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Laggan-Tormore “Development Well Location Based On Optimized
Seismic Attributes In Seismically Tuned Reservoir”
O.Duplantier, P.Thore, N.Taylor, K.Jones, H.Kheidri, G.Vizé,
TOTAL E&P UK
DEVEX2012, AECC 9-10th May 2012
PSTM Density IP (log scale) GR Vp
C Sand
B Sand
Wavelet at the
same scale as
geology
55ms
Laggan field, a seismic tuned reservoir
- DEVEX2012, AECC 9-10th May 2012
45m (theoretical
resolution)
A Sand
MD TWT
SSTVD
1:288
0.00 100.00GR
A S
and
AB Shale
Up_B
San
dBC
Sha
le
Zone log linked t o 'Reser voir int er val Used I n M odel'1.95 2.95RHO8
0.45 -0.15NPHI
1.0000 0.0000SWT
206/1a-4a [SSTVD]SSTVD
1:288
0.00 100.00GR
A S
and
AB S
hale
Up_B
San
dLw
_B S
and
BC S
hale
Lw_C
Zone log linked t o 'Reser voir int er val Used I n M odel'1.95 2.95RHO8
0.45 -0.15NPHI
1.0000 0.0000SWT
Core
d
Cor e_I nt er val
206/1a-4AZ [SSTVD]SSTVD
1:288
0.00 100.00GR
A S
and
AB S
hale
Up_B
San
dLw
_B S
and
BC S
hale
Up_C
Lw_C
Zone log linked t o 'Reser voir int er val Used I n M odel'1.95 2.95RHO8
0.45 -0.15NPHI
1.0000 0.0000SWT
Core
d
Cor e_I nt er val
206/1-2 [SSTVD]SSTVD
1:288
0.00 100.00GR
A S
and
AB S
hale
Up_B
San
dBC
Sha
le
Up_C
Lw_C
Zone log linked t o 'Reser voir int er val Used I n M odel'1.95 2.95RHO8
0.45 -0.15NPHI
1.0000 0.0000SWT_U
Core
d
Cor e_I nt er val
206/1-3 [SSTVD]
SSTVD
1:288
0.00 100.00GR
S3
Shale2
Shale
1
S3
AZ_S
hale
A S
and
AB S
hale
Up_B
San
d
BC Shale
Up_C
Zone log linked t o 'Reser voir int er val Used I n M odel'1.95 2.95RHO8
0.45 -0.15NPHI
1.0000 0.0000SWT
205/5a-1 [SSTVD]
Z Sand
Turbidite lobe complex composed of 3 main sequences
Sw SwSw Sw
Sw
C C
C
A
A
B
A
206/1-4a 206/1-4aZ 206/1-2 206/1-3
205/5a-1
TORMORELAGGAN
UB UB
UB
LB LB
FWL
10
A
LB
C
A sand
Upper B sand
Lower B Sand
C Sand
Cored Interval
T 35.3 Ichron sequence
T 35.2 Ichron sequence
UB
Use of seismic attributes to tackle this tuning issue
Reservoir thickness below seismic resolution
SYNTH Reference seismic dataset
(3D baseline 2009)
A Sand
B Sand
C Sand
2
Outline
1. Laggan and Tormore fields overview
2. Inversion results extensively used (PR & AI)
3. Ranking of seismic attributes in seismically tuned reservoir
Way forward (a): New approach to minimise tuning effect
Way forward (b): Modelling with 2D Broadband seismic data
Conclusion
- DEVEX2012, AECC 9-10th May 2012
Optimized seismic attributes in seismically tuned reservoir
3
1. Laggan & Tormore fields overview
- DEVEX2012, AECC 9-10th May 2012
206/1a-4AZ
206/1a-4A
206/1-2
206/1-3
Top Reservoir depth structure map Mixed structural/stratigraphic trap
GWC 3909m
3430m
Crest
206/1a-4AZ 206/1-2 206/1-3
20m
ᶲ ᶲ ᶲ
125km West of
Shetland
600m water depth
Gas condensate fields
First gas
planned in
July 2014
Paleocene reservoirs : 3000m of burial - 3 sand rich turbidite lobes
LAGGAN
FIELD
Development wells drilling
PHASE I
4 wells on Laggan
& 3 wells on Tormore
Start of drilling
Sept 2012
4
2. Inversion results extensively used
- DEVEX2012, AECC 9-10th May 2012
206/1-3
206/1a-4AZ
Relative Poisson
Ratio
Acoustic Impedance
Used to constrain the
Porosity model
Relative Poisson’s
