| Title | Pre-stimulation Coupled THM Modeling Related to the Northwest Geysers EGS Demonstrations Project |
|---|---|
| Authors | Jonny RUTQVIST, Patrick F. DOBSON, Julio GARCIA, Curtis M. OLDENBURG, Donald W. VASCO, Mark WALTERS, Craig HARTLINE |
| Year | 2013 |
| Conference | Stanford Geothermal Workshop |
| Keywords | Modeling, Stimulation, Geysers, EGS, thermal, seismicity |
| Abstract | The northwest Geyser EGS demonstration project aims at creating an Enhance Geothermal System (EGS) by directly and systematically injecting cool water at relatively low pressure into a known High Temperature (400„aC) Reservoir (HTR) located under the conventional (240„aC) steam reservoir. It is an unconventional EGS to enhance the production from untapped resources below the conventional steam field. In this paper we present the current status of coupled thermal, hydraulic, and mechanical (THM) modeling made as part of a pre-stimulation project phase. The model simulations were conducted to investigate injection strategies and effects cold water and pressure upon the EGS system, in particular to predict the extent of the EGS for a given injection schedule. The actual injection (stimulation) begun in October 2012, and we present a comparison of pre-stimulation model predictions to micro-earthquake (MEQ) monitoring data over the first several months of injection. The results show that, with a calibration of the geomechanical model against historic injection and MEQ data at a nearby well, we were able to make a reasonable prediction of the extent of the new EGS, given that the MEQ events are the results of shear activation of pre-existing fractures. However, from monitoring of reservoir pressure, MEQ and ground-surface movements we show evidence of more complex geology, such as minor faults and fractures that provide preferential flow paths or are hydraulically bounding. |