Development of Fluorescence Tagged Scale Inhibitors for Squeeze Applications in Gulf of Mexico

Abstract

Fluorescence tagged (F-tagged) scale inhibitors are drawing more interest in the oil industry and are being applied in the field. One main reason is being easily detectable and differentiable from other scale inhibitors. However, when applied to a new oilfield, it is necessary to evaluate their thermal stability, limit of detection (LOD), and fluorescence measurement interference from other chemicals. Two F-tagged scale inhibitors were tested in this study. They are the same polymeric inhibitors with different and differentiable fluorescent tags. Both F-tagged inhibitors were able to be detected in synthetic brine and field brine from a Gulf of Mexico (GoM) field, with LOD of 1ppm. A coreflood test was also conducted for inhibitor squeeze treatment evaluation. The residual scale inhibitor in core flooding samples was measured by both fluorescence method and high performance liquid chromatography (HPLC). The results from two methods generally match with each other. This strongly indicates that the F-tag is stable on scale inhibitors and fluorescence measurement is a reliable method for scale inhibitor detection. Thermal aging test and long storage test were conducted. For both F-tagged scale inhibitors, the thermal aged samples and samples with different storage lifetime did not show significant difference on scale inhibition performance and fluorescence measurement. The two F-tagged inhibitors tested can tolerate high temperature up to at least 130°C (266°F). With proper storage, F-tagged inhibitors after long shelf storage were still as effective as fresh inhibitors. Based on all the test results in this paper, these two scale inhibitors are ready for squeeze application in GoM.