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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: [email protected]
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.