DepthTeam Express
Fast and easy depth conversion for interpreters
R. Sigit
DepthTeam Solutions
Outline
Overview of DepthTeam Express
What’s New in the Latest Version?
How does Calibration work?
Using DepthTeam Express with Complex Velocities
Using DepthTeam Express with Complex Structures
Beyond DepthTeam Express
DepthTeam Solutions
Outline
Overview of DepthTeam Express
What’s New in the Latest Version?
How does Calibration work?
Using DepthTeam Express with Complex Velocities
Using DepthTeam Express with Complex Structures
Beyond DepthTeam Express
DepthTeam Solutions
Workflow Continuum
Cost
Accuracy
Time
Requirements
Geologic
Complexity
DepthTeam Solutions
Workflow Continuum
Cost
Accuracy
Time
Requirements
DepthTeam
Extreme
Geologic
DepthTeam
Complexity
Explorer
DepthTeam
DepthTeam Interpreter
Express
DepthTeam Express
Objective
Construct a velocity model as quickly as possible,
using as much data as possible.
Detail
DepthTeam Express
General Information
Incorporates major sources of velocity information
Seismic Velocities
T/D Curves (Checkshot corrected sonic logs)
Well Tops
Enhanced Integration
One data loader for all data types
3D Voxcet Velocity Representation
Arbitrary X,Y,Z,V velocity cube
Model Calibration
Vertical depth conversion will tie well control.
DepthTeam Express
Enhanced Integration
Makes data loading simple!
• OpenWorks
• SeisWorks
• EarthCube
• ProMAX
• Sierra
Workflow Managers
• Model Manager
Workflow Managers
• Model Manager
• Pick Manager
Workflow Managers
• Model Manager
• Pick Manager
• Time/Depth Function Manager
Workflow Managers
• Model Manager
• Pick Manager
• Time/Depth Function Manager
• Surface Manager
Workflow Managers
• Model Manager
• Pick Manager
• Time/Depth Function Manager
• Surface Manager
• Velocity Cube Manager
DepthTeam Express
Data Used to Build Your Model
Incorporates three major sources of velocity information
Data Type
Contribution
Seismic Velocities
Lateral Variations
T/D Curves
Vertical Variations
Well Tops
Accuracy
Each data type makes an important
contribution to the final velocity model!
DepthTeam Express
Model Building Workflow
Depth Conversion
(TDQ, SeisWorks, EarthCube)
Well Picks
Pseudo-velocity Model
Calibration
Calibrated Velocity Model
(Seismic Velocities
and T/D Curves)
T/D Curve
Velocity Model
Seismic Velocities
or
Analytic Velocity Model
Calibration
Final Calibrated Velocity Model
(Seismic Velocities,
T/D Curves, and
Well Picks)
DepthTeam Express
Model Building Workflow
Depth Conversion
(TDQ, SeisWorks, EarthCube)
Well Picks
Pseudo-velocity Model
Calibration
Calibrated Velocity Model
(Seismic Velocities
and T/D Curves)
T/D Curve
Velocity Model
Seismic Velocities
or
Analytic Velocity Model
Calibration
Final Calibrated Velocity Model
(Seismic Velocities,
T/D Curves, and
Well Picks)
DepthTeam Express
Model Building Workflow
Depth Conversion
(TDQ, SeisWorks, EarthCube)
Well Picks
Pseudo-velocity Model
Calibration
Calibrated Velocity Model
(Seismic Velocities
and T/D Curves)
T/D Curve
Velocity Model
Seismic Velocities
or
Analytic Velocity Model
Calibration
Final Calibrated Velocity Model
(Seismic Velocities,
T/D Curves, and
Well Picks)
DepthTeam Express
Seismic Velocity Model
Load Stacking Velocities
DepthTeam Express
Seismic Velocity Model
Constrained Dix Inversion
Contributes Lateral Velocity Trends
DepthTeam Express
Model Building Workflow
Depth Conversion
(TDQ, SeisWorks, EarthCube)
Well Picks
Pseudo-velocity Model
Calibration
Calibrated Velocity Model
(Seismic Velocities
and T/D Curves)
T/D Curve
Velocity Model
Seismic Velocities
or
Analytic Velocity Model
Calibration
Final Calibrated Velocity Model
(Seismic Velocities,
T/D Curves, and
Well Picks)
DepthTeam Express
T/D Curve Velocity Model
Automatically convert T/D curves to interval velocity
DepthTeam Express
T/D Curve Velocity Model
Use surfaces to structurally interpolate velocities
Contributes Vertical Velocity Variations
DepthTeam Express
Model Building Workflow
Depth Conversion
(TDQ, SeisWorks, EarthCube)
Well Picks
Pseudo-velocity Model
Calibration
Calibrated Velocity Model
(Seismic Velocities
and T/D Curves)
T/D Curve
Velocity Model
Seismic Velocities
or
Analytic Velocity Model
Calibration
Final Calibrated Velocity Model
(Seismic Velocities,
T/D Curves, and
Well Picks)
DepthTeam Express
Well Picks Velocity Model
Time Horizons Required!
