Statistical a priori model
AI
Horizontal covariance
Vertical
covariance
0
1
0
time
Mean Mean +/- 2*s.d.
20ms
After: Marion, Robotham and Swaby, TFE
Schlumberger Private
❖copy $sp1/workstation/*.msi to Windows NTFS partition
Petrel things
GF-Petrel connection
GeoFrame part
Basemap -> send -> export to Petrel
Geology Office -> tools -> export well data to Petrel
seismic domain. Possibility of extending beyond the seismic bandwidth.
Inversion Limitations
Estimate the frequencies available within the seismic by wavelet estimation or spectral analysis.
Removes the effects of the wavelet within the seismic bandwidth. Forces well ties to be made and understood. Reservoir properties are separated from the overburden. May provide quantitative predictions on the reservoir properties. Stratigraphic interpretation may be improved. Interpreting in the impedance domain is frequently easier than in the
4 DPsaila 7/5/2007
Geostatistical Inversion
Impedance models are geologically constrained:
• Stratigraphic framework
• 3D a priori model
• 3D heterogeneity model
Benefits of Seismic Inversion Inversion Limitations Major applications on the market Petrel things
What is Seismic Inversion?
What is Seismic Inversion?
Now the normal assumption is that the seismic trace is considered to be a primary only reflectivity model convolved with the seismic wavelet which is summed with some uncorrelated noise and can be represented by the equation:
Petrel things
GF-Petrel connection
Petrel part
❖install GeoFrameDataConnectorForPetrel2009.1.msi
Petrel things
GF-Petrel connection
Petrel part
Petrel things
Normal
Wavelet extraction Time-shift wavelet Sonic calibration curve
Abnormal
Sonic filter/smoothing/blocking Squeeze/stretch Space-shift wavelet Average wavelet
where Vp is p-wave velocity and ρ is density
Seismic reflections are given by the change in the Acoustic Impedance of the layers and are represented by the equation
Initial modeling
Post-stack Inversion steps
Inversion
Post-stack Inversion steps
Post-inversion
Benefits of Seismic Inversion
More geoscientists understand the concept of impedance and geology than the seismic trace. Thus, working in the impedance domain is a great mechanism for integrating with the various disciplines in a multidisciplinary asset team.
Post-stack Inversion steps
Well to seismic calibration
Wavelet extraction
❖For every well ❖Short time window analysis ❖Not care about the shape of wavelet
Background and Theory
Post-stack Inversion steps
Well to seismic calibration Initial modeling Inversion Post-inversion
Post-stack Inversion steps
Well to seismic calibration
There are no facts, only interpretations.
Friedrich Nietzsche
Contents
What is seismic inversion Background and theory Post-stack Inversion steps
Well to seismic calibration Initial modeling Inversion Post-inversion
Petrel things
High Resolution Geostatistical Inversion(SSI)
/display/index.do?id=id3010054
/GTeC/Projects/MMRD/RSConceptStudies/2006-Inversion/
The algorithm is a stochastic simulation approach producing multiple high resolution realizations of acoustic impedance that tie at the well control and are consistent with the seismic data. A prior model is used to constrain the vertical and lateral trends of acoustic impedance and a variogram model is used to constrain the patterns of spatial variability of the inverted acoustic impedance. The method can also be extended to handle AVA inversion of multiple seismic angle stacks.
Mean producing many high resolution
3D AI results
SD
8 DPsaila 7/5/2007
0
AI (km/s . g/cc) 0.7
After: Marion, Robotham and Swaby, TFE
Geostatistical Inversion - Products
Major applications
PrismSeismic – CRYSTAL
Major applications
PrismSeismic – REFRACT
DFN
Petrel things
GF-Petrel connection
GeoFrame part
❖fuse 2.7.4 + ntfs-3g 2009.4.4, NTFS driver for Linux ❖GeoFrame 4.4 + TK-2 patch
Schlumberger Private
Geostatistical Inversion - Products
One realization
• Impedance results are at high
resolution (~2-8 m, ~1-4 ms)
4
AI (km/s . g/cc)
9
• Describes non-uniqueness by
Background and Theory