Evaluation of wellbore parameters for well HE-4, Hellisheiði, SW-Iceland

Abstract

The Hellisheidi geothermal prospect is part of the Hengill high-temperature geothermal area and is considered to be a promising potential field for further exploration. Two deep exploration wells, HE-3 and HE-4, were directionally drilled in 2001. After completion of drilling, HE-4 was tested for its pressure response to step injection flow rates of 20.7, 30.6 and 45 l/s. The data was analysed to evaluate transmissivity, formation storage, wellbore storage and the skin of well HE-4 using semi-log analysis, type curve matching and the Lokur program. Furthermore, temperature and pressure logs were performed during injection, dynamic and warm-up periods of well HE-4. These profiles were analysed and revealed three main feed zones and two minor feed zones. They were also used to estimate the formation temperature and initial pressure near the well. Initial pressure at the well is evaluated using the PREDYP program and the formation temperature is estimated using the BERGHITI program. The program BERGHITI has two options, the Horner method and the Albright method. These two methods were used to evaluate the formation temperature of well HE-4 from the warm-up temperature profiles. The dynamic profiles were simulated by varying the number of feed zones, flow rate, and enthalpy contribution of each feed zone and the total enthalpy at wellhead, at wellhead pressure of 15 bar-a, using the wellbore simulator HOLA. A long-term production test was performed for well HE-4 in the year 2002. The well’s discharge history for 147 days was analysed. Enthalpy of the well simulated by HOLA and the enthalpy obtained from the production test were compared and discussed.