# Presentation: 187713

## Cooperative Research on Induced Seismicity Associated with Enhanced Geothermal Systems:An  Update

**Ernest Majer, Roy Baria and Mike Fehler**** ****LBNL, Mil-Tech, LANL**

## Objectives

- Provide  mechanism for the industry and the  research community  to  gain a  critical mass to  identify  priority  activities to understand  and if possible ( and  necessary) to mitigate the effects of  EGS activities on seismic activity.

## History

- Numerous examples of  induced seismicity associated with fluid  injection (  waste disposal, reservoir  impoundment ( dams), mining, oil production, geothermal.
- Both natural and artificial ( induced permeability) systems demonstrate  induced seismicity
- As  more and  more injection occurs to increase geothermal energy production seismicity may  become an issue with the community and the field operator
- US DOE is participating in an international agreement with the IEA to  address environmental issues associated with EGS.
- To initiate  the  induced seismicity activity the first workshop was convened at  Stanford in  Feb  2005 after the Geothermal workshop

## GIA Annex I Subtask D

- “Participants will pursue a collaborative effort to address an issue of significant concern to the acceptance of geothermal energy in general but EGS in particular.”...
- “The objective is to investigate these events to obtain a better understanding of why they occur so that they can either be avoided or mitigated”.

## EGS Workshop Results

- Two day DOE/IEA meeting held at Stanford/USGS in Feb 05 to develop a path forward on assessing and mitigating seismic risk.
- 38 participants from international community from universities, industry and labs
- Interdisciplinary
- Case histories
- Technical discussions

## Induced Seismicity and EGS

**Over all Goal**
**Provide information to improve the overall understanding of the relation between enhancing geothermal systems (reservoir manipulation)  and seismicity.**
**Understand characteristics of seismicity**
**Magnitude distribution (space and time) of seismicity**
**Is it possible to mitigate and optimize production and injection activities at bathe same time?**
**Does the reservoir reach equilibrium?**
**Hazard ( to local communities and facilities)**
**What parameters are critical to controlling/estimating  Seismic activity during EGS  activities?**
**What is the minimum knowledge we need to determine how EGS (injection and production) affect seismic activity?**
**Stress distribution**
**Geologic conditions/history**
**Historical seismicity**
**Reservoir  pressure and temperatures**
**Geochemistry**
**Rate/pressure/volume of injection**
**Spatial and temporal distribution of wells**
**Etc.**

**Notes:**
Top Figure a): Vertical cross section through Rye Patch model with wave front time snapshots at two time steps. Interaction of waves with fault reveals attenuation of seismic energy and reflection and refraction off fault. Bottom Figure b): Seismogram section of the waves as recorded in the receiver array along the top of the model. The attenuation of the waves by the fault can be seen as a gap in the amplitudes of the first arriving P-wave. The reflected and refracted waves can be seen originating from the location of the fault as indicated by the red line.

Fit of Work within Program Structure:
	Develop state-of-the-art seismic imaging techniques for geothermal resources exploration in EGS
Objectives: 
	Investigate how state-of-the-art seismic imaging techniques, developed for hydro-carbon exploration, can be applied to geothermal 	resources exploration
Work Scope: 
	Numerical 2-D finite difference modeling based on real subsurface parameters obtained at Rye Patch over past years
	Investigate what signatures faults and fracture zones produce in 2-D seismic data
	Provide suggestions as to how to reinterpret existing 2-D seismic data sets
	Investigate how time- and financially expensive 3-D seismic surveys can be optimized for pre-defined targets based on 2-D results
Work Organization and Performance: 
	Work is performed at LBNL’s Center for Computational Seismology
	Work is carried out by Roland Gritto and Ernest Majer of LBNL
Current and Future Accomplishments: 
	Result obtained thus far indicate intriguing footprints of blind faults and fracture zones even for single receiver lines, suggesting the 	reinterpretation of previously acquired 2-D seismic data sets to detect these features 
	Results can be used to optimized design of planned 3-D seismic surveys to maximize definition of target properties
	Currently no future plans due to stop in funding 
Knowledge Gaps: 
	Although 3-D state-of-the-art seismic imaging has been successfully used in hydro-carbon exploration, the targets and geological 	settings in EGS are different such that developed approaches cannot be easily converted to geothermal systems
	Need to better investigate and understand the kinematics and dynamics of seismic wave propagation in geothermal settings using 	modeling approaches based on real subsurface geothermal models
Advantage of Industry Collaboration: 
	Industry collaboration can provide the required physical parameters and geometries of the EGS systems under investigation.
	Industry can provide outside review to keep research goals close to industry needs