Vpseudo
= Depth Thickness/ Time Thickness
= Isopach / Isochron
Associate a time horizon with a depth pick.
Isopachs and isochrons are automatically calculated at each
well location.
May need to use SynTool to determine time/depth
associations.
DepthTeam Express
Well Picks Velocity Model
DepthTeam Express
Well Picks Velocity Model
Pseudo-velocity Model
Contributes Accuracy – Model Ties Well Control
DepthTeam Express
Model Building Workflow
Depth Conversion
(TDQ, SeisWorks, EarthCube)
Well Picks
Pseudo-velocity Model
Calibration
Calibrated Velocity Model
(Seismic Velocities
and T/D Curves)
T/D Curve
Velocity Model
Seismic Velocities
or
Analytic Velocity Model
Calibration
Final Calibrated Velocity Model
(Seismic Velocities,
T/D Curves, and
Well Picks)
DepthTeam Express
Seismic Velocity Cube
DepthTeam Express
T/D Velocity Cube
DepthTeam Express
Calibration: Seismic and T/D Velocities
DepthTeam Express
Calibration: Seismic, T/D, Well Picks
DepthTeam Express
Model Building Workflow
Depth Conversion
(TDQ, SeisWorks, EarthCube)
Well Picks
Pseudo-velocity Model
Calibration
Calibrated Velocity Model
(Seismic Velocities
and T/D Curves)
T/D Curve
Velocity Model
Seismic Velocities
or
Analytic Velocity Model
Calibration
Final Calibrated Velocity Model
(Seismic Velocities,
T/D Curves, and
Well Picks)
DepthTeam Express
Vertical Depth Conversion
DepthTeam Express
Conclusions
Easy to learn
Easy to use
May not be appropriate for every situation
• High Resolution
• Big Data Volumes
• Complex Structures
Very useful tool for most situations
Give it a try!
DepthTeam Solutions
Outline
Overview of DepthTeam Express
What’s New in the Latest Version?
How does Calibration work?
Using DepthTeam Express with Complex Velocities
Using DepthTeam Express with Complex Structures
Beyond DepthTeam Express
DepthTeam Express
1998.6 - What’s New?
Highlights:
Significant improvements in performance (5x)
- you can now make bigger, more detailed models
Stacking Velocity Function Manager
– you can now see and edit your stacking velocities
Consistent use of Tables
- data managers, reports, data loading
- sorting data, selected items to top
- search, filter
Well Pick Interpolators
- Linear, First-order, Sierra gridder
Data Storage
- Everything loaded gets saved – whether it’s used or not
DepthTeam Solutions
Outline
Overview of DepthTeam Express
What’s New in the Latest Version?
How does Calibration work?
Using DepthTeam Express with Complex Velocities
Using DepthTeam Express with Complex Structures
Beyond DepthTeam Express
DepthTeam Express
How does Calibration Work?
Click me.
DepthTeam Solutions
Outline
Overview of DepthTeam Express
What’s New in the Latest Version?
How does Calibration work?
Using DepthTeam Express with Complex Velocities
Using DepthTeam Express with Complex Structures
Beyond DepthTeam Express
DepthTeam Express
Working with Complex Velocities
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3000 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3000 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3000 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3000 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3000 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3500 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3500 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3500 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3500 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Hard-Rock:
The velocity remains the same, regardless of where the rock is.
