oil caverns
TRANSCRIPT
OIL CAVERNS Risk mitigation through awareness and vigilance
Thierry YOU
OSR2G Nancy Fr 2013
Geotechnical Risk Mitigation for Hydrocarbon Storage
Panorama of Hydrocarbon Storage
Design Methodology
Feedbacks
Conclusions
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Geotechnical Risks
Reference list
- Manuel de Mécanique des roches Tome III
- EC7 Eurocode 7
- NF94-500 Geotechnical Tasks
- ISRM WG Design Methodology, Hudson & Feng
- ASCE Geotechnical Baseline Report
- AFTES GT1, GT25, GT32
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Géostock Expertise
Different types of hydrocarbon storage:
Salt leached caverns Mined cavern Aquifer, depleted field
Natural Gas, LPG, liquid hydrocarbons LPG, Liquid Hydrocarbons Natural Gas
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DISSUSED MINES MINED CAVERN
Underground storage Mined caverns technologies
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Lavera LPG Storage Caverns
Operation Shaft Area Lavera Butane Cavern – Construction
Underground storage Mined caverns technologies
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Construction of mined caverns
Geostock Designer or owner’s assistant:
UNDERGROUND STORAGE IN MINED CAVERN
GEOSTOCK EXPERIENCE
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(C
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SITE UNDER CONSTRUCTION
PROJECTS COMPLETED
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Operability
Stability
Hydraulic Containment
Mined caverns technologies and associated risks
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Principes
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Caverns are unlined
Tightness only depends on natural
convergent flowrates from the
rockmass towards the cavern :
this is the hydrodynamic
containment principle
Containment principle = HYDRODYNAMIC PRINCIPLE
UNDERGROUND STORAGE MINED CAVERNS TECHNOLOGIES
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maj
11
/01
ground level
water table
water gallery water curtain
flow-lines
unlined caverns
UNDERGROUND STORAGE MINED CAVERNS TECHNOLOGIES
Product containment Criteria
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Operation shafts
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Various lay-out adapted to geological conditions
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Access Shaft (Fontenay-le-Marmion) Upper Levels – (Morts terrains)
UNDERGROUND STORAGE MINED CAVERNS TECHNOLOGIES
Diesel Oil Storage of May–sur-Orne
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Cavern dimensions: large variations
Volume :
from 8 000 m3 (LPG) to 2 Mm3 (Crude Oil)
Height:
from 6 m (chalk) to 32 m (granite / gneiss)
Section :
Up to 650 m²
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U-1 Crude Oil Cavern
18m
30m
12.8m
22m 17.5m
Pyongtaek LPG Cavern
CONSTRUCTION METHODOLOGY
UNDERGROUND STORAGE MINED CAVERNS
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A mined storage cavern is neither
A mine
A civil work
A laboratory
But our design team learns from all and from all projects
UNDERGROUND STORAGE DESIGN METHODOLOGY
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Methodology & Codes why?
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Rockbolting alternatives based on a individual judgement. (Drawing from a cartoon in a brochure on rockfalls published by the Department of Mines of Western Australia)
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GEOGAZ - LAVERA Propane and Butane Storage Caverns Layout
GEOGAZ - Butane
GEOGAZ - Propane
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Underground storage Mined caverns
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SIMPLIFIED DESIGN CHART FOR ROCK ENGINEERING ( BIENIAWSKY - 1987 )
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Typical mode of failure, rock falls
J. Fine 1993
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Flowchart of rock mechanics modeling and rock engineering design approaches (Feung and Hudson, 2004).
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Typical failure modes of large underground cavern group and its related tunnels
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Specificities of large sections
Likelihood of toe/wall failure
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Conclusions 1
Methodological advance will bring us huge progresses but also brakes to new ideas.
We still have to learn!
Feedback loops and validations remain essential.
“No theory can be considered satisfactory until it has been adequately checked by actual observations”. Prof. Ralf B. Peck.
Designers and regulatory bodies tend to place increasingly reliance on analytical procedures of growing complexity and to discount judgement as a nonquantitive, undependable contributor to design Prof. Ralf B. Peck.
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Mined Caverns ULSAN (South Korea)
Owner: SK-GAS
310 000 m3 Propane - 240 000 m3 Butane
Main features: Parallel galleries
Andesite and metasedimentary sandstone
Depth: 119 m (propane) - 63 m (butane)
Propane: length 830 m - Section 308 m2
Butane: length 629 m - Section 342 m2
Beginning of construction: 1984
Commissioning: 1988
Main Geotechnical features: Fault crossing
Careful mapping
Rock fall and repair works
Scale effect on wedges
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Main Geotechnical features:
Highly anisotropic environment
High horizontal stresses
Roof falls
Grouting works
Smooth blasting and tolerance control
Difficult construction supervision and
contractual environment
Design ‘model’ difficulties
Post construction environment
Main features:
Parallel galleries - Sandstone
Length: 910 m - Section 142 m3
Depth: 124 m
Beginning of construction: 1996
Commissioning: 2000
Owner: ELGAS
83 000 m3 Propane
Mined Caverns SYDNEY (Australia)
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ROCK FALL EXPLANATIONS (20+)
A large number of explanations were put forward by the parties involved, many of them with ulterior motives: unsuitable section, inappropriate and damaging explosive, poor workmanship (drilling, bolting, etc.), untested rock bolts, too differed bolt grouting, poor site organisation, unsuitable numerical and structural models, underdesigned rockbolts, inappropriate bolting patterns, unsuitable excavation sequence, poor and inefficient quality control, lack of design methodology (EC7), lack of monitoring and inspection, unforeseen stress release, random vertical joints, lack of spot bolt decision on visible instabilities, inclined defects in sheet facies, too high water pressure imposed in the fissures, etc.
