Mahmoud Hefny (1), Alba Zappone (1, 2, 3), Claudio Madonna (1), Andrea Moscariello (4), and Jean-Pierre Burg (1)

(1) Department of Earth Sciences, ETH Zürich, (2) Swiss Seismological Service, ETH Zürich, (3) Institute of Process Engineering, ETH Zurich, (4) Department of Earth Sciences, University of Geneva

email: mahmoud.hefny@erdw.ethz.ch

GG87 - 4

Fig A.1: Location Map after SwissTop 2005.

N ● Reservoirs-characterization of geothermal systems, integrating multiscale seismic data, is key towards predicting reservoir-performances. In a joint project by the Canton of Geneva and SIG (Services Industriels de Geneve), a geothermal exploration program GEothermie 2020 integrate the subsurface geological and geophysical data and evaluate the potential of geothermal energy production in the Geneva basin.

● This area is located in the westernmost part of Swiss Molasse Basin, where the “case history” for the ongoing study consists of five main aquifer/aquitard pairs of the Swiss Molasse basin. These pairs have been indicated in literature as potential reservoirs for deep CO2 sequestration.

● One of our main goals is to quantify the effect of porosity, mineral composition and micro-textural characteristics, such as banding and layering of minerals in sedimentary rocks, on their seismic properties. The final aim is to offer a key to interpret the seismic reflectivity zones identified in the seismic survey (Gorin et al., 1993) and to identify a calibration key for borehole logging data where no coring was performed.

● The stratigraphy of Savoy-Geneva pilot area consists of a 3000-5000 m thick sequence of Mesozoic and Cenozoic sedimentary rocks overlying the Variscan crystalline rocks and dipping gently (1-3°) to the Southeast toward the frontal depression of the Pre-Alps (see the seismic transect profile in: E. Discussion panel).

Fig B.1: Stratigraphic succession of Humilly-2 borehole, show the six majors seismic reflectors (red). For the location “Hum”, refer to Fig A.1

● High-resolution mineralogical maps and automated quantitative mineralogical compositions identification are assessed using a combination of back-scattered electron values, energy-dispersive X-ray spectra, and X-ray count rates (QEMSCAN); at University of Geneva.

1.0 mmA

HF

TS

LS

B 1.0 mm

BC

BC

1.0 mmG

Ms

PQz

1.0 mm H

Unclassi�ed; 1%Biotite; 1%

Dolomite; 4%

Illite; 3%

Kaolinite; 8%

K-Feldspar; 4%

Muscovite; 22%Quartz; 51%

Siderite; 6%

1.0 mmF

Anh

1.0 mmE

Dol

C 0.5 mm

Qz

Dol

D 0.5 mm

MF

C o r e (I)

C o r e (II)

C o r e (III)

C o r e (V)

HU01

HU13

HU23

HU27

HU01

HU14

HU24

HU27

Olig

ocen

e - M

ioce

neBa

rrem

ian

Haut

eriv

.Va

lang

inia

n

Tith

onia

nKi

mm

erid

gian

Oxf

ordi

an

Plie

nsb.

Toar

cian

Bajo

cian

Sinn

emur

ian

Rhét

ien

Cam

ian

Ladi

nian

Anisi

a.No

rian

Bath

o.

T E

R T

I A

R Y

L

O W

E R

C R

E T

A C

E O

U S

T

R I

A S

S I

C

PERMO-CARBO.

J U

R

A

S S

I

C

QUATERNARY

Mol

asse

sed

imen

ts

Urgo

nian

Mal

m

Lias

Keup

er

Latte

nkoh

lM

usch

elk.

Dog

ger

Buntsandstein

A.

Chrono-stratigraphy

I

II

III

IV

V

Core Lithology

30393027

29092896

2728

25482530.5

2347

2088

18581855.6

1644

1271

1118

812

667

562

437.5430

67

Depth [m]

Density log [g.cm-3]

2.2 2.4 2.6 2.8 3.0

Transit time [μsec.m-1]150 250 350 450

Top Urgonian

Top Argil. Upper Jurassic

Top evaporitic Triassic

Top carbonate Triassic

Top Argil. Middle Jurassic

Top Argil. Lower Jurassic

Sandstone

Limestone

Salt

Bioclastic limestone Dolomitic limestoneOolitic limestoneArg. limestone

Anhydrite ClaystoneConglomerate Marl

Depth×100 m

Lithology log Core Sample

Chrono-stratigraphy

3029

2880.0m

3062.0m

TRIA

SSIC

CARBONIF.

