ernest majer
TRANSCRIPT
Latest Developments in Best Practices and Mitigation Efforts for Induced Seismicity
(Injection related)
GWPC Feb 10, 2015
Ernie Majer (LBNL), Stefan Wiemer (ETH), Austin Holland (OGS), Bill Foxall (LBNL) and Katie Freeman (LBNL)
Acknowledgements
USGS Powell Center Induced Seismicity Group
USDOE Geothermal and the IEA/IGPT program
BLM
Hal Macartney (Pioneer Natural Resources)
Kris Nygaard (Exxon Mobil)
Mark Zoback (Stanford U.)
Craig Hartline (Calpine)
Josh White, LLNL
Bill Foxall , LBNL
KCC/KGS/KDHE Induced Seismicity State Task Force
Relevant Questions
Is the operation safe and in compliance with regulations?
While maximizing at the same time the chance of commercial success.
What alternative injection strategy should be followed to be safe and commercially successful?
What mitigation strategy should be followed when things develop in unfavorable ways?
Logic Chain for Protocol
Need to address main question ( how to make energy application “safe”, economical and accepted?)
Perform Preliminary Screening Evaluation
Purpose: Identify any factors that will automatically disqualify a site from being a successful injection site (W.R.T. induced seismicity)
For example, any known significant induced seismicity history, in a populated seismogenic zone, near sensitive, near large favorably oriented faults,hostile public, etc.
Involve and communicate to all stake holders
Monitor and characterize the site
Define hazard
Calculate risk
Design mitigation
Main Challenges (some)
How to regulate/manage/mitigate a process that:
Is often (always?) site specific
Often has unknown or “fuzzy” boundary conditions
Stress, faults, varying levels of acceptability (lack of data!!!)
Has a variety of stakeholders (some hostile)
Upsetting but not necessarily high risk
May occur in areas of no measured historical seismicity
Occurs in rare instances of fluid injection
Is rate/pressure dependent (non stationary)
Still under study by the research community
Balances risk with energy needs
Some Good News
Induced seismicity (I.S.) is not new
The basics of injection I.S. is understood
Occur on faults, stress and pressure perturbation
Given a reasonable amount of data, in almost all cases the causes can be identified (mitigated?)
Industry is coming on board and recognizing that it must be dealt with (provide data?)
AXPC, States First Initiative I.S. working group – led by state regulators with active involvement by industry
Active industry trade groups (AXPC,API,OIPA, TXOGA, etc.)
Science and technology of understanding I.S. is advancing
Experience shows that once the stakeholders are well informed acceptance increases (risk understood)
Damaging events are extremely rare
Current “Practices”No national guide or regulations are in place (good thing?)
One size does not fit all (each site has different conditions and risks)
Progress from screening to more detail as situation dictates
Can be regulated at the state or even local level
e.g. OK, KS, CO, TX, OH
There are a few current “suggested” protocols
National Academy Report
DOE geothermal/IEA Protocol/best practices
Not regulation but suggestions that are updated as knowledge changes
BLM and EPA are developing “permitting procedures”
Mainly for geothermal and carbon sequestration
Courtesy Mark Zoback
Most hydraulic fractures
Most other injection
Maximum seismic moment and magnitude as functions of total volume of injected fluid from the start of injection until
the largest induced earthquake. (McGarr 2014, JGR)
CalpineThe Geysers 1960 through 2011Field-wide Steam Production, Water Injection and Seismicity
SE
GE
P S
tart
SR
GR
P S
tart
Note: As injection increaseslarger seismicity is decreasing!But, net volume change is decreasing
Calpine Mitigation (Geothermal)
Seismic Monitoring and Advisory Committee (SMAC) Biannual meetings
Field activity and seismicity update to community, industry and academic rep.’s
Seismic Hotline: 877-4-GEYSER, 707-431-6161 ( & alternate number)
Provides Detailed Reporting of Events of M>/= 4.0 (or M >/=3.5; MMI >/= 5; PGA >/= 3.9%)
Santa Rosa Geysers Recharge Project (SRGRP) Injection and seismicity relationships
URS Corporation geophysicists perform independent data analysis and report generation
Meet Monthly with Community: Each Community has Geothermal Mitigation and Community Investment Committee:
Review seismicity related claims and funding for community benefit projects
Geothermal operators provide geysers operational updates and announcements
Calpine Geothermal Visitors Center: Open to the public / Geysers tours: free community tours offered spring through fall
Injection modified to reduce ground motion in near by communities
Simulation-based Induced Seismicity Risk Analysis
NUFT flow simulation
• Injection begins 200 years after burn-
in• Injection duration 50 years• Flow rate 0.6 Mton/yr• Injection depth 1800 m• Reservoir thickness 25 m
• Permeabilities: reservoir 10-15 m2
faults 10-13 m2
P
fault
Oklahoma Geological Survey Recommendations
Fluid injection near known faults/known seismicity should be avoided: potential of deeper faulting, especially faults favorably oriented within either the regional or local stress field.
Injection in to, or close to, Precambrian basement should be avoided. (Pore pressure may concentrate in networks of existing natural fractures and faults.)
Monitoring (in real time if possible) of:
Injection pressures/formations/volumes
Seismicity
Best to balance injection volumes with produced fluids in areas of I.S. that involve both production and injection of fluids in nearby wells (assuming permeability and operating conditions are right).
In cases where fluid injection is occurring in higher risk environments, additional geotechnical information may help to provide further constraints on injection limits.
