2026-10-31
Operating 210 kilometers off the coast of Rio de Janeiro in the pre-salt Santos Basin, a major Floating Production Storage and Offloading (FPSO) vessel processes 180,000 barrels of crude oil per day. To maintain reservoir pressure and maximize secondary oil recovery, the vessel operates a continuous seawater injection system with a total treatment flow rate of 3,800 m³/h. Raw seawater drawn from a depth of 60 meters contains fine suspended marine solids, plankton micro-organisms, silt particulates, and organic detritus.
The raw seawater must be purified to stringent water quality standards before passing into ultra-filtration (UF) and sulfate removal units (SRU) to prevent barium and strontium sulfate scaling inside the subsea reservoir formations. The vessel originally relied on conventional dual-basket manual strainers and automatic disc filters. However, deepwater biological blooms and fine silica sand rapidly clogged the original systems, causing severe pressure drops across the water injection skid and threatening subsea reservoir delivery rates. The offshore platform operator contracted LEFILTER to engineer an automated, ultra-compact, high-pressure primary filtration solution compliant with stringent marine and offshore oil & gas standards (NORSOK / DNV GL).
Rapid Blinding During Marine Algae Blooms: Seasonal plankton and micro-algae blooms created a gelatinous biofilm across the legacy screen filters. Differential pressure ($\Delta P$) spiked from 0.03 MPa to over 0.25 MPa within minutes, triggering emergency bypass valves and threatening membrane damage downstream.
Severe Marine Environment Corrosion: High-salinity raw Atlantic seawater, combined with hydrogen sulfide traces and ambient marine air, caused severe pitting and crevice corrosion on standard 316L stainless steel strainers within 4 months of offshore deployment.
Space and Weight Constraints on the FPSO Topsides: Space and structural deck load limits on the FPSO topside module were extremely tight. Replacing the filtration skid required a high-capacity system with a compact footprint and low operating weight.
High Risk of Subsea Reservoir Siltation: Filtration bypass allowed fine suspended solids ($> 50\,\mu\text{m}$) into the SRU membranes. Pin-hole failures on membranes allowed silt to enter subsea injection wells, risking permanent formation damage and costly well-workover interventions.
LEFILTER’s offshore oil & gas engineering division designed and delivered a skid-mounted, lightweight filtration array comprising five parallel LEFILTER LF-FC Series Automatic Multi-Chamber Backwash Filters constructed entirely from Super Duplex Stainless Steel 2507 (UNS S32750).
Super Duplex 2507 Metallurgy: All wetted components—including filter shells, internal drives, wedge wire elements, and flange connections—were fabricated from Super Duplex 2507, providing absolute immunity to seawater pitting ($PREN > 42$) and stress corrosion cracking.
Precision 50 $\mu\text{m}$ Anti-Fouling Elements: The system integrated 50 $\mu\text{m}$ V-shaped wedge wire elements polished to an ultra-smooth finish ($Ra < 0.2\,\mu\text{m}$). The inverted V-slot geometry prevents fibrous organic matter and marine micro-organisms from lodging inside the filter apertures.
Non-Stop Isolated Backwash Sequence: Each vessel features six independent filtration chambers. When differential pressure reaches 0.10 MPa, an internal motor rotates the cleaning shoe beneath one chamber at a time, using clean system fluid to purge trapped organic solids overboard in 25-second bursts, maintaining 100% continuous flow to the UF membranes.
Offshore-Certified Redundant Controls: The explosion-proof (ATEX Zone 1 / IECEx) control cabinet houses a dual-redundant Siemens S7-1500FH safety PLC. The system features dual PROFINET communication channels for real-time integration into the FPSO’s central ICSS platform.
Turnkey Offshore Delivery: LEFILTER managed complete DNV GL third-party pressure vessel certification, non-destructive testing (NDT), skid lifting frame load testing, and dispatched offshore-certified field service engineers directly to the Santos Basin for topside installation and commissioning.
Following 22 months of continuous deepwater offshore operation in Brazil, the LEFILTER Super Duplex filtration skid delivered outstanding operational metrics:
UF & SRU Membrane Protection: Suspended solids and organic particulates $> 50\,\mu\text{m}$ were 100% eliminated from the SRU feed stream, extending downstream ultra-filtration membrane element lifespans from 8 months to over 28 months.
Zero Corrosion Defect: Comprehensive ultrasonic wall-thickness testing and boroscope inspections conducted during annual shutdown confirmed zero pitting, crevice corrosion, or structural wall thinning across all five Super Duplex vessels.
Uninterrupted Seawater Injection: The system maintained continuous 3,800 m³/h seawater delivery throughout two major seasonal marine algae blooms, eliminating water-injection-related crude oil production cutbacks.
Weight and Footprint Optimization: The compact LEFILTER skid reduced the structural footprint by 38% and overall dry weight by 27% compared to traditional automatic media beds, satisfying FPSO deck loading requirements.
Project Amortization: Increased crude oil production uptime and reduced membrane replacement costs fully amortized the capital expenditure of the LEFILTER system within 5.4 months of offshore commissioning.
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