The following 2 types of Junk retrievers are discussed in this article: Coring Type Basket and Reverse Circulation Junk Basket or Jet Retriever.

Coring Type Basket

The coring type basket cuts a short core. As the core is being cut, junk is forced into the barrel of the tool.

The following procedure shall be used:

1. Tag bottom using maximum pump volume and ensure that all fill has been washed away.
2. Pull back off bottom, reduce the pump rate, and start slow rotation (about 20 rpm).
3. Lower the string to bottom and with light weight to allow the shoe to form a pattern. Gradually increase the weight.
4. When enough penetration has been made to retrieve the fish, stop rotation and circulation and break the core. The upper and lower catchers of the tool maintain the core in place.

5. POOH.

Reverse Circulation Junk Basket

This tool works on the Venturi principle; mud is diverted through jets by pumping a drop ball from surface causing the mud to be directed outward and downward from the body of the tool. This causes a pressure drop inside the tool resulting in a flow from the bottom of the hole into the junk sleeve. Once the junk has been washed into the tool, catch fingers prevent it from dropping out.

This type of junk basket may also be available with a coring shoe, which is recommended for use in some circumstances

The following procedure shall be used:

1. Make up to the bottom of the fishing string and RIH to within a metre of the bottom.

2. While slowly rotating the string, start the pump slowly and incrase to maximum safe circulating pressure.

Note:   All of the drilling fluid circulates through the centre of the tool and none through the jet nozzles.

3. Upon completion of pumping operations, drop the ball and pump down at a moderate speed.

Note:   When the ball seats itself in the junk retriever, the fluid flow shall be diverted through the jet nozzles to the outside of the   retriever causing a drop in pressure inside the retriever.

It must be ensured that the ball can pass freely through the fishing string. It may be necessary to drift the string while running in the hole.

4. increase the pump pressure to the safe maximum operating pressure. The reverse flow of the drilling fluid shall wash the junk up inside the retriever to be retained by the catch fingers of the catchers.

5. Hold the pump pressure at maximum safe operating pressure while slowly rotating. Reciprocate to gently contact the bottom of the hole. The shoe fingers shall be hardfaced.

6. When the rotary shoe no longer hangs up and runs smoothly, the junk has been removed and the string can be pulled (2 -3 ft is reasonable).