The operator should have a plan in place to recognize and respond in a timely manner to unexpected seismicity or changes in injection pressure or volume.
Note: All of the above requires data!!!!!
Courtesy Kris Nygaard
This represents the collective thoughts of subject matter experts drawn from AXPC member companies and other Oil and Gas Industry companies.This presentation does not represent the views of any specific trade association or company.
This represents the collective thoughts of subject matter experts drawn from AXPC member companies and other Oil and Gas Industry companies.This presentation does not represent the views of any specific trade association or company.
Courtesy Kris Nygaard
BLM Geothermal Approach
Provide information and data to make a simplified bounding risk analysis to help in making decision to pursue EGS project
if so what critical information and plans will be needed
Needed is accurate enough information to estimate:
Maximum event size and seismicity rates
Radius of influence of seismicity as a function of time
Timely and high enough quality data for performing mitigation measures
Examples
Past seismicity
Location relative to people / structures
Proposed injection volumes / rates, length
Geologic data, known faults / sizes, stress directions, formation pressures
Mitigation plans
Outreach and communication plans
Adaptive Traffic Light System (ATLS)
S. Wiemer, et al (2014)
Proposed Adaptive Traffic Light System
a) Decisions are based on observed
magnitudes and ground motions.
Thresholds are defined in a static
manner taking geotechnical information
into account to the extent possible.
Current
b) Decisions are based on a forward looking, probabilistic and adaptive framework.
Models are assessed in near real time and weighted accordingly.
Current Approach
Proposed Approach
S. Wiemer, et al (2014)
• Dynamic
• Physics based
Proposed
Needs
Data and continuous communication
Improved sharing of data sets between industry and other stakeholders (seismicity, injection, geology)
Easier said than done, complex issue
Improved mitigation methods that can be tailored for different applications (adaptive)
Implies better fundamental understanding and modeling of I.S.
Communicate in an understandable way (engender public trust)
Recognition by all stakeholders that I.S. need not be a major issue if properly addressed
Technical Needs
Improving the knowledge of natural tectonics and subsurface stress / pressure conditions
Identify significant fault systems prone to slip (consider both the deeper basement and shallower geologic horizons)
Improving the understanding of ground shaking behavior and seismic wave attenuation characteristics
Ground motion not magnitude is important
More broadly establishing a cohesive, integrated, and interdisciplinary technical framework
Define fit-for-purpose approaches for risk management of potential I.S.
Differentiating naturally-occurring earthquakes from induced earthquakes
Develop effective capabilities and methods, based on sound-science
ConclusionsEconomic drivers are advancing the knowledge base
I.S. is also a tool in addition to a concern
Industry is “on board”
How do small operators with limited resources comply
There are some accepted “best practices” models and procedures for mitigating induced seismicity
More being developed by industry with public input
Scientific community needs to interface with private and public bodies
Transfer knowledge in an understandable fashion
The regulatory side needs to recognize that induced seismicity knowledge is still evolving
Technical expertise will be needed to properly oversee permitting
All stakeholders must communicate and make data available
Permitting agencies are moving towards adopting an adaptive approach to regulate and mitigate induced seismicity
Implies need for better “stoplight” methods
Backup
The Geysers Seismicity (two months) around Aug 24, 2014
Red = number of events located per dayBlue = Number of triggers/day
Mag 6 “Napa” Earthquake, 70 Km away
Elevated Fluid Pressure:
• Reduces effective normal stress on fault, lowering resistance to
shearing. Implies that if pressure balance can be maintained seismicity can be controlled
Role of Fluid Pressure in Earthquake Generation
For an earthquake to occur one must exceed the critical shear stress on the fault:
c + (n – p)
Normal (clamping)
Stress = n
In situ Shear
Stress Water/fluid pressurein fault = p
C = Rock strength = coefficient of friction on slip plane
Some Basic Assumptions
Most earthquakes occurs on existing faults/fractures
There is a relation between fault size and magnitude (Kanamori and Anderson(1975), Kanamori (1975), Wells and Coppersmith (1994) Shaw (2009))
Mw = 1.23 X 10 e22 S (3/2) dyne-cm ( S in sq KM (K & A))
Mw = log A + 3.98 ( A = area in sq km, Shaw)
Larger events tend to nucleate deeper than smaller events (Das and Scholz 1983)
i.e stress increases with depth
Size of earthquake depends upon fault area, and stress (drop)
Most injection related seismicity depends on amount of net fluid injected ( and temperature of rock versus temp of fluid)
Damage is a function of shaking not magnitude(shaking is a function energy reaching the surface and surface conditions)
EGS Site 1 Seismicity before (2 years) Injection and during injection (11,363 M cubed) 12 days
Before After
EGS Site 2: Seismicity before (3 years) Stimulation (11,320 M cubed ) and during stimulation ( 3 days)
Historical seismicity Injection seismicity
Risk calculationSIMRISK
Earthquake mag - frequency
Ground motion
Flow model:DP(x,t)
Green’s fns.
stress & fault
params
EqCatalog
Ground motion
Hazard curve
Eq. source params
Risk Curve
Fragility
Some references
Majer, E, Nelson, J., Robertson-Tait, A, Savy, J., and Wong I. 2013 Protocol for
Addressing Induced Seismicity Associated with Enhanced Geothermal Systems (EGS) DOE/EE publication 0662
Majer, E, Nelson, J., Robertson-Tait, A, Savy, J., and Wong I. 2014 Best Practices for Addressing Induced Seismicity Associated with Enhanced Geothermal Systems (EGS) LBNL – 6532E