Phosphonated Inulin as an Eco-Friendly Thermally Stable Scale Inhibitor for the Oil and Gas Industry: Synthesis, Characterization, Efficacy, and Molecular Insights
Mirza T. Baig, Safwat Abdel‐Azeim, Showkat Ali Ganie, Maryam Warsame, Mohamed F. Mady
Abstract
The oil and gas industry grapples with mineral scale deposits during production, which hinder efficiency and damage equipment. The need for eco-friendly scale inhibitors for high-pressure, high-temperature (HPHT) applications has risen due to offshore regulations. This study investigates phosphonated Inulin (PIn), a modified biopolymer, as an eco-friendly scale inhibitor against calcite, gypsum, and Barite in harsh environments. Inulin, a natural polysaccharide, was functionalized with phosphonate groups, achieving a degree of substitution (DS) of 48.78%. Characterization through NMR and FTIR spectroscopy confirmed the successful modification. The scale inhibition effectiveness of PIn was tested in high-pressure dynamic tube-blocking tests at 100 °C and 80 bar compared to commercial carboxymethyl inulin (CMI). PIn effectively inhibited calcite and gypsum at 5 ppm under dynamic conditions and showed excellent thermal stability after 7 days at 130 °C, along with compatibility with high calcium ion concentrations, though it had minimal impact on barite scale. Molecular simulations offered insights into the morphology of the functionalized polysaccharides with GFN2-xTB MD simulations indicating a transition to a more compact structure. DFT analysis revealed that hydrogen bonds from phosphonate groups are stronger than those from hydroxyl or carboxylic groups, explaining PIn’s higher thermal stability compared to CMI.