Thermal stability of generic barium sulphate scale inhibitor species under static and dynamic conditions

Polyvinyl sulphonate (PVS), phosphino polycarboxylic acid (PPCA), and penta-phosphonate (DETPMP) scale inhibitor species have been investigated for their suitability for application in high pressure and high temperature (HP/HT) reservoirs. The thermal stabilities of solid and solution samples of these generic scale inhibitors have been determined at temperatures of 175 and 200 °C at low pressure (<15 bar) and at 175 °C at high pressure (515 bar). The potential stabilising effect of adsorption onto Clashach core has also been investigated for the PVS and DETPMP species and the effect of acid hydrolysis on the stability of PPCA and PVS has been considered. The results of this study indicate that PVS was the most thermally stable scale inhibitor species tested and was not degraded after thermal ageing in aqueous solution at 200 °C for 14 days, whereas DETPMP was rapidly degraded when thermally aged at 175 °C. The stability of PPCA at 180°C was dependent on solution pH, but the thermal stability of PVS was unaffected by the solution pH.