Identification of MHF Fracture Planes and Flow Paths: A Correlation of Well Log Data with Patterns in Locations of Induced Seismicity

Abstract

One of the critical steps in developing a hot dry rock geothermal system is the creation of flow paths through the rock between two wellbores. To date, circulation systems have only been created by drilling one wellbore, hydraulically fracturing the well (which induces microearthquakes), locating the microearthquakes and then drilling a second wellbore through the zone of seismicity. A technique for analyzing the pattern of seismicity to determine where fracture planes are located in the seismically active region has recently been developed. This allows us to distinguish portions of the seismically active volume which are most likely to contain significant flow paths. We applied this technique to seismic data collected during a massive hydraulic fracturing (MHF) treatment and found that the fracture planes determined by the seismic method are confirmed by borehole temperature and caliper logs which indicate where permeable fractures an/or zones of weakness intersect the wellbores. A geometric model based on these planes and well log data has enhanced our understanding of the reservoir flow paths created by fracturing and is consistent with results obtained during production testing of the reservoir.