Efficient Oilfield Produced Water Reinjection Treatment Process
Oilfield produced water reinjection treatment process
After an oilfield is put into development, the reservoir's own energy is continuously consumed as production continues, causing reservoir pressure to keep falling; the underground crude oil degasses heavily and its viscosity rises, so well output drops markedly and wells may even stop flowing, leaving large amounts of crude oil underground that cannot be recovered. To make up the underground void formed after oil production, maintain or raise reservoir pressure, achieve stable high output and improve recovery, water injection is essential.
Sources of injection water mainly include surface fresh water, shallow groundwater and the reservoir water produced along with the crude oil (produced water). At present, most of the water injected into reservoirs comes from water separated out during oil production, about 80% of total injection. Different reservoirs require corresponding water quality standards, but in general injection water quality should meet the following requirements:
Suspended solids control: The injection water should contain as few suspended impurities as possible; their content and particle size must not clog the injection well face or the reservoir.
Scale control: The injection water should not form scale or precipitates as temperature, pressure and other conditions change, nor when mixed with formation water or surface water.
Corrosion control: The injection water must not corrode the injection equipment.
Bacteria control: Bacterial growth in the injection water should not create new suspended impurities or affect the normal operation of the injection system.
Clay swelling inhibition: The injection water should prevent clay in the reservoir from swelling.
To meet the above strict requirements, we developed the produced water reinjection treatment process:
The process uses the CDFU cyclonic dissolved air flotation, the KFM activated filter-media filter and the modified inorganic membrane filter as core equipment; different process combinations meet the reinjection requirements of high-permeability, low-permeability and ultra-low-permeability formations.
Wide application range: The process can treat both conventional oily wastewater and low-polymer-containing oily wastewater.
Efficient oil removal: High-efficiency cyclonic dissolved air flotation replaces large-tank gravity settling, using microbubbles for purely physical demulsification without chemical agents, markedly reducing the generation of oily sludge.
Compact and efficient flow: Short process flow, compact equipment, short hydraulic retention time, high treatment efficiency and a small footprint.
Intelligent and automated: The equipment is skid-mounted and intelligent, supporting unattended fully automatic operation.
Stable and reliable operation: The process runs stably with strong shock-load resistance, ensuring stable compliant effluent.
Actual application results:
Verified by an oilfield produced water project, the process effectively removes 99% of the oils and suspended solids in produced water. The effluent is clear, with oil content and suspended solids both below 10 ppm, meeting reuse standards. Treatment is stable with outstanding shock-load resistance; even with large fluctuations in influent quality and flow, the effluent continuously meets reinjection requirements.
