Thursday, 13 July 2017

GeoTeric 2017 Adaptive Horizons: Part 2 – Tracking and Fill Modes

GeoTeric’s Adaptive Horizons have a variety of tracking and fill modes to allow the interpreter to extract a horizons surface in a fast and accurate way, while being cognitively intuitive. GeoTeric’s tracking modes are interactive as all the possible routes through the data are determined using Graph Theory, and can be previewed in both the 3D viewer and in the 2D Interpretation window. The Fill modes can be easily chosen in the Base Map window or in the 3D window if tracking on a probe.


Tracking Modes:
Full Line Tracking: this will utilize Graph Theory to find the best possible interpretation across the entire line. This option is useful when interpreting regional events that are laterally continuous and not heavily faulted. If “Stop at Faults” is enabled, the line will stop at discontinuities and faults, allowing the interpreter to make the cross fault interpretation.

Piecewise Tracking: allows the user to pick points along a reflector, the tracker will find the best path between points along the horizon (also using Graph Theory). A preview of the line is available interactively as the mouse is moved to aide with the interpretation.  The preview line ensures that picks are only placed where they are needed thus reducing the amount of clicking required to complete your interpretation.

Manual Line Tracking: This is helpful when the data quality is very poor and the interpreter would like to force an interpretation through, for example through salt diapirs such as below:


Complete Line: this option will join up previously tracked points along a slice. This is useful to create a grid of the interpretation if the horizon has been interpreted in one direction. Enabling the horizon to be quickly QC’d and completed saving time and aiding efficiency whilst maintaining the accuracy of the interpretation.


Fill Modes:
The fill modes auto-track the data always honouring any interpreted lines and is constrained laterally either by the extent of the probe or the defined area on the base map.

Waveform: Correlates the waveform of each point along all interpreted/accepted lines to guide the tracking over the selected area on the base map or the probe. The acceptance level controls how close the tracked area needs to be to the seed points, the lower the acceptance level, the closer to the input, the higher the acceptance level, the more room for growth. This method, is the fastest and is best suited for regular seismic data. The waveform of each point is treated individually, so if the character of the horizon changes laterally the horizon adapts to this change.


Amplitude: Correlates the amplitude of each point along all interpreted/accepted lines to guide the tracking over the selected area on the base map or the probe. The acceptance level controls how close the tracked area needs to be to the seed points.

PDF: Calculates a Probability Density Function (PDF) of the interpreted/accepted seeds and uses this to guide the tracking. The acceptance level controls the PDF and how much of its data is used to track. When tracking on the HSV blend, all 3 volumes of the blend are used as inputs, so the PDF option is the only way to capture this information, and is therefore the only choice available when tracking on a blend.

Graph Theory: Calculates the optimum surface that intersects with the interpreted/accepted seed points using graph theory. This option fills the area selected completely, without leaving any holes, however it is also the most computationally intensive, so it is recommended to select smaller grid areas to fill.
In the example below, a potential base slump event was filled using the waveform option and has a Frequency Decomposition RGB blend mapped prior to the surface generation, therefore giving the interpreter a better understanding of the geology throughout the interpretation process.




A video demonstration is available here. Next week’s blog post will give more details on the 3D surface editing option. 

Thursday, 6 July 2017

GeoTeric’s New Adaptive Horizons: Part 1 - Overview

As part of the Cognitive Interpretation workflow, GeoTeric’s new Adaptive Horizons use Regional Structural Awareness to create the fastest and most accurate 3D seismic interpretation. Any seismic, attribute or HSV colour blend volume can be used as a source for the Adaptive Horizons (which can be interpreted in both the 3D scene or using a 2D interpretation window), with different auto-track fill options ranging from Waveform, Amplitude, PDF and Graph Theory depending on the source data and objectives. A variety of tracking modes are also available: Full line, Piecewise and Manual, all with interactive previews due to the Regional Structural Awareness. More details on these and other options will be covered in the next blog post.


GeoTeric’s Adaptive Horizon tool is based on Graph Theory to deliver the most accurate interpretation based on the entire line, not just the next trace along. Graph theory correlates all the points in the data and determines all the potential routes. The route with the highest score will be selected as the initial interpreted horizon. All the other routes are remembered creating the Regional Structural Awareness so the user can preview and choose alternative interpretations, which makes the process of picking a horizon quicker and easier.




 The ability to preview the alternative routes in an interactive way allows the user to ensure the correct event is picked, for example when investigating cross-fault correlations as in the image below.



