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SEISMIC INTERPRETATION
&
RESERVOIR CHARACTERIZATION
UNIVERSITAS GAJAH MADA
20 OCT 2012
GERANICKY DELISATRA
PHE ONWJ
Geranicky Delisatra, Geophysicist – PHE ONWJ
Presentation Outline
• Introduction
• Fundamental of Seismic
• Seismic Data Acquisition & Processing
• Seismic Interpretation
• Reservoir Characterization Method
Geranicky Delisatra, Geophysicist – PHE ONWJ
Presentation Outline
• Introduction
• Fundamental of Seismic
• Seismic Data Acquisition & Processing
• Seismic Interpretation
• Reservoir Characterization Method
Geranicky Delisatra, Geophysicist – PHE ONWJ
Introduction
• Seismic play an important role in every phase of oil &
gas industry
• Exploration phase usually 2D seismic data;
exploration play concept, prospect identification,
exploration well drilling, appraisal well drilling
• Development phase usually 3D seismic data;
reservoir characterization, geological modeling, infill well
drilling, field development
• EOR usually 4D seismic data; reservoir monitoring
Geranicky Delisatra, Geophysicist – PHE ONWJ
Exploration
Source Rock ?
Structural Trap
Stratigraphic Trap
• Working with minimum
data; wells, seismic, etc
• Building exploration
concept
• Prospect identification
• Prove petroleum system
• If exploration well succeed,
drill appraisal well to
estimate reserve
accumulation
Mass
Transport
ComplexBasement high/
Thinned section
Figure 7: Idealized GDE Highlighting Additional Features with Patterns
SLOPE
MUDSTONES
SHELF
MUDSTONES
BASIN FLOOR
MUDSTONES
Nonmarine
Deep Water Sands
(Fans)
Deep Water Sands
(Fans)
Geranicky Delisatra, Geophysicist – PHE ONWJ
Development
• Dealing with numbers of well data, 3D seismic, engineering
data
• More detailed work; field scale to reservoir scale
• Reservoir characterization; property prediction, fluid
identification
• Building geological model as an input for reservoir
simulation
Geranicky Delisatra, Geophysicist – PHE ONWJ
EOR
• Using 4D seismic data
• Monitoring movement of CO2 injection
Geranicky Delisatra, Geophysicist – PHE ONWJ
Presentation Outline
• Introduction
• Fundamental of Seismic
• Seismic Data Acquisition & Processing
• Seismic Interpretation
• Reservoir Characterization Method
Geranicky Delisatra, Geophysicist – PHE ONWJ
Basic Seismic Concepts
S = R * W
S = Seismic
R = Reflection Coeff.
W = Wavelet
RC
IA1
IA2
Geranicky Delisatra, Geophysicist – PHE ONWJ
Polarity & Phase
Normal Polarity Reverse Polarity
Minimum Phase
Zero-Phase
RC +
RC +
Geranicky Delisatra, Geophysicist – PHE ONWJ
Knowing Polarity & Phase
What is the polarity and phase of the above seismic section?
Geranicky Delisatra, Geophysicist – PHE ONWJ
Exercise
Shale
ρ = 2.4 g/cc
V = 3000 m/s
Tight Limestone
ρ = 2.7 g/cc
V = 6000 m/s
Shale
ρ = 2.4 g/cc
V = 3000 m/s
RC = (IA2 – IA1)
(IA2+IA1) IA = ρ x V
Wet Sandstone
ρ = 2.6 g/cc
V = 4000 m/s
RC1
RC2
RC3
* =
RC S
Geranicky Delisatra, Geophysicist – PHE ONWJ
Vertical Resolution
Remember:
λ = V x f
Where
λ = wave length (m)
V = velocity (m/s)
f = frequency (Hz)
Geranicky Delisatra, Geophysicist – PHE ONWJ
Presentation Outline
• Introduction
• Fundamental of Seismic
• Seismic Data Acquisition & Processing
• Seismic Interpretation
• Reservoir Characterization Method
Geranicky Delisatra, Geophysicist – PHE ONWJ
Seismic Data Acquisition
• Type of survey:
– Land
– Transition
– Marine
• Type of data:
– 2D
– 3D
Geranicky Delisatra, Geophysicist – PHE ONWJ
Land Acquisition
Geranicky Delisatra, Geophysicist – PHE ONWJ
Transition Zone Acquisition
Geranicky Delisatra, Geophysicist – PHE ONWJ
Marine Acquisition
Geranicky Delisatra, Geophysicist – PHE ONWJ
Seismic Processing
Geranicky Delisatra, Geophysicist – PHE ONWJ
Presentation Outline
• Introduction
• Fundamental of Seismic
• Seismic Data Acquisition & Processing
• Seismic Interpretation
• Reservoir Characterization Method
Seismic 2D/3D data Subsurface Geological
Information
What is seismic interpretation?
