The prediction and optimisation of scale inhibitor squeeze treatments demands careful attention to both aqueous phase behaviour and the resulting retention mechanisms in consolidated core material. Phase behaviour patterns for single and binary systems of acrylate and phosphonate scale inhibitors in sea water have been generated over a range of pH values and concentrations appropriate to flooding and field conditions. The phase maps were utilised to define coreflooding strategies that would yield separate adsorption and precipitation retention mechanisms for detailed study under a controlled pH environment.
Retention and desorption characteristics of the single component inhibitor agents were performed at 80°C on Clashach sandstone core specimens in both adsorption and precipitation regimes where possible. Return curve analyses were quantified using inductively coupled plasma spectroscopy and an analytical colourimetric method for the phosphonate and acrylate respectively. Desorption profiles have been fitted to mathematical expressions and the physical significance of the models used have been interrogated.
Binary inhibitor systems capable of yielding both adsorption and precipitation phase behaviour at 80°C were selected for test purposes to establish the prevailing retention mechanisms of both agents in competition. Separate desorption profiles for each inhibitor following a binary system shut-in were generated. The role and suitability of simple mathematical models to aid the interpretation and impact for future formulations has been addressed.