|The Gotco Series 150 Releasing and Circulating Overshot is an external catch fishing tool designed to retrieve tubular items from the well bore. It is rugged, economical, and easy to use. Gotco overshots come with a wide range of available accessories. These fishing tools have proven to be the most versatile and reliable in the field.|
|The basic assembly consists of a top sub, bowl, and standard guide. The internal components are used to establish a secure grip on the fish to retrieve it easily. The selection of these components is determined by the diameter of the fish to be retrieved. When the fish diameter approaches the maximum catch of the overshot, a spiral grapple is required. This must also be equipped with a spiral grapple control and type A packer. When the diameter is approximately 1/2 inch (or more) under the maximum catch of the overshot, a basket grapple is used. It must be assembled with either a basket grapple control or a mill control packer.|
Assembly and Operation
|Spiral Catch Equipment - Place the type A packer (with inside lip pointed up) in overshot bowl between upper thread and helix. (Note: The lower end of overshot bowl has a longitudinal slot cut into helix.) Assemble top sub to overshot bowl. Thread spiral grapple into left-hand helix in overshot bowl. Stop threading when the grapple has fully entered the helix and the grapple tang has aligned with the keyway in the bowl. Slide the grapple control, tang end first, into overshot bowl until the grapple control tang slides beside tang on grapple. Grapple tang also slides into slot in grapple control. Now assemble the guide to overshot bowl.|
Basket Catch Equipment - Assemble top sub to overshot bowl. Thread basket grapple into left-hand helix in overshot bowl. Stop threading when the grapple has fully entered the helix and the slot in grapple has aligned with keyway in the bowl. The inside lip on inner seal must point up in the grapple control. Outer seal must be placed around lower end of grapple control. Now slide grapple control into bowl (tang end first) so that the tang engages the slots in both the bowl and basket grapple. Assemble guide to overshot bowl.
Operation - The overshot should be equipped with the proper size grapple and related equipment. Hole size or damage to the fish may necessitate using an oversized guide, wall hook guide, extension sub, or milling shoe.
Engagement and Retrieval of Fish - Attach the overshot to the bottom of the fIshing string and fW1 in the hole. When the overshot nears the top of the fish, engage it by slowly rotating to the right while gradually lowering the fishing string. To pull up the fish, release any right-hand torque in the fIshing string. Circulation through the fish . may be used to help retrieve it. If applying torque to the fish, maintain an upward strain while the fishing string rotates; this will maintain grapple engagement.
Release of Fish - Bump down the full weight of fishing string. Rotate to the right while picking up slowly. The left-hand wicker threads on the inner surface of the grapple will allow the grapple to unscrew from the fish.
|Top sub - The top sub is the uppermost component of the assembly. It is equipped with a box connection, as specified by the customer, to assure proper make-up with the fishing string.|
Bowl - The bowl is the major working component of the overshot. The upper end of the bowl is threaded for assembly with the top sub. The lower end is threaded for assembly with the standard guide. A helix-shaped configuration inside the overshot bowl provides a tapered spiral surface on which the grapple will be assembled. Once the grapple has engaged the fish, an upward strain will cause the grapple to be compressed by the movement of the matching tapers. The greater the pull, the stronger the grip. The strain is evenly distributed over the entire working surface of the bowl and the grapple. This minimizes any possible damage to the bowl or the fish.
Standard guide - The standard guide is the lowermost component of the assembly. It guides the fish into the overshot, allowing the internal gripping mechanism to properly engage and grip the fish. The guide also prohibits the entry of a fish that exceeds the maximum catch of the overshot. This minimizes any possible damage to the overshot assembly.
Spiral Grapple - The spiral grapple is a left-hand helix that conforms to the inside of the overshot bowl. Specially hardened wicker threads assure a positive grip to engage the fish securely.
Basket Grapple - The basket grapple is a slotted cylinder with an external helix that conforms to the interior of the overshot bowl. Specially hardened wicker threads assure a positive grip to engage the fish securely. Three types of basket grapples are available:
- The standard basket grapple is used to catch a fish with a uniform outside diameter. The fish passes completely through the grapple during engagement. This type of grapple is standard equipment.
- The long catch stop basket grapple has an internal shoulder at its upper end to prevent the fish from passing completely through the grapple. When engaging a coupling or upset section of a tool joint, this shoulder positions the control packer for optimum pack-off around the fish.
- The short catch stop basket grapple has two sets of internal wickers cut on different diameters. It is used to engage a coupling with a short section of pipe protruding above it. The upper or smaller diameter wickers catch the pipe above the collar, providing a stop against the coupling so that it can be caught by the lower set of wickers and packed-off by the control packer.
|Grapple Controls - Grapple controls transmit torque from the overshot bowl to the grapple while allowing the grapple to move vertically inside the bowl.Spiral grapple controls are furnished without milling teeth or a pack-off mechanism. Basket grapple controls can be furnished plain, with pack-off capabilities, or with milling teeth and pack-off capabilities.|
Pack-off Mechanism - A pack-off mechanism is necessary if circulation is required during the fishing operotion. Packing off assures circulation through, rather than around, the fish. The pack-off system employed will depend on the type of grapple selected. If the overshot is equipped with a spiral grapple, a type A packer is used to seal between the overshot bowl and the fish. If a basket grapple is used, pack-off is achieved by the inner seal on the control packer.
|For sizes, specifications, and ordering instructions download this page in PDF.|