Mus

chel

kalk

Le

tten.

Bunt

sand

stei

n

Ladi

nian

Anisi

an C o

r e V

HU-17HU-18HU-19HU-20HU-21

HU-22HU-23HU-24

HU-25HU-26HU-27HU-29

27

2630.0m

2790.0m

Cam

ian

Nor

ian

TRIA

SSIC

K e

u p

e r

C o

r e I

V

BX-107 (a)

Goderichsalt (c)

126 (b)

2524

2322

2210.0m

2568.5m

Lia

s Rh

é.

Keup

er

LOW

ER J

URA

SSIC

TR

IA.

Plie

nsba

chia

nSi

nnem

uria

nTo

ar.

C o

r e I

II

HU-13

HU-14HU-15

HU-16

No.

2019

1829.0m

2028.0m

Mal

mD

ogge

r

Oxfo

rdian

Ba

joci

anBa

thon

ian

MID

DLE

JU

RASS

IC

UPP

ER

C o

r e

II

HU-07HU-08HU-09

HU-10HU-11HU-12

1014.8m

1020.6m

Mal

m

UPP

ER J

URA

SSIC

Kim

mer

idgi

an

C o

r e

I

HU-01aHU-01b

HU-03

HU-06

Plate B.1: Optical photomicrograph of representative samples. Longitudinal (LS) and transversal (TS) cross-sections of a high-spired gastropod. Fractures (HF) were healed by a sparite cement. Quartz (Qz). Dolomite (Dol). A few of shell fragment (benthonic forams) which are preserved as a mold (MF). fibrous anhydrite (Anh). The kaolinization (Kln) of K-feldspar (Kfs) is occurring to form the clay cement for pore-filling and grains coating firm on Quartz (Qz) grains.

● We bored three mutually orthogonal plugs: one in the vertical Z direction, parallel to the drilling axis, and two in the horizontal plane at 900 between each other, in the so-called X and Y directions. The experiments were performed under hydrostatic pressure. ● P- and S- wave velocities were measured using pulse transmission technique (Birch 1961) at 1 MHz resonance frequency.

Experimental conditions:

- Confining pressure: 260 MPa- Temperature: 25 °C- Pore pressure: 0 MPa (dry conditions)

Vp,s : seismic velocities, L : plug’s length, tobs : total travel time, tsys : time delay, δVp,s: uncertainity propagation.

V Lt t

Vp sobs sys

p s, ,=−

±δ

Fig C.2: Schematic set-up of seismic apparatus used to measure the ultrasonic velocities.

Hydrostatic cell

Confining medium

Core

ass

embl

y

Pulse Generation

OscilloscopeWaveform Analyzer

Seismic signal cablesO

il Re

serv

oir

Con�ning Fluid Flow Line

V3

Con�ning Fluid Flow Line

V2 V1

>>Hand

(Screw-)pump

Gauge Pconf

Com

pres

sed

air

sup

ply

Air driven pump

Air L

ine

V4

100500 150 200 250 300Con�ning pressure [MPa]

4.6

4.7

4.8

4.9

5.0

5.1

5.2

5.3

5.4

5.5

5.6

Com

pres

sion

al v

eloc

ity [k

m/s

] VP (0)

2nd run1st run

Curve-�tDepressurizationPressurization

Error Bar

● The seismic hystersis is due to the closure of microcracks at the high-confining pressure that do not reopen during depressurization.

● Intrinsic velocity at room pressure, calculated from the experiment curves by linear regression above 150 MPa (V0), ranges from 4.34 to 6.79 km/s and 2.71 to 3.79 km/s, respectively.

V P A P MPa B ep s

abP

, ( ) =

+ −( )−

1001

Wepfer Equation

Fig D.1: Example of velocity measurments under two successive cycle of pressurization-depressurization. Sample HU25X; depth 3028.3 m.

● Seismic Anisotropies are very low (< 6%).

● The dynamic seismic anisotropy, as a function of the confining pressure, shows strong variations controlled by a complex interaction between the effects of the closure of oriented microcracks, lattice-preferred orientation (LPO) and confining pressure.

