Geomechanical investigation of CO

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Présentation EPFL-Public | 01.01.2013 1

Geomechanical investigation of CO ₂ sequestration

R. Makhnenko, C. Li & L. Laloui

September 1, 2014 “Kraftwerk 2020”

Laboratoire de Mécanique des Sols

(LMS EPFL)

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CO

₂

storage, no thank you

Motivation CCS

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Carbon capture and storage

Motivation CCS

Switzerland:

decommission of nuclear power plants

combined-cycle gas-fired power plants might be temporatily used (each produces 0.7 Mt CO₂/year)

Kyoto protocol (1997): reduction of CO₂ emissions

www.avenirelectricite.ch

Problem:

Concentrations of the greenhouse gas carbon dioxide in the global atmosphere are approaching 400 parts per million (ppm) for the first time in human history

- Temperature raise ( anomaly: 0.56 ºC, 2 ºC by 2100 ) - Ocean level raise ( + 3 mm/year)

- Human health issues cdiac.ornl.gov

The Keeling Curve (University of San Diego)

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Geologic sequestration

Motivation Geologic sequestration

CO₂ can be sequestrated in one of the following three geological formations, widely spread, available and safe:

• abandoned oil and gas reservoirs,

• unmineable coal seams and

• deep saline aquifers:

 highly permeable and porous rocks,

 > 800m depth and saturated with undrinkable water

 widespread and available practically anywhere

deep saline aquifer

abandoned oil/gas reservoirs (675 – 900 Gt C)

(1,000 – 10,000 Gt C)

unmineable coal seams (3 – 200 Gt C)

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CO

₂

sequestration – worldwide

Motivation IPCC 2005

Depth: 800 - 2500 m

Overburden pressure: 20 – 100 MPa Water pressure: 7 – 40 MPa

Temperature range: 25 – 125 ºC

Geologic sequestration

250 km offshore, 800 m under sea floor Injection: 2.5 kt CO₂/day (since 1996), 0.03 GT CO₂ have been sequestered so far

Snohvit

2600m below the sea floor

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CO

₂

sequestration – Switzerland

Motivation

Diamond et al., 2010

Geologic sequestration

PSI ETHZ

Univ. Bern EPFL

Pilot for demonstrating CO₂ capture on gas-fired power plant

Pilot for assessing onshore CO₂ storage in Switzerland Proposed sites for

gas-fired power plant

Switzerland (total):

- 2.7 Gt of CO₂can be stored

- current annual emission 11.3 Mt

-capacity of saline aquifers is sufficient for > 200 years

Upper Muschelkalk:

65 m thickness, Dolomite

8.7 % of interconnected porosity 0.7 Gt CO₂ can be stored

Malm-Lower Cretaceous:

50-1200 m thickness, Limestone 5 % of interconnected porosity 1.5 Gt CO₂ can be stored

Aquifers:

Chevalier et al., 2010 800 - 2500 meters

deep aquifers

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Reservoir materials

Motivation CO2 sequestration

Sandstone

Limestone Shale

Mainly quartz and feldspar Porosity: 3 - 30%

Intrinsic permeability: 10^-7 – 10^-2 cm/sec Stiffness: 1’000 – 20’000 MPa

Dominant pore size: dozens of µm

Caprock

Aquifer

Under relevant CO₂ geological storage conditions, limestone suffers from potential

alteration through chemical reactions with CO₂

saturated water.

On the contrary, sandstone remains intact during the injection period.

Candidate for sealing material

Candidates for host rock material

Mainly clay minerals and tiny fragments Porosity: 5 - 30%

Intrinsic permeability: 10^-10 – 10^-7 cm/s Stiffness: 1’000 – 70’000 MPa

Dominant pore size: dozens of nm

Mainly calcite Porosity: 5 - 35%

Intrinsic permeability: 10^-8 – 10^-3 cm/sec Stiffness: 1’500 – 55’000 MPa

Dominant pore size: dozens of µm

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Injection of supercritical CO

₂

Motivation CO2 sequestration CO2CRC

Beneath 800m underground CO₂ exists in the supercritical state:

temperature > 31.1 ºC, pressure >

7.4 MPa, density > 600 kg/m³ Injection of CO₂

Nova Sterilis, 2014.

