Geysering Discharge of a Geothermal Wellbore at Zunil, Guatemala Geothermal Field

Abstract

Within two hours after discharge began, for a production test in 1989 of well ZCQ-4, pressure variations changed from approximately sinusoidal to a cycle of sudden and complex peak discharge pressures, to 9 bar, separated by irregular pressure declines to 5 bar. Initial cycle periods of 42 minutes evolved to 150 minutes by day 20 of continuous testing, when three of four surge peaks were well separated. Chemical signatures of fluids discharged with pressure surges were distinctive. When combined with downwell pressure measurements, assignments can be made for elevations of fluid entry points. The variety of chemical signatures indicates a scarcity of interzone connectivity. These constrained discharges are suspected to derive from altered rubble zones between layered volcanic rocks.