Seismic data is acquired in time - the time taken for the sound to travel
from the source to reflectors and to return to receivers. However, wells are
drilled in depth, not time. Variations in velocity can distort the depth, size,
and shape of possible reservoirs. Therefore, conversion from time to depth is
needed for a clear picture of the prospect and the risks involved.
This course
will teach you how to use velocity information and structural inputs to build a
consistent velocity models & how to make Depth conversion using different
methodologies and to choose the best fit depth conversion model by adjusting
Sensitivity Analysis.
How will this
Training Course be Presented?
The course will not only presented by showing and interpreting the
material in detail, but also the participants will work together using a real
Seismic data to apply all the workflow and to project their previous knowledge
and experience onto the course, they also encouraged to bring their own data so
that real working examples can be reviewed and interpreted.
Target Audience
This course is designed for all Oil industry Technical Professionals,
which will cover from fundamental theoretical background to high-level real
work information/techniques/workshop.
This training course is suitable to a wide range of professionals but will
greatly benefit:
- Seismic Interpreters.
- Geophysicists
- Geologists
- Geo-Modelers
- Petrophysicists
- Drilling Engineers
- Reservoir Engineers
- Technical Support Personnel
- Team Leaders
- Managers
Agenda
Module One: Seismic Wavelet
·
Wavelet Determination.
o Wavelet Parameters.
o Amplitude Spectrum.
o Phase Spectrum.
o Time Spectrum.
o Bandwidth.
o Wavelet Extraction Parameters.
o Wavelet Phase.
o Wavelet Length (L).
o Taper Length.
o Wavelet extraction Time Window
(T).
o Reservoir Zone.
o Statistical Wavelet Extraction.
o Deterministic Wavelet
Extraction.
o Idealised Wavelets.
Ø Butterworth Wavelet.
Ø Ricker Wavelet.
Ø Mexican hat Wavelet.
Ø Ormsby Wavelet.
o Usage of Wavelets.
o Wavelet Extraction Sensitivity
Analysis.
Ø Spectral Smoothing Factor
(bT).
Ø Proportion of Energy Predicted
(PEP).
Ø Cross Correlation (R).
Ø Normalized Mean Square Error.
Ø Determining the best Wavelet.
Module Two: VSP &
Checkshot data Analysis
·
Vertical Seismic Profiling (VSP).
·
Checkshot (CS) data QC & Velocity Analysis.
o Checkshot Data QC.
o Velocity Analysis QC.
Ø Instantaneous Average Velocity
Analysis.
Ø Instantaneous Interval
Velocity Analysis.
o Drift Analysis & Checkshot
Correction.
Ø Linear trends/ fits.
Ø Polynomial trends/ fits.
Ø Spline trends/ fits.
Ø What if we don’t have a Sonic
log?
Module Three: Well to Seismic
Tie (Synthetics).
·
Tie of Well & Seismic data by using Synthetics and VSP.
o Theory of well correlation and
synthetics.
o Objectives of Synthetics.
o Log Calibration - depth to
time.
o Well tie approaches.
o Well to Seismic Tie
(Synthetics) Sensitivity Analysis.
Ø Proportion of Energy Predicted
(PEP).
Ø Normalized Mean Square Error
(NMSE).
o Calibrated CS QC.
o Tie of Well markers with
Seismic Markers to define the Geological markers and its corresponding Seismic
Reflectors to be interpreted.
Module Four: Depth Conversion Basics.
·
Depth
Conversion Concepts.
o What is Depth Conversion?
o Why do we need Depth Conversion?
o When is Depth Conversion important?
o Objectives of Depth Conversion.
o Geological factors influencing Velocity.
o Seismic reflection mode conversion.
o Sources of Velocity data and their limitations.
Ø Well data-sonic log, check shots, and VSPs.
Ø Pseudo velocities.
Ø Seismic velocities.
Ø Seismic velocity analysis.
Ø Review definitions and characteristics of
velocities.
Ø Conversion of velocity types.
o Seismic velocity issues.
Ø Gas seepages and chimneys.
Ø Fault shadows.
Ø Salt structures.
Ø Gas reservoir masking.
o Time Interpretation Pitfalls.
Module Five: Depth Conversion using Different
Methodologies.
·
Depth
Conversion Methods.
o The Basic Methodology.
o Seismic Velocity Model.
o Single-Layer Models.
Ø Single (Constant) Function.
§ Linear 1st Order.
§ Polynomial 2nd Order.
Ø Average Velocity (Vavg) Map (Pseudo Velocity).
o Multi-Layer Models.
Ø Layer Cake Model (Well data).
§ Downward Layer Building using (Excel V0/K –
Vavg Map).
§ Time Slices Vel. Model using (Excel V0/K –
Constant TDR V0/K – Surface TDR V0/K).
§ Horizon/Sequence Boundary Vel. Model using
(Excel V0/K – Constant TDR V0/K – Surface TDR V0/K).
Ø Layer Cake Model (Well data + Seismic data).
o Parameter Optimization.
o Choosing Your Method.
·
Velocity
modeling uncertainty assessment and QC.
o Uncertainty, non-uniqueness, and ambiguity.
o Limits on resolution.
o Quantifying error.
o Velocity model QC.
·
Depth
Conversion Sensitivity Analysis.
o Calculating Error Maps.
o Choose the best method for depth conversion.