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Preparation of a Geo-body

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Transcript of Preparation of a Geo-body

Stratigraphic Visualization
Critical to understand what kind of features we want to highlight.

Is it an igneous intrusion?
Is it a clastic depositional?
Is it a metamorphic rock dyke?
Is this our potential reservoir?
What is our aim of interpreting this data?
What should we use in the software?

Many tools that lets us to better visualize our target.
a) First-pass opacity curve to sort the features into 3 +ve zones

b) the geo-features we get from sorting in (a)

c & d) Visual @ amplitude inventory of each zone is made according to color & identified geo-features are chosen for enhancement.

Z1 & Z2 amplitudes are increased and opacity in Z3 is decreased to optimized our target
Monday, 01/06/2015
SN Fathiyah Jamaludin Covers: CLO2 and CLO3

An interpreted 3D object that contains cells or voxels that have similiar seismic amplitudes/attributes to the original seismic

Always representing the interpreter's target of interpretation.

Can be a any geological features (sand bar, carbonate platform, delta, channel/river, slopes, salt body, gas cloud etc)

In connected or disconnected groups of targets

Combined with other seismic from your 3D Data

Extraction of the targetted geo-body for property modelling/ volumetric calculation/ reservoir prediction etc

Usually it is based on opacity threshold.

Eg: We set the threshold value to 20%, so if a cell in a 3D volume is having an opacity threshold < 20%, it will not be included in the extraction process.
2. Isolation
Objective: To define the depositional environment & delineate prospective stratigraphic facies in the upper portion of a ~400ms channelized section with variable amplitudes (continuous, non-parallel)
1. Identification
Volume Rendering
Seismic Attributes
Isolting the target based on characteristics of the amplitudes.

1. Either to make it partially opaque (high amplitudes only) or partially transparent (cross-over amplitudes ranges)

2. Using RGB (Red-Green-Blue) Blending technique
*always preferred because allows blending of different attributes to be viewed on the same display)

A display of all data within a seismic volume at the same time

A display of all data within a seismic volume at the same time

3. Extraction
Stratigraphic Visualization
Stratigraphic Visualization
Lowstand channel-fan system with sand bypassing the incised valley and wide channelized zone.
deposited by basinward.

the southern most channel shows a south-trending crevasse splay with two delta-like progradational lobes.

Correlation between volume visualization and 2D cross-lines.
a) Proximal contourite (A)
crevesse splay (B)

b) Distal contourite (C)

c) Braided Fan (D)
The need of volume visualization to avoid
mis-interpretation in line 210 (c).
Can be interpreted as massive contorted
slump deposites.
To make things more obvious
"Things here means structural feature"

So, we can quickly show subtle and complex fault patterns.

How does this technique different from the conventional way?

* Interpreter's bias as interpreter is responsible to choose what to mark as a fault and what not a fault.

*Variable from one interpreter to the other
Structural Visualization
Structural Visualization
But, for volume visualization, the goal is
to reveal all the faults in the seismic record.

At prospect level, subtle faults definition
is very critical.

Since each faults are having different properties (different dips, strike etc), the fault data must be viewed from different points.

Use Zone System together with seismic

Remember what is Zone System?
How to Prepare a Geo-Body?
Fault Picking
Observation in lateral amplitude changes is usually represented by decrease in amplitude (usually in Z3 amplitude)
Fault Picking
By lowering the opacity of Z3 amplitudes to transparent or semi-transparent levels, the gaps within the horizon, the fault will appear as physical gaps
Fault Picking
Use of black backgrounds color over bright colored surface. Also suitable for carbonate reef visualization or fractures.

Fault picking
Faults are picked at abrupt amplitude terminations with associated offsets displacement within the wavelet
Criteria of Fault Picking
in Volume
a) Volume rendering; b) Revealed of Z1 amplitudes and select particular amplitude; c) Sub-volume detection to isolate the amplitude to extent structural relief, possible stratigraphic info; d-f) Application of ZS on detecting the isolated body
Advantages & Disadvantages
Establish significant conclusion in few hours of viewing the volume.
Leads can be identified and prioritized.
Key horizon can be selected at the beginning of the project.
May resolve interpretation problems.
Recommended to document all steps before proceeds to the next step.
Need to have experienced in volume interpretation and has seen many prospects.
Required thorough understanding of the whole volume.
Can mislead to wrong interpretation cause sometime we interpret false/unrelated events due to physical limit of 3D volume
Always need to quality check with 2-D lines
Objectives: Understanding the
geo-body and how to create &
interpret it
2. Isolation
Kidd. Gerald D., Fundamentals of 3D Seismic Volume Visualization, The Leading Edge, June 1999 pp702-709

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