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