Control of inorganic scale within oilfield production wells via the scale squeeze process is well documented. The life time of the squeeze treatment is dictated by the cumulative volume of produced water flowing through the treated interval until the minimum inhibitor concentration (MIC) of the scale inhibitor is reached. Inhibitor chemicals with strong retention and low MIC values have been developed, deployed and for many years phosphonates and polymers containing phosphonate functional groups have been widely used.

This study looks at the issues faced by an operator with a low temperature sandstone reservoir of only 40°C and the challenges this low temperature brought which include high MIC for sulphate scale control and poor chemical retention & release observed during the reservoir condition corefloods. These findings will be compared and contrasted with two other higher temperature (71°C and 95°C) sandstone reservoirs where phosphonates and phosphate ester chemicals have been evaluated and deployed in the field.

The findings from this detailed coreflood study and review of previous experimental/field deployed scale squeeze treatment data shows that phosphonates work very well at elevated temperatures at and above 70°C where their stronger retention and excellent release profiles makes them a favoured chemical for such treatments, however at lower temperatures these molecules are not well retained on the rock and it is the phosphate ester chemicals that are more effective and provided the longer squeeze life. Comments on the interaction/performance of polymer scale inhibitors will also be made for these low temperature conditions

The implication of these findings clearly show that phosphate esters offer the potential for extended squeeze lifetime in the <50°C sandstone reservoirs which are being developed in Northern Norway (Barents Sea) and the shallow depth, cool reservoirs being developed in offshore Brazil.

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