laggan-tormore - devex · pdf filegeology 55ms laggan field, ... new reservoir model will be...

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


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


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


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


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


Optimized seismic attributes in seismically tuned reservoir

3

1. Laggan & Tormore fields overview


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


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


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


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


GR IP

LOG

IP Log Filt

Inverted trace

NOT RELIABLE

206/1a-4AZ

Porosity = 23% *NGS = 47m

206/1-3


206/1-2


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


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


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]


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


206/1-3 206/1-2 A sand

B sand

C sand

18m

13m

12m

11m

Pseudo-well

12


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


206/1-3 206/1-2

Pseudo-well

18m

13m

12m

11m

13


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.


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


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

laggan-tormore - devex · pdf filegeology 55ms laggan field, ... new reservoir model will be...

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