Laboratory Synthesis and Evaluation of Phosphorous-Tagged Polymeric Scale Inhibitors

Abstract

Abstract Polymeric scale inhibitors (SIs) possess excellent dispersive and scale inhibition properties. In this study, a series of phosphorous-tagged polymeric SIs (PPSIs) were synthesized to inhibit calcium scale formation in synthetic brines. The design of chemical structure followed previous evaluation results from commercial polymeric SIs to make the synthesized products maintain a high efficiency of scale inhibition. The phosphorus tag of PPSIs will facilitate the detection of SIs for operators to plan a reasonable squeeze treatment. Among three commercial SIs, AA/AMPS was the best one with a scale inhibitory efficiency of 100% at above 75 ppm. While HPMA exhibited little effects on inhibiting scale formation. Regarding the synthesis work, two polymer series including six specific PPSI samples were synthesized using 1 mol% of diethyl allylphosphonate and various AMPS or SSA and AA. 31P NMR spectra exhibited only one peak which corresponds to DEAP as the phosphorous tag. 1H NMR spectra indicated correct chemical structures of the PPSIs. The synthesized PPSI products showed good thermal stability, high efficiency in scale inhibition, and most importantly, the phosphorous detection by ICP. SEM images showed that the cubic and needle-like morphology of CaCO3 and CaSO4 scales were both significantly deformed upon addition of the PPSI to avoid the scale formation at a macroscopic level. After injection of one synthesized PPSI sample at a high concentration (10 wt%) followed by a shut-in period of 24 hours, permeability of the carbonate core plug was slightly changed, suggesting a low formation damage to the carbonate reservoir. After the post-flush of reservoir brine, the concentration of PPSI was still higher than the minimum inhibitor concentration (MIC), indicating an effective scale control during the squeeze lifetime.