Slickline Overshot

Description

Slickline Non-Releasable Overshot

Technical Description and Specifications

The Slickline Non-Releasable Overshot (often referred to simply as the Slickline Overshot) is a robust, primary fishing tool designed for the secure retrieval of lost equipment (the “fish”) that presents an accessible fish neck or suitable cylindrical profile. This tool is chosen when the priority is maximum gripping strength and positive engagement, as the overshot is designed to remain latched onto the fish until both are recovered from the well.

Key Technical Specifications and Operation

• Function: To firmly latch onto a fish body’s accessible shoulder or fish neck profile and facilitate its retrieval to the surface using jarring force.

• Design: A simple yet powerful BHA tool consisting of a main body (bowl) and a slip or grapple assembly. The design prioritizes gripping strength and positive retention.

• Engagement Mechanism: The slips or grapple are actuated by driving the overshot bowl over the fish neck. Downward jarring ensures the slips bite and lock firmly onto the fish OD. Upward jarring is then applied to pull the fish free.

• Non-Releasable Nature: Once engaged, the slips are securely locked into the bowl, providing a high-strength connection. This design does not incorporate a mechanism for controlled disengagement downhole. The fishing operation concludes when both the overshot and the fish are retrieved together.

• Fish Size Match: The overshot must be precisely matched to the outer diameter of the specific fish neck being recovered. Overshots are sized by the maximum OD they can catch.

• Connection (Customizable):

  • Standard interfaces include proprietary slickline pin threads.

  • Custom order connections are available to ensure compatibility with proprietary quick-connect systems (e.g., HQC, QLS) and non-standard tool string threads.

• Material (Customizable):

  • Standard construction uses high-strength alloy steel (e.g., AISI 4140/4340) for durability under extreme jarring loads.

  • Custom material options are available, including NACE MR0175 compliant alloys for the bowl and slips for use in sour service environments ($\text{H}_2\text{S}$).

• Critical Parameters (Customizable Catching OD):

  • Catching Range: The most crucial specification is the range of Outer Diameters (ODs) that the slips can securely engage.

  • Custom Slip Sizes: The overshot bowl can be fitted with custom-machined slips to precisely match non-standard or unusual ODs found on specialized downhole tools. Clients must specify the exact fish neck OD and the maximum required tensile load rating when placing a custom order.