Geranicky Delisatra, Geophysicist – PHE ONWJ
Required Data for Seismic Interpretation
• Basemap
• Well Data
• …and of course…Seismic Data
Basemap
• Basemap is useful to know your map
view location while interpreting seismic
section
• Basemap will give us information about
coordinates, well location, 2D seismic
lines, 3D seismic area, scale bar, etc.
Well Data • Type of well data:
Digital data (LAS or ASCII
format)
Hardcopy (Final well report,
well completion, etc.)
• Well Data:
Logs: Gamma Ray, SP,
Resistivity, Density, Porosity,
Sonic
Checkshot
• Well data will give us information
about geological condition, interest
zone, tested zone, top formation, etc.
CS KORINCI-1A
y = 0.0003x2 + 0.6078x + 9.5
R2 = 0.9992
0
200
400
600
800
1000
1200
0 200 400 600 800 1000 1200
TIME (ms)
DE
PT
H (
m)
General Steps in Seismic Interpretation
WELL-SEISMIC-TIE
FRAMEWORK MAPPING
- HORIZON PICKING
- FAULT MAPPING
TIME-STRUCTURE
MAP
DEPTH-STRUCTURE
MAP
TIME-DEPTH
CONVERSION
Well-to-Seismic Tie
• A process of tying well data
with seismic data by
correlating synthetic
seismogram with seismic
data
• Matching between well
marker (formation top,
top/bottom reservoir, etc.)
with certain reflector event in
seismic data
• Decide which reflector event
will be picked as horizon
Top B2a
Top B2b
Top B3a
Top B4a
Horizon Picking • This step is done after defining
which recletor event will be
picked as horizon
• Most of seismic interpretation
work is horizon picking
• Purpose : framework mapping,
amplitude mapping
What event to be picked? Well-to-seismic
tie will give you the answer
Horizon Picking
Amplitude Extraction
Structure Mapping
Geranicky Delisatra, Geophysicist – PHE ONWJ
Fault Interpretation
• Fault interpretation must be
confirmed with regional geology
(strike/dip), tectonic regime
(extensional/compressional), etc.
• Know your fault better; is it normal
fault? Thrust fault? Wrong fault
interpretation will lead into wrong
framework
Geranicky Delisatra, Geophysicist – PHE ONWJ
Time-Structure Map
• Picked horizon and fault will be grid to
generate structure map. Since horizon
value is in time domain, the structure map
is called time-structure map
• To have a real subsurface information,
time-structure map should be converted
into depth-structure map
Time-Depth Conversion
• Required data to convert time-structure map to depth-structure map is velocity
• Remember; D = V x t
• Velocity data can be obtained from:
– Checkshot
– Stacking data
– VSP
• Depth-structure map is a product of multiplying time-structure map with velocity function. Velocity is varied with depth and geological condition
CS KORINCI-1A
y = 0.0003x2 + 0.6078x + 9.5
R2 = 0.9992
0
200
400
600
800
1000
1200
0 200 400 600 800 1000 1200
TIME (ms)
DE
PT
H (
m)
Geranicky Delisatra, Geophysicist – PHE ONWJ
Depth-Structure Map Time-structure Map Depth-structure Map
• Depth-structure map represent subsurface structural condition
• Due to velocity variation, depth-structure map can be different with time-
structure map
• Depth-structure map should be confirmed with depth at well location
Geranicky Delisatra, Geophysicist – PHE ONWJ
Direct Hydrocarbon Indicator (DHI)
• A quick look for hydrocarbon indicator
• Common DHI:
– Bright spot
– Dim spot
– Polarity reversal
– Flat spot
• Can be a pitfall too!