CO2CRC

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Trapping mechanisms

Motivation CO2 sequestration

Trapping processes take place over many years at different rates from days to thousands of years.

In general, CO₂ becomes more securely trapped with geological time.

THM coupling behaviour during the injection phase is crucial to secure the CO₂ storage.

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Chair « Gaz Naturel »

Motivation

- understanding and prediction of the effects of surrounding environment, of mechanical and chemical changes as well as heat effect during CO₂ injection and storage

- experimental and numerical interdisciplinary research on the interplay between transport, reaction and mechanics

- advance scientific knowledge and provide reliable solutions to the industry.

Assessment of CCS

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Présentation EPFL-Public | 01.01.2013 11 Objective

Objectives of laboratory research

Geological sequestration

sandstone limestone shale

precipitation, cooling effect, chemical

degradation, suction effect, permeability mechanical integrity Characterization of thermo-hydro-mechanical

behavior of possible host and cap rocks in contact with water, brine, supercritical and liquid CO₂

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Chemical reactions Dissolution

Reaction with carbonates (days/weeks)

Reaction with silicates (years)

Host rocks: issues

Theory CO2 effect

Oye et al., 2012 Ciantia & Hueckel, 2013

- Change in poroelastic response due to chemical effect caused by CO₂ injection - Change in inelastic parameters and failure characteristics

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Poroelastic regimes

Theory Poroelasticity

Drained Undrained Unjacketed

=0

∆ ∆

= ∆

V p

V P K

“drained” ∆p= 0 “undrained” ∆m_f= 0

=0

∆ ∆

= ∆

mf

u V

V P K

=0

∆ ∆

= ∆

mf

P B p

=0

∆ ∆

= ∆

mf

f f

f V

V p K

Skempton’s coefficient:

bulk modulus of pore fluid:

“unjacketed” ∆P = ∆p

P p

s V

V p K

∆

=

∆ ∆

= ∆ '

unjacketed pore bulk modulus:

P p

s V

V p K

∆

=

∆ ∆

= ∆

φ

" φ

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Slightly anisotropic (5% difference for ultrasonic velocities and 7-8% in UCS)

Porosity = 23%, density = 2100 kg/m³ ,

UCS= 41-43 MPa, E = 13-15 GPa, and ν _{= 0.31} Permeability k = 40 mD (at 5 MPa mean stress)

Diffusivity

sec 2 m . ) 0

1 ( ) 2 1 (

) )(

1 (

2

²

2

=

−

= −

u

kG

u

c µα ν ν

ν ν

ν

Berchenko et al., 2004

sec 01 . 4 0

2

=

≈ c

t L

- time to equilibrate ∆p due to ∆P = 1 MPa

Host rock: sandstone

Lab testing Sandstones

Mineralogical composition:

Quartz ∼ 90%

Feldspar ∼ 7%

Calcite ∼ 1%

Clay – traces

Quartz grain size ∼ 0.2 mm

Berea sandstone (Ohio):

Makhnenko, 2013

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Poroelastic response: sandstone

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

0 1 2 3 4 5 6

Back pressure [MPa]

B cor

B^max = 0.58

P′ = 5 MPa

f L u

cor

K K V V p

B

α σ

σ

ν ₋



 





∆

∆ +

∆

= +

3

) )(

1 (

1

3 1

3.10 3.15 3.20 3.25 3.30

0 1 2 3 4 5 6

Back pressure [MPa]

P-wave velocity [km/s]

P' = 5 MPa











 −

+

=

"

1 1

s

f K

K K B

φ α

α

Makhnenko and Labuz, 2013

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Constitutive response: sandstone

0 5 10 15 20 25 30 35

0 2 4 6 8

γ [10^-3]

τ [MPa]

Triaxial, undrained Plane strain,

undrained

Triaxial, drained

Model, undrained

Initial conditions:

P = 20 MPa p_o = 3 MPa Drained:

∆p = 0 Undrained:

∆m_f = 0

Undrained:

(

^K ^K

)

