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Geostreamer technology
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GeoStreamer Technology:Complete Waveform Imaging (CWI) -
Johan Sverdrup Case Study
J.E.Lie (Lundin), M. Farouki, G. Rnholt, . Korsmo, B. Danielsen, S.Brown, S. Brandsberg-Dahl, A.V. Mavilio, N. Chemingui, D.Whitmore (PGS)
Presented by Rick Irving
2014 HAGI WorkshopBandung, June 23rd 2014
Overview
Survey background
Brief description of CWI technology
Case Study - Johan Sverdrup
Summary & Conclusions
Introduction: Johan Sverdrup Case Study 1st proprietary 3D Dual-Sensor survey, 2009 1600km2 over Luno discovery, North Sea Led to Johan Sverdrup discovery in 2010 - largest oil discovery in last 10 years
Legacy 3D 3D OBC Dual-Sensor 3D
Low relief oil reservoir covering 180 km2 - porous Jurassic sandstone at 1900m Recoverable reserves estimate: 1.7 - 3.3 billion barrels Large uncertainty due to complex shallow section, weathered basement & conglomerates Reprocessed many times by numerous contractors - unable to tie well Accurate depth measurement crucial for estimating reserves and field development Reprocessing using Complete Wavefield Imaging technology
Johan Sverdrup Field
Overview
Survey background
Brief description of CWI technologyhyperTomo - Reflection tomographyFWI - Full waveform InversionSWIM - Separated Wavefield Imaging
Case Study
Summary & Conclusions
Complete Wavefield Imaging (CWI)
The Multiple Benefits of GeoStreamer
hyperTomo using Primary ReflectionsSeparated Wavefield Imaging (SWIM) using Multiples
FWI using Refractions & Diving Waves
GeoStreamer - Dual-Sensor Acquisition
Wavefield Separation Notch DiversityMulti-Sensor streamer technology. Conventional hydrophone-only
streamer.
Vector measurement -incorporates particle velocity.
Scalar measurement -pressure only.
Acquisition solution. Processing solution.
BenefitsBroader bandwidth. Broader bandwidth.
No flat sea assumption.
Insensitive to sea surface & receiver depth variations.
Deterministic Workflow;No multi-dimensional transforms.
No artificial whitening.
4D compliant.
Pre-stack amplitude & phase integrity.Quantitatively accurate AVO/AVA, QI.
Processing & Imaging applications using separated wavefields.
Wavefield Separation
Leveraging wavefields from dual-sensor systemVelocity model building workflow
SEISMIC EVENT WAVEFIELD ALGORITHM APPLICATION
PRIMARY REFLECTIONS UPGOING TOMOGRAPHY Background model for robust FWI
REFRACTIONS RAW HYDROPHONE FWI Hi-res iterative approach for model 0-500m
MULTIPLES UP- & DOWN-GOING SWIM Validation of shallow overburden
PRIMARY REFLECTIONS UPGOING TOMOGRAPHY Hi-res update for deep overburden & target
Wavelet Shift Tomography - hyperTomo
1. Decompose input data into wavelets
2. Migrate wavelets
map from data to model space
3. Estimate 3D residual for each wavelet
data and model space attributes preserved
4. Form equation for each wavelet
5. Invert for velocity update
Beam Migration
RMO
Iterative Tomography
Refines the velocity model byiterative matching of modelled data with recorded data
Refraction-based FWI Driven by refractions and diving
waves Shallow updates Minimum pre-processing,
Reflection-based FWI Designed for use with
backscattered arrivals Allows for deep updates Preprocessing required
- Requires input data with low frequencies- Ideally suited to broad-band seismic data- Provides short wavelength velocity information
Full Waveform Inversion
Etgen & Brandsberg-Dahl: The pseudo-analytical method: Application to acoustic wave propagation. SEG 2009
1-Way WEM is reconfigured to use up-going & down-going wavefields to image the earth with free surface multiple data
Replace S (forward propagated shot - impulse wavelet) with down-going wavefieldReplace R (back-propagated P-total at receivers) with up-going wavefieldApply imaging condition
More extensive illumination of earth; areal wide azimuth source array
S R
Primaries Multiples