3500 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
1580 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
3800 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
2760 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
1600 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
5000 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
1700 - 1800 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
3500 - 4200 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
2250 - 3700 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
1800 - 3900 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
1650 - 4000 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
1650 m/sec
1800 m/sec
3500 m/sec
4000 m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
Soft-Rock:
The velocity changes, depending on the depth of burial.
1650 m/sec
Water Bottom
1800 m/sec
3500 m/sec
4000 m/sec
Soft-Rock Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
In most areas, the velocity is a combination of hard-rock and soft-rock
Soft-rock near the surface, hard-rock in deeper areas.
1650 m/sec
1800 m/sec
2500 m/sec
3200 m/sec
3600 m/sec
3500
4200m/sec
m/sec
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
In most areas, the velocity is a combination of hard-rock and soft-rock
Soft-rock near the surface, hard-rock in deeper areas.
Water Bottom
1650 m/sec
1800 m/sec
Soft-Rock
2500 m/sec
3200 m/sec
3600 m/sec
4200 m/sec
Hard-Rock
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
In most areas, the velocity is a combination of hard-rock and soft-rock
Soft-rock near the surface, hard-rock in deeper areas.
There may also be small stringers of hard-rock within soft-rock.
Water Bottom
Sand Channel
Salt
Reef
Shale / Coals
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
In most areas, the velocity is a combination of hard-rock and soft-rock
Soft-rock near the surface, hard-rock in deeper areas.
There may also be small stringers of hard-rock within soft-rock.
Gas can cause strange soft-rock effects!
Water Bottom
Gas
Gas
Cross Section
Complex Velocities
Hard-Rock vs. Soft-Rock
How do you tell hard-rock from soft-rock?
Velocity (m/sec)
Look at the Well Logs
OpenWorks Curve Viewer
Soft Rock
If you see a trend like this on your
log curves, be sure to interpret a
seismic horizon associated with
this depth!
Depth (m)
Look at the T/D Tables
DepthTeam Express Function Viewer
Hard Rock
Complex Velocities
Hard-Rock vs. Soft-Rock
How do you tell hard-rock from soft-rock?
Velocity (m/sec)
DepthTeam Express Function Viewer
Why not?
Time (ms)
Straight-line will not fit data.
Complex Velocities
Analytic Velocity Equations
Linear compaction gradient in depth
equals EXPONENTIAL compaction gradient in time.
Vint = Vo + KZ
Equation for gradient in depth
Vint = Vo Exp(KT)
Equation for gradient in time
These two equations give the same result!
One is in depth, one is in time
Complex Velocities
Analytic Velocity Equations
Linear compaction gradient in depth
Vint = Vo + KZ
Gradient (K):
Equation for gradient in depth
Complex Velocities
Analytic Velocity Equations
Exponential compaction gradient in time (linear in depth)
Vint = Vo Exp(KT)
Gradient (K):
Equation for gradient in time
Complex Velocities
Hard-Rock vs. Soft-Rock
How do you tell hard-rock from soft-rock?
Velocity (m/sec)
DepthTeam Express Function Viewer
Why not?
The vertical axis is in TIME, not DEPTH
An exponential curve will fit the data
properly.
Time (ms)
Straight-line will not fit data.
Complex Velocities
Hard-Rock vs. Soft-Rock
How do you tell hard-rock from soft-rock?
Velocity (m/sec)
DepthTeam Express Function Viewer
Why not?
The vertical axis is in TIME, not DEPTH
An exponential curve will fit the data
properly.
Sometimes these gradients are
misinterpreted!
Time (ms)
Straight-line will not fit data.
Complex Velocities
Hard-Rock vs. Soft-Rock
How do you tell hard-rock from soft-rock?
Velocity (m/sec)
DepthTeam Express Function Viewer
Soft Rock
If you see a trend like this on your
T/D Curves, be sure to interpret
this horizon on your seismic data!
Time (ms)
Exponential curves in Time are vertical
compaction gradients in Depth.
Hard Rock
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
Water Bottom
Gas
Gas
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
Water Bottom
Gas
Gas
Correctly Sampled
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
Water Bottom
Gas
Gas
Poorly Sampled
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
Water Bottom
Gas
Gas
Poorly Sampled
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
Water Bottom
Gas
Gas
Poorly Sampled
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
Water Bottom
Gas
Poorly Sampled
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
Water Bottom
Gas
Poorly Sampled
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
Water Bottom
Poorly Sampled
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Bad sampling may cause you to miss important features!
