Temperature Prediction by Multigeophysical Inversion: Application to the IDDP-2 Well at Reykjanes, Iceland

摘要

The target of the RN-15/EDDP-2 well at Reykjanes is geothermal resources at supercritical temperatures. The drill site has been mapped by electromagnetic and gravimetric surveys. Here, a method for subsurface temperature prediction by multigeophysical inversion is presented and demonstrated on the IDDP-2 drill site. Using resistivity from magnetotelluric inversion and density from gravity inversion, followed by Bayesian rock-physics inversion, the predrill prediction of temperature was 513± 62 °C at 5 km vertical depth along the planned well path. While-drilling updates using resistivity logs, acquired at approximately 2900m and 3450m depth, indicate that the formation temperature is most likely on the high side of the predrill estimate. The well was drilled down to approximately 4500m, and cores were taken at selected depths. The temperature predictions from geophysical data are within temperature ranges indicated by alteration minerals observed in the cores and changes in rock parameters based on well description.