Downhole · Rod Pump
Sucker Rod String
Steel or fiberglass rods screwed together with couplings that connect the polished rod to the downhole pump plunger.
What it does
Transmits the up and down motion from surface to the pump. Strings can be tapered, with smaller rods at the bottom, and include sinker bars, guides and rotators.
Basics
| Standard | API Spec 11B, grades C, D and K |
| Lengths | 25 and 30 ft; pony rods 20 to 140 in |
| Options | Fiberglass rods, sinker bars, molded rod guides, rod rotator |
| Taper | Two or three sizes, smaller at the bottom |
Common failures
- Parted rods from fatigue or overload
- Coupling and tubing wear in deviated sections
- Buckling on the downstroke
- Paraffin build up
Troubleshooting
- Symptom
- Card shows no fluid load and light rod weight
- Likely cause
- Parted rod string
- What to check
- Confirm with the dynamometer, plan a fishing job
- Symptom
- Tubing holes at the same depths
- Likely cause
- Rod on tubing wear
- What to check
- Add rod guides or sinker bars there, review deviation survey