Produced Water Reinjection Treatment Process in Oilfields
After an oilfield is put into production, the reservoir's natural energy is continuously depleted over time as production proceeds. This leads to a steady decline in reservoir pressure, causing significant gas liberation from the crude oil underground, increased oil viscosity, and a marked reduction—or even complete cessation—of well production. Consequently, substantial volumes of crude oil remain trapped underground and become unrecoverable.
To compensate for the subsurface void created by oil extraction and to maintain or enhance reservoir pressure—thereby ensuring stable, high production rates and improving ultimate recovery—it is essential to implement water injection in the oilfield.
Sources of injection water typically include surface freshwater, shallow groundwater, and formation water (produced water) co-produced with crude oil. Currently, the majority of water injected into reservoirs—approximately 80% of the total injection volume—originates from produced water separated during oil production.
Depending on the specific characteristics of the reservoir, reinjected water must meet corresponding water quality standards. Generally speaking, injection water should satisfy the following requirements:
1. Suspended Solids (SS) Control: Injection water should contain as few suspended impurities as possible. Both the concentration and particle size of suspended solids must be controlled to prevent plugging of the injection wellbore, near-well formation face, and reservoir pores.
2. Scale Prevention: The injection water must not form scale or precipitates due to changes in temperature, pressure, or upon mixing with formation water or surface water.
3. Corrosion Resistance: The injection water must not cause corrosion to injection equipment and pipelines.
4. Bacterial Inhibition: Bacterial proliferation in the injection water should not generate new suspended solids or otherwise interfere with the normal operation of the water injection system.
5. Clay Swelling Suppression: The injection water should be formulated or treated to prevent swelling of clay minerals present in the reservoir rock.
To meet these stringent requirements, we have developed a produced water reinjection treatment process specifically designed for application in oil depots, onshore oilfields, and offshore platforms.
This treatment process centers on three key technologies: CDFU (Cyclonic Dissolved Gas Flotation Unit), KFM Activated Media Filter, and modified inorganic membrane filter. By flexibly combining these units, the system can meet the distinct water quality requirements for reinjection into high-permeability, low-permeability, and ultra-low-permeability reservoirs.
Broad Applicability: The process effectively treats both conventional oily wastewater and low-polymer-containing oily produced water, demonstrating wide adaptability across diverse field conditions.
High-Efficiency Oil Removal: It replaces traditional large gravity settling tanks with a high-efficiency cyclonic dissolved air flotation unit. Microbubbles facilitate purely physical demulsification—without chemical additives—significantly reducing oily sludge generation.
Compact and Efficient Process Flow: The system features a short process flow, compact equipment layout, short hydraulic retention time, high treatment efficiency, and minimal footprint.
Intelligent and Automated Operation: All units are skid-mounted and integrated with intelligent control systems, enabling fully automatic, unattended operation.
Stable and Reliable Performance:
The process demonstrates robust operational stability and excellent resistance to shock loads, consistently delivering treated water that meets reinjection standards.
Validated in a real-world produced water treatment project at an oilfield, this technology achieved over 99% removal of oil and suspended solids from produced water. The effluent is crystal clear, with both oil content and suspended solids concentration consistently below 10 ppm, satisfying stringent reinjection specifications. Even under significant fluctuations in influent quality and flow rate, the system reliably maintains stable, compliant effluent quality.
Application Performance:
Validated in a real-world produced water treatment project at an oilfield, this technology achieved over 99% removal of oil and suspended solids from produced water. The effluent is crystal clear, with both oil content and suspended solids concentration consistently below 10 ppm, satisfying stringent reinjection specifications. Even under significant fluctuations in influent quality and flow rate, the system reliably maintains stable, compliant effluent quality.
