Tigress Ltd - Interpretation tools: Tigress Geophysics

The Tigress Geophysics module allows you to generate synthetic seismic traces from sonic and density logs, tie geological interpretations to the seismic data, and interpret horizons and faults on multiple 2D and 3D surveys. You can also extract interpretation-based attributes from the 2D and 3D seismic data and (simultaneously) from other non-seismic data sets. In the special Cross Section application you can view seismic and other data sets in either time or depth.

You can use Tigress Geophysics as part of an integrated multi-disciplinary workflow for:

fast seismic data quality control (QC)
velocity QC and model building
time-lapse (4D) interpretation
multi-component (4C) interpretation.

The results generated by Tigress Geophysics are used extensively in other Tigress applications, including:

Map Editor, for producing maps and structural grids for model building
Crossplot, where relationships between seismic attributesand petrophysical parameters are established
Cross Section, where geophysical and geological data are used to produce an integrated interpretation
3D viewer, where geophysical data can be displayed alongside maps, wells and reservoir models.

On this page you can find out more about:

Synthetic trace generation

In synthetic trace generation you use sonic and density log traces to derive a reflection coefficient trace. This trace is then convolved with one or more wavelets to generate a suite of synthetic traces. You can then use synthetic traces to match well depths to seismic loops. If the project includes shear-wave sonic log traces (Dw) you can also generate synthetic gathers.

Features of the synthetic trace generation module include:

batch generation of synthetic trace sets
creation of a density log if it doesn't exist
generation of PP, PS or SS synthetics, including multiples
simultaneous creation/display of geological zonations based on the synthetic traces
display of data in time or depth
saving of synthetic traces in depth for use in geological and petrophysical interpretation.

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Velocity calibration

You use the velocity calibration utility to interactively tie Time-depth (TZ) checkshot data, that has been corrected for wellbore and acquisition geometry, to an integrated sonic (Dt) log trace acquired down the well. This gives a calibrated TZ relationship at each well, which you can then use to tie geological interpretations (in depth) to seismic interpretations (in time).

You can use the calibrated TZ relationship for multiple wells to derive regional velocity-depth curves for time-depth conversion.

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Seismic interpretation

Features of the seismic interpretation module include:

multi-window interpretation allowing simultaneous interpretation of horizons and faults on multiple 2D and 3D surveys
support for non-seismic data types and linked volumes
a 'hot link' to Tigress Well Correlation allowing the streamlined loading of well data (logs, cores, zonations, RFT) into seismic interpretation
display of fault data and horizon in the basmap window, or posted onto seismic section displays
posting of well data onto any seismic display
fault prediction to estimate the likely location of fault segments along a profile, based on nearby fault picks
a full suite of seismic attribute generation tools
volume operations
real-time links to Tigress Mapping, Petrophysics and Geology modules.

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Seismic attribute generation

The Tigress Geophysics module provides a number of utilities for extracting interpretation-based attribute information from a seismic (or non-seismic) data volume, namely:

All of the above generate attribute surfaces which can be displayed as a profile above their equivalent seismic data or as a map surface in the Geophysics Basemap window. Once created, attribute surfaces can be spatially filtered using Horizon Manipulation, which can also be used to perform unary or binary arithmetic operations on horizons and attribute surfaces, or to derive surface properties such as dip and azimuth.

You can copy attribute surfaces from one volume to another, to allow multi-volume interpretation and time lapse studies.

Loop measurements

Loop measurements allow you to characterise and map variations in loop behaviour over an area. The measurements are based on a time window (or depth window, if the volume is in depth) about a single interpreted surface (horizon). Within the specified time window, you can refine the measurements further by selecting wavelet characteristics, including closest peak, trough or zero crossing, to define the start and end points of the measurement window.

Loop measurements include:

time of start or end point
amplitude of start or end point
time difference
amplitude difference
loop length
tortuosity
area (loop area from zero)
chord area (chord loop area).

Window measurements

Window measurements are based on a time or depth window defined by two input horizons, or by a user-specified window about a single horizon. Window measurements include:

mean power
RMS amplitude
average or maximum absolute amplitude
maximum power
zero crossings
minimum or maximum amplitude
total loop length.