The objects that are left may be distorted due to under sampling!
Water Bottom
This model still
ties the wells
pretty good,
but volumetric
estimates will
be inaccurate
away from well
control!
Poorly Sampled
Cross Section
Complex Velocities
Model Resolution
Correct Sampling is Important!
Water Bottom
Gas
Gas
Correctly Sampled
Cross Section
This model ties
the wells
better, and is
more accurate
away from the
wells.
Complex Velocities
Model Resolution
Lateral Sampling
At least two grid nodes covering the smallest velocity feature you want to
include in the model.
Water Bottom
Gas
Gas
Cross Section
Complex Velocities
Model Resolution
Lateral Sampling
At least two grid nodes covering the smallest velocity feature you want to
include in the model.
Gas Sag
Time Horizon - Contour Map
Complex Velocities
Model Resolution
Lateral Sampling
At least two grid nodes covering the smallest velocity feature you want to
include in the model.
2000 meters
Gas Sag
1000 meters
Time Horizon - Contour Map
Complex Velocities
Model Resolution
Lateral Sampling
At least two grid nodes covering the smallest velocity feature you want to
include in the model.
2000 meters
Easting: 1000m
Gas Sag
1000 meters
Northing: 500m
Time Horizon - Contour Map
Complex Velocities
Model Resolution
Lateral Sampling
At least two grid nodes covering the smallest velocity feature you want to
include in the model.
Easting: 1000m
Gas Sag
Time Horizon - Contour Map
Complex Velocities
Model Resolution
Lateral Sampling
At least two grid nodes covering the smallest velocity feature you want to
include in the model.
Gas Sag
Northing: 500m
Time Horizon - Contour Map
Complex Velocities
Model Resolution
Lateral Sampling
At least two grid nodes covering the smallest velocity feature you want to
include in the model.
Easting: 1000m
Northing: 500m
Gas Sag
Time Horizon - Contour Map
Complex Velocities
Model Resolution
Vertical Sampling
At least two grid nodes covering the smallest vertical feature you want to
include in the model.
Water Bottom
Gas
Gas
Cross Section
Complex Velocities
Model Resolution
Vertical Sampling
At least two grid nodes covering the smallest
Velocity (m/sec)
vertical feature you want to include in the
model.
Time (ms)
Vertical sampling = 50 msec
MODEL
T/D Curve
Complex Velocities
Model Resolution
Vertical Sampling
At least two grid nodes covering the smallest
Velocity (m/sec)
vertical feature you want to include in the
model.
Time (ms)
Vertical sampling = 25 msec
MODEL
T/D Curve
Complex Velocities
Model Resolution
Vertical Sampling
At least two grid nodes covering the smallest
Velocity (m/sec)
vertical feature you want to include in the
model.
As vertical sampling decreases, the
model comes closer to matching the
checkshot.
MODEL
T/D Curve
Time (ms)
Vertical sampling = 10 msec
Complex Velocities
Data Problems
Even with correct sampling, you may not observe velocity anomalies
if they are of limited extent.
Why?
If the velocity anomaly is not recorded somehow, it will be
impossible to model it!
• Wells not logged over entire model interval
• Checkshot surveys not recorded from top to bottom of the well
• Wells do not penetrate velocity anomaly (gas, sand channels, etc.)
• Seismic velocities create the best stack; not the most accurate
velocity model
Complex Velocities
Data Problems
If you didn’t record it, you can’t model it!
Gas Sag
lPetronas #1
lPetronas #2
lPetronas #3
Time Horizon - Contour Map
The gas velocity
anomaly was not
recorded by these
wells, so the velocity
model will not include
the gas sag.
Complex Velocities
Data Problems
If you didn’t record it, you can’t model it!
Gas Sag
lPetronas #1
lPetronas #2
lPetronas #4
lPetronas #3
Time Horizon - Contour Map
The gas anomaly can be
included in the model,
provided that the model
is properly sampled, and
the well data properly
recorded.
