Geohazard Assessments as Part of Risk Management for
Underground Natural Gas Storage
Presented to Southern Gas Association
By
James L. Gooding, Ph.D., PG
Geoclime, LLC
July 15, 2019
Making the Climate of Quality Work for Your Enterprise ©
Geohazard Assessments for Underground Natural Gas Storage
Information Review
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC2
Geohazards Affecting Underground Natural Gas Storage (UNGS)
Regulatory Perspectives
Geohazard Assessment Process
Case History: Location-Specific Assessment
Geoclime Services
Geohazard Assessments for Underground Natural Gas Storage
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC3
Geohazards Affecting Underground Natural Gas Storage
(UNGS)
Geohazard Assessments for Underground Natural Gas Storage
Definition of UNGS Geohazard
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC4
A geohazard for underground gas storage is any natural force or event that can compromise mechanical or functional integrity of the reservoir (or cavern), wells or well control.
Geohazard Assessments for Underground Natural Gas Storage
UNGS Geohazards: Surface and Sub-Surface
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC5
Geohazard Assessments for Underground Natural Gas Storage
UNGS Surface Geohazards: Severe Weather
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC6
Geohazard Assessments for Underground Natural Gas Storage
UNGS Sub-Surface Geohazards: Earth Movement
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC7
Geohazard Assessments for Underground Natural Gas Storage
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC8
Regulatory Perspectives
Geohazard Assessments for Underground Natural Gas Storage
Regulatory Perspectives on Geohazards
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC9
Prior to the Aliso Canyon, California, gas leak (2015-2016), geohazards were not formally addressed in regulations
PHMSA Interim Final Rule (IFR) for UNGS safety (as directed by the PIPES Act of 2016) — effective Jan 2018 —adopted geohazard assessments by reference to:
• API RP 1170 (Salt Caverns)
• API RP 1171 (Depleted Reservoirs and Aquifers)
Root-cause analysis (May 2019) of Aliso Canyon Well SS-25 implicated groundwater in casing
corrosion that led to gas leak.
Geohazard Assessments for Underground Natural Gas Storage
Regulatory Perspectives on Geohazards
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC10
Reservoir Type
Geohazard Description per Adopted Standard
Standard Adopted in PHMSA IFR
(2016)
“Shall” or “Should” Statement*
Salt Cavern
“Elements of uncertainty that pose particular risks in salt include but are not limited to the edge of salt, shear zones, faults, high impurity zones, K-Mg salts, weak zones, zones with high creep potential, dissolution or collapse zones, nearby wells or other subsurface activities.”
API RP 1170;
Section 5.3.4.2
(Geologic Uncertainty)
“Additional buffer should be assessed on a site by site basis by a qualified geologist to account for uncertainty in locating the exact edge of salt and to allow for the possibility that salt quality with regard to geomechanical strength properties and impurity content tends to degrade towards the edge of salt.”
* Quoted from Standard but with emphasis added on “shall” and “should” as they occur.
Geohazard Assessments for Underground Natural Gas Storage
Regulatory Perspectives on Geohazards
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC11
Reservoir Type
Geohazard Description per Adopted Standard
Standard Adopted in PHMSA IFR
(2016)
“Shall” or “Should” Statement*
Depleted Oil / Gas Reservoir or Aquifer
“Outside force ‒ natural causes
Weather related and ground movement
• Heavy rains, floods, lightning, earth movements, groundwater table changes, subsidence, etc. that could result in:
• damage to facilities/impact to service reliability.”
API RP 1171;
Section 8.4.2
(Threat and Hazard Identification and Analysis ― Methodology)
“The operator shall evaluate the potential threats and hazards impacting storage wells and reservoirs.”
“The operator should estimate risk from potential events that could occur related to potential threats and hazards to individual facilities, such as wells, and by region when considering the reservoir.”
“The operator should perform periodic evaluations of hazards, threats, and risks related to potential events in order to account for changes in perception of likelihood or consequence in event potential.”
* Quoted from Standard but with emphasis added on “shall” and “should” as they occur.
