Pressure Drops Due to Silica Scaling

Abstract

Experience with reinjection returns in many geothermal fields ha^ prompted a move towards injecting waste fluids at some distance from the production field. This means that often, reinjection pipelines cover vely long distances. If the waste water in the pipelines is supersaturated with respect to amorphous silica, then the deposition of silica in these pipelines is almost certain. Although the deposit may be of negligble thickness, the inner sutface characteristics of the pipe will be diyferent to those of clean mild steel.

During a silica scaling experiment, geothermal brine was passed through a series of pipes of diyferent sizes and over a period of three weeks, silica scale formed on the inner sutface. The pressure drop along a distance of approximately 5m was measured by a water manometer in all test pipe sections. Signiyicantpressure drop was observed during this time and can be correlated with the increase in the friction factor of the pipe walls due to silica scaling.