Attribute analysis & AVO
Attribute analysis software
Two halves of quantitative interpretation in one place. Attributes are calculated on the fly inside the view you are working in, so you can tell in seconds whether one is worth a full volume — and the AVO workspace turns migrated gathers into intercept, gradient and cross-plot evidence about lithology and fluid.
On-fly or full
Screen first, compute second
Intercept & gradient
Maps, volumes and their products
Six AVO views
Gathers, graphs and cross-plots
In view
AVO workspace
Most attributes are wrong for most datasets. The useful question is not which attribute is best but which one says anything on this survey — and that is a question you answer by trying, not by reading. g-Space calculates attributes two ways: on the fly, in seconds, straight into the section you are already looking at, and in full, over a horizon or a whole dataset, once the screening has earned it. AVO gets its own workspace on the same principle: enable it on a horizon, look at the gather, the graph and the cross-plot together, and pick the polygon that isolates the anomaly before you commit to calculating maps.
Seismic attributes
Try it in the view first, compute it after.
Attributes run on 2D and 3D data for volume analysis, horizon interpretation and fault detection, and every setting lives in one Attributes bar — on-fly calculation, common settings, spectral decomposition and execute.
On-fly, in seconds
Pick one attribute or several from the Attributes bar, set a time window where the attribute needs one, and the result is drawn on the seismic view you are already in — the progress reported in the Progress View while it runs.
Or the full volume
Choose horizon or seismic as the calculation type, open the wizard from Execute and pick the data and attributes. Run computes now; Save to workflow stores the same settings as a task to run later.
Exactly on a surface, or in a window
Extract exactly along a horizon, or over an interval: between two times, between two surfaces, or in a window above, below or centred on one horizon — summarised as interval average, RMS, maximum, minimum, average positive or negative, or most common value.
On the bin grid, not interpolated
With one 3D volume selected, the attribute map is written directly on the seismic bin grid instead of being interpolated onto a map grid; a project polygon can restrict the result to the area you care about.
Dynamic and structural families
Envelope, instantaneous phase and its unwrapped and cosine forms, instantaneous frequency and bandwidth, frequency and envelope derivatives, dominant frequency, thin bed indicator and instantaneous Q — alongside coherence, similarity, chaos and seismic relief for structure.
Spectral decomposition, three ways
Short-window DFT for stable, thick-bedded sequences; continuous wavelet transform where frequency content changes fast, as in thin beds and fault zones; the S-transform when both time and frequency localisation matter. Set the cycles, noise level, frequency range and step, and assign frequencies to red, green and blue for the blend.
The settings travel with the file
Each calculated attribute goes to its own SEG-Y, and the parameters that produced it are written into that file's text header — attribute name, time step, the date in UTC and the window, plus each attribute's own settings. A volume can still be traced back to how it was made after it is passed on.
Displayed like any other volume
Attribute maps land under Maps in the Data Manager and draw on the location map; attribute volumes are cached in RAM or to file and then displayed like 3D seismic, with a dedicated volume palette in the 3D view. Several attributes can be shown at once with their own palettes and transparency.
AVO
Amplitude against offset, read six ways at once.
AVO analysis measures rock properties from how reflection amplitude changes with source-receiver distance. Migrated gathers and interpreted horizons go in; intercept, gradient and their products come out. The dedicated AVO workspace gives each part of that argument its own window.
Gathers
Image gather
How amplitude varies with offset or angle across the traces of a gather — the raw material of AVO, examined before anything is cross-plotted. The current AVO horizon is drawn across it as you work.
Angles
AVA gather
The same data against angle of incidence rather than offset, for reading the angle-dependent behaviour that lithology and fluid changes actually produce.
3D
3D image gathers
AVO and AVA data in a 3D perspective, with colour scaling, amplitude thresholds, transparency and offset or angle filtering, so an amplitude anomaly can be isolated across the range it lives in.
Cross-plot
AVO cross-plot
Intercept on the horizontal axis, gradient on the vertical. Clusters point at a lithology or a fluid type — and a polygon picked around one puts its bins straight back onto the location map and the picked horizon, in a colour you choose.
Graph
AVO graph
Amplitude against offset for the selected points, with the two-term Aki-Richards approximation for a quick trend and the three-term version, which adds the curvature that matters at long offsets.
Reference
Stack gather
The stacked response over time inside the same workspace — the conventional image to check the anomaly against while the pre-stack windows are open.
Workflow
Six steps from raw gathers to a mapped anomaly.
1
Condition the gathers
Right-click the seismic in the Data Manager and choose Process Data. g-Space Navigator opens, you add the processing modules you need, and each one shows its input beside its output for the bin selected on the location map.
2
Screen attributes on the fly
On the section you are working on, try the attributes that might carry the story — envelope, frequency, coherence — and keep the ones that actually separate something.
3
Calculate what survived
Set the calculation type and the extraction — exactly along a horizon, or in a window with the statistic that suits it — and run it over the volume, or add it to a workflow to run in batch.
4
Open the AVO workspace
Add a location map, choose the image bin, then bring up the image gather, the AVO graph and the AVO cross-plot. Enable AVO and the current horizon appears on the gather with the Aki-Richards curves on the graph.
