Development of an Ecofriendly Scale Inhibitor for Harsh Scaling Environments

Abstract

Abstract The recent advances in drilling and completion technology have led to the development of more complex reservoirs including high pressure, high temperature, and high salinity (HP/HT/HS) fields. A combination of high calcium and barium concentrations in the produced water, coupled to high reservoir temperatures presents a particularly harsh scaling environment which dictates the need for high concentrations of exotic scale inhibitor chemistry for effective downhole scale control. These high levels of inhibitor, typically 10–200 ppm, are particularly difficult to sustain over long production periods leading to a relatively short squeeze life and thus, high well intervention frequency and deferred oil costs. In addition, increasing environmental regulations have made the development of green chemistry a high priority. A number of scale inhibitor chemistries have been shown to be thermally stable and effective at controlling scale deposition under harsh conditions, however, their retention characteristics are less than ideal, leading to short treatment life. In addition, some of these chemistries do not have favourable environmental properties. To meet the challenges presented by the more severe water chemistries and producing environments a new chemistry was developed. The new chemistry contained vinyl sulphonate monomer species, which were expected to provide the polymer with a high level of thermal stability, calcium tolerance and effective barium inhibition properties. The incorporation of a phosphorus containing monomer was expected to provide good retention properties and relative ease of detection. In addition, the use of the novel phosphorus containing monomer offered the opportunity to increase the biodegradation characteristics of the developed polymer. Laboratory studies have suggested that the new inhibitor combines significantly improved thermal stability, calcium tolerance, and barium inhibition with superior retention and environmental properties. Nine squeezes with the new inhibitor have been completed in the North Sea, which have already achieved a significant increase in squeeze life1.