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Title: The Northwest Geysers EGS Demonstration Project, California. Pre-stimulation Modeling and Interpretation of the Stimulation

Abstract

The Northwest Geysers Enhanced Geothermal System (EGS) demonstration project aims to create an EGS by directly and systematically injecting cool water at relatively low pressure into a known High Temperature (280–400 °C) Zone (HTZ) located under the conventional (240 °C) geothermal steam reservoir at The Geysers geothermal field in California. Here we report that , the results of coupled thermal, hydraulic, and mechanical (THM) analyses made using a model developed as part of the pre-stimulation phase of the EGS demonstration project is presented. The model simulations were conducted in order to investigate injection strategies and the resulting effects of cold-water injection upon the EGS system; in particular to predict the extent of the stimulation zone for a given injection schedule. The actual injection began on October 6, 2011, and in this paper a comparison of pre-stimulation model predictions with micro-earthquake (MEQ) monitoring data over the first few months of a one-year injection program is presented. The results show that, by using a calibrated THM model based on historic injection and MEQ data at a nearby well, the predicted extent of the stimulation zone (defined as a zone of high MEQ density around the injection well) compares well with observed seismicity.more » The modeling indicates that the MEQ events are related to shear reactivation of preexisting fractures, which is triggered by the combined effects of injection-induced cooling around the injection well and small changes in steam pressure as far as half a kilometer away from the injection well. Pressure-monitoring data at adjacent wells and satellite-based ground-surface deformation data were also used to validate and further calibrate reservoir-scale hydraulic and mechanical model properties. The pressure signature monitored from the start of the injection was particularly useful for a precise back-calculation of reservoir porosity. Ultimately, the first few months of reservoir pressure and surface deformation data were useful for estimating the reservoir-rock permeability and elastic modulus. Finally, although the extent of the calculated stimulation zone matches the field observations over the first few months of injection, the observed surface deformations and MEQ evolution showed more heterogeneous behavior as a result of more complex geology, including minor faults and fracture zones that are important for consideration in the analysis of energy production and the long-term evolution of the EGS system.« less

Authors:
 [1];  [1];  [2];  [2];  [1];  [1];  [1];  [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Calpine Corporation, Middletown, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1254437
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Mathematical Geosciences
Additional Journal Information:
Journal Volume: 47; Journal Issue: 1; Journal ID: ISSN 1874-8961
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; EGS; Modeling; Coupled processes; Geomechanics; Induced seismicity; Fluid injection

Citation Formats

Rutqvist, Jonny, Dobson, Patrick F., Garcia, Julio, Hartline, Craig, Jeanne, Pierre, Oldenburg, Curtis M., Vasco, Donald W., and Walters, Mark. The Northwest Geysers EGS Demonstration Project, California. Pre-stimulation Modeling and Interpretation of the Stimulation. United States: N. p., 2013. Web. doi:10.1007/s11004-013-9493-y.
Rutqvist, Jonny, Dobson, Patrick F., Garcia, Julio, Hartline, Craig, Jeanne, Pierre, Oldenburg, Curtis M., Vasco, Donald W., & Walters, Mark. The Northwest Geysers EGS Demonstration Project, California. Pre-stimulation Modeling and Interpretation of the Stimulation. United States. doi:10.1007/s11004-013-9493-y.
Rutqvist, Jonny, Dobson, Patrick F., Garcia, Julio, Hartline, Craig, Jeanne, Pierre, Oldenburg, Curtis M., Vasco, Donald W., and Walters, Mark. Thu . "The Northwest Geysers EGS Demonstration Project, California. Pre-stimulation Modeling and Interpretation of the Stimulation". United States. doi:10.1007/s11004-013-9493-y. https://www.osti.gov/servlets/purl/1254437.
@article{osti_1254437,
title = {The Northwest Geysers EGS Demonstration Project, California. Pre-stimulation Modeling and Interpretation of the Stimulation},
author = {Rutqvist, Jonny and Dobson, Patrick F. and Garcia, Julio and Hartline, Craig and Jeanne, Pierre and Oldenburg, Curtis M. and Vasco, Donald W. and Walters, Mark},
abstractNote = {The Northwest Geysers Enhanced Geothermal System (EGS) demonstration project aims to create an EGS by directly and systematically injecting cool water at relatively low pressure into a known High Temperature (280–400 °C) Zone (HTZ) located under the conventional (240 °C) geothermal steam reservoir at The Geysers geothermal field in California. Here we report that , the results of coupled thermal, hydraulic, and mechanical (THM) analyses made using a model developed as part of the pre-stimulation phase of the EGS demonstration project is presented. The model simulations were conducted in order to investigate injection strategies and the resulting effects of cold-water injection upon the EGS system; in particular to predict the extent of the stimulation zone for a given injection schedule. The actual injection began on October 6, 2011, and in this paper a comparison of pre-stimulation model predictions with micro-earthquake (MEQ) monitoring data over the first few months of a one-year injection program is presented. The results show that, by using a calibrated THM model based on historic injection and MEQ data at a nearby well, the predicted extent of the stimulation zone (defined as a zone of high MEQ density around the injection well) compares well with observed seismicity. The modeling indicates that the MEQ events are related to shear reactivation of preexisting fractures, which is triggered by the combined effects of injection-induced cooling around the injection well and small changes in steam pressure as far as half a kilometer away from the injection well. Pressure-monitoring data at adjacent wells and satellite-based ground-surface deformation data were also used to validate and further calibrate reservoir-scale hydraulic and mechanical model properties. The pressure signature monitored from the start of the injection was particularly useful for a precise back-calculation of reservoir porosity. Ultimately, the first few months of reservoir pressure and surface deformation data were useful for estimating the reservoir-rock permeability and elastic modulus. Finally, although the extent of the calculated stimulation zone matches the field observations over the first few months of injection, the observed surface deformations and MEQ evolution showed more heterogeneous behavior as a result of more complex geology, including minor faults and fracture zones that are important for consideration in the analysis of energy production and the long-term evolution of the EGS system.},
doi = {10.1007/s11004-013-9493-y},
journal = {Mathematical Geosciences},
number = 1,
volume = 47,
place = {United States},
year = {2013},
month = {10}
}

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    Works referencing / citing this record:

    Effects of long-term fluid injection on induced seismicity parameters and maximum magnitude in northwestern part of The Geysers geothermal field: EFFECTS OF INJECTION AT THE GEYSERS
    journal, October 2015

    • Kwiatek, Grzegorz; Martínez-Garzón, Patricia; Dresen, Georg
    • Journal of Geophysical Research: Solid Earth, Vol. 120, Issue 10
    • DOI: 10.1002/2015jb012362

    A multi-stage 3-D stress field modelling approach exemplified in the Bavarian Molasse Basin
    journal, January 2016

    • Ziegler, Moritz O.; Heidbach, Oliver; Reinecker, John
    • Solid Earth, Vol. 7, Issue 5
    • DOI: 10.5194/se-7-1365-2016

    Effects of long-term fluid injection on induced seismicity parameters and maximum magnitude in northwestern part of The Geysers geothermal field: EFFECTS OF INJECTION AT THE GEYSERS
    journal, October 2015

    • Kwiatek, Grzegorz; Martínez-Garzón, Patricia; Dresen, Georg
    • Journal of Geophysical Research: Solid Earth, Vol. 120, Issue 10
    • DOI: 10.1002/2015jb012362

    A multi-stage 3-D stress field modelling approach exemplified in the Bavarian Molasse Basin
    text, January 2016