1. CEGAL.COM
*Petrel is a mark of Schlumberger
• Jointly inverts to both facies and rock
properties (Porosity, net to gross)
• Simultaneous inversion of color
inverted angle stacks
• Follows real well facies distributions
and rock properties by computing
thousands of statistically correct
pseudo wells per trace
• No low frequency model required
• No lateral / spatial constraints
• Best matching pseudo wells are se-
lected to provide rock property values
and their associated uncertainties
HIGH QUALITY IMAGES OF RESERVOIR PROPERTY ESTIMATES AND ASSOCIATED UNCERTAINTIES
3D views of Net Fraction, a part of lithofacies and
higher porosity zones after voxel transparency at
the target reservoir zone
BLUEBACK
ODISI
ONE DIMENSIONAL STOCHASTIC INVERSION
BLUEBACK ODiSI is a One Dimensional Stochastic In-
version method that produces high quality reservoir
property estimates with associated uncertainties, to
predict net fraction, porosity and lithofacies distribution
in geological plays.
It is a unique seismic inversion method that specifically
includes only the most robust prior information in order
to apply additional constraints to the solution.
Blueback ODiSI does not require any prior lateral con-
straints: the algorithm converges so that each trace
can be inverted independently of its neighbors yet lat-
erally continuity is still achieved.
The technology was originally developed by BP (Con-
nolly & Hughes, 2013, 2014, 2016) while a Petrel* ver-
sion has been developed jointly by Cegal and BP.
The solution is robust yet logical and comes fully inte-
grated into Petrel, complementing Cegal’s Quantitative
Interpretation solution Blueback Rocks QI.
INPUT
Color Inverted Extended
Elastic Impedance (EEI)
OUTPUT
ODiSI Inverted Net Fraction
ODiSI Inverted Lithofacies

2. 01
SEISMIC DATA
CONDITIONING
Check for zero
phase, frequency,
spectral and ampli-
tude balance
Create intercept
and gradient
volumes
02
EEI WORKFLOW
Find optimum CHI
angles
Normally, fluid and
lithology angle vol-
umes are required
03
IMPEDANCE
INVERSION
Apply Bayesian
Invert seismic data
using well-proved
Colored Inversion
04
WELL LOGS
Condition well log
data
Create dry bulk and
shear bulk modulus
logs
Create a facies well
log
05
NOT REQUIRED
Wells do not need
to be tied
Wavelets do not
need to be extract-
ed - frequencies
come from the color
inversion operator
06
ODISI
Create parameters
Statistics QC
Inversion QC
Inversion (multi-
threaded process)
GENERAL WORKFLOW
To perform an Blueback ODiSI inversion, the input
data needs to be quality checked and conditioned. The
necessary tools to prepare the data are available in the
Cegal quantitative interpretation software Blueback
Rocks QI.
Stochastic Inversion by
matching to large numbers
of pseudo wells workflows
We are more than 340 employees, of which more than 50 are highly skilled geoscientists. The unique combination of geoscience
and IT expertise puts us in an excellent position for serving customers in the oil and gas industry.
CEGAL.COM