Complex measurements

Complex measurements are calculated using a time window extending 10 samples above and below a user-specified horizon. The value assigned to each location is the complex trace attribute value at the corresponding horizon time. Supported complex measurements are:

Reflection strength
Instantaneous phase and frequency
Quadrature
Cosine of Phase.

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Time to depth conversion

You use the velocity QC and time-depth (TZ) conversion application to:

generate interval and RMS velocity profiles
use structural horizon data to constrain the extraction of velocity attributes
depth-convert seismic and velocity data together with associate interpretation, using interpolated interval velocities
review all data in seismic interpretation.

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Seismic data QC

The preparation of volume data for interactive review is a highly manual, iterative process. It can require a significant amount of interaction from the user before a satisfactory data set can be produced. The types of decision which might need to be made include:

determination of optimal scaling and clipping parameters (important when producing an 8-bit data set)
definition of display-specific processing parameters
identification of the best available data set (or part thereof) for QC purposes.

Tigress Geophysics gives you tools that let you make these decisions interactively, and review them in real time, without creating any new data sets and without compromising the integrity of data which may require further processing.

Seismic data QC is activated by the automatic linking of volume data (seismic or non-seismic) to the Tigress PDS database. You can then use Tigress 'virtual volume' technology to:

save disk space and improve data set management by eliminating unnecessary generation of intermediate volumes
allow the user to test and compare multiple scenarios using multi-source input data before choosing optimal parameters.

Various volume data formats are already supported by this link. A programming interface is also available to automate the process of linking volumes to the database.

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Velocity QC and model building

Velocity profiles generated using the Tigress velocity QC and time-depth (TZ) conversion utility can be reviewed in seismic interpretation. The same input velocity data can be loaded into the database as velocity wells, or as velocity maps.

Velocity well

A velocity well is a vertical well located at the velocity CDP. Data associated with the well includes:

Multi-well zonations containing interval number and velocity range.
Interval and stacking velocities stored as zone parameters
Interval velocity stored as a square trace.

Velocity well data can be used to generate maps, or loaded into Tigress Petrophysics and Geology applications for further QC and analysis.

Velocity map

A velocity map is a set of control points representing the velocity values for a particular interval. Velocity maps can be used for additional QC, or directly for building velocity models. Maps are generated automatically for each interval in the input data set.

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Time-lapse interpretation

Time-lapse or 4D seismic monitoring is an integrated reservoir exploitation technique based on the analysis of multiple 3D seismic surveys. The primary purpose of this technique is to identify and quantify bypassed pay.

Tigress Geophysics can be used as an integral component of a multi-disciplinary time-lapse processing and interpretation workflow. A typical workflow will include a number of stages:

Perform fluid replacement modelling in order to determine whether it is worth shooting a second survey.
Shoot a second survey and compare the two vintages.
Perform interpretation-based quantitative analysis on the two data sets.
Re-process and match the two surveys.

Each stage requires a decision before proceeding to the next stage.

Features of Tigress that support time-lapse processing and interpretation include:

Seismic interpretation

General features of seismic interpretation used in time-lapse interpretation include:

Generation of interpretation data (horizons, faults)
Manual or autopicking of horizon surfaces
Multiple volume capability. Load/display/interpret several 3D volumes simultaneously
Multiple volume-type capability. Load/display/interpret any 3D data type including seismic, coherency and velocity
Extract a trace along the well path from any volume type. Such a trace can be employed for comparison, for example, with synthetically generated traces in the Tigress Petrophysics module (TraceEdit)
Hot link to the Well Correlation & Zonation application for streamlined loading of well data (log and core traces, wellbore schematics, zonations and RFT)
Export of horizon data in ASCII format

The horizons can then be:

viewed in 3D
used in Tigress Cross-Section to assist in defining inter-well regions
used in Tigress Petrophysics CrossPlot to investigate relationships with other horizons and with Petrophysics parameters
used in Mapping to derive surfaces for input into the Simulation module.