Other unique features such as “Complete Line” and “Accept Tracked Line” enable the horizon to be quickly QC’d and completed saving time and aiding efficiency whilst maintaining the accuracy of the interpretation.



The 3D editing capability of the tracked surface along with Data Mappingas you interpret greatly aids the interpreter in QC’ing the horizon. Any attribute or blend can be mapped prior to surface generation, to identify mis-picks and correct them in the 3D or 2D windows. In the example below, the Interpretation HSV colour blend effectively highlights mis-picks (in blue).


The interpreted horizons can be exported or integrated with other GeoTeric functionality such as the Horizon Packs and the Stratigraphic Slicing workflow.

Next week’s blog post will give more details on the Tracking and Fill Modes, but in the meantime a tutorial video is available here.



Tuesday, 27 June 2017

GeoTeric 2017.1 - New Release!

GeoTeric 2017.1 is our biggest release yet with lots of new functionality. 2017.1 launches our brand new unified seismic interpretation platform with the new Adaptive Horizons, harnessing the power of cognitive decision making.


The new Adaptive Horizons use Regional Structural Awareness, based on a patent pending graph theory approach to guide the tracker through the data whilst still allowing the user full control over the interpretation result. 

Due to its Regional Structural Awareness the Adaptive Horizons know how to cross events

Users get an interactive preview of alternative routes
3D edit functionality allows you to edit the surface
 on the fly in the 3D scene, saving time

When upgrading old projects, any previously interpreted Adaptive Horizons will be  converted to the new format automatically.
You can also convert a static Horizon surface that has been imported from file or via one of the 3rd party links to an Adaptive Horizon for further editing. The new Adaptive Interpretation platform also contains a 2D interpretation and base map window, fully synchronised with the 3D view.

We have also made many general improvements to GeoTeric to enhance the interpretation experience, including:
  • Linked Cursors between all the windows
  • Easy slice manipulation with playback controls
  • Automatic Save session - GeoTeric now starts up where you left off
  • New survey grid in the 3D scene
  • Extended the surface overlays functionality
  • Right-click option in the 3D scene on volume to create slices
  • Right-click option in the 3D scene to Reset probe
  • Arbitrary Lines can now be moved and edited and the draped data updates on the fly
    • To move the entire line, simply click on it and drag it
    • To edit individual points on the Arbitrary Line, right-click on and select Edit line.
    • We have also improved performance and added cursor location reporting.

·          
GeoTeric 2017.1 also contains several extensions for handling well data in GeoTeric:

Well correlation panel

  • Multi well and log display
  • Correlate your markers
  • Assign lithologies
  • Synchronised 3D and 2D edit
  • Scaled plotting 
Seismic to Well ties
  • Sonic Calibration
  • Synthetic seismic
  • Single or multi point stretch and squeeze
  • User defined Ricker wavelet


Well cross sections: right click on any well(s) to draw a section between them. The section can then be draped with any attribute in the standard GeoTeic way. 

Multiple well marker import using a simple ASCII loader

Further general enhancements:
  • Improved Fault Detect algorithm, where the value has a more direct relation to the confidence level.
  • If the Expression tools cant detect a supported graphic card they will throw an error.


Extensions and issues resolved with GeoTeric's 3rd party Links:

Link for Petrel:

Compatible with Petrel 2015 & 2016
  • Extended CRS handling when transferring wells, faults and polygons
  • Improved depth to time unit conversion between GeoTeric and Petrel
  • Scale for volume import now defaults to Auto Scale

Resolved issues with:
  • If the Petrel project contained lots of volumes, in some circumstances no volumes appeared in the link UI. This has been resolved. 
  • For some blends the Z value was modified during transfer- again this is resolved.
  • We have also changed it so that names with @ no longer throws an error when transferred. 


Link for DecisionSpace

Compatible with DSG 10.ep2, ep3 and ep4. 
Certified by Landmark to be used with 10 ep.3.
  • All the functionality that was in previous version of the Link is still there as well as
  • Polygons can now be transferred both ways


Link for PaleoScan
  • Issues around scaling of floating point data have been resolved

If you would like more information on the release or a link to download it, please contact our Support team. 

Thursday, 11 May 2017

Frequency Decomposition Part 3 - HDFD (High Definition FD)

The previous two blog posts looked at 'standard' frequency decomposition techniques which applied convolution of the trace with bandpass filters in a traditional manner.  This post focuses on the High Definition Frequency Decomposition or HDFD.

