No abstract

The implementation of highly effective polishing filter technologies plays a key role in polymer EOR where reservoir characteristics require extremely good water qualities. Few filter technologies are capable of handling volatile inlet fluid conditions such as back-produced polymer concentrations up to 420 ppm and OIW contents up to 70 ppm while targeting treated water qualities of less than 5 ppm OIW. A fully integrated field trial was set up in the Matzen field in Austria where producing wells from EOR operations provide sufficiently high polymer concentrations for technology evaluations. A three-phase separator and a multi-chamber flotation unit were used as upstream treatment to supply produced water to the different filtration technologies under evaluation. With this setup, a broad range of entry criteria like OIW, solid content, polymer concentration and oil droplet size could be adjusted to challenge each filtration technology to its limit. None of the tested technologies such as nutshell filters, conventional multi-media-filters, coated media, or vendor specific technologies were able to handle the challenging inlet water conditions while providing the required water qualities for polymer flooding projects. A new concept was developed, combining conventional multi-media filtration design with a type of media that, thus far, was not common in the oil and gas industry. A system-specific operating envelope was developed, describing the strong impact of inlet water conditions such as oil droplet size D50 values down to 15 micron, OIW concentrations up to 70 ppm, solid contents up to 10 mg/l and viscosities up to 3 cp. Where state-of-the-art technologies did not fulfill the performance criteria, it was possible to achieve less than 5 ppm at the filter outlet. Not only the filter performance but also the crucial aspect of effective media regeneration was solved with a novel filter backwash design, since known backwash systems completely failed with the newly implemented media.