We report an integrated study on silica and silicate scales in steam generator tube and water injection wells based on scale modeling and testing, scale sample characterization, and field observations.
For the steam generator tube scenario, significant amount of metal silicates in field scale sample were identified, which is consistent with the extremely high scaling potential indicated by scale modeling. Halite formation was not predicted by scale modeling but significant amount of halite was identified in the scale sampled from inside of a generator tube. It is suspected the formation of metal silicates, especially Fe silicates, can facilitate/accelerate the formation of other type of scales and eventually lead to the tube plugging, overheating, and failure.
For the injection well scale management study, silica and silicate were identified in the scale precipitates from waters sampled at upstream of the injection point. While scale modeling (based on the composition of the filtered water samples) indicates potential further metal silicate scale deposition at wellbore temperature and pressure conditions, no significant amount of metal silicate scale was identified in lab testing with current available field water samples. Lab testing shows the dominating scale for injection well is calcite, which appears consistent with learnings from an initial field trial testing.