Sustaining Hot Spring Activity in the Vicinity of Geothermal Developments

Abstract

Hot springs represent a continuum of surface features associated with hydrothermal activity and high-medium enthalpy geothermal resources. In some fields, such surface expression has proven to be vulnerable to what appears to be irreversible change in the wake of geothermal development, particularly at early stages of fluid production. The record of activities in New Zealand and the western USA shows that near boiling springs and geysers, are particularly sensitive to pressure induced lowering of the water table, becoming inactive, and in some cases replaced by zones of steaming ground. The geological control on the flow and ascent of hot water is an important factor in governing the magnitude of induced effects. But permeability is a unique geological attribute, and no two hydrothermal systems are exactly alike. For this reason, there are also examples where hot spring activity is unaffected by and much less sensitive to geothermal production due to structural and stratigraphic compartmentalization. Such geological factors in combination with injection strategies minimize induced pressure change and provide insights of how surface thermal activity can be protected and monitored in the vicinity of geothermal production fields. Case studies of fields in New Zealand and the western USA will be covered to illustrate these points.