## Induced Seismicity and EGS

**What data and results exist?- What can we learn from other similar situations? - Path forward.**
**Existing data sets**
**Seismicity**
**Reservoir/geologic**
**Production **
**Case histories**
**Experience with  communities**
**Non geothermal but  similar**
**Oil and Gas**
**Fluid disposal**
**Dam impoundment**
**Excavation/Blast**
**Earthquake Hazard Program**
**Current and future monitoring**
**Etc.  **

**Notes:**
Top Figure a): Vertical cross section through Rye Patch model with wave front time snapshots at two time steps. Interaction of waves with fault reveals attenuation of seismic energy and reflection and refraction off fault. Bottom Figure b): Seismogram section of the waves as recorded in the receiver array along the top of the model. The attenuation of the waves by the fault can be seen as a gap in the amplitudes of the first arriving P-wave. The reflected and refracted waves can be seen originating from the location of the fault as indicated by the red line.

Fit of Work within Program Structure:
	Develop state-of-the-art seismic imaging techniques for geothermal resources exploration in EGS
Objectives: 
	Investigate how state-of-the-art seismic imaging techniques, developed for hydro-carbon exploration, can be applied to geothermal 	resources exploration
Work Scope: 
	Numerical 2-D finite difference modeling based on real subsurface parameters obtained at Rye Patch over past years
	Investigate what signatures faults and fracture zones produce in 2-D seismic data
	Provide suggestions as to how to reinterpret existing 2-D seismic data sets
	Investigate how time- and financially expensive 3-D seismic surveys can be optimized for pre-defined targets based on 2-D results
Work Organization and Performance: 
	Work is performed at LBNL’s Center for Computational Seismology
	Work is carried out by Roland Gritto and Ernest Majer of LBNL
Current and Future Accomplishments: 
	Result obtained thus far indicate intriguing footprints of blind faults and fracture zones even for single receiver lines, suggesting the 	reinterpretation of previously acquired 2-D seismic data sets to detect these features 
	Results can be used to optimized design of planned 3-D seismic surveys to maximize definition of target properties
	Currently no future plans due to stop in funding 
Knowledge Gaps: 
	Although 3-D state-of-the-art seismic imaging has been successfully used in hydro-carbon exploration, the targets and geological 	settings in EGS are different such that developed approaches cannot be easily converted to geothermal systems
	Need to better investigate and understand the kinematics and dynamics of seismic wave propagation in geothermal settings using 	modeling approaches based on real subsurface geothermal models
Advantage of Industry Collaboration: 
	Industry collaboration can provide the required physical parameters and geometries of the EGS systems under investigation.
	Industry can provide outside review to keep research goals close to industry needs

## Induced Seismicity and EGS

**What measurements and data are needed and for how long?**
**Seismic**
**Surface versus borehole**
**Single versus multi-component**
**Bandwidth and dynamic range ( Remote sensing/tilt to AE?)**
**Spatial and temporal  coverage**
**Reservoir**
**Pressure, temperature**
**Stress**
**Geochemistry **
**Fluid state**
**Local ground response**
**Geologic**
**Faults/fracture **
**Lithology**
**Other**
**Gravity**
**EM/Resistivity**
**Etc**

**Notes:**
Top Figure a): Vertical cross section through Rye Patch model with wave front time snapshots at two time steps. Interaction of waves with fault reveals attenuation of seismic energy and reflection and refraction off fault. Bottom Figure b): Seismogram section of the waves as recorded in the receiver array along the top of the model. The attenuation of the waves by the fault can be seen as a gap in the amplitudes of the first arriving P-wave. The reflected and refracted waves can be seen originating from the location of the fault as indicated by the red line.

Fit of Work within Program Structure:
	Develop state-of-the-art seismic imaging techniques for geothermal resources exploration in EGS
Objectives: 
	Investigate how state-of-the-art seismic imaging techniques, developed for hydro-carbon exploration, can be applied to geothermal 	resources exploration
Work Scope: 
	Numerical 2-D finite difference modeling based on real subsurface parameters obtained at Rye Patch over past years
	Investigate what signatures faults and fracture zones produce in 2-D seismic data
	Provide suggestions as to how to reinterpret existing 2-D seismic data sets
	Investigate how time- and financially expensive 3-D seismic surveys can be optimized for pre-defined targets based on 2-D results
Work Organization and Performance: 
	Work is performed at LBNL’s Center for Computational Seismology
	Work is carried out by Roland Gritto and Ernest Majer of LBNL
Current and Future Accomplishments: 
	Result obtained thus far indicate intriguing footprints of blind faults and fracture zones even for single receiver lines, suggesting the 	reinterpretation of previously acquired 2-D seismic data sets to detect these features 
	Results can be used to optimized design of planned 3-D seismic surveys to maximize definition of target properties
	Currently no future plans due to stop in funding 
Knowledge Gaps: 
	Although 3-D state-of-the-art seismic imaging has been successfully used in hydro-carbon exploration, the targets and geological 	settings in EGS are different such that developed approaches cannot be easily converted to geothermal systems
	Need to better investigate and understand the kinematics and dynamics of seismic wave propagation in geothermal settings using 	modeling approaches based on real subsurface geothermal models
Advantage of Industry Collaboration: 
	Industry collaboration can provide the required physical parameters and geometries of the EGS systems under investigation.
	Industry can provide outside review to keep research goals close to industry needs