Part 1 - Constant Bandwidth
Part 2 - Constant Q

Part 3 – High Definition Frequency Decomposition (HDFD)

Link to tutorial video here

The High Definition Frequency Decomposition (HDFD) algorithm uses a different approach to the ‘standard’ frequency decomposition filters. The application of a modified matching pursuit algorithm allows trace reconstruction with precise vertical localisation.

Matching pursuit is a trace based form of frequency analysis and decomposition. It uses a dictionary of Gabor wavelets which are correlated to each event in the seismic data individually. Once an event has been matched to a wavelet, it is extracted from the trace and the next event is matched. This iterative process continues until 99% of the trace energy has been matched and a synthetic trace has been generated.

Reconstruction of a particular frequency response is achieved by summation of the response of all wavelets that intersect the desired frequency. The relative proportion of the response included from each wavelet is determined by the degree of overlap of the bandwidth of each wavelet with the desired frequency. This is why the bandwidth of HDFD responses is so wide (and why the vertical resolution is so good).


First optimisation pass. a) Atoms matched during the first matching pass (red, blue and green) have been co-optimised to find the best combination of amplitudes to fit the seismic trace (black) over the region of the atoms’ overlap. b) The effect of co-optimising multiple atoms at once is to provide a better approximation (orange) to the seismic trace in regions of constructive or destructive interference between the atoms.





Two options of HDFD are available, one producing the best possible vertical resolution and one with an improved colour resolution.

When using the colour resolution option, the data is split into three band-limited versions of the input data using a modified FFT. Then the modified matching pursuit algorithm is applied separately to each of the three components and the results are combined to produce the final outputs.

Illustrative example of frequency splitting used in HDFD with colour resolution option

When using the vertical resolution option, no splitting is carried out and the modified matching pursuit algorithm is applied directly to the input data.


Monday, 24 April 2017

Frequency Decomposition Part 2 - Constant Q

This weeks blog post continues to look at frequency decomposition techniques available in GeoTeric. We previously looked at the Constant Bandwidth technique, we now look at another Standard Frequency Decomposition technique, the Constant Q.

Link to Part 1 - Constant Bandwidth

Part 2 – Constant Q

Tutorial video can be found here.

The Constant Q method utilises bandpass filters to carry out decomposition with properties similar to a Constant Wavelet Transform (CWT).  The main benefit of this technique is that due to variable filter lengths and bandwidths there is a reduced filter length at higher frequencies, therefore these bands provide an increased vertical resolution whilst the result can still be processed quickly over large volumes.


Comparison of Constant Q Blend Vs Seismic 

There are two Constant Q options available: Uniform Constant Q and Exponential Constant Q. One may be beneficial over the other to achieve a good frequency decomposition colour blend depending on the frequency spectrum of the data.



Friday, 14 April 2017

Frequency Decomposition Part 1 - Constant Bandwidth

The Standard Frequency Decomposition module uses bandpass filters to carry out decomposition with properties similar to either a Fast Fourier Transform (FFT) or to a Constant Wavelet Transform (CWT).  Due to the nature of the waveform transformation between the frequency and time domains there is resulting uncertainty, as defined by uncertainty principle. Therefore, the different frequency decomposition methods show differences between the frequency resolution and temporal resolution with the two being traded off against each other.

Over the next three weeks the blog will focus on the different frequency decomposition techniques available in GeoTeric with accompanying tutorial videos. In part 1 we will look at the Constant Bandwidth decomposition method.

Part 1 – Constant Bandwidth

Watch the Tutorial Video here

The Constant Bandwidth method utilises bandpass filters to carry out decomposition with properties similar to a Fast Fourier Transform (FFT). It is a good reconnaissance option since it provides excellent frequency resolution and is fast to process; however, it tends to lack the vertical resolution of other available techniques required for detailed reservoir scale analysis. Constant Bandwidth mode is generally used when the aim of the decomposition is to differentiate between different geological elements on the basis of their bulk properties, for example delineation of large channel systems, salt bodies or gas chimneys.


When using the Constant Bandwidth method the bandwidths and filter lengths of the individual frequency bands are the same, which allows a like-for-like comparison between the bands. The filter lengths are generally high and therefore there is a large amount of vertical smearing, however due to the relatively narrow bandwidths high frequency resolution can be achieved.

The filter length is controlled by the minimum frequency set; a low minimum frequency will require a longer filter length to sample, if this is increased a smaller filter length can be achieved. The bandwidth scale can also impact the filter length – a narrower bandwidth will require a larger filter length and vice-versa.

