Stauper Offshore hopes its inventive work in CFU design will make the technology suitable for a wide range of applications.
In December 2019, technology provider Stauper Offshore announced that the Norwegian national oil company (NOC) Equinor had qualified its latest-generation compact flotation unit (CFU) for first use after undergoing extensive due diligence co-financed by both parties.
Stauper’s CFU went through lab testing at the NOC’s R&D center in the summer of 2016 prior to pilot testing at the Grane field in the North Sea in June 2017. During the latter phase, two CFUs were tested in series while tied into the platform’s separator and hydrocyclones, achieving as much as 99.5% oil removal.
MEAN OIL IN WATER (OIW) RESULTS OF STAUPER OFFSHORE CFU TESTS AT THE GRANE FIELD
|Tie-in location||Flocculant (ppm)||In CFU 1(ppm)||Out CFU 1(ppm)||Out CFU 2(ppm)||OiW removal CFU 1(%)||OiW removal CFU 1 + CFU 2 (%)|
|Downstream first-stage separator||10||590||12.3||2.7||97.9||99.5|
|Downstream first-stage separator||0||506||68.2||19.2||88.2||95.6|
The successful results can be attributed to Stauper’s design, which is an innovation of well-established induced gas flotation technology. By utilizing a closed conical chamber and generating an upwards cyclonic flow, oil droplets are forced to coalesce, rising with light suspended solids to the top where they can be skimmed off, while larger solids are pushed to the bottom. During this process, clean water flows into a larger vessel that encompasses the conical chamber.
Stauper’s technology can typically process 120,000 bbl/d, or 800 m3/h, in one vessel. Larger flow rates are typically split into several vessels. Highly emulsified water often requires multi-stage cleaning, which is usually carried out through a series of separate units. Stauper’s managing director, Rune G. Nilssen, told Water in Oil that the company’s CFU can be adapted to include stacked isolated chambers within one vessel, allowing for a continuous cleaning process. Installation costs for stacked units would be reduced due to their smaller footprints relative to traditional CFU configurations.
“There is no limit to the number of stages we can put in one vessel,” Nilssen said. “We have proposals out for multiple stages in one vessel, but none have been installed yet.”
The company already has five single-vessel CFUs installed at platforms and FPSOs owned by China National Offshore Oil Corporation in the South China Sea. The two smallest units are treating 90 m3/h each at the Wenchang field, while the largest installation processes 1,650 m3/h through three units at the Caofeidian field. Nilssen explained that that project is achieving over 90% oil removal through a single-stage process using no flocculant.
While Stauper does not yet have installations with Equinor, the company is currently pursuing several opportunities with the NOC and other operators. Nilssen said that tests are in the planning or development stages in Norway, Canada, Africa, the Middle East, and even at onshore projects in Europe.
The company is now working with an unnamed major operator to test its autonomous CFU for installation on unmanned production platforms where remote operations could take place over 6-12-month intervals. The operator is pursuing the program to achieve reductions in capital and operational expenditures by 30% and 50%, respectively.
Stauper is also embarking on other applications for its technology. The company can debottleneck and upgrade existing CFUs and degassers by retrofitting them with its patented internals.
“One leading operator has commissioned Stauper to conduct a study to enhance an oil-water separator vessel with our internals, and another well-known operator has given us the go-ahead for a similar project where they have technology that isn’t working,” Nilssen told Water in Oil.
The company has several patents pending, including for its retrofitting work. Others pertain to a gas mixer that is intended to improve mixing and allow the CFUs to operate below 10% of their designed flow rate, as well as one for gas mixing reliability that would be ideal for subsea and unmanned operations.