Effects of Phosphonate Structures on Brine–Biotite Interactions under Subsurface Relevant Conditions

Abstract

Phosphonates have been widely used as scale inhibitors in energy-related subsurface operations, where their performance is greatly affected by interactions with rocks and minerals. However, information about commonly used phosphonate scale inhibitor–shale interactions is limited. In this study, using Fe-bearing mica (biotite) as a model phyllosilicate mineral, the effects of three common phosphonates, namely, iminodi(methylene)phosphonate (IDMP), nitrilotris(methylene)phosphonate (NTMP), and diethylenetriaminepenta(methylene)phosphonate (DTPMP), were studied at 95 °C and 102 atm CO2. During the experiments (0–70 h), IDMP remained stable, while NTMP and DTPMP were degraded and released phosphate, formate, and new phosphonates with smaller molecular weights. As a result of the differences in complexation capability, IDMP, with the fewest phosphonate functional groups, promoted biotite dissolution mainly through surface complexation and DTPMP, with the most functional groups, promoted biotite dissolution mai...