5
Pick the anomaly on the cross-plot
Run the cross-plot, draw a polygon around the cluster, colour it, and watch the corresponding bins light up on the location map and on the picked horizon.
6
Calculate the maps and volumes
Choose intercept, gradient or their products from Map parameters and calculate AVO maps, or run the wizard to produce AVO attribute volumes and 2D sections over the interval you set.
Run & settings
Every knob in two ribbon bars, and nothing hidden.
Attribute work is configured in the Attributes bar and AVO work in the AVO bar. Both end in an Execute group, and both can put their current settings into a project workflow instead of running immediately.
Attribute calculation
The Attributes bar, from screening to a written volume
Calculation type
Horizon or the whole seismic dataset, with the horizon and the time window set alongside it in Common settings.
Extraction
Exact along horizon, or a window: between times, between horizons, or above, below and centred on a single one — with the statistic applied inside it.
Seismic-mode limits
Start and end taken from the entire gather, a constant time or a horizon limit, with the time or depth step you set.
Output grid
Use seismic resolution writes the map on the bin grid of a single selected 3D volume; a polygon confines the result to one area.
Spectral decomposition
Method, number of cycles, noise level, minimum, maximum and step frequency, and the frequency assigned to each colour channel — then run from the Execute group, with a QC pass available for a picked horizon.
Run or schedule
Run calculates now and saves the result; Save to workflow stores the same input and settings as a task the workflow executes later.
AVO settings
The AVO bar, from enabling the analysis to the maps
Map parameters
Intercept, gradient, their product, and the two sign-combined forms — intercept times the sign of gradient, and gradient times the sign of intercept — selected together or one at a time.
Offsets or angles
The analysis runs on offsets or on incidence angles, and the choice changes how the attributes are derived. Start, stop and step angle set the range used for pre-stack display.
Velocity for the conversion
Offsets become angles using velocities from the same geometry, a velocity volume, a project velocity model, or a constant — the constant being the default until you point it at something better.
Scope
Along a selected horizon or across the whole dataset, with an optional bounding polygon and a 2D-line or inline/crossline visualisation.
Execute
Run the cross-plot, calculate the AVO attribute maps, or calculate AVO attributes as a 3D volume or as 2D sections over the time interval you specify.
Where results land
Maps appear under Horizon attributes in the location map's Visual Settings; calculated volumes go to the Seismic folder in the Data Manager and open in the AVO views.
Views and tools in this group
The parts of g-Space this topic is built from
Attributes bar
AVO bar
AVO views
Spectral decomposition
Image gather
AVA gather
3D image gathers
AVO cross-plot
AVO graph
Stack gather
Gather conditioning
g-Space Flow
Workflows
More g-Space capabilities
An anomaly is only worth as much as the interpretation around it.
Attributes are picked on horizons, calibrated against wells and carried into property models. These are the other topics in the g-Space workflow.
FAQ
Questions, answered.
What is the difference between on-the-fly and full-volume attributes?
On-fly calculation is the quick route: pick one or several attributes from the Attributes bar, set a time window where the attribute needs one, and the result appears in seconds on the seismic view you are already looking at, with its progress reported in the Progress View. It is meant for deciding whether an attribute is worth computing at all. Full calculation runs the Calculate attributes wizard over a horizon or a whole dataset and writes real volumes and maps into the project. The two share the same attribute set, so what you screen on the fly is what you later compute in full.
Which seismic attributes does g-Space calculate?
Amplitude and phase rotation; the complex-trace family of envelope, envelope derivative and its second derivative, instantaneous phase, unwrapped instantaneous phase, cosine of instantaneous phase, instantaneous frequency, frequency derivative, instantaneous bandwidth, dominant frequency, thin bed indicator and instantaneous Q; and the structural family of coherence, similarity, chaos and seismic relief. Spectral decomposition sits alongside them with its own settings. The manual gives each attribute a short theoretical note and what it is normally used for, so the list reads as a toolkit rather than a menu.
What does an AVO analysis in g-Space need, and what does it produce?
It needs migrated gathers and interpreted horizons. From the AVO bar you enable AVO, choose whether to work along a horizon or over the whole dataset, and choose whether the analysis runs on offsets or on incidence angles — with the velocity for the offset-to-angle conversion taken from the same geometry, a velocity volume, a project velocity model or a constant. It produces intercept and gradient maps and their products, an AVO cross-plot whose picked polygons highlight the corresponding bins back on the location map and the horizon, an AVO graph with the two- and three-term Aki-Richards approximations overlaid, and AVO attribute volumes or 2D sections.
How are pre-stack gathers conditioned before AVO?
Inside g-Space, by connecting the g-Navigator processing package through the g-Space Flow module. Right-click the seismic data in the Data Manager and choose Process Data; g-Space Navigator opens, you build a workspace and a view, add the processing modules you need from the Module Manager and add a location map, and each module shows its input and its output for the bin currently selected on that map, so parameters can be judged before the flow is executed. The g-Space Flow module itself controls how the result is written, and the processed files come back into the Seismic Data workspace.
Get started
Screen your own attributes before you compute them.
Load a volume, try three attributes on the section in front of you, then take the survivors into a full calculation and an AVO cross-plot — take g-Space for a trial run, or talk to Geomage about a demo on your data.