture)
• Mills are used to “mill up” lost metal into smaller pieces which can be circulated out of the hole. There are a range of sizes, dressing types, and configurations depending on what is being milled and whether it is in open hole or cased hole. Example off different mills are shown. Specifics of the job should be discussed with a Tango representative before choosing the appropriate mill.
• Junk or boot baskets are used to recover small items like swarf created during milling operations.
• Hydraulic or Mechanical Cutting Tools are generally used to cut casing or tubing where the upper section is pulled from the well and the lower section is either left or subsequently fished out.
• Section mills are often used when permanently abandoning a well. A “section” of the casing is milled away allowing for a cement plug to be set isolating both the inside of the casing and the casing annulus. This generally results in better annular isolation than simply perforating the casing and squeezing cement into the annulus.

What fishing tools or services can Tango provide?

Tango has a full range of fishing tools sized to fish inside 12-1/4” Open Hole down to 2-3/8” Tubing and catch anything from 9-5/8” Casing to ¾” Sucker Rods. Tango is backed by over 100 years of industry experience covering drilling, completions, and fishing operations both in Australia and Internationally. Tango can provide pre-job planning, fishing recommendations, and fishing tool supervisors as required.

Tango can also provide customized well intervention support in the form of multi-lateral systems, sidetracking/whipstocks, and specialty tool design. Please contact us 24/7 for more details on 1300 082 646.