Geohazard Assessments for Underground Natural Gas Storage
Regulatory Perspectives on Geohazards
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC12
Main takeaways from PHMSA IFR (2016)
Geohazard assessment is part of risk management — which is a shall requirement in effect as of 2018
The limited references to geohazards are:
• Broadly defined, with a few examples, in API RP 1171
• Focused on “Salt creep or collapse” in API RP 1170
• Implied [49 CFR 192.12] that all geohazards are to be considered for all reservoir/aquifer and salt-cavern UNGS
• NOTE: PHMSA audits include “risk management” even though only API RP 1171 explicitly includes risk-management plans
• UNGS Operator is responsible for identification and assessment of facility-specific geohazards
Geohazard Assessments for Underground Natural Gas Storage
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC13
Geohazard Assessment Process
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment with Time-Dependent Changes
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC14
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment as Annualized Risk Priorities
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC15
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment in Three Stages
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC16
Geohazard Assessments for Underground Natural Gas Storage
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC17
Case History: Location-Specific Assessment
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC18
“Cornhusker Gas Storage” (hypothetical UNGS facility in Nebraska)
Logan County
41.505° N, 100.429° W
Exercise the assessment process (one surface and one sub-surface geohazard)
Flood (or Flash Flood)
Earthquake
Illustrate the assessment results
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC19
“Cornhusker”
U.S. UNGS Facilities
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Flood Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC20
U.S. UNGS Facilities
River, stream or potential flood channel
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Flood Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC21
U.S. UNGS Facilities
Area affected by historical flood events
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Flood Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC22
5 Miles
South Loup River
Wild Horse Creek
“Cornhusker”
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Flood Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC23
Damaging Heavy-Rain & Floods
“Cornhusker” area has experienced multiple drought-flood cycles
Records show damaging events during 2009-2012
Most recent trend (2019) possibly into another “flood” cycle
Annualized flood risk estimated from 1996-2018 records
NL = 9% ± 16% (long term)
NL = 29% ± 5% (flood cycle)
NC = $50K damage / eventData Sources:
NOAA SPC Storm Events Database
NOAA NCEI Precipitation Timeseries
New Flood Cycle?
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Flood Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC24
“Cornhusker” area is vulnerable to floods from South Loup River Stream-gauge data not
available before 2017
At least one flood-stage event in early 2019
Flash flood warnings depend upon weather radar
NEXRAD KLNX (North Platte NE), 32-mile range
Annualized flood risk estimated from 1996-2018 records ND = 12–24 hr (Flood - gauge)
ND = 1–2 hr (Flash Flood - radar)
Data Sources:
USGS 06781900 South Loup River at Pressey WMA (northeast of Oconto).
USGS National Water Information System
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Seismic Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC25
U.S. UNGS Facilities
Potential ground acceleration (PGA; %g) over 50 yr (USGS 2014)
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Seismic Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC26
U.S. UNGS Facilities
Potential ground acceleration (PGA; %g) over 50 yr (USGS 2014)
Potential for ground-shaking damage (%) over 1 yr (USGS 2018)
Only 1-Yr Model for Central &
East is displayed
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Seismic Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC27
“Cornhusker”
Seismic Activity
PGA (% g) in 50 yr (USGS 2014)
Ground-shaking damage
(% likelihood) in 1 yr (USGS 2018)
Earthquake epicenter (2000-2018)
100 Miles
2
4
4
6
1 - 2
2 - 3
8 - 10
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Seismic Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC28
PGA (% g) in 50 yr (USGS 2014)
Ground-shaking damage (% likelihood) in 1 yr (USGS 2018)
Earthquake epicenter (2000-2018), within 100 miles
Depth (feet) to Pre-Cambrian (NGS)
50 Miles
4,000
3,500
3,500
6,000
2,500
3,500
