China Offshore Produced Water Treatment Technologies & Systems

Offshore separators and compact flotation units (CFUs) encounter dynamic angular pitch and roll on FPSOs and drillships. Our engineering teams apply Computational Fluid Dynamics (CFD) multiphase sloshing simulations to model free surface behavior under 100-year storm conditions. We incorporate structured cyclonic internals, perforated baffle plates, longitudinal calming vanes, and vortex breakers. These internal elements dampen standing waves, eliminate liquid churning, and prevent re-entrainment of collected oil droplets into the treated water stream.

Produced water often contains elevated hydrogen sulfide (H₂S) alongside chloride concentrations exceeding 60,000 to 120,000 mg/L at temperatures up to 80°C. Standard 316L stainless steel is vulnerable to chloride stress corrosion cracking (CSCC) and severe pitting under these conditions. We engineer wetted surfaces using Super Duplex Stainless Steel (UNS S32750 / 2507) with a Pitting Resistance Equivalent Number (PREN) ≥ 42, or utilize Grade 2 and Grade 7 Titanium for high-pressure membrane housings. For severe sour duties, all materials comply fully with NACE MR0175 / ISO 15156 limits for sulfide stress cracking resistance.

Polymeric membranes can suffer severe fouling if exposed directly to raw produced water containing free hydrocarbons and asphaltenes. Our process design mitigates this by enforcing strict primary and secondary de-oiling (hydrocyclone + CFU) to lower free oil-in-water levels below 20 ppm prior to membrane polishing. When using tubular ceramic membranes (silicon carbide or alumina), the surface exhibits hydrophilic properties and withstands solvent washing, high temperatures, and back-pulsing up to 10 bar. For high-salinity brine reduction, Disc Tube Reverse Osmosis (DTRO) uses open-channel hydrodynamic spacers that eliminate stagnant flow areas, preventing organic cake adhesion and facilitating effective Clean-in-Place (CIP) cleaning cycles.

All electrical instruments, control consoles, level transmitters, solenoid manifolds, and drive motors installed on offshore skids undergo certified explosion-proof compliance reviews matching the platform hazardous area classification (Zone 1 or Zone 2, Gas Group IIA, IIB, or IIB+H₂). Certificates of conformity from international notified bodies (such as Baseefa, DEKRA, or PTB) are compiled in the manufacturer record book. During the Factory Acceptance Test (FAT), purging pressure switches, intrinsic safety barrier resistance, and earthing bonding continuity (<0.1 ohm) are verified by third-party inspection agencies.

Equipment handovers include an exhaustive Manufacturer’s Data Report (MDR). This covers Mill Test Certificates (EN 10204 Type 3.1/3.2), Non-Destructive Examination records (Radiographic, Ultrasonic, Magnetic Particle, and Liquid Penetrant inspection), hydrostatic test charts witnessed by class inspectors, helium leak testing logs, protective coating dry film thickness (DFT) logs conforming to ISO 12944 C5-M / CX offshore marine standards, functional logic validation dossiers, and complete operation and maintenance (O&M) manuals.