Thursday, 6 April 2017

The Stratigraphic Slicing Workflow

With the release of GeoTeric 2016.2.1, the user can now take advantage of the new Stratigraphic Slicing workflow. This workflow allows the user to rapidly create a series of stratigraphically conformant slices which can then be used to extract data from any of the volumes or colour blends available in their project. The Stratigraphic Slicing workflow consists of the following steps:

  • Creating the Interpretation HSV colour blend
  • Picking top and bottom surfaces
  • Creating intermediate slices using the Iso-Proportional Slicing (IPS) tool
  • Creating a Horizon Pack, which is new to GeoTeric 2016.2.1, and
  • Using the Horizon Pack to extract data from a volume or blend

Key benefits

The Stratigraphic Slicing workflow provides a rapid, novel approach to understanding both the structural and stratigraphic features of your dataset. Key benefits include:
  1. Interpretation based on detailed phase information
  2. Better visual separation of packages
Image 1. Picking on a particular phase angle and comparison of visual character

  1. Reduced cycle skipping in auto-tracking algorithms
Image 2. Explicitly encoded phase information reduces cycle skipping.


  1. The ability to see and honour fault information
Image 3. Picked horizon stops at faults.

  1. The ability to create meaningful surfaces through very challenging packages
Image 4. Challenging package can be imaged meaningfully and rapidly.

  1. A very short turn around time, allowing the user to quickly build up a full package of slices through their dataset.

Below is an example of the results that can be achieved in a few short hours.


video

Instructions for the the Stratigraphic Slicing workflow can be found in the following VIDEO

For further information please contact GeoTeric support on support@geoteric.com

Monday, 27 March 2017

GeoTeric 2D

GeoTeric 2D was released last week!

GeoTeric 2D is an Expression Tool optimised for attenuating noise in 2D data. The example driven, preview based interface allows you to rapidly optimise the filters for each 2D line. Multi-line batch processing means that you can easily apply the optimised parameters over your full 2D data set.

GeoTeric 2D Interface

GeoTeric 2D reads and writes the data directly from SEG-Y, avoiding any data loading/exporting issues.

Three filters are available:
  • SO FMH: It is a structurally oriented and edge-preserving filter which uses a combination of median and mean calculations, ensuring that both the coherent and random noise are attenuated. This filter ensures that details like edges, corners and sharp dips in the structure are preserved.
  • SO Mean: It is also a structurally oriented filter, using a more aggressive mean calculation, which increases the continuity of the reflectors and produces a smoother result.
  • Mean: It is a grid oriented filter. It is useful for situations of very low coherency and chaotic data, where structurally oriented filters will struggle.
The choice of filter to use will depend on the objectives of the noise cancellation: if the objective is to map a regional horizon, an aggressive filter like SO Mean will produce a smooth result and allow for an easier auto-tracking of the data. When looking at a reservoir scale, preserving subtle changes in the data is important, so SO FMH will produce a result which preserves the subtle breaks and amplitude changes in the data.

The interface shows 9 swatches, with three default filter sizes for each of the filters. Each filter can be further optimised by changing the filter size using the slider bar at the bottom of the main display.

A before/after comparison slider is available in the main panel, allowing for an easy QC of the results. The difference (result minus original) can also be visualised by clicking on the Difference button at the top.

The multi-line batch processing allows you to apply the same filter to multiple lines in a batch process, so a whole 2D survey can be conditioned in a matter of minutes.

This video shows how to use the GeoTeric 2D Noise Expression tool.

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Thursday, 16 March 2017

Attenuating Migration Smiles in Your Data

Written by Thomas Proença, Geoscientist, Brazil

A common issue observed in sub-salt imaging is migration artifacts such as "smiles" (Figure 1).  Migration smiles occur when the velocity survey used in the depth correction contains imperfections.  When re-processing is not an option, a specific data conditioning workflow can be applied within GeoTeric with the aim of removing/reducing migration noise and increasing the signal to noise ratio in the data; thus making it clearer and easier to interpret.

Figure 1 - Migration smiles

Noise Attenuation Workflow



The first step to removing the migration smiles is to create smooth steering volumes, with the aim of reducing the contamination of the steering dip and azimuth.  This is done by applying a grid oriented smoothing filter of the original seismic data. Migration smiles are the most problematic part in the Z direction of the seismic data, using a large filter in X and Y directions will attenuate its vertical response. A typical filter size for this process is 9x9x5. 

The smoothing attribute can be found at:

Reveal tab > Processes and Workflows > Processes > Attributes > Stratigraphic attributes


After the original data has been smoothed, the steering volumes can now be calculated.  The recommended filter size for dip and azimuth is above 15 (note that if the bin sizes are different between the X, Y and Z directions, the filter size for the steering volumes should be adjusted to compensate for the difference and make them square).


