Production testing in miravalles geothermal field, Costa Rica

Wellbore deposition of calcium carbonate has occurred in the first wells drilled in the Miravalles geothermal field, Costa Rica. Well PGM-1 was flowtested for periods of 1, 5 and 6 months in 1980, 1981 and 1982, respectively. The well is 1300 m deep and produces from a liquid-dominated reservoir at about 240°C. The flowtests illustrate the time behavior of wells suffering from wellbore deposition. At early time the decrease in output flow rate and wellhead pressure is slow but at late time it becomes rapid; the curves are concave down. The ratio (flow rate/wellhead pressure) remains nearly constant with time for wells suffering calcium carbonate wellbore deposition, at least in the Miravalles geothermal field.