Complex Velocities
Data Problems
Petronas #4 Well - Two checkshots
Velocity (m/sec)
Time (ms)
Time (ms)
Velocity (m/sec)
Checkshot recorded
only within pay zone
Checkshot recorded
top to bottom
Complex Velocities
Data Problems
T/D tie to top pay is the same in both checkshots.
Velocity (m/sec)
Top Pay
Checkshot recorded
only within pay zone
Time (ms)
Time (ms)
Velocity (m/sec)
Checkshot recorded
top to bottom
Complex Velocities
Data Problems
Suite of checkshots that all have the same tie at Top Pay.
Velocity (m/sec)
Top Pay
Checkshot recorded
only within pay zone
Time (ms)
Time (ms)
Velocity (m/sec)
Checkshot recorded
top to bottom
Complex Velocities
Data Problems
Suite of checkshots that all have the same tie at Top Pay.
Velocity (m/sec)
Which one is right?
How do you know?
Time (ms)
If you don’t log the entire well,
you don’t know which is right!
Top Pay
Checkshot recorded
only within pay zone
Complex Velocities
Data Problems
If possible, log the entire borehole.
Typically this is not done, due to high costs.
Logging the entire well is less important for the well just drilled, but
very important to build an accurate velocity model for the next well.
Trends extrapolated from one well can affect the velocity model
away from that well. This can change estimated thickness,
volumetrics, etc.
Complex Velocities
Things to remember…
• Always try to determine if your geologic area is
dominated by hard-rocks or soft-rocks.
• Usually, geologic areas are a mixture of hard and soft
rock environments.
• Young sediments are often soft-rock, old sediments are
often hard rock. Carbonates are usually hard-rock.
Soft-Rock
Hard-Rock
Complex Velocities
Things to remember…
• If possible, log wells from top to bottom of
the well.
• Some velocity effects are difficult to
record, but still cause significant distortions
on the seismic data. Shallow gas is especially
problematic.
• If possible, try to include as many sources
of velocity as you can.
Time (ms)
• If possible, run checkshot surveys from
top to bottom of the well.
Velocity (m/sec)
Checkshot recorded
only within pay zone
DepthTeam Solutions
Outline
Overview of DepthTeam Express
What’s New in the Latest Version?
How does Calibration work?
Using DepthTeam Express with Complex Velocities
Using DepthTeam Express with Complex Structures
Beyond DepthTeam Express
DepthTeam Express
Working with Complex Structures
Click me.
Final Thoughts…
Calibration
Remember:
It’s easy to tie wells.
The hard part is what happens away from the wells!
All three maps tie the wells - Which one is right?
How do you know?
Final Thoughts…
Calibration
Important!
Don’t be tricked into thinking that your model is correct, just
because it ties well control!
All three maps tie the wells - Which one is right?
How do you know?
Final Thoughts...
Interpretation Uncertainty
Velocity Estimation
Depth Conversion Method
Amount of error
Anisotropy
Gridding Errors
Well Deviation Uncertainty
Wavelet Estimation
Well Log Interpretation...
Source of error
Work on the biggest source of error first. Move on to next
biggest source of error ONLY after the most significant
source of error has been addressed.
Amount of error
Final Thoughts...
Source of error
Don’t worry about this...
Amount of error
Final Thoughts...
Source of error
… if you haven’t corrected for this.
DepthTeam Solutions
Outline
Overview of DepthTeam Express
What’s New in the Latest Version?
How does Calibration work?
Using DepthTeam Express with Complex Velocities
Using DepthTeam Express with Complex Structures
Beyond DepthTeam Express
Zero-offset Ray Tracing with Salim
DepthTeam Solutions
Beyond DepthTeam Express
Salim’s Big Adventure into Ray Tracing!
DepthTeam Solutions
Validating 2D Data
Problem:
2D Seismic Data can be difficult to interpret.
Reflections often come from out of the plane (sideswipe)
DepthTeam Solutions
Validating 2D Data
Problem:
2D Seismic Data can be difficult to interpret.
Reflections often come from out of the plane (sideswipe)
Seismic data can have multiple reflections!