^K

K_eff =υ 1 _f −1 _s" +α 1

G K

H

K H

d d

eff eff

) (

1 µβ

µβ γ

τ

+ +

= + G

H H d

d

= + γ 1 τ

Drained:

Rice 1975, Rudnicki 1985

0.0 0.2 0.4 0.6 0.8 1.0

0.0 1.5 3.0 4.5 6.0 7.5 9.0

Plastic shear strain [10^-3]

µ

0.0 0.2 0.4 0.6 0.8 1.0

β

µ

β

Makhnenko and Labuz, JGR-2014

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Host rock: limestone

Lab testing Limestone

Close to be isotropic

(2% difference in ultrasonic velocities) Porosity = 33%, density = 1400 kg/m³ , UCS= 15 MPa, E = 7.3 GPa, and ν _{= 0.25} Permeability k = 3-5 mD (at P′ = 5 MPa)

Mineralogical composition:

Calcite ∼ 98%

Traces of other minerals Grain size = 0.05 - 3 mm

Calcarenite (Apulian limestone):

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Poroelastic response: limestone

GPa 1

.

= 5 K

GPa 7

. 42 ' = K

s

88 .

= 0 α

0 5 10 15 20 25 30 35

0 1 2 3 4 5 6

Volume strain [10^-3]

Hydrostatic pressure [MPa]

K = 5.1 GPa K_s' = 42.7 GPa

0 5 10 15 20 25 30 35 40 45 50

0 2 4 6 8 10 12

Hydrostatic pressure [MPa]

Strain [10^-3]

1.1 1.3 1.2

K_s′ is significally smaller than K_calcite – a lot of very small and non-connected pores

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Characterization of dissolution

Viscoporoelastic formulation for undrained constant mean stress response:

( ) (

P p

)

dt dp K

K dt

d

s

−

 −



 





− −

=

ηφ

φ

φ 1

' 1

1 1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

1.5 2.0 2.5 3.0 3.5 4.0 4.5

Pore pressure [MPa]

B

P' = 5 MPa B^max = 0.70

Connolly and Podladchikov 1998

( )(

^P ^p

)

dt dp

BK −

= −

φ η

α

φ 1 1

η_φ - matrix bulk viscosity

Makhnenko and Podladchikov, 2015

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Scanning Electron Microscopy (SEM) X-ray CT scanning Mercury Intrusion

Porosimetry (MIP)

Non-destructive

Qualitative Destructive

Quantitative Destructive/non destructive Qualitative

- microstructures

- pore space morphology and porosity

- fluid saturation

- mineralogical composition

- pore size ditribution - relation between Hg pressure and volume of intruded pores.

- surface morphology and topography

8 μm/pixel 100-0.003 μm 4 nm/pixel

Romero et al, 2008

Characterization of chemical effect

Lab testing Change in composition

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Not treated

1 MPa water

Complexity of pore morphology

Scanning Electron Microscopy (SEM)

Water injection (1 MPa for 4 days) Goal: observe change in porosity and pore morphology

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- Cumulative volume of pores with radius larger than 5 µm increases from 3 to 10%

- Increase in total porosity is about 2-3%

Dry specimen Treated specimen

Mercury Intrusion Porosimetry (MIP)

Treated and dry specimens of similar size were tested with MIP

0 10 20 30 40 50 60 70 80 90 100

0.001 0.010 0.100 1.000 10.000 100.000 1000.000 10000.000

Cum. Volume [%]

Pore Radius [µm]

MIP results: dry specimen

0 10 20 30 40 50 60 70 80 90 100

0.001 0.010

0.100 1.000

10.000 100.000 1000.000 10000.000

Cum. Volume [%]

Pore Radius [µm]

MIP results: treated specimen

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MatLab©

- Pixel size 8.41 μm - Grey-scale 0-255

- Each mineral has the same density - Grey intensity is

in proportion to pore size

- Normal distribution MIP ϕ = 0.385

X-ray CT scanning

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CO

₂

injection project at Mont Terri

Lab testing Shales

• Main Objectives

– Build well elements

– Measure of the flow inside and and and outside the casing

-> sealing changes

– Sample fluid across time -> fluid changes

– Take samples of the different elements (overcoring)

