Development of a Geological and Geomechanical Framework for the Analysis of MEQ in EGS Experiments (Geysers) Geothermal Project

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Last modified on July 22, 2011.

Project Title Development of a Geological and Geomechanical Framework for the Analysis of MEQ in EGS Experiments (Geysers)
Project Type / Topic 1 Recovery Act: Enhanced Geothermal Systems Component Research and Development/Analysis
Project Type / Topic 2 Induced Seismicity

Project Description Water injection is used in engineered or enhanced geothermal systems (EGS) to increase rock permeability, a process which involves fracture initiation and/or reactivation of joints through pore pressure and stress perturbations. This stimulation process is often accompanied by multiple microseismic events associated with rock failure or shear slip on pre-existing fractures. The microseismic signals can be used to understand the hydraulic fracturing process and the properties of the created reservoir. Despite progress in quantitative and qualitative analysis of reservoir stimulation using MEQs, the fundamental mechanisms still are poorly understood and several key questions remain unresolved namely, the variation of seismic activity with injection rate, delayed micro-seismicity, the relation of the stimulated zone to the injected volume and its rate, the connectivity of fractures hosting MEQs, and the resulting reservoir permeability. In addition, longer term phenomena such as permeability evolution related to thermal contraction remain to be investigated.

The proposed work will be carried out using samples extracted from fresh core to be obtained from Geysers well E-8 supplemented by samples from surface outcrops and existing core from the University of Utah core library. The resulting methodologies and catalog of rock mechanical properties and their sensitivity to different tectonic settings will guide development of future EGS projects. As the project aims to identify causal mechanisms of induced seismicity and the relationship between the physical properties of the reservoir and MEQs (as identified in the current FOA), it will facilitate development of large untapped portions of hot rock systems through. This is consistent with the GTP goal of recovering heat energy from low permeability rocks at commercial rates and competitive costs.

State Texas
Objectives - Develop a framework for investigating processes that contribute to the occurrence of seismicity in enhanced geothermal systems with particular reference to the Geysers EGS demonstration experiment.


- Utilize an integrated geological and geomechanical approach to identify the causal mechanisms of MEQs, and to relate their occurrence to the characteristics of porosity and permeability.

Awardees (Company / Institution) Texas A&M University
Legal Name of Awardee Texas Engineering Experiment Station
Awardee Website http://www.tamu.edu/
Partner 1 Temple University
Partner 2 New England Research
Partner 3 AltaRock


Partner 6 Environ International Corp.
Partner 7 Princeton Engineering Group




Funding Opportunity Announcement DE-FOA-0000075

DOE Funding Level (total award amount) $1,061,245.00
Awardee Cost Share $546,197.00
Total Project Cost $1,607,442.00



Principal Investigator(s) Ahmad Ghassemi, Texas A&M University
Other Principal Investigators Nicholas Davatzes, Temple University; Susan Petty, AltaRock Energy; Dr. Greg Boitnott, New England Research, Inc

Targets / Milestones - Characterize the intact rock and natural fractures in the Felsite to establish a fracturing history;


- Characterize the petrophysical and geomechanical properties of the Felsite using advanced experimental rock deformation experiments under conditions of pressure and temperature applicable to EGS;
- Experimentally study generation of MEQ’s and permeability in response to water injection under a triaxial stress state;
- Identify the mechanisms associated with the generation MEQ’s in relation to dynamic of fracture permeability using analytical and numerical analyses benchmarked by observations of naturally and experimentally deformed samples.





Location of Project College Station, TX
30.627977°, -96.3344068°



Impacts If successful, will provide a fundamental understanding of the relationship between geothermal operations and the generation of earthquakes.
Funding Source American Recovery and Reinvestment Act of 2009

References EERE Geothermal Technologies Programs[1]

References

  1. EERE Geothermal Technologies Programs