Ratio
Net Gas Sand thickness estimation
Top Reservoir
Base Reservoir
206/1a-4AZ
206/1-3 206/1a-4AZ Gross
A sand 3m
B sand 33m
C sand 13m
206/1-3 Gross
A sand 5m
B sand 12m
C sand 10m
SE NW
206/1a-4AZ
206/1-3
206/1a-4AZ
206/1-3
Reference PSTM
Relative Poisson’s Ratio (Inversion)
Absolute Acoustic Impedance (Inversion)
5
206/1206/1--33
206/1206/1--22
206/1206/1--4AZ4AZ
206/1206/1--4A4A
205/5a205/5a--11
RR22 = 0.86= 0.86
NGS = 0.7023*NGS = 0.7023*RelPRRelPR
Reg on Avg values around
well locations
Relative Relative PoisPois. Ratio. Ratio
NetPayNetPay((NetGasSandNetGasSand))
LowLow--Pass filtered PR (20Hz Pass filtered PR (20Hz --6dB) 6dB) –– Min in reservoirMin in reservoir
50
0
Laggan and Tormore Exploration wells
(from Inversion)
2a. Net Gas Sand thickness from Relative Poisson’s Ratio
- DEVEX2012, AECC 9-10th May 2012
Cumulated Net Gas Sand (m)
206/1-3
206/1-2
206/1a-4AZ
GWC 3909m
TVDSS
1km
0
14
28
42
57
206/1a-4A
Net Gas Sand Thickness [TopA - BaseC] interval
Net Gas Sand thickness away from wells derived
from Seismic
LAGGAN
FIELD
me
ters
Seis
mic
am
plitu
de
True
thickness
(ms)
Single interface
contrast
Detected Resolved
Tuning thickness
Resolution limit
Noise level
Detection
limit
6
- DEVEX2012, AECC 9-10th May 2012
Acoustic Impedance 206/1-3 206/1-4aZ
206/1-4a
SE
B C
B C
Acoustic Impedance shut-off interpreted to be related to a
sand quality reduction
AI shut-off in B sand
P impedance
Total
porosity VCL Log scale
Good correlation at all scales
0.1
0.2
8000 10000
2b. Porosity and Acoustic Impedance relationships
No shut-off in C sand
Poisson’s Ratio
8000
10000
0.7
0
NO PR shut-off
gas bearing interval
260
360
SE
B sand Acoustic Impedance map
206/1-3
206/1-4aZ
206/1-2
8000
10000
Low Porosity area in B sand integrated in the
model using the Acoustic Impedance
Laggan & Tormore wells
7
2c. Acoustic Impedance from inversion: well calibration and limitations
- DEVEX2012, AECC 9-10th May 2012
GR IP
LOG
IP Log Filt
Inverted trace
NOT RELIABLE
206/1a-4AZ
Porosity = 23% *NGS = 47m
206/1-3
Porosity = 22% *NGS = 12m
206/1-2
Porosity = 19% *NGS = 35m
The Acoustic Impedance is not always a
reliable indicator of the sand quality
TUNING
8300 8300
IP Log Filt
Inverted trace
IP Log Filt
Inverted trace
*NGS = Cumulated
Net Gas Sand
OK
NOT RELIABLE
INTERFERENCES (A&B sands + Shale)
NOT RELIABLE
GR IP
LOG GR IP
LOG
7400
GWC
8
- DEVEX2012, AECC 9-10th May 2012
206/1-3
206/1a-4AZ
Relative Poisson’s Ratio (Inversion)
Eq. Net Gas Sand
47 m
27 m
20 m
12 m
AVO seismofacies
Seismic
attribute Description : Pros & Cons
Poisson’s Ratio
Inversion
HC anomalies are caused by a drop in effective fluid
modulus (K): the compressional wave velocity decreases
while the shear wave velocity stays relatively unchanged.
Increasing compressible hydrocarbon saturation in a
porous reservoir generates a drop in Vp/Vs, or
equivalently Poisson’s Ratio.
AVO seismofacies
Near amplitude reflects IP while Relative Amplitude
variations between Far angle and Near angle help to
capture Poisson’s Ratio Relative changes.
Amplitudes and AVO joint analysis allows to define
lithology and fluid content.