-> mineralog. changes

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Caprock - issues

Lab testing Shales

~ 1nm

Wellbore

- Seal permeability

(w/ respect to H₂Oand CO₂) - Seal capacity

(CO₂ retention properties) - Seal integrity (propensity for

brittle or ductile behavior) - Pressure build-up due to

injection of CO₂

- Geomechanical/failure

characteristics (effect of in- situ stress variations)

- Change in mineralogy/

porosity/ permeability due to the chemical effect

mont-terri.ch

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Geomechanical testing of shales

Lab testing Shales

Opalinus clay behavior at different mean stresses and temperatures:

HIGH-PRESSURE OEDOMETER

Water retention curve of Swiss shale

SORBTION BENCH

Oedometric curve of a Swiss shale [Ferrari, Manca, Laloui]

[Ferrari, Manca, Laloui]

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Caprock: failure

Lab testing Shales

Mechanical weakness:

the interface between the caprock and the aquifer:

• Primary barrier to prevent CO₂ from leakage

• Failure potentials to be evaluated

Φ

cohesion

Friction angle

σ'= −σ

= _{c c}+ _{w w}

f

p S p S p p

Shear stress Shear stress

Laloui and Li, 2014

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Capillary effects

Lab testing Shales

2

4 cos 2

w CO

T T

p p

d R

− = − θ = −

Capillary stress : Non-wetting phase : CO₂

Wetting phase : water

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«Capillary» failure

Lab testing Shales

• CO₂ pressure increase / capillary stress

increase / effective stress increase mass shrinkage (free shrinkage)

• If shrinkage is constrained, reaction forces arise.

• Three main causes of shrinkage constraint:

(1) Boundary restraint

(2) Moisture gradients inside the body (3) Internal structure

tensile stresses are built up, tensile strength is reached cracks appear and propagate.

Laloui and Li, 2014

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CO

₂

retention behavior

Lab testing Shales

Water retention curve with CO₂ at 20 ˚C and pressure of 8 MPa : σ = 0.030 [N/m]

θ = 20 [˚]

(Espinoza and Santamarina, 2010) Water retention curve with air at room temperature

and atmospheric pressure : σ = 0.073 [N/m]

θ = 0 [˚]

Water retention curve of Opalinus Clay:

Ferrari et al., 2014

Reduction of gas entry value from 13 to 8 [MPa]

Laloui and Li, 2014

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Host rock and caprock microcracking

Lab testing Microcracking

undrained compression

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0 5 10 15 20

Shear strain [10^-3] Volume strain [10-3 ]

0 300 600 900 1200 1500

AE events

peak load inelastic deformation

drained compression

0.0 0.3 0.6 0.9 1.2

0.0 2.5 5.0 7.5 10.0 12.5

Shear strain [10^-3] Volume strain [10-3 ]

0 200 400 600 800

AE events

inelastic deformation peak load

transducer microcrack

elastic wave

t V

Inelastic response (yielding) of rock is associated with microcracks, which generate elastic waves called acoustic emission, AE.

Makhnenko and Labuz, JGR-2014

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Host rock: AE events locations

0-1 1-2 2-3 3-4

0 50 100 150 200 250 300 350 400 450

0 0.05 0.1 0.15 0.2 0.25 0.3

Lateral displacement [mm]

Load [kN]

0 500 1000 1500 2000 2500

AE events

1 2 3 4 all events fractured specimen

Makhnenko, Ge and Labuz, 2015

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Summary

Group business

Gaz Naturel Projects

- Geologic sequestration of carbon dioxide is promising option for reducing greenhouse gas emissions

- Thermo-hydro-mechanical processes occur during CO₂ storage:

deformation and failure potentials triggered by injection-induced overpressure and cooling are the key issues to be addressed

- Laboratory testing is needed to characterize different aspects of rock-water- CO₂ interactions and an advanced equipment has to be used to get accurate results and make reliable predictions

- Geomechanics will play a key role in seeking a balance between injectivity and integrity/safety of host and caprocks

Geomechanical investigation of CO