HEDP•Na₂ is widely used in oil fields for scale inhibition, corrosion control, and metal ion chelation, particularly in water injection systems, drilling fluids, and production pipelines. Below is a step-by-step guide for its application:
**1. Determine the Dosage
The dosage depends on water chemistry (Ca²⁺, Mg²⁺, Ba²⁺, Fe²⁺, and pH). Typical ranges:
| Application | Dosage (ppm) | Notes |
|---|---|---|
| Water Flooding (Injection Water) | 10–50 ppm | Prevents CaCO₃/CaSO₄ scaling |
| Drilling Fluids | 5–20 ppm | Controls scaling in mud systems |
| Produced Water Treatment | 20–100 ppm | For high-hardness or high-iron water |
| Squeeze Treatment | 0.5–2% solution | Temporary scale inhibition in wells |
**2. Preparation & Dilution
-
HEDP•Na₂ is water-soluble, but for better dispersion:
-
Dilute in freshwater (1:5 to 1:10 ratio) before injection.
-
Adjust pH to 7–9 (if needed, using NaOH or HCl).
-
**3. Application Methods
A. Continuous Injection (Water Flooding)
-
Set up a dosing pump connected to the injection water line.
-
Inject diluted HEDP•Na₂ (10–50 ppm) continuously.
-
Monitor scaling tendency (via ion analysis or scale coupons).
B. Batch Treatment (Squeeze Application)
-
Prepare 0.5–2% HEDP•Na₂ solution in freshwater or brine.
-
Pump into the wellbore and shut in for 6–24 hours.
-
Flush with water to distribute the inhibitor into the formation.
-
Repeat every 3–6 months (depending on scaling tendency).
C. Drilling Fluid Additive
-
Add 5–20 ppm HEDP•Na₂ directly to the mud system.
-
Helps prevent Ca²⁺/Ba²⁺ scaling in downhole tools.
**4. Compatibility & Synergistic Use
-
Works well with:
-
Polymeric scale inhibitors (e.g., PAA, PVS).
-
Corrosion inhibitors (e.g., imidazolines, thiourea).
-
Oxygen scavengers (e.g., sodium sulfite).
-
-
Avoid mixing with:
-
High concentrations of Fe³⁺ (can form insoluble complexes).
-
Strong oxidizers (e.g., hypochlorite, H₂O₂).
-
**5. Monitoring & Maintenance
-
Check scaling tendency (via lab tests or online sensors).
-
Adjust dosage if water chemistry changes (e.g., increased Ca²⁺).
-
Inspect pipelines for scale buildup (ultrasonic testing or coupons).
**6. Advantages of HEDP•Na₂ in Oil Fields
✔ Excellent thermal stability (up to 200°C).
✔ Effective at low dosages (cost-efficient).
✔ Biodegradable (better than ATMP/EDTA).
✔ Works in high-salinity & high-hardness water.
**7. When to Use HEDP•Na₂ vs. Other Phosphonates?
-
For high-temperature wells → HEDP•Na₂ (better than ATMP).
-
For Fe³⁺ stabilization → HEMPA (better than HEDP).
-
For low-cost treatment → ATMP•Na₄ (cheaper but less stable).