bandwidth extension applied to 3d seismic data on heather ... · well data phase information...

Bandwidth Extension

applied to 3D seismic data

on Heather and Broom

Fields, UK North Sea

DEVEX Maximising Our Diverse Resources 15-16th May 2013

1. EnQuest Plc

2. Geotrace Technologies Ltd

Tim Trimble1., Clare White2., Heather Poore2.

Heather Field Background: Seismic Dataset

Heather and Broom fields are situated in UK

Block 2/5 and 2/4a at the western

margin of the East Shetlands Basin

Heather Field 100% EnQuest, Broom Field

partners EnQuest, Wintershall Norge

ASA, Ithaca Energy (UK) Limited

316km2 pre stack depth migration

• stretched back to time.

Shot by PGS 2006

• East-West shooting

• 5100m solid streamers at 6m depth

• Source depth 5m.

Processed 2007 – also PGS

• much effort on multiple suppression

below Base Cretaceous

2

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Heather Platform

2/05-25 (BR2)

2/05-26Z

2/05-26

H62Y

H61Z

H60

H59Z

H58Z

H57

H57Z

H56

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H13

H12

H11Z

H10Z H10

H09

H08

H07

H06Z

H05YH05

H04

H03

H02

H01

H63

2/5-24 (BR1)

2/5-23 (BR4)

2/5-22Z (BW 6)

2/5-22

2/5-21 (BW 3)

2/5-20 (BR5)

2/5-19Y

2/5-18

2/5-17

2/5-16Z

2/5-15

2/5-14Z

2/5-13Z

2/5-12A

2/5-11

2/5-10

2/5-9

2/5-8B

2/5-7

2/5-62/5-5

2/5-4

2/5-3

2/5-2

2/5-1

378800 379200 379600 380000 380400 380800 381200 381600 382000 382400 382800 383200 383600 384000 384400 384800 385200 385600 386000 386400 386800 387200 387600 388000 388400 388800 389200 389600 390000 390400 390800 391200 391600 392000 392400 392800 393200 393600 394000

378800 379200 379600 380000 380400 380800 381200 381600 382000 382400 382800 383200 383600 384000 384400 384800 385200 385600 386000 386400 386800 387200 387600 388000 388400 388800 389200 389600 390000 390400 390800 391200 391600 392000 392400 392800 393200 393600 394000

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6758000

6758400

6758800

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6760000

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6760800

6761200

6761600

6762000

6762400

6762800

6763200

6763600

6764000

6764400

6764800

0 500 1000 1500m

1:50000

-13500-13250-13000-12750-12500-12250-12000-11750-11500-11250-11000-10750-10500-10250-10000-9750-9500-9250-9000-8750-8500-8250-8000-7750-7500-7250-7000

Depth

Top Brent 2012

Scale

Contour inc

J Milne

Date

1:50000

100

09/06/2012

Map

Heather-Broom: Ongoing Development Issues

Heather

STOOIP ~500mmbbls

Recovered ~120mmbbls

Broom

STOOIP ~152mmbbls

Recovered ~33mmbbls

Thin Brent Sandstones

– 125ft-375ft, typically ~1 cycle on conventional seismic

Shallow marine to deltaic clastic system

– individual formations exhibit highly variable reservoir qualities

Heavily faulted reservoir

– Faults with minor throws can operate as baffles/barriers to flow

Complex Diagenetic History

– Kaolinite, Quartz, Illite and Calcite all occur

Variable Acoustic Impedances

– Above and within the Brent

• Variable pick at Top (and Base) Brent

Seismic resolution is critical for further development

A simplified rendition of Bandwidth Extension theory

4

1. BE® utilises the Continuous Wavelet

Transform (CWT) to perform a time

series analysis of the input seismic

trace that decomposes the trace into

its respective amplitude and phase

components in both frequency and

time.

Smith et al, 2008 (Leading Edge)

A simplified rendition of Bandwidth Extension theory

5

One

Octave

1. BE® utilises the Continuous Wavelet

Transform (CWT) to perform a time

series analysis of the input seismic

trace that decomposes the trace into

its respective amplitude and phase

components in both frequency and

time.

2. The frequencies present in the

bandwidth of the input seismic trace

(the fundamental frequencies) are

used to predict harmonics (and

possibly subharmonics) beyond the

chosen pivot frequency.

Smith et al, 2008 (Leading Edge)

3. A convolution-like process is employed to convolve the predicted harmonic (and sub-harmonic)

information onto the initial seismic trace. If reflectivity at low amplitudes is present in the input data

that corresponds to the harmonic (and sub-harmonic) predictions, the extended frequencies will

remain in the result. However, if extended harmonics or sub-harmonics frequencies do not correspond

to reflectivity in the input data, these extended harmonics will drop out of the result.

A simplified rendition of Bandwidth Extension theory

6

First

Harmonic

One

Octave

1. BE® utilises the Continuous Wavelet

Transform (CWT) to perform a time

series analysis of the input seismic

trace that decomposes the trace into

its respective amplitude and phase

components in both frequency and

time.

2. The frequencies present in the

bandwidth of the input seismic trace

(the fundamental frequencies) are

used to predict harmonics (and

possibly subharmonics) beyond the

chosen pivot frequency.

Smith et al, 2008 (Leading Edge)

4. The resulting broader bandwidth amplitude and phase spectra are used to reconstruct the modified

seismic trace. The resulting modified seismic traces has broader bandwidth and thus increased

temporal resolution. Result is less noisy than traditional bandwidth enhancement techniques.