Imaging with separated wavefields - SWIM
SWIMsubset
First commercial SWIM applicationLundin Malaysia - PM307
Long et al: Mitigation of the 3D cross-line acquisition footprint using wavefield separation of dual-sensor streamer seismic data.PGCE 2013 Kuala Lumpur
70-90m shallow water
Streamers 12 x 4050m @ 75m
Dual-source, 18.75m spacing
SWIM subset:47 sail lines
427 km = 51,000 shots
Data output:6.25m x 8.75m bins (P-UP)
Limited trial:Migration pursued to 60Hz
No velocity update
No anisotropy investigation
Time slice 120ms Conventional WEM
Time slice 120ms SWIM
PSDM of Primaries - xline
SWIM - xline
Overview
Survey background
Brief description of CWI technology
Case Study:Complete Waveform Imaging (CWI) -Advanced Depth Imaging using Primaries, Multiples & Refractions
Summary & Conclusions
CWI workflow
hyperTomo
FWI
SWIM
hyperTomo
Background model match refracted events in modeled and real data
Iterative approach model down to 600 m below water bottom
SWIM gathers and stack for validation of the shallow overburden
High resolution tomographic update for deep overburden and target
18
Separated Wavefields Imaging (SWIM) -Yields greater illumination from multiples
Full Waveform Inversion (FWI) -Exploits low frequency content from dual-sensor streamer acquisition
CWI - Complete Wavefield ImagingNoise becomes useful
chalk
Reflection tomography - chalk layer updated (model provided by Lundin)
Beam gathers (2012 PSDM model)
chalk
hyperTomo high resolution chalk layer update
Beam gathers (hyperTomo model)
Shot record filtered 3-10hz
Shot record filtered 3-5hz
Low frequencies captured in Dual-Sensor raw hydrophone
Kirchhoff PSDM stack - input to FWI
Kirchhoff PSDM stack - FWI velocity model
channels gas caps
Shaleplug
Kirchhoff PSDM gathers - input model
Kirchhoff PSDM gathers - FWI velocity model
Solving for refraction velocities correspondsto flattening primary reflections
FWI velocity, depth = 240m
FWI velocity, depth = 240m
Channels
Buried pockmarks Shale Plug
Gas
PSDM image and FWI velocity overlay, depth = 240m
FWI velocity, depth = 320m
PSDM image and FWI velocity overlay, depth = 320m
SWIM vs Kirchhoff PSDM
Shallow hazards
High fold
SWIM STACK
KIRCHHOFF PSDM STACK
SWIM 3D view - 250m depth
Seismic - Imaging of multiples
SWIM 3D view with FWI model overlay
Velocity Model from refractions
Comparison SWIM and Kirchhoff at 225m depth slice
Shallow hazards
Resolution of channel
Illumination
KIRCHHOFF PSDM STACK SWIM STACK
SWIM - gathers for velocity model buildingSWIM stack
SWIM common angle gathers
Kirchhoff common offset gathers
PSDM - Input
- Depth mistie- Uncertainty in
estimating reserves;1.7 - 3.3 billion barrels
Impact at target:- Well ties seismic- Oil/Water contact
defined- Confident estimation of
reserves
PSDM - Revised
Robust, high-resolution velocity model in near surface, 0-500m.
Overview
Survey background
Brief description of CWI technology
Case Study:
Summary & Conclusions
Dual-Sensor Acquisition
High resolution velocity model at depth
Kirch WEMBeam RTM
SWIMFWIExploits GeoStreamer low frequencies Exploits near surface illumination
High resolution shallow velocity model
Reflection Tomography
Validation of shallow velocity model
Exploits GeoStreamer S/N
Complete Wavefield Imaging
Wavefield separation
REFRACTIONS MULTIPLES
PRIMARIES
Summary
The dual sensor broadband solution provides:- an acquisition platform for Wavefield Separation- improved S/N reflection data- low frequencies important for FWI- ability to exploit multiples for superior illumination- Complete Wavefield Imaging
Modern imaging technologies are applied to a vintage dual-sensor 3D surveyfor hi-res velocity model building and imaging:
- Independently, shallow small-scale features correlate very well:- velocity model built from refraction FWI- imaging of primaries- imaging of multiples
- Significantly impacts correct structural imaging at target.
Thank you for your attention!