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Seismic Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC29
“Cornhusker” earthquakes probably originate within p€bedrock
Depth to pre-Cambrian bedrock is 1.1 – 1.2 km (3,500 – 4,000 ft)
Earthquake focal depths are 1.2 – 15 km
Not correlated with known faults (i.e., none mapped)
2018 “Swarm” was at same depth range as 2000-2017 background
1.2 – 15 km
Cluster at 5 km
Data Sources:
USGS National Earthquake Catalog
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Seismic Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC30
Data Sources:
USGS National Earthquake Catalog
“Cornhusker” earthquake magnitudes most often M ≤ 3.5
Most frequent model magnitude is M ≈ 3.0
Model short tail predicts other earthquakes of M < 2
Model long tail suggests very few earthquakes of M > 4.5
Reference Information
M = 2 (felt by people)
M = 4 ‒ 5 (scattered, minor damage)
M ≥ 6 (significant damage)
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Seismic Risks
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC31
“Cornhusker” area is subject to weak earthquakes
Steady background of M = 2-3 events since 2000
Spike in activity in 2018, including one M = 4.1
Not correlated with known faults (i.e., none mapped)
Annualized earthquake risk estimated from 2000-2018 records
NL (M ≥ 2) = 53% ± 9%
NL (M ≥ 4) = 5% ± 8%
NL (Damage, USGS) = 2% ± 1%
NC = $500 (FEMA-USGS Hazus, 2017)
ND = 0 hr (no earthquake warning)
Data Sources:
USGS National Earthquake Catalog
Date
RangeEvents
2000 -
201714
2018 27
Total 41
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment Case Study: Risk Priorities
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC32
Calculate risk priorities Risk Priority Number (RPN)
RPN = AL • AC • AD
L, C and D converted from decimal estimates (N) to integers (A; look-up table)
RPN for “Cornhusker” flood risk NL = 9% AL = 1
NC = $50K AC = 2
ND = 1 hr AD = 4
RPN = 1 • 2 • 4 = 8
RPN for “Cornhusker” earthquake risk NL = 2% AL = 1
NC = $0.5 K AC = 1
ND = 0 hr AD = 5
RPN = 1 • 1 • 5 = 5
Annualized
Index of
Importance
(A)
Likelihood
(Probability of
at Least One
Event per
Year)
Consequence
(Damage per
event)
Detectability
(Warning Time
before Impact
of Event)
5 ≥ 90% ≥ $500 K < 1 hr
4 70 – 89% $300 - $499 K 1 - 12 hr
3 50 – 69% $100 - $299 K 13 – 24 hr
2 30 – 49% $10 - $99 K 25 – 36 hr
1 1 – 29% < $10 K > 36 hr
IMPORTANT NOTE: This table is illustrative only. Its
actual content will depend upon detailed attributes of
individual facilities and their risk tolerances.
This assessment indicates that mitigation against flood risk (RPN = 8) should be a higher priority than mitigation against earthquake risk (RPN = 5).
Geohazard Assessments for Underground Natural Gas Storage
Geohazard Assessment: Summary
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC33
Assessment of geohazards at UNGS facilities is required by PHMSA as part of risk management.
A complete geohazard assessment should include the following checklists:
Initial assessments can be done as desktop studies; site visits later.
Assessment results should include risk priority numbers (RPNs).
• Surface Geohazards (Severe Weather)
• Flood or flash flood• Tornado or strong winds• Hail• Lightning• Ice / snow storm• Tropical cyclone• Wildfire
• Sub-Surface Geohazards
(Earth movement)
• Earthquake• Natural• Human-induced
• Landslide• Subsidence
• Aquifer• Karst• Mine / other
• Mass movement• Soil expansion / contraction• Salt creep
Geohazard Assessments for Underground Natural Gas Storage
Geoclime Services
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC34
Geoclime provides quality and risk management consulting for organizations involved in energy, water, science and engineering. We help our clients with geotechnical pursuits to achieve and document compliance with operational regulations, contracted quality requirements and process integrity:
We are a small enterprise that specializes in support for businesses where outsourced services must add clear value and be affordable. No project is too small when a client asks for our help.
Geoclime is chartered as a limited liability company (LLC) in the State of Texas, United States of America, and is licensed by the Texas Board of Professional Geoscientists (Geoscience Firm #50225).
Geoclime, LLC Telephone: +1 281-451-8375P.O. Box 13 Website: https://www.geoclime.com1600 Main Street E-mail: [email protected], Texas 77586 USA
• Geohazard assessments
• Root-cause analyses• Risk management plans
• Process audits
• Gap analyses• Management plans & procedures
Geohazard Assessments for Underground Natural Gas Storage
July 15, 2019Presented to Southern Gas Association
by Geoclime, LLC35
Question & Answer Session