## EGS Workshop Results

**Technical Issues**
**Is it possible to mitigate and optimise production at the same time? **
**Does the reservoir reach an equilibrium**
**What are the critical parameters necessary to estimate the seismicity hazard. **
**What are the factors controlling the seismicity? **
**What measurements and data are lacking, and if additional  data are needed, how much  and how long should monitoring continue? **
**What can we learn from other induced seismicity cases? general seismicity? **
**Can Probabilistic Seismic Hazard Analysis (PSHA) be used for Geothermal areas to estimate the largest events?**
**How  does one explain  the occurrence of large events  when  there are no large faults? **
**Are there experiments  that can be performed which will shed light on  key mechanisms causing EGS seismicity? **
**How does induced seismicity mitigation differ in natural fractured systems versus hydrofracturing environments**

## Hot  Dry / Tight Rock

**1995**
**1996**
**2000**
**2003**

- Upper Reservoir
- 1987 - 1997

- Deep Reservoir
- 1988 - 2003

- Soultz  Project

- Michelet  et al  2005

- 5000 M Depth

## Slide 11

## More information can be obtained from source parameter calculation:

**Same area with large seismic moments in 2000 & 2003**
**	****  ****high seismic activity zone**

**Larger stress drop located all around the stimulated area ****	****	****     **
**                 ****stress front propagation **

- Michelet  et al  2005

## EGS Workshop Results

**Path Forward**
**Put the results of the meeting on a web with links to data and other results**
**Form a working group to prioritize efforts  and keep the collaboration  current.**
**Have a short and intermediate term goal of understanding mechanisms of larger  “hazardous” events and develop mitigation techniques.**
**Longer term goal of understanding induced seismicity in general.**
**Publish summary of workshop in EOS.**
**Organize a dedicated issues of International Journal of Rock Mechanics addressing EGS Induced seismicity .**
**Schedule the next workshop at the annual meeting of the GRC.**

## Slide 14

## Summary

- Unique data set
- Research community
- Public
- Seismicity may be Achilles' heal, addressing this issue now is required for EGS to be successful
- New information on induced seismicity will be generated for mitigation purposes and reservoir management
- Publications
- White paper on induced seismicity
- Report on First EGS induced seismicity workshop
- EOS article on result of workshop
- Special issue in IJRM being developed on EGS Induced seismicity
- Web  site  for information exchange
-  _[http://esd.lbl.gov/](http://esd.lbl.gov/egs)__[egs](http://esd.lbl.gov/egs)_
- Next  workshop at  2005 GRC ( wed at 5:00PM in N-1, Thur 8:00 – 3:00 PM  , N1)

## Second  Workshop on EGS Induced SeimicityReno , NevadaSept 28- 29, 2005Reno , Hilton Day 1 (  5 pm to  7 pm wed night) ( N1 Conference Room)The purpose of the workshop and suggested topics to be covered:     1.  Update on activities since the Stanford  meeting ( Majer and Baria)     Confirmation of the establishment of Home Page: comments on the improvement & publicity. Confirmation of the establishment of a Data Base: comments on the accessibility, format, sharing and acknowledgement. Formation of an entity (club with access privileges), to encourage cooperation between researchers and industry.  Discussion on  priorities of  future work  Possible mechanisms for the generation of  large  events     Cooperative  experiments    Industry  needs              Would it be possible to coordinate some investigations from various angle by forming a working group and working as an entity?Communication  with  others 

## Day 2 ( 8:00 am to 3:00pm)  Do we understand enough to reduce large induced seismic events? If so, how can we validate it or devise a procedure to validate it. Need a way forward ?   Method of characterisation and evaluation of bigger induced events: Do we need down hole sensors or are the surface sensors sufficient. What is the appropriate model to characterise these types of events? Can we agree on the bandwidth and sensitivity needed for evaluation. Is coda method the right approach for estimating the energy output?  Is there an inherent process before a big or bigger events occur? Are there extraneous circumstances, which assist in the generation of bigger events i.e. large injected volume of fluid, large extraction of fluid, specific state of the in-situ stresses, rock type, in-situ fluids, temperature gradient, geological settings, one shock wave initiate a second, etc.