Once the steering volumes are generated, they are used along with the original seismic data as inputs to the SO Noise filter found under the Processes and Workflow menu. The recommended filter size for this process is between 5 and 9. If the data is extremely noise to get better result the SO Noise filter can be run twice.

Results

Figure 2 - Original (left) x attenuated (right)



Friday, 3 March 2017

Interactive Facies Classification

By Tom Wooltorton, Senior Geoscientist

Why do Interactive Facies Classification (IFC+) in GeoTeric?


IFC+ offers the interpreter an advanced method of Seismic Facies classification in a rich multi-attribute environment. By utilizing the optimized blends, attributes and volumes created in GeoTeric, the IFC+ provides the optimal solution for translating the geology that you see in your data, into classified facies that can be embedded directly into the reservoir model.

The IFC+:

·    Provides a means to transform the geology revealed in colour blends, attributes and volumes into facies, and bridge the gap between visual interpretation and classification.

·    Affords the interpreter full control to delineate and tune the facies classes they see, or can operate in a partially supervised manner to discriminate subtle changes in the data that may be visually undetectable.

·    Allows the results to be clearly interrogated and validated against hard data.

·    Generates 3D results that can be directly imported into the reservoir model or volumetric estimates.

IFC+ tool interface.



Setting up your classification


To start, the interpreter chooses the optimized inputs they want to interpret facies classes from. These can include Frequency Decomposition RGB Blends, attributes, or imported results such as rock property inversions that highlight the features or geological bodies of interest. The best inputs are the ones that have been most effectively optimized to capture the facies variations, by carefully adjusting the frequency ranges or parameters in GeoTeric’s interactive tools. Up to ten volumes and one RGB blend can be used simultaneously in the tool.

By default the IFC+ will generate facies classes across the whole survey extent, however the classification can also be constrained to a 3D geobody that may delineate the reservoir or zone of interest. The geobody can be obtained by converting an Adaptive Geobody to a volume, and used in the classification by setting the opacity such that it does not obscure the other volumes. For information on how to do that, please see the video here.

Picking sample areas


Facies classes are interpreted by drawing small sample areas that capture the features of interest. This can be done in a localized manner, where the interpreter defines a single sample area to specify each individual facies, or pick sample areas crossing multiple features, which allows the IFC+ to detect the trends present in the data using a Gaussian Mixture Model and output a number of sub-facies, matching these trends. The interpreter then has the option to accept or adjust these detected sub-facies. To see how to pick sample areas, click here. Picking sample areas along wellbores is equally easy: simply by specifying two markers along a well trajectory, the IFC+ captures the seismic data values along the path between them and builds the sample area that way, also defining sub-facies according to the trends detected in the data. For picking sample areas along wellbores, see the video here.
Instead of using simple contouring to describe a complex range of data (left), the IFC+ uses a Gaussian Mixture Model to detect trends in the data and assign best-fit class centres (right).  This provides a more accurate reflection of the true facies being interpreted.


Facies tuning

Tuning these facies and sub-facies is easy and the interpreter can use the immediate, interactive feedback to ensure they capture the heterogeneity of the features of interest perfectly. Adjusting the acceptance controls how similar or dissimilar the data ranges to be classified are. Changing the opacity lets the interpreter inspect the facies distribution with respect to the underlying seismic. Watch a short video on facies tuning here.


Altering the acceptance level for a facies or set of sub-facies allows the interpreter to interactively decide what data ranges are appropriate for delineating the features of interest.


Evaluating facies using the Scatter Plot


To evaluate and ground truth the interpreted facies classes, the Scatter Plot tool is used to compare attribute values against each other and well logs. While the facies themselves are picked from specific volume combinations, they can be scatter plotted for any dataset available in the project, for example a sample area picked using the geomorphology shown in an RGB blend can be used to compare Near and Far amplitudes for AVO analysis, to relate the qualitative and the quantitative. Sample areas picked from well markers can be used to compare seismic values with log values, directly relating the geology to geophysics and providing vital calibration for the modelling of facies. To learn how to Scatter Plot facies, click here.

Finally, once the facies classes are interpreted, tuned, and calibrated, they can be generated in seismic volume form with each class given a discrete value. These are then ready to be integrated back into the GeoTeric workflow, exported using the software links, or embedded directly into the reservoir model and populated with reservoir properties.
Finished facies model, displayed in 3D render mode, this volume can be used as part of a geologic modelling workflow.