A N D R E A C R O O K 1 , B A L A Z S N E M E T H 2 , C H R I S T I A N E S C A L A N T E 2 , Y E Z H E N G 3 , L A U R I E R O S S 3 , K E I T H M I L L I S 1

1 O P T I S E I S S O L U T I O N S L T D . 2 B H P B I L L I T O N 3 G E O - X E X P L O R A T I O N S E R V I C E S I N C .

3D SEISMIC ACQUISITION

SURVEY DESIGN FOR INTERPOLATION

OUTLINE

• Project Objectives • Designing for Interpolation • Limitations • Multi-Year Acquisition • Conclusions

OBJECTIVE Regional Focused Infill High Resolution ? +

=

METHODOLOGY Input Decimated

Geometries Combined Infill

PROCESSING • Decimated Raw Shots • Original Input Statics &

Velocities • Multi-dimension interpolation

• Anti-Leakage Fourier Transform (ALFT)

• inline, xline, offset, azimuth and time

• Post Stack Migration

DECIMATED GEOMETRIES

½ Station

DECIMATED GEOMETRIES

½ Station

Random ½ Station

DECIMATED GEOMETRIES

½ Station Random ½ Station ½ Line

DECIMATED GEOMETRIES

½ Station ½ Line

½ Sources Removed Same Average Fold & Trace Density

½ Sources & Receivers Removed Same Average Fold & Trace Density

Random ½ Station

DECIMATED GEOMETRIES

½ Station ½ Line Increasing

Fold & Trace

Density

½ Sources Removed Same Average Fold & Trace Density

½ Sources & Receivers Removed Same Average Fold & Trace Density

Random ½ Station

GEOMETRY COMPARISON

Trac

e D

ensi

ty

Offset

Fold

Based on Constant Bin Size

OFFSET LIMITED FOLD

Low Fold

High Fold

OFFSET LIMITED FOLD

Low Fold

High Fold ½ Sources Removed

½ Sources & Receivers Removed

INTERPOLATION RESULTS

½ Station Random ½ Station ½ Line

INTERPOLATION COMPARISONS

• Near Offsets

• Trace Density

• Operational Efficiencies

• Randomization

NEAR OFFSET EFFECT ½ Source & Rec Stations ½ Source & Rec Lines

NEAR OFFSET DISTRIBUTION

Small Offset

Large Offset

½ Source & Rec Stations ½ Source & Rec Lines

NEAR OFFSET EFFECT ½ Stations ½ Lines

NEAR OFFSET EFFECT ½ Stations ½ Lines

TRACE DENSITY EFFECT ½ Source & Rec Stations ½ Source Station

TRACE DENSITY

Low

High ½ Source & Rec Stations ½ Source Station

TRACE DENSITY EFFECT ½ Source & Rec Stations ½ Source Station

TRACE DENSITY EFFECT ½ Source & Rec Stations ½ Source Station

OPERATIONAL EFFICIENCY EFFECT ½ Source Line ½ Source Station

OPERATIONAL EFFICIENCY

Source Density

Source Density =

Source Linear Km

Source Linear Km >

OPERATIONAL EFFICIENCY EFFECT ½ Source Line ½ Source Station

Regular ½ Source Station Random ½ Source Station

RANDOMIZATION EFFECT

RANDOMIZATION Regular ½ Source Station Random ½ Source Station

Regular ½ Source Station Random ½ Source Station

RANDOMIZATION EFFECT

INTERPOLATION RESULTS

½ Station Random ½ Station ½ Line

LIMITATIONS

32

Original Survey Decimation with

Original Velocities & Refraction Statics

Decimation with New Velocities & Refraction Statics

REPROCESSING WITH/WITHOUT RE-PICKING VELOCITIES & STATICS

Inline

Crossline

MULTI-YEAR ACQUISITION

+ ≠

+ ≠

INCORRECT MULTI- YEAR SURVEYS

OFFSET & AZIMUTH DISTRIBUTIONS

Offset Azimuth

+

+

+ =

+ =

Correct Multi-Year Surveys

OFFSET & AZIMUTH DISTRIBUTIONS

Offset Azimuth

+

+

+ =

+ =

Multi-Year Survey Fold

Bin Size = Double Original Bin Size = Original Bin Size = Original

MULTI-YEAR RESULTS

+ +

MULTI-YEAR RESULTS

Inline Difference

+

+

MULTI-YEAR RESULTS

+

+

Crossline Difference

MULTI-YEAR ACQUISITION

+

CONCLUSIONS • Best Interpolation results achieved when:

• High-density sampling maintained in one direction • Guided Randomization applied • Well sampled near offsets

• Multi-Year acquisition possible when:

• Infill survey has complimentary attributes • high-density sampling maintained in one direction

• Design account for all processes, not just 5D interpolation

ACKNOWLEDGEMENTS

BHP Billiton

Geo-X Exploration Services Inc.

OptiSeis Solutions Ltd.