Three Dimensional Modeling of Fracture Systems Using Images from Boreholes

A Fracture Modeling System has been developed by Electric Power Development Company (EPDC) to facilitate the interpretation, display and analysis of fractures identified by borehole imaging tools. Borehole images of individual fractures provide understanding of the local properties of the fracture itself. If an integrated model of the field’s large-scale fracture system could be developed, it would help optimize the further exploration and exploitation of the geothermal field. Such a representation would enhance the likelihood of penetrating permeable targets during drilling and aid in reservoir modeling and long-term field management. Recently, numerous fractures have been detected and characterized using downhole electrical resistivity and/or ultrasonic imaging in EPDC’s operating geothermal fields in Japan using Fullbore Formation MicroImager (FMI) logs and BoreHole TeleViewer (BHTV) logs. Integrated three-dimensional fracture modeling was then accomplished by extrapolating individual fracture properties (dip, azimuth and depth) from image data obtained in boreholes. As a result, 3-D trends of fracture orientation were successfully obtained which correlate with other data from nearby wells, such as lost circulation zones and mapped fracture distributions. The 3-D fracture system representations constructed using the Fracture Modeling System can provide useful information for geothermal reservoir characterization.