Produced water treatment methods

Most of the modern methods of produced water treatment (PW), which are functionally and geographically coincide with commercial products preparation installation, may be classified as follows:

1. Treatment of PW – based on the use of vertical steel tanks-sumps (TS).
2. Treatment of PW by settling in TS and filtration in pressure filters.
3. Treatment of PW in head settler (HS).
4. Treatment of PW by settling in HS and filtration in pressure filters.
5. Open treatment of PW.
6. Treatment of PW by settling in oil traps and ponds, followed by head filtration.

In addition to these methods of PW treatment, different special technologies are used at oil, water and gas treatment plants.

Specialists of STC «AhmadullinS – Science and Technology” has developed technology of hydrogen sulfide-containing produced water treatment, which are used to maintain reservoir pressure during oilfield flooding.
The technology is based on catalytic oxidation of hydrogen sulfide and sodium hydrosulfide with molecular oxygen to odorless sulfate and thiosulfate. Wastes treatment process with KSM catalyst proceeds at 60 ÷ 90°C and pressure of 0.5 ÷ 0.8 MPa.

H₂S +2 NaHS + 4O₂ →NaHSO₄ + NaHS₂O₃ + H₂O (1)

9NaSH + 10O₂ → 4Na₂S₂O₃ + NaHSO₄ + 4Н₂О (2)

Concentration of sulfide sulfur in produced water before treatment may be up to 1000 mg/dm³. The residual content of sulfide sulfur (hydrogen sulfide) not more than 2.0 mg/dm³ (0.0002 wt.%). Detailed description of the process.