Stimulation · Intervention
Acid Stimulation
Pumping a reactive acid into the formation to improve how easily oil and gas flow to the well.
What it does
Matrix acidizing is pumped below fracture pressure. In sandstone the acid dissolves soluble material and widens the pores; in carbonate it dissolves the rock matrix itself.
Basics
| Matrix acidizing | Below fracture pressure |
| Carbonates | Hydrochloric acid, commonly 15% or 28% |
| Sandstones | Mud acid, HF with HCl or an organic acid |
| Preflush | Removes calcareous material and iron scale |
Common failures
- Secondary precipitates that plug the pores after a sandstone job
Troubleshooting
- Symptom
- Production drops after the acid job
- Likely cause
- Precipitates such as ferric hydroxide or calcium fluoride
- What to check
- Use a preflush and keep the pH low in the next design