Risk Assessment for Geothermal Wells ? A Probabilistic Approach to Time and Cost Estimation

Abstract

In the last five years about 30 deep geothermal wells have been drilled in the Southern German Molasse Basin. 16 of them have been planned and/or supervised by ERDWERK GmbH who supports the operator as a consultant throughout the project. One of the main duties of a consultant like ERDWERK GmbH is cost planning and time schedule forecasting for the well construction process. To date, these estimates have been based on a historic average time for the main operations which have been added up to the total well construction time. Uncertainties have been taken into account by adding a contingency factor. This approach has the advantage of being simple, fast and easy to communicate. However, it does not give any idea about the variability of the estimate and the risks involved, which limits its application. Therefore, the aim of the work presented in this paper was to establish a well construction model based on statistical methods to allow probabilistic time and cost estimation.