Geranicky Delisatra, Geophysicist – PHE ONWJ
Bright Spot
Geranicky Delisatra, Geophysicist – PHE ONWJ
Dim Spot
Geranicky Delisatra, Geophysicist – PHE ONWJ
Polarity Reversal
Geranicky Delisatra, Geophysicist – PHE ONWJ
Flat Spot
Geranicky Delisatra, Geophysicist – PHE ONWJ
Some Technique to Guide Seismic Interpretation
• There are some technique to guide seismic interpretation
• Using seismic attributes (phase, frequency, amplitude)
• Good for quick interpretation
Geranicky Delisatra, Geophysicist – PHE ONWJ
Coherency
Coherence Reflectivity (amplitude)
• Coherency attribute
detects discontinuity
in seismic reflector
• Good in detecting
fault or stratigraphic
features
Geranicky Delisatra, Geophysicist – PHE ONWJ
Instantaneous Phase Reflectivity (Amplitude)
Instantaneous Phase
• Instantaneous Phase
attribute balance the
weak and strong
reflector
• Good in tracing
reflector continuity
Geranicky Delisatra, Geophysicist – PHE ONWJ
Instantaneous Frequency Reflectivity (Amplitude)
Instantaneous Frequency
• Instantaneous Frequency gives an information
regarding frequency at certain time
• Gas column will absorp frequency content,
therefore, frequency below gas column will be
decreased
• Good in analyzing bright spots
Geranicky Delisatra, Geophysicist – PHE ONWJ
Some Problems & Pitfall
• False Bright Spot
• Pull-up effect
• Mis-tie
Geranicky Delisatra, Geophysicist – PHE ONWJ
False Bright Spot
• Gas sand and coal have a low impedance contrast with overlying shale
• Both gas sand and coal will give strong negative amplitude
• Lesson learned: bright spot is not always a good news!
Geranicky Delisatra, Geophysicist – PHE ONWJ
Pull-up Effect
Mis-tie
• Mis-tie is a time gap between
intersecting seismic lines due
to different vintage or different
processing parameter ataupun
parameter processing yang
berbeda
• Mis-tie only occur in 2D
seismic data
Geranicky Delisatra, Geophysicist – PHE ONWJ
Presentation Outline
• Introduction
• Fundamental of Seismic
• Seismic Data Acquisition & Processing
• Seismic Interpretation
• Reservoir Characterization Method
Geranicky Delisatra, Geophysicist – PHE ONWJ
Reservoir Characterization Method
• Seismic reservoir characterization is necessary
to predict reservoir property (porosity, Sw, etc.)
and its fluid contents (oil, gas, water)
• More quantitative analysis
• Require Rock Physics
• Basically, there are 2 main methods:
– Seismic AI Inversion
– Amplitude Variation with Offset (AVO)
– Multi-attribute
Geranicky Delisatra, Geophysicist – PHE ONWJ
Seismic AI Inversion
Geranicky Delisatra, Geophysicist – PHE ONWJ
Basic Theory
Seismic Acquisition
Earth * Wavelet = Seismic
Seismic / Wavelet = AI
Seismic Inversion
AI Earth
Reservoir Characterization
Geranicky Delisatra, Geophysicist – PHE ONWJ
Workflow
Wavelet
Estimation
Feasibilty
Study
Buidling
Initial Model
Invert
Seismic
Geranicky Delisatra, Geophysicist – PHE ONWJ
Workflow
Wavelet
Estimation
Feasibilty
Study
Buidling
Initial Model
Invert
Seismic
Geranicky Delisatra, Geophysicist – PHE ONWJ
Workflow
Wavelet
Estimation
Feasibilty
Study
Buidling
Initial Model
Invert
Seismic
Geranicky Delisatra, Geophysicist – PHE ONWJ
Workflow
Wavelet
Estimation
Feasibilty
Study
Buidling
Initial Model
Invert
Seismic
Geranicky Delisatra, Geophysicist – PHE ONWJ
AVO
AVO stands for Amplitude Variations with Offset, or
Amplitude Versus Offset
The AVO technique uses the amplitude variations of pre-
stack seismic reflections to predict reservoir fluid effects
Geranicky Delisatra, Geophysicist – PHE ONWJ
Basic Concept
Velocity
NMO
+ + + =
Geranicky Delisatra, Geophysicist – PHE ONWJ
Basic Theory
56
Offset
Time
Geranicky Delisatra, Geophysicist – PHE ONWJ
AVO Classification
57
The Rutherford and Williams classification scheme as
modified by Ross and Kinman (1995).
