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

详细信息    查看全文

• 作者：Jonny Rutqvist ; Patrick F. Dobson ; Julio Garcia ; Craig Hartline…
• 关键词：EGS ; Modeling ; Coupled processes ; Geomechanics ; Induced seismicity ; Fluid injection
• 刊名：Mathematical Geosciences
• 出版年：2015
• 出版时间：January 2015
• 年：2015
• 卷：47
• 期：1
• 页码：3-29
• 全文大小：4,156 KB
• 参考文献：1. Barton CA, Zoback MD, Moos D (1995) Fluid flow along potentially active faults in crystalline rock. Geology 23:683-86 CrossRef
  2. Catalli F, Meier M-A, Wiemer S (2013) The role of Coulomb stress changes for injection-induced seismicity: the Basel enhanced geothermal system. Geophys Res Lett 40:72-7 CrossRef
  3. Ferretti A, Prati C, Rocca F (2001) Permanent scatterers in SAR interferometry. IEEE Trans Geosci Remote Sens 39:8-0 CrossRef
  4. Ferretti A, Fumagalli A, Novali F, Prati C, Rocca F, Rucci A (2011) A new algorithm for processing interferometric data-stacks: SqueeSAR. IEEE Trans Geosci Remote Sens 49:3460-470 CrossRef
  5. Garcia J, Walters M, Beal J, Hartline C, Pingol A, Pistone S, Wright M (2012) Overview of the northwest Geysers EGS demonstration project. In: Proceedings of the thirty-seventh workshop on geothermal reservoir engineering, Stanford University, Stanford, California, January 30–February 1, 2012
  6. Itasca (2009) FLAC3D, fast Lagrangian analysis of continua in 3 dimensions, version 4.0. Minneapolis, Minnesota, Itasca Consulting Group
  7. Jaeger JC, Cook NGW (1979) Fundamentals of rock mechanics. Chapman and Hall, London, p?593
  8. Khan MA, Truschel J (2010) The Geysers geothermal field, an injection success story. GRC Trans 34:1239-242
  9. Lockner DA, Summer R, Moore D, Byerlee JD (1982) Laboratory measurements of reservoir rock from the Geysers Geothermal Field, California. Int J Rock Mech Min Sci 19:65-0 CrossRef
  10. Majer EL, Peterson JE (2007) The impact of injection on seismicity at the Geysers, California geothermal field. Int J Rock Mech Min Sci 44:1079-090 CrossRef
  11. McClure MW, Horne RN (2012) Investigation of injection-induced seismicity using a coupled fluid flow and rate/state friction model. Geophysics 76:WC183
  12. Mossop AP, Segall P (1997) Subsidence at the Geysers geothermal field, N. California from a comparison of GPS and leveling surveys. Geophys Res Lett 24:1839-842 CrossRef
  13. Nielson D, Moore JN (2000) The deeper parts of the Geysers thermal system—implications for heat recovery. GRC Trans 24:299-02
  14. Oppenheimer DC (1986) Extensional tectonics at the Geysers geothermal area, California. J Geophys Res 91:11463-1476 CrossRef
  15. Pruess K, Oldenburg C, Moridis G (2011) TOUGH2 user’s guide, Version 2.1. LBNL-43134 (revised), Lawrence Berkeley National Laboratory, Berkeley, California
  16. Rutqvist J (2011) Status of the TOUGH-FLAC simulator and recent applications related to coupled fluid flow and crustal deformations. Comput Geosci 37:739-50 CrossRef
  17. Rutqvist J, Oldenburg C (2007) Analysis of cause and mechanism for injection-induced seismicity at the Geysers geothermal field. GRC Trans 31:441-45
  18. Rutqvist J, Oldenburg CM (2008) Analysis of injection-induced micro-earthquakes in a geothermal steam reservoir, Geysers geothermal field, California. In: Proceedings of the 42th US rock mechanics symposium, San Francisco, California, USA, June 29–July 2, 2008. American Rock Mechanics Association, San Francisco. Paper no?151
  19. Rutqvist J, Wu Y-S, Tsang C-F, Bodvarsson G (2002) A modeling approach for analysis of coupled multiphase fluid flow, heat transfer, and deformation in fractured porous rock. Int J Rock Mech Min Sci 39:429-42 CrossRef
  20. Rutqvist J, Dobson PF, Oldenburg CM, Garcia J, Walters M (2010) The northwest Geysers EGS demonstration project phase 1: pre-stimulation coupled geomechanical modeling to guide stimulation and monitoring plans. GRC Trans 34:1243-250
  21. Schmitt AK, Grove M, Harrison TM, Lovera O, Hulen J, Walters M (2003) The Geysers–Cobb mountain magma system, California (part 2): timescales of
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Mathematical Applications in Geosciences
  Statistics for Engineering, Physics, Computer Science, Chemistry and Geosciences
  Geotechnical Engineering
  Hydrogeology
  
• 出版者：Springer Berlin Heidelberg
• ISSN：1874-8953

文摘

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 (280-00?°C) Zone (HTZ) located under the conventional (240?°C) geothermal steam reservoir at The Geysers geothermal field in California. In this paper, 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. 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.