Cross-over sub acts for conversion and connection and is the basic component in downhole work.It is divided into drill string cross-over sub and tubing Cross-over sub.Drill string Cross-over sub is divided into type A, type B and type C.
Specification
Description | Upper connection
| Lower connection | Type |
Kelly sub | Kelly | Drill pipe sub | Type A or B |
Drill pipe sub | Drill pipe sub | Drill pipe sub | Type A or B |
Cross over sub | Kelly | Drill collar | Type A or B |
Drill collar sub | Drill collar | Drill collar | Type A or B |
Bit sub | Drill collar | Bit | Type A or B |
Swivel sub | Swivel lower sub | Kelly | Type C |
Fish Sub | Kelly | Drill pipe sub | Type C |
Drill pipe sub | Fishing tool | Type C |