Measurement of Injectivity Indexes in Geothermal Wells with Two Permeable Zones

Injectivity tests in wells with two permeable zones and internal flow is analyzed in order to include the usually severe thermal transient effects. A theoretical analysis is performed and a method devised to obtain information from the thermal transient,,provided that temperature is measured simultaneously with pressure. The technique is illustrated with two real tests performed at Miravalles, Costa Rica. It allows to estimate total injectivity index as well as the injectivity index of each one of the two zones separately. Correct position of measuring tools and nature of spontaneous internal flow is also discussed.