Evaluation of polyelectrolytic complexes based on poly(epichlorohydrin-co-dimethylamine) and poly (4-styrene-sulfonic acid-co-maleic acid) in the delivery of polyphosphates for the control of CaCO3 scale in oil wells

Abstract Polyelectrolytes complexes (PEC) based on poly(epichlorohydrin-co-dimethylamine) (EPI-DMA) and poly(4-styrene-sulfonic acid-co-maleic acid) (PSSMA) for polyphosphates encapsulation were prepared for the first time. The sodium hexametaphosphate (SHMP) was used as a model polyphosphate in this work. A factorial design 23 was applied to optimize PEC formulations. The resultant PEC suspensions were characterized by dynamic light scattering (DLS), zeta potential and encapsulation efficiency (EE) of SHMP. The best results were found by formulation using 1% (w/w) of EPI-DMA, 0.1% (w/w) of PSSMA and addition of SHMP before PSSMA. This optimized formulation was applied in real oil well conditions and showed good stability at 25 °C and reduced stability with increasing temperature. PEC showed excellent inhibition efficiency against calcium carbonate scale with minimum inhibitory concentration (MIC) of 2.0 mg L-1 at 100 °C and 1000 psi. PEC suspension also showed exceptional performance on assessment to sandstone, improving not only the adsorption of the material on the rock grains but also the durability of the scale inhibitor squeeze process by 100%.