The Client's Needs
Production operations at the oilfield use a steam injection process to decrease the viscosity of the oil and push it toward the production wells. The Produced Water rises to the surface with the oil. Prior to building the water reclamation facility, this water was reinjected into the ground, which put unwanted pressure on the formation. In addition, the reinjected water cooled the steam used to heat the oil, making it less efficient in oil extraction.
The oil company sought a means of eliminating Produced Water reinjection to enhance oil recovery. Advanced water treatment was required to generate a water quality suitable for discharge to the local waterways, a habitat for Steelhead Trout.
To meet the challenges of the oilfield, Veolia proposed a water reclamation facility utilizing OPUS® II technology. The system treats 50,000 barrels per day (bpd) of Produced Water, resulting in a high quality effluent. About 25,000 bpd are used for steam generation.
This high-quality water enhances the steam purity, making it more efficient in the oil production process. The remainder is discharged to a local creek under an NPDES permit that addresses 100 parameters to ensure the discharge water quality. The augmented flow in the creek improves the habitat for aquatic life.
OPUS II technology utilizes Veolia’s Turbomix® technology and ceramic membranes, followed by its Whittier® ion exchange softener and a reverse osmosis system operated in a double-pass mode at an elevated pH. (See Process Description below.) Post-treatment steps are also included at this site to meet the stringent requirements of the NPDES permit.
The water reclamation facility was delivered as a Design-Build-Operate-Maintain project. Under this 12-year agreement, Veolia guarantees the performance of the system for the life of the contract. Over time, eliminating the Produced Water reinjection is expected to increase oil production by a factor of 8 to 10.
OPUS II technology consists of multiple treatment processes involving chemical softening, membrane filtration, ion exchange softening and reverse osmosis operated at an elevated pH. The pretreatment processes ahead of the RO are designed to reduce free oil, hardness, metals and suspended solids in the feed water. The RO process operates at an elevated pH, which effectively controls biological, organic and particulate fouling, eliminates scaling due to silica and increases the rejection of silica, organics and boron.
In the OPUS II technology, the feed water is chemically softened, and free oil and solids are removed in a pretreatment process that uses ultrafiltration technology. This process consists of a series of reaction tanks followed by a crystallization tank fitted with our patented Turbomix® mixing technology, which facilitates precipitation of hardness and metals in the feed water and crystallization of the solids generated by precipitation. The softened water and crystalline solids are then processed through the ceramic membrane ultrafiltration system operated in crossflow mode for removal of free oil, total hardness and suspended solids to lower concentrations. The solids waste from the ultrafiltration process is intermittently recycled to the crystallization tank and purged intermittently for dewatering and subsequent hauling to landfill for disposal.
The filtrate from the ultrafiltration process is further treated with ion exchange softening utilizing Weak Acid Cation (WAC) resin in sodium form for further removal of hardness and metals to lower concentrations, without pH change across the resin. The pretreated water is then pressurized through the RO, operated at an elevated pH in double pass mode, to reduce the TDS, boron and organics. Following the OPUS II process, post-treatment consists of ammonia removal, organics polishing, pH control, and remineralization