Oilfield Produced Water Reinjection Treatment Process
As oilfields enter the mid-to-late stage of production, produced water treatment has become a key constraint on sustainable development. Oilfield produced water is the formation water produced together with crude oil during extraction; it is characterised by high oil content, complex suspended solids and poor chemical stability, and conventional processes can no longer meet increasingly strict environmental requirements.
Characteristics of oilfield produced water and treatment challenges
Oilfield produced water is a by-product of crude oil extraction with a complex and variable composition, typically containing crude oil, suspended solids, dissolved salts and various chemical additives. It is characterised by high oil content (up to 1,000-2,000 mg/L) and high suspended solids (≤500 mg/L), and is highly stable and difficult to treat.
Conventional processes and their limitations
The "inclined-plate settling tank + walnut shell/fibre-ball filtration" process commonly used in oilfields has obvious shortcomings. Treatment results are unstable, shock resistance is poor, effluent quality fluctuates widely, and chemical dosing is required, easily producing aged oil and oily sludge and causing secondary pollution. Another combination process - "settling tank + centripetal flotation + fibre-ball/multi-media filtration + ceramic membrane" - performs somewhat better, but the flow is complex, costs are high, operation and maintenance are difficult and the footprint is large, making it hard to adapt to the production needs of modern oilfields.
SINOKLECDFU new process technical breakthrough
The new-generation process developed by SINOKLE Technology, centred on CDFU (cyclonic dissolved-air flotation), has achieved multiple breakthroughs through technical innovation:
Core technical principle
CDFU ingeniously integrates centrifugal separation, dissolved-air flotation and ultra-fine bubble generation into a highly efficient hybrid separation device. Its unique design creates a stable vortex flow field inside the unit, using strong centrifugal force for rapid separation.
Process flow advantages
The new process uses the simple flow "produced fluid → three-phase separator → first-stage CDFU→ second-stage CDFU→ activated filter media filter", offering three treatment schemes according to different reinjection requirements:
· Scheme 1 (high-permeability formations): effluent oil ≤10 mg/L, suspended solids ≤5 mg/L
· Scheme 2 (low-permeability formations): effluent oil ≤6 mg/L, suspended solids ≤2 mg/L
· Scheme 3 (ultra-low-permeability formations): effluent oil ≤5 mg/L, suspended solids ≤1 mg/L
Schematic diagram of the oilfield reinjection water treatment process
Significant advantages of the new process
High efficiency and stability: single-stage oil removal efficiency exceeds 90% and the minimum removable particle size reaches 2 μm, far exceeding the 60%-85% of conventional processes.
Energy saving and environmental protection: the purely physical demulsification requires no chemicals, eliminating oily sludge at the source and achieving green treatment.
Compact and intelligent: the hydraulic retention time is only 1-5 minutes, the footprint is one third of conventional processes, and the skid-mounted design supports rapid deployment and fully automatic operation.
Economical and practical: operation and maintenance costs are greatly reduced, and the recovered oil is of high quality and can be reused directly, creating economic value.
Successful application cases
The process has achieved remarkable results in several oilfield projects:
CNOOC Suizhong terminal project (2023), capacity 260 m³/d, using two-stage CDFU to treat power-fluid separator produced fluid, with oil removal efficiency stably above 80%.
PetroChina Changqing oilfield project (2017), capacity 20 m³/h, inlet oil ≤1,500 ppm; after CDFU treatment the effluent oil is ≤30 ppm, and after fine treatment with an AFM filter it can reach ≤10 ppm.
Yanchang oilfield project (2017), capacity 15 m³/h, inlet oil ≤150 ppm; CDFU effluent oil ≤10 ppm and suspended solids ≤10 ppm, with all indicators stably meeting standards.
Two-stage CDFU cyclonic dissolved-air flotation treatment process for reinjection water at an oilfield
Development prospects
SINOKLE's CDFU new process, with its efficiency, stability and environmental friendliness, has become a technical benchmark in oilfield produced water treatment. As environmental requirements rise and oilfield production continues to deepen, this innovative technology will provide strong support for green and sustainable oilfield development, driving the whole industry towards greater efficiency and environmental sustainability.