Seis

mic

ani

sotr

opy

[%]

1.5

1.0

2.5

4.0

3.5

5.0

0.5

0.0

2.0

3.0

4.5

Pois

son

ratio

[%]

0.275

0.285

0.295

0.305

0.270

0.265

0.280

0.290

0.300

AVp

AVs

vertical

horizontal

cracks-closure

Mineral Compressibility

A

Pois

son

ratio

[%]

0.210

0.220

0.230

0.240

0.250

0.260

0.270

0.280

0.290

2.5

2.0

3.5

5.0

4.5

6.0

1.5

3.0

4.0

5.5

Seis

mic

ani

sotr

opy

[%]

05 50 100 150 200 250Con�ning pressure [MPa]

B

AVV VVp s

p s p s

p smean,

,max

.min

,

=−

×100

Fig D.2: Two examples (A: sample HU03, B: sample HU20) of dynamic seismic anisotropy and Poisson ratio corresponding to confining pressure.

● The seismic velocities were calculated at 40 MPa using Wepfer’s parameters and plotted against porosity. ● The Vp and Vs are dependent not only on the porosity as it is evident within the large scatter data for the velocity-porosity relationship, but also on the constituent minerals.

Com

pres

sion

al v

eloc

ity [

km/s

]

4.5

5.0

5.5

6.0

6.5

E�ective porosity [%]10-1 100 101 102

Shea

r vel

ocity

[km

/s]

2.4

2.8

2.6

3.0

3.2

3.4

3.6

HU25; SandstoneHU26; SandstoneHU27; SandstoneHU29; Sandstone

Buntsandstein

HU17; DolomiteHU20; Dolomite/AnhydriteHU21; Dolomite/AnhydriteHU24; Dolomite/Anhydrite

Muschelkalk

HU01; LimestoneHU03; LimestoneHU06; Limestone

KimmeridgianBX107; AnhydriteCL126; ClaystoneGDHlt; Halite

Keuper

HU14; LimestoneHU13; Posidonia shale

Liassic

HU07; Arg. limestoneOxfordian

HU09; Arg. limestoneBathonian

HU12; Arg. limestone Bajocian

Fig D.3: Effect of porosity on velocity at 40 MPa.

● The highest acoustic impedance was found within the Muschelkalk rock where the dolomite is the major constituent. The lowest acoustic impedance was found in the halite layer of Keuper. ● Within the contact between two lithotype, the difference in acoustic impedance over the sum of acoustic impedance will give arise the Reflection Coefficient (Rc).

V P(Z

) [km

/s]

4.0

4.5

5.0

5.5

6.0

6.5

7.0

09.5

15.5

17.0

20.0

12.5

RC=0.051RC=0.046

RC=0.073

RC=0.125

2.2 2.4 2.6 2.8 3.0Density [g/cm3]

2.2 2.4 2.6 2.8 3.0Density [g/cm3]

2.5

3.0

3.5

4.0

V S(Z

) [km

/s]

11.0

08.0

06.5

RC=0.103

RC=0.130

RC=0.086

Fig D.4: Grain density vs seismic velocities with isoline of constant impedence

● The larger the contrast in seismic impedance, the larger the amount of incident energy that is reflected (and the smaller the amount that is transmitted). ● Assuming reflection coefficient >0.05 will cause a reflector in the upper crust, we interpret the source for seismic reflectors.

Depth×100 m

Lithology log Core Sample

Chrono-stratigraphy

3029

2880.0m

3062.0m

TRIA

SSIC

CARBONIF.

Mus

chel

kalk

Le

tten.

Bunt

sand

stei

n

Ladi

nian

Anisi

an C o

r e V

HU-17HU-18HU-19HU-20HU-21

HU-22HU-23HU-24

HU-25HU-26HU-27HU-29

27

2630.0m

2790.0m

Cam

ian

Nor

ian

TRIA

SSIC

K e

u p

e r

C o

r e I

V

BX-107 (a)

Goderichsalt (c)

126 (b)

2524

2322

2210.0m

2568.5m

Lia

s Rh

é.

Keup

er

LOW

ER J

URA

SSIC

TR

IA.