3a. Ranking of seismic attributes in seismically tuned reservoir
0
A careful step by step procedure is
necessary to a successful AVO application
206/1-2
Relative
Poisson’s Ratio
Cumulated
Net Gas Sand of
unresolved reservoirs
Tuning (interferences) = affects seismic amplitudes
L2
L1
L3
L4
-5000
206/1-3
206/1a-4AZ
206/1-2
L2
L1
L3
L4
206/1a-4A
206/1a-4A
E&A wells
Planned DEV wells
9
Abs Acoustic Impedance (Inversion)
Amplitude map on Top Reservoir
Seismic
attribute Description : Pros & Cons
Acoustic Impedance
Inversion
Increasing fluid compressibility (1/K) always decreases
Acoustic Impedance (softening).
P Impedance and Poisson’s Ratio are needed to
predict lithology and fluid content.
The Relative Ip inversion has to be also considered:
the Low Frequency model based on a unresolved
reservoir could imply a bias (second order).
Seismic Amplitude
10 000
7800
- DEVEX2012, AECC 9-10th May 2012
3b. Ranking of seismic attributes in seismically tuned reservoir
The Absolute Acoustic Impedance is not
always a reliable indicator of the sand quality.
Tuning (internal interferences)
Amplitude mixed between contrasts
seal/reservoir and thickness
Acoustic
Impedance
Porosity at
wells
Tuning (interferences) = affects seismic amplitudes
and the INVERSION results
206/1-3
206/1a-4AZ
206/1-2
L2
L1
L3
L4
206/1-3
206/1a-4AZ
206/1-2
L2
L1
L3
L4 206/1a-4A
206/1a-4A
E&A wells
Planned DEV wells
10
Methodology based on the generation of geologically consistent
pseudo-wells to assess :
Uncertainties on seismic interpretation (due to seismic interferences)
Quality of seismic inversion results
Case study on LAGGAN field using:
3 real wells
extracted wavelet (3D baseline 2009 - Reference dataset)
[BC shales and C Sand thicknesses assumed to be anti-correlated, as demonstrated at wells]
- DEVEX2012, AECC 9-10th May 2012
Used in the next
reservoir model
Pseudo-geo-
statistics Optimise
tuning effect
integration
Stochastic
Inversion
Way forward (a): New approach to minimise tuning effect
11
Combined with
inversion results
(e.g stochastic)
TEP UK / Geosciences Research Center proprietary
Way forward (a): Modelling with reference seismic wavelet
Top reservoir only detected 206/1-3 206/1-2
Reference seismic too narrow bandwidth for correct reservoir resolution
Pseudo-well
A sand
B sand
C sand
Base reservoir picked
on the synthetic Thickness of C sand - = f
Use of INVERSION (e.g stochastic)
TUNED Reservoir thickness
CORRECTED Reservoir
thickness
True base C of
pseudo-wells
18m
13m BC shale
12m
11m
Base reservoir tuned for all realizations
Synthetic
Density model
- DEVEX2012, AECC 9-10th May 2012
206/1-3 206/1-2 A sand
B sand
C sand
18m
13m
12m
11m
Pseudo-well
12
TEP UK / Geosciences Research Center proprietary
3D baseline 2009
2D Broadband 2011
(from actual data on field)
Frequency (Hz)
Amplitude
dB
Way forward (b): Modelling with 2D Broadband seismic data
C sand is tuned (picked horizon below actual base reservoir)
Synthetic
Density model
Better seismic resolution when preserving the low frequency content
206/1-3 206/1-2
Pseudo-well
A sand
B sand
C sand
18m
13m BC shale
12m
11m
- DEVEX2012, AECC 9-10th May 2012
206/1-3 206/1-2
Pseudo-well
18m
13m
12m
11m
13
TEP UK / Geosciences Research Center proprietary
Broadband would allow a reliable quantitative
evaluation through lower frequencies content
3D Broadband acquisition test ongoing
on Laggan Tormore
Poisson’s Ratio from inversion shows a good relationship with the cumulated Net
Gas Sand of unresolved reservoirs in Laggan field.
- DEVEX2012, AECC 9-10th May 2012
Conclusion
Together with other selected seismic attributes, Poisson’s Ratio
is used to optimise Phase I development well locations.
Two approaches are being developed for further improvements :
1. A pseudo-geo-statistics approach based on the generation of pseudo-wells will
be used to minimize the tuning effect in the next model.
2. Broadband acquisition: The wider spectral bandwidth should enable to improve
the resolution of the reservoir interval and permit a more reliable quantitative
evaluation.
New reservoir model will be used for Phase II development wells.
14
The authors acknowledge
- DEVEX2012, AECC 9-10th May 2012
The contributions of many colleagues at
TOTAL to the Laggan-Tormore project
Laggan – Tormore & Edradour partner, DONG
Energy, for permission to make this presentation
15