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Extension Sub
Extension Sub is installed between the top sub and bowl to help an overshot reach deeper and securely engage damaged fish. Available in multiple lengths with customizable OD and connections to match your fishing string.
Category:
Downhole Tools
The Extension Sub is a fishing accessory installed between the top sub and the bowl in an overshot assembly. It is commonly used when the upper portion of the fish is damaged, shortened, or cannot be effectively engaged at the planned depth.
By providing additional length, the Extension Sub allows the overshot to be positioned far enough over the fish to achieve secure engagement and improved pack-off performance, supporting more reliable recovery during workover and fishing operations.
- Extension Subs for overshot assemblies (various lengths)
- Sizes matched to your overshot OD and fishing string configuration
- Connections per specification (NC / REG / IF / FH and other thread types upon request)
- Material and heat treatment per project requirement (standard alloy steel options available)
- Marking, coating, and packaging aligned with your maintenance workflow (optional)
- Improves overshot positioning to reach deeper over damaged or inaccessible fish
- Supports secure engagement and more stable pack-off in challenging recovery scenarios
- Configurable length range to match the actual fish condition and required set-down depth
- Connection flexibility to match the fishing string and overshot assembly
- Workshop-ready repeatability based on size/connection records for fast re-ordering
- Overshot fishing when the upper portion of the fish is damaged or cannot be engaged
- Workover and intervention operations requiring deeper overshot coverage for reliable engagement
- Fishing runs where adjustment of assembly length helps optimize set-down, bite, and pack-off behavior
Extension Sub is typically confirmed by overshot size, required length, OD, and thread connections. Final dimensions and tolerances follow customer specification and assembly matching requirements.
| Item | Typical Option / Notes |
|---|---|
| Tool Function | Installed between top sub and bowl to extend overshot assembly and improve engagement |
| Length | Customizable; commonly supplied in multiple standard lengths per requirement (e.g., 24–60 in or equivalent) |
| Outer Diameter (OD) | Matched to overshot OD and clearance requirement |
| Connections | Top & bottom connections per spec (NC / REG / IF / FH etc.) |
| Material | Alloy steel options; material and heat treatment per project requirement |
| Compatibility | Designed to match overshot assemblies; confirmation by size/connection and drawing when available |
- Incoming material verification (MTC review when provided / requested)
- Dimensional inspection on OD, length, and key datums per drawing/spec
- Thread inspection per specified connection type
- Final inspection before packing; photos available upon request
- Third-party inspection support (SGS / BV / TPI) available when required
- Repeat-order support by size/connection and configuration record
- Marking and packaging aligned with your workshop and inventory workflow
- Drawing/spec revision record support to reduce reconfirmation time
To provide an accurate quotation and ensure assembly compatibility, please share the following information. If some items are not available, you can send drawings or the overshot model details and we will help complete the missing parameters.
- Overshot type & size: model / OD / series (if available)
- Required length: target extension length or the range you prefer
- OD requirement: clearance limit or matched OD to overshot assembly
- Connections: top & bottom thread type, size, and standard (NC / REG / IF / FH etc.)
- Operating notes: fish condition (damaged top / short fish / restricted engagement) and well profile (if relevant)
- Quantity & delivery window: target lead time and shipping term
Unionlever OFS supports fishing tool accessories with an engineering-led workflow: we confirm overshot compatibility, connection details, and target length up front to reduce back-and-forth and avoid field mismatch risk. For repeat orders, we keep configuration records to improve consistency, shorten reconfirmation time, and make trial orders easier to scale into stable long-term supply.
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sales@unionleverofs.com
ofs@unionlever.com
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Related Products
Building upon more than a decade of field experience, Unionlever OFS offers a comprehensive portfolio covering downhole drilling tools, fishing tools, handling tools, well control equipment, cementing tools, and solid-control systems.
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Unionlever Oilfield Equipment Co., Limited
A Member of
Unionlever International Group Limited
(Established Since 2010)
"To be a globally trusted leader in oilfield equipment and integrated supply solutions."
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