Plie

nsba

chia

nSi

nnem

uria

nTo

ar.

C o

r e I

II

HU-13

HU-14HU-15

HU-16

No.

2019

1829.0m

2028.0m

Mal

mD

ogge

r

Oxfo

rdian

Ba

joci

anBa

thon

ian

MID

DLE

JU

RASS

IC

UPP

ER

C o

r e

II

HU-07HU-08HU-09

HU-10HU-11HU-12

1014.8m

1020.6m

Mal

m

UPP

ER J

URA

SSIC

Kim

mer

idgi

an

C o

r e

I

HU-01aHU-01b

HU-03

HU-06

2.2 2.4 2.6 2.8 3.0

Grain Density [g/cm3]

Density log

3.0 4.0 5.0 6.0

Compressional Velocity [km/s]

Sonic log

0.8 1.2 1.6 2.0×107

Acoustic Impedance [Pa.s/m3]

-0.1 0.0 0.1 0.2

Reflection Coefficient

Vs

Vp

Horizontal plugsLaboratory experiments; Vertical plugs

Fig D.5: Intregration between laboratory measurment and well-loggings.

2.0 2.5 3.5 4.0 4.53.0Shear velocity [km/s]

Com

pres

sion

al v

eloc

ity [

km/s

]

3.5

4.5

5.5

7.5

6.5

Vp/Vs=

1.70

Vp/Vs=

1.91

Vp/Vs=

1.85

Vp/Vs=

1.48

Seismic velocities of common mineralsQuartz

Calcite

Dolomite

GG87-2 GG87-4 GG87-5

● The measurements along the Z-direction were used to simulate the normal incidence of seismic waves encountering the sub-horizontal layering during a near-vertical incidence reflection survey. Figure D.5 shows that the strongest reflecting interfaces were found within the evaporitic facies of the Keuper (Lettenkohle) between the overlying Liassic carbonates and downward Muschelkalk unit (Rc= 0.27) and between the Dogger and the Kimmeridgian carbonates (Rc= 0.09). Reflective interfaces could be between Keuper and Sinemurian carbonates.

● The influence of mineral content on Vp/Vs ratio is summarized in Figure E.1, where shear vs compressional waves of our samples are plotted together with the single crystal values for single crystals of quartz, calcite, and dolomite, i.e. the main components of our rocks.

Fig E.1: Effect of minerals on Vp/Vs Ratio. Fig E.2: Interpreted Seismic transact. For the location, refer to Fig A.1.

● The highest values of the seismic velocity and density were measured in Muschelkalk; therefore, those rocks might give raise to good reflectors if in contact with almost all the other lithotypes.

● The reflection coefficients calculated for the stratigraphic sequence in Humilly borehole show possible good reflectors at: - The top of Muschelkalk, at the top of Keuper (with the caveat that we used samples from different boreholes or literature due to absence of Keuper samples in Humilly borehole). - A good reflector can also be the contact between Buntsandstein and Muschelkalk.

● Laboratory measurements on core samples shows significant variations in the physical rock properties and mineralogical content:

- Grain densities [kg.m-3]: range from 2165 to 2948 - Seismic velocities [m.s-1]: ranges 3955 to 6771 ±16 and 2426 to 3975 ±6 for P- and S-waves propagation modes, respectively. - Seismic anisotropy (%) seems to be quite low (< 6), except the anhydrite sample (AVp = 20, AVs = 7).

● The variations in seismic characteristics are due to small-scale heterogeneities, mineral composition and micro-textural features.

Birch, F., 1961. The velocity of compressional waves in rocks to 10 kilobars, Part 2. JGR 66, 2199-2224.Gorin, G.E., Signer, C., Amberger, G., 1993. Structural configuration of the western Swiss Molasse Basin as defined by reflection seismic data. Eclogae Geologicae Helvetiae 86, 693-716.SwissTopo 2005. Tektonische Karte der Schweiz. Karte 1:500 000. - Bundesamt für Landestopografie Swisstopo, Wabern

We acknowledge the funding from the Structural Geology and Tectonics Group at ETH Zürich and the Swiss Governmental Excellence scholarship to perform the experiments in tthe Rock Deformation Laboratory at ETH Zurich. Some experimental data were provided by the SAPHYR project, from Swiss Geophysical Commission.