At that stage, none of the specified monitoring measures that had been prepared for design validation (geological joint mapping, convergence measurement, profile mapping, pull-out test, etc.), that certainly would have helped as new design basic data, had been implemented.
Maintaining roof integrity was crucial for stability, as was established latter
(You et al. Johannesburg ISRM2003)
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Mined Caverns VISAKHPATNAM (India)
Owner: SALPG
127 600 m3 Propane - Butane mixture
Main features: Parallel galleries + 1 central access tunnel
Depth: 162m/msl
Length: 342 m
Section: 338 m2
2 operation shafts
Construction: 2004-2007
Main Geotechnical features: Design adaptation
High horizontal stress consideration
Joint opening model
-200
-100
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0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1
Slenderness W/H
Ta
ng
en
tia
l s
tre
ss
(b
ar)
elliptic - crown
ovaloid - crown
rectangle - haunch
elliptic - sidewall
ovaloid - sidewall
rectangle - sidewall
3.5 Sv
Sv = 48 bar
W
H
haunch
sidewall
crown
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DURING SITE INVESTIGATION :
Supervision by design team during drilling and testing
==> RQD on fresh cores
==> representative sample selection
==> site adaptation of water test
DURING CONSTRUCTION :
GEO SURVEY sometime after each blast
==> cartography geo-geo-hydro+ geometry
==> rock quality «i.e. Q factor »
==> adaptative support
==> water monitoring
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Feedbacks
Specificity of large caverns(2)
Need of a fine tuned structural investigation in order to adapt bolt support:
V.1
0.2
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V.6
.287
MUW-10 MUW-6 MUW-8
Section V9 Ch.242.6
MUB2 WMUB1 WMUA2 WMUA1 W
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GEOTECHNICAL RISKS
Geological Mapping: … collection and interpretations
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Mined Caverns GARGENVILLE (near Paris - France)
Owner: GEOVEXIN
130 000 m3 Propane Main features: Chalk
Galleries EW and NS
Length: 1400 m (EW) - 1300 m (NS)
Section: 49 m2
Depth: 132 m
Beginning of construction: 1972
Commissioning: 1977
Abandonment: 2008+
Main Geotechnical features: Post peak behavior
Construction tolerances
Importance of construction record and operation
monitoring
Adaptative design
Closure design for abandonment procedure
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dewatering
Maj
08
/98
water pumps
CAVERN
gas LPG liquid LPG water clay concrete fail safe valve
LPG outlet
LPG inlet
vent
instrumentation
LPG underground storage Operation shaft
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STEPS OF GEOTECHNICAL RISK MANAGEMENT ( From AFTES GT 32+..)
1) Risk identification:
Each project is a prototype, no universal approach available
2) Hierarchize, assess and evaluate the risk:
Danger of subjectivity, explain to share
3) Risk treatment ( risk matrix, risk register, event tree)
Share between parties, role of insurance ( GBR, GDR)
4) Monitor and control
Check actions, vigilance
5) Memorize and capitalise lessons learned ( feedbacks)
Difficult but needed.
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Project studies and phasing
Project Development
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Risk Tree prepared for one known mined cavern storage 1/2
Possible exclusion under certain conditions (INERIS DRS-09-103911-09771A)
Local or general collapse
Local drop of hydraulic gradient and confinement.
D
Loss of hydrodynamic containment of the cavern
C Cavern pressure
exceeding critical pressure for leak
Zone poorly supplied with natural water
Local increase of permeability
on walls
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Ageing of supports
Increase of interstitial
pressure and gradients
Seismic shaking
Weathering of rock walls
Collapse of Cavern
or Accesses
A 1
2
3
4
Séquence 2 : Risk assessment (2/2)
J. PIRAUD – Incertitudes et risques géotechniques - 29/01/13
Exemple of risk matrix Colours represent the resulting level of risk for each event (green : acceptable without further action ; red unacceptable risk).
The level of risk related to an event may be deemed more or les acceptable depending of targets and priority of Owner.
Decision to take action against a risk is therefore a task devoted to Owners and Engineers.
Possible 4 8 12 16
Peu Probable 3 6 9 12
Très peu Probable 2 4 6 8
Improbable 1 2 3 4
Faibles Moyennes Fortes Très fortes
Matrice des risques
Vra
isem
bla
nce
Conséquences
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Conclusions 2
”If something is discovered that does not agree with the hypothesis, rejoice! You can then really learn something new. You are on your way to an understanding of the problem”. Ralf B. Peck.
Feedbacks and Design Validation Loops remain essential.
Awareness and vigilance naturally lead to design validation and monitoring.
We need to carry out a vast amount of observational work, but what we do should be done for a purpose and done well- R.B.Peck
Complexity of geotechnical risks encourage us toward the virtue of humility and listening.
Nature to be commanded must be obeyed- Francis Bacon
Discover the truth through practice and again through practice verify and develop the truth- Mao Tse Toung