3. A convolution-like process is employed to convolve the predicted harmonic (and sub-harmonic)

information onto the initial seismic trace. If reflectivity at low amplitudes is present in the input data

that corresponds to the harmonic (and sub-harmonic) predictions, the extended frequencies will

remain in the result. However, if extended harmonics or sub-harmonics frequencies do not correspond

to reflectivity in the input data, these extended harmonics will drop out of the result.

A simplified rendition of Bandwidth Extension theory

7

1. BE® utilises the Continuous Wavelet

Transform (CWT) to perform a time

series analysis of the input seismic

trace that decomposes the trace into

its respective amplitude and phase

components in both frequency and

time.

2. The frequencies present in the

bandwidth of the input seismic trace

(the fundamental frequencies) are

used to predict harmonics (and

possibly subharmonics) beyond the

chosen pivot frequency.

Smith et al, 2008 (Leading Edge)

Bandwidth Extension: Key Steps

8

Well Data Phase

Information

Post-Stack

“Normal

Bandwidth”

Input

Zero Phase

Input Data

Well-to-

seismic Tie

Horizons Interpretation?

Windows for BE®

parameterisation

BE® Result

Ba

nd

wid

th

An

aly

sis

BE® Well

Tie

Final BE®

Result

De

term

inis

tic

Wavele

ts

Bandwidth Extension: Key Steps – Phase Analysis

Well Data Phase

Information

Post-Stack

“Normal

Bandwidth”

Input

Zero Phase

Input Data

Well-to-

seismic Tie

Average

Average phase of the input

volume was assessed to be

+123˚. Seismic data must be

rotated in the opposite

direction (-123˚) in order to

zero phase the data to a

polarity convention in which an

acoustic impedance is a peak,

as required by the algorithm.

VSP Corridor

Stack

‘Normal

Bandwidth’ Stack

(Example: Well 2/5-17 Tie)

Bandwidth Extension: Key Steps – Frequency Analysis

10

Post-Stack

“Normal

Bandwidth”

Input

Horizons Interpretation?

Windows for BE®

parameterisation

Spatially the frequency content

appeared relatively constant

across the survey (multiple

inlines and xlines tested), and

temporally the frequency

content supported the use of a

three window parameterisation

Results

11

Normal Bandwidth Stack, Inline 3055

12

42 Hz

Window 3 (Primary Target Interval) Window 3 (Primary Target Interval)

13

42 Hz

Window 3 (Primary Target Interval)

72 Hz

Window 3 (Primary Target Interval)

Bandwidth Extension Stack, Inline 3055

PSDM data with Noise

Cancellation

500m North South

PSDM data with Noise

Cancellation and Spectral

Whitening

500m North South

PSDM data after Blueing

500m North South

PSDM data (Noise Cancelled)

with 1 Octave Bandwidth

Extension

500m North South

PSDM data (Noise Cancelled)

with filtered 2 Octave

Bandwidth Extension

500m North South

PSDM data (Noise Cancelled)

with unfiltered 2 Octave

Bandwidth Extension

500m North South

Combined Amplitude Spectra (Xline 771, 2.4-3.0 secs)

2/5-17 Synthetic-Seismic Tie:

Input PSDM-Bandwidth Extended Comparison

NW NW SE SE

INPUT PSDM DATA BANDWIDTH EXTENDED DATA

2/5-17

Synthetic Trace- 25Hz Ricker 2/5-17

Synthetic Trace- 40Hz Ricker

Top Brent

300ms-3000ms Window

500m

Sonic

TW

T (s)

Well 2/5-3: Synthetic ties before and after 1 Octave Bandwidth Extension

Input PSDM

Data

1 Octave

Extended Data

TW

T (s)

23

Well 2/5-3 Seismic Tie:

Input PSDM-Bandwidth Extended Comparisons

INPUT PSDM DATA BANDWIDTH EXTENDED DATA (1 Octave)

Extracted Wavelet Extracted Wavelet 45Hz Ricker Wavelet

BANDWIDTH EXTENDED DATA (2 Octave- Filtered)

Summary Synthetic to Stack Correlation and Phase Analysis:

1 Octave Bandwidth Extension® stack

24

Well 2/5-17: Phase behaviour of deterministic wavelets before and after

Bandwidth Extension

25

Normal

Bandwidth

1 Octave

Bandwidth Extension

1 Octave

Bandwidth Extension

with Stretch-Squeeze

Well 2/5-17

2100-2600 ms

Improved fault plane definition on Bandwidth Extended data

26

INPUT PSDM DATA BANDWIDTH EXTENDED DATA (1 Octave)

Top Brent Top Brent

1km

Similarity Extractions Comparison at Top Brent

27

INPUT PSDM DATA BANDWIDTH EXTENDED DATA (1 Octave)

Broom Field:

Comparison of Top Brent fault mapping with Bandwidth Extended data

INPUT PSDM DATA BANDWIDTH EXTENDED DATA (1 Octave)

Conclusions

• Bandwidth Extension has significantly improved the

resolution of the Heather-Broom seismic dataset

• Synthetic ties confirm little loss of Signal/Noise

• Improvement over previous frequency enhancement

techniques

• Most improvement in fault definition

• Brent formation properties and diagenesis remain a

challenge

• But more work to be done

29

Acknowledgements

• Thanks to EnQuest and Geotrace Technologies for permission to

publish this paper

• Also to Broom partners - Wintershall (UK North Sea) Limited and Ithaca

Energy (UK) Limited

• All colleagues at EnQuest and Geotrace for input and help throughout

Contact: Clare White, cwhite@geotrace.com

30

Awarded for

Bandwidth Extension®

Geotrace Technologies, Ltd

May, 2013