DepthTeam Solutions
Validating 2D Data
Solution:
Use DepthTeam Express to build a model
Ray-trace validate the model using QUIKRAY+
Ray Tracing in QUIK+
Forward Modeling
Ray Tracing in QUIK+
Forward vs. Inverse Modeling
Z
Earth Model
Forward Modeling
Simulates seismic response of the earth.
(Generates synthetic seismic data)
Inverse Modeling
Simulates the earth from a seismic response.
(Generates an earth model in depth)
T
Seismic Section
Ray Tracing in QUIK+
Zero offset ray tracing
Source and receivers are at the same surface location.
Downgoing and upgoing rays follow identical paths.
Ray Tracing in QUIK+
Offset ray tracing
Source and receivers are not at the same location.
Simulates pre-stack seismic data (shot gathers, CMP gathers,
receiver gathers, VSPs, etc.)
Ray Tracing in QUIK+
Image Rays
Rays shot from surface to reflector.
Rays begin perpendicular to surface.
Simulates time migrated data.
Ray Tracing in QUIK+
Normal Rays
Rays shot from reflector back to surface.
Rays begin perpendicular to reflector.
Simulates Stacked (unmigrated) data.
Ray Tracing in QUIK+
Modules
QUIKRAY+
Image Ray Tracing
simulates poststack time migrated data.
Useful for validating vertical depth conversion (TDQ)
Normal Incidence
simulates unmigrated (stacked) data.
Useful for validating quality of 2D seismic lines (sideswipe)
DepthTeam Solutions
Beyond DepthTeam Express
Salim’s Big Adventure into Ray Tracing!
Velocity Estimation Techniques
Dix Inversion
Description
Interval velocity estimation technique derived from RMS (stacking) velocities.
Vi2= (Vrms22*T2 - Vrms12*T1) / (T2 - T1)
Assumptions
•
•
•
•
•
CMP gathers follow hyperbolic move-out.
Seismic horizons are flat.
No CDP scatter on CMP gathers.
CMP and CDP are at the same (X,Y) location.
Time maps are zero-offset, UNMIGRATED times.
Velocity Estimation Techniques
Hyperbolic Moveout
t
2
t
2
0

x
2
2
Vrms
True Seismic Ray Path
=
Straight Path Assumed by NMO
Velocity Estimation Techniques
Non-Hyperbolic Moveout
t
2
t
2
0

x
2
2
Vrms
True Seismic Ray Path
=\
Straight Path Assumed by NMO
Wave Influenced Delta
Velocity Type
Velocity Estimation Techniques
CDP Scatter
Velocity Estimation Techniques
CDP Mispositioning
CMPs
CDPs
Velocity Estimation Techniques
Unmigrated Times vs Migrated Times
Tunmigrated
Vrms
Unmigrated Interval
Velocity Estimation Techniques
Unmigrated Times vs Migrated Times
Tunmigrated
Vrms
Migrated Interval
Using migrated time maps samples the Vrms
curve at the wrong location and the wrong
thickness.
Amount of incorrect sampling varies with
reflector dip.
Velocity Estimation Techniques
Unmigrated Times vs Migrated Times
Why is this important?
Time
1.8
2.0
TRUE
Vrms Vint
2000
3521
2200
1% Error - Vrms2
Vrms Vint
Verr
2000
3657 3.8%
2222
Depth Error
13.6 meters!
Velocity Estimation Techniques
Dix Inversion
Strengths
Fast and easy to calculate.
Weaknesses
• Rarely are the assumptions of Dix inversion honored by data.
• Very unstable. A 1% error in Vrms can lead to a 3-5% error in Vint.
• Using time migrated horizons can easily account for 1% Vrms error!
Time
1.8
2.0
TRUE
Vrms Vint
2000
3521
2200
1% Error - Vrms2
Vrms Vint
Verr
2000
3657 3.8%
2222
Depth Error
13.6 meters!
Velocity Estimation Techniques
Dix Inversion
Use
• Depth conversion (if properly reduced and calibrated to well velocities).
• Depth imaging (do not calibrate to well velocities).
Comments
• Vdix values are typically multiplied by scalar of .85 - 1.00 to better match
well velocities. Shallow intervals honor Dix assumptions better, and do not
require as much reduction as deeper intervals.
• Dix velocities can be useful to understand basic trends in interval velocity,
but are typically inaccurate for detailed work.