Summary
Several squeeze treatments in the Ekofisk field have tested various squeeze parameters, such as the overflush volume and the displacement means to maximize the scale squeeze life time, to prevent the formation of downhole scale cost-effectively. Scale may form when incompatible waters are mixed or the physicochemical parameters of the fluid (temperature, pressure, and chemical composition) change. This paper presents experience gained from treatment of high-salinity produced water on the Tor platform (2/4E) in the Norwegian sector of the North Sea, which has a total-dissolved-solids (TDS) content of about 200, 000 mg/L, compared with the typical average of about 70, 000 mg/L in some other Ekofisk fields. The high-salinity water requires extra care for predicting the scaling tendency, inhibiting scale formation, and preventing upsets in the downstream production facilities, like the oily-water treatment system. The high content of calcium and iron ions present in the produced water makes it even more difficult to treat. Because the scale inhibitor selected is nearly always a compromise, no one single laboratory test can determine the best scale inhibitor. This paper, however, discusses an approach for examining the sulfate-scale-inhibition efficiency with a reference to field experience for both down-hole and topside treatments.