Abstract
The scale control challenges of two North Sea carbonate reservoirs are reviewed in this paper. This paper outlines the mechanism of scale inhibitor retention observed for three different generic types of chemical (phosphonate, polymer, and vinyl sulfonate co-polymer) within carbonate reservoirs. The methods of chemical placement will also be reviewed with the technical challenges faced when performing scale inhibitor squeeze treatments into fractured chalk reservoirs being detailed. Deployment methods discussed for chemical placement into carbonate reservoirs includes conventional bullhead squeeze and more novel methods such as chemical blending within the fracture fluid and the deployment of scale inhibitor as solids within the fracture proppant. Furthermore, this paper focuses on field results of for over 50 treatments applied in reservoirs E and V where both phosphonate and vinyl sulfonate polymer chemicals have been scale squeezed. The different retention mechanisms suggested by laboratory studies were validated in the field and by changing from a phosphonate to a vinyl sulphate co-polymer scale a significant extension in treatment lifetime was achieved. Field data will also be presented on the deployment of scale inhibitor within fracture fluids and scale inhibitor impregnated proppant packs. It is clear that a complete understanding of scale control during the life cycle of water injection within a carbonate reservoir is vital to select the correct chemical and to apply it effectively to extend treatment life time whilst, moreover, minimising operational downtime and associated cost. To this end novel technologies to enhance conventional chemical placement are vital to economic success during water flood projects.
