*Physical & theoretical chemistry, *Molecular structure, *Materials science, *Crystal morphology, *Crystal lattices, *Montmorillonite, *Acrylic acid

In this study, based on the escalating demand for thermally stable scale inhibitors in high-pressure/high-temperature (HPHT) water–gas reservoirs, an organic–inorganic composite scale inhibitor (CT-5) was successfully synthesized via solution polymerization-mediated in situ intercalation using acrylic acid (AA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and diallyldimethylammonium chloride (DMDAAC) as monomers, with surface-modified montmorillonite (MMT) as reactive filler. Orthogonal optimization established ideal synthesis parameters, which including a reaction temperature of 75 °C, an initiator dosage of 0.6%, a solution pH of 7, a reaction time of 12 h, and a monomer ratio of m (AMPS): m (AA): m (DMDAAC): m (MMT) = 48:25:23:4. Moreover, the molecular structure and thermal stability of CT-5 were characterized by FTIR, XRD, and TG-DTG, as a result, the polymer intercalated MMT was successful, and CT-5 had a composite intercalation structure of organic polymer/inorganic montmorillonite, with a thermal decomposition temperature of 235.24 °C. Salt tolerance evaluation demonstrated robust performance under saline conditions. The scale inhibition mechanism of CT-5 was explored through scale inhibition rate testing, interlayer spacing testing at different temperatures, characterization of CaCO3 scale crystal structure and morphology, and chemical binding energy testing of CaCO3 scale crystals. The CT-5 can release effective chelating groups in the intercalation layer at high temperature, which inhibits the formation of CaCO3 scale by chelating Ca2+ to form chelates, and also forms an adsorption layer on the surface of CaCO3 scale crystals to interfere with the normal growth of CaCO3 scale crystals and change the lattice structure of CaCO3 scale crystals, thereby achieving the scale inhibition effect. [ABSTRACT FROM AUTHOR]

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