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The Veslefrikk field, located in block 30/3 of the Norwegian sector of the North Sea, has been on production since 1989 and is in the decline phase. Due to seawater injection, commingled production and high reservoir temperature, severe tendency towards deposition of sulphate and carbonate scale has been observed. The economic consequences of scale and the benefit from scale control work had been assessed quantitatively and presented at the 2001 SPE Third International Symposium on Oilfield Scale (Tjomsland et al., 2001). The study showed that the scale control strategy had been an economic success. However, annually more than 4% of the well productivity was still lost due to scale deposition, and in consequence it was recommended to intensify the scale management procedures. A task force involving scale control experts from the licence partners was established. In co-operation with service companies, the group systematically assessed new scale control measures for use at Veslefrikk. In 2006 a benchmark against the 2001 study was performed to investigate if the scale control work had been improved. The results showed that the scale potential was approximately the same in the second period (June 1999–2005) as in the first (1993- May 1999), but a significant improvement in downhole scale control was now obtained through a more aggressive use of preventive scale inhibitor squeezes and the implementation of new technology. However, the study also concluded that scale inhibitor squeezes themselves in some cases caused formation damage, most likely due to the formation of water blocks. Recently a mutual solvent that can be incorporated as part of the squeeze pre-flush was qualified for use on Veslefrikk. This has not only reduced the risk of formation damage, but in some cases even increased productivity has been observed. Introduction The Veslefrikk field is located in block 30/3 of the Norwegian sector of the North Sea. The field has been on production since 1989. It was developed by a 24 slot wellhead platform with drilling facilities in combination with a semi-submersible process platform with a living quarter, Figure 1. The production rate peaked in 1995, and the field is now far into the tail production phase. Seawater injection has been the main method of pressure support, but gas injection has also been performed to increase the recovery factor. The first water breakthrough was observed during 1992. The field water cut has now reached 80–85%, and in average the produced water contains 50–60% seawater. The Veslefrikk reservoir is layered, consisting of several zones with independent pressure regimes and to some degree also different fluid systems. Commingled production is extensively used at the field, due to the limited number of well slots and to optimize the production rate. Scale potential at Veslefrikk The two most common types of scale in the Veslefrikk field are calcium carbonate (CaCO3) and barium sulphate (BaSO4). Calcium carbonate can precipitate if produced fluid containing formation water is pressure depleted, for instance when flowing into or inside the well. The calcium carbonate saturation ratio (SR) increases as the pressure is reduced (see Figure 2), mainly due to the reduced amount of carbon dioxide (CO2) dissolved in the water phase when the pressure is reduced (Tjomsland et al., 2001).