Scale Inhibitor Solutions for High Temperature Wells in a Steam Drive Reservoir

Steam drive is an enhanced oil recovery method which reduces the viscosity of crude and cleans the near-wellbore area through steam injection. Application of high temperature and high pressure steam provides a challenge on downhole scale mitigation.

Heavy scale has been reported for high temperature wells in a steam drive reservoir in western US. The incumbent PBTC (2-phosphonobutane-1,2,4-tricarboxylic acid)-based scale inhibitor, which worked very well in relatively low temperature wells, was suspected to fail in high temperature wells because of thermal stability limitations due to molecular instability. Therefore, a group of polymeric scale inhibitors with various chemistries were selected for investigation to replace the incumbent chemical for high temperature wells. The scale inhibition performance of the polymeric inhibitors was evaluated in dynamic scale loop equipment at 350°F (177°C). Sulphonated carboxylic acid copolymer was determined to be the best candidate for calcite scale control in the high temperature wells in the steam drive reservoir. The polymer was recommended to be continuously deployed downhole to prevent the formation of the calcite scale.