Performance evaluation of hybrid polymer-phosphonate scale inhibitors in oilfield water flooding operations

The formation of inorganic scales such as calcium sulfate and barium sulfate during water injection in oilfields can severely impair productivity by clogging pores and reducing rock permeability. This study evaluates the performance of two industrial scale inhibitors—diethylenetriaminepenta (methylene phosphonic acid) (DTPMP) and polyphosphinocarboxylic acid (PPCA)—and their hybrid blends in mitigating scale formation under laboratory and simulated reservoir conditions. Laboratory assessments included scale prediction modeling, static bottle tests, dynamic tube blocking, turbidity, and coreflooding experiments to determine inhibition efficiency, retention behavior, and formation damage potential. Thermodynamic modeling using OLI Studio predicted the maximum scaling tendency at a mixture of 70% injection water and 30% formation water, which was used as the baseline brine for testing. The 50:50 PPCA:DTPMP blend achieved the highest inhibition efficiency (>90%) for both calcium and barium sulfate scales at only 50 ppm, outperforming individual inhibitors. Under dynamic tube blocking conditions, the hybrid system maintained stable pressure profiles, effectively delaying scale nucleation and reducing pressure buildup. Turbidity analyses showed lower light transmittance values (5.6%–6.1%) for the blend, confirming its superior resistance to particle formation and growth. Coreflooding experiments further revealed that the hybrid inhibitor minimized permeability loss to only 5%, compared with 72% in the blank and 9–13% for the single-inhibitor cases. Adsorption/desorption experiments confirmed rapid adsorption (equilibrium in <2 pore volumes) and sustained desorption over 20 pore volumes, indicating strong and prolonged retention. These results demonstrate a positive synergistic effect between the nucleation inhibition mechanism of PPCA and the crystal growth suppression mechanism of DTPMP. The 50:50 hybrid formulation offers a practical, efficient, and economically viable solution for long-term scale management under reservoir conditions.