Produced Water Treatment And Oil Recovery
Esmil Industrial Group and Esmil together with our partners have conducted much research and constructed many plants gaining vast experience in the Natural Gas industry. From bench scale studies right the way through to full scale plant operations we strive to offer BAT (Best Available Technology) using state of the art membrane separation and dewatering processes.
General Process Description
Natural gas wells contain a certain proportion of water which is extracted as a by-product of gas extraction. This is referred to as ‘Produced Water (PW)’ containing suspended solids, organics, oil and salts. Discharge to sea requires primary treatment on site or transportation to a suitable primary treatment facility.
Depending on the desired treated water quality, the Esmil philosophy for Produced Water Treatment utilises conventional separation processes for the removal of bulk contaminants – oil & solids or combination of the conventional separation process and state of the art membrane separation and absorption processes. This philosophy enables the plant to function reliably, even with wide ranging variations in feed quality.
Examples Of Technologies
The degree of treatment is designed to meet client specified limits such that the treated water is suitable for reuse on site or discharge to overboard.
Moderate Discharge Consents (Typical For Offshore Platforms)
Conventional Treatment involves Hydrocyclones / Corrugated Plate Separation followed by Induced Gas
Floatation and Media Filtration to remove oil and suspended solids below 10-30 mg/l limit. The treated
water is suitable for on board discharge or for reinjection purpose.
Stringent Discharge Consents For The Costal Areas (Advanced Process Technology)
The pre-treated water is polished by Ultrafiltration membranes, which reduces oil concentration to less than 0.3 mg/l, and suspended solids to below the limits of detection. The Ultrafiltration membranes utilise a modified Polyacrylonitrile (PAN) chemistry, which has been developed to be extremely oleophobic and thus resistant to free-oil fouling.
The oil and suspended solid free water is treated using Nanofiltration membranes, which removes the bulk of heavy metals and organic compounds. Although the pores size of the membrane is around 1 nm the nanofiltration provides negligible resistance to the passage of monovalent ions such as chlorides, so it is able to operate on high salinity waters where the inefficient productivity of Reverse Osmosis would render it uneconomical.
Trace organics and heavy metals in the Nanofiltration permeate are removed by Activated Carbon absorbers and selective Ion-Exchange resin. The pre-treatment by Nanofiltration significantly increases the bed life of these two media.
Ultrafiltration reject stream is recycled to the front end of the process and the concentrated oil is reclaimed on site from TPS unit. The various sludge and aqueous waste streams from the main process are combined before undergoing precipitation, flocculation and filtration, to produce a ‘cake’ for landfill, and a filtrate that can be recycled through the process.
References
- 10 m3/h Shell, Corrib Gas Terminal, Ireland
- 250 m3/h ONGC Indian Offshore Platform, India
- 240 m3/d Produced Water, Petrofac Ltd, Siberia