Class 1
AI Sand >
AI Shale
Class 2
AI Sand ≈
AI Shale
Class 3
AI Sand <
AI Shale
Geranicky Delisatra, Geophysicist – PHE ONWJ
Straight to…Case Study!!!
Geranicky Delisatra, Geophysicist – PHE ONWJ
Background • Shallow biogenic gas in Lower Petani
Fm. → main exploration target
• Appear as ‘bright spot’ on Post-stack seismic section
• Coal in Upper Petani Fm. also appear as ‘bright spot’
• Bright spot can be a DHI, but also a pitfall as well
• Several dry-holes by the same pitfall
Coal
Gas Sand
UGM-1 UGM-2
Geranicky Delisatra, Geophysicist – PHE ONWJ
Decrease Impedance
Decrease Impedance
Top
Gas
Sand
Top
Coal
What Makes it Happen?
Decrease in Impedance cause a negative Reflective
Coefficient, and therefore appear as strong negative
amplitude in seismic section
UGM-1 UGM-2
Geranicky Delisatra, Geophysicist – PHE ONWJ
Relationship Between AI & AVO Class
• Shallow biogenic gas are above 1200 m
• AI value of gas sands < shale Low impedance sand
• The crossplot between AI and depth suggest that those shallow gas is classified into class 3 gas sand
Geranicky Delisatra, Geophysicist – PHE ONWJ
AVO Modeling of Gas Sand and Coal
Property Synthetic Modeling AVO Curve
Geranicky Delisatra, Geophysicist – PHE ONWJ
AVO Classification
Gas Sand
Coal
Intercept (-)
Gradient (-)
AVO Class 3
Intercept (-)
Gradient (+/-)
AVO Class ???
Geranicky Delisatra, Geophysicist – PHE ONWJ
AVO cross-plotting involves plotting the intercept against the gradient and
identifying anomalies. The theory of cross-plotting was developed by
Castagna et al (TLE, 1997, Geophysics, 1998) and Verm and Hilterman
(TLE, 1995)
AVO Cross-plot Theory
Geranicky Delisatra, Geophysicist – PHE ONWJ
AVO Crossplot Analysis
• Cross-plot between intercept and gradient of pre-stack data confirms the model
• Gas sand anomaly is fall into class 3 gas sand region, while coal is tend to fall between mud-rock line and class 4 region
Geranicky Delisatra, Geophysicist – PHE ONWJ
Multi-attribute
Multi-attribute analysis is a method
which uses more than one seismic
attribute to predict reservoir
physical properties based on well
logs data (Russell et. al, 1997)
You don’t have to
remember this!
Geranicky Delisatra, Geophysicist – PHE ONWJ
Comparison between Inversion and
Multi-atttribute
Multi-attribute
Geranicky Delisatra, Geophysicist – PHE ONWJ
Workflow
Log
Prediction
Feasibilty
Study
Generate
Pseudo-log
Volume
Geranicky Delisatra, Geophysicist – PHE ONWJ
Workflow
Log
Prediction
Feasibilty
Study
Generate
Pseudo-log
Volume
Geranicky Delisatra, Geophysicist – PHE ONWJ
Workflow
Log
Prediction
Feasibilty
Study
Generate
Pseudo-log
Volume
Geranicky Delisatra, Geophysicist – PHE ONWJ
Other Methods
• Other methods in seismic reservoir
characterization is a combination of
Inversion and AVO
• For example:
– Lamda Mu Rho (AVO inversion)
– Simultaneous inversion (AVO inversion)
– Elastic Impedance/Extended Elastic
Impedance (AVO inversion)
Geranicky Delisatra, Geophysicist – PHE ONWJ
Image Rights
Images are courtesy of:
• BP
• PHE ONWJ
• Chevron
• Fugro-Jason
• PGS
• Elnusa
• EMP
Geranicky Delisatra, Geophysicist – PHE ONWJ
Thank You