Multi-volume interpretation

Multiple 3D data can be associated through a common survey grid.

Copy horizon and fault interpretations from one 3D volume data set to another, for example in time-lapsed 3D interpretation.

Volume based operations include:

generation of sub-volumes and time slices
arithmetical and logical operations, for example the difference of two time lapsed impedance volumes
derivation of various attributes, including Runsum Integration and Recursive Inversion
application of filters such as AGC, Band Pass and Trace Inversion.

Surface based operations include:

arithmetical operations.
derivation of complex trace, loop and window attributes.
other attributes including Dip and Azimuth.

Any volume can be viewed in the 3D viewer.

Horizon attributes are commonly used in:

Tigress Petrophysics (CrossPlot) to investigate relationships with other horizon attributes, and with Petrophysics parameters.
Tigress Mapping to derive surface attributes for input into the Tigress Simulation module.

Synthetic trace generation

You can generate acoustic impedance traces, reflection coefficient traces and synthetic seismograms to tie in geological models. These seismograms can then help in the creation of zonations in the Tigress Geology module.

This Geophysics module also helps with the following:

correction of raw checkshot times to TVDSS datum times
interactive calibration of integrated sonic with corrected checkshot data
interactive editing, de-spiking and merging of traces at different stages of synthetic trace generation
application of Ormsby, Butterworth, Ricker and user-defined filters
generation of PP, PS and SS synthetics
generation of synthetic gathers/stacks using Backus or Crewes blocking algorithms
export of synthetic and derived traces in time or depth units in ASCII format for use in third party applications.

Synthetic traces are commonly used for comparison purposes, for example with a trace extracted from volume in Tigress Petrophysics (TraceEdit).

Association of seismic and well data

The Tigress Cross-Section application can help geoscientists associate well data with seismic, and define the structure of the inter-well regions using seismic data and geophysics interpretations. Features include:

display of multi-wells and data in true trajectory
display of log and core traces, wellbore schematics, zonations, RFT and dipmeter data
display of the correlation panel between wells that can be shaped using horizons and mapping surfaces
hot link with Well correlation and zonation for quick data loading and automatic updating of zone edits.

Well correlation and zonation generation

The Geology module in Tigress lets you:

create well stratigraphy and the correlation of zones between wells
generate single level and hierarchical zonation schemes which can contain repeat zones and gaps
display log, core, RFT, dipmeter, wellbore schematic, tests and multiple reference zonations, synthetic traces, and traces extracted from volume data.

It also allows hot links to:

Tigress Mapping to select wells for the display
Cross Section to show effects of zone editing between wells
Cross Plot, Histogram and Cluster Analysis to help create lithological and facies related stratigraphy.

Zonations are then typically used in deriving zonal parameters in Tigress Petrophysics Interpretation.

Petrophysical interpretation

Zonations are used with log data to derive interpreted traces and averaged zonal parameters. These are then used in Tigress Mapping to derive parameter (attribute) surfaces. The parameter surfaces can be used in Tigress Simulation to derive a reservoir model, or they can be compared with parameters derived from different log runs.

Crossplot

The Tigress Petrophysics module allows you to display and analyse the following with cross-plots:

Multi-well data (log, core and zonal parameters)
Geophysics horizons and mapping surfaces for reservoir characterisation.

One attribute/parameter is plotted against another (for example, Poisson's Ratio against Impedance to help identify oil sands, water sands and shales within the reservoir). The results allow geoscientists to establish inter- and intra-relationships between seismic attributes and Petrophysics parameters. These relationships (regressions) are described in the form of equations, and can be saved to the database and used in Tigress Mapping.

Mapping

The Tigress Mapping module allows:

modelling of the structural and lithological properties of the reservoir using the regression (equations) derived from CrossPlot
geophysical, geological and petrophysical data to be integrated to generate structural and attribute surfaces for input to the reservoir model
complex arithmetic or logical operations to be performed on data using standard or user-defined equations, the results of which can be incorporated into the reservoir model
volumetric calculations to be performed on the model.

The static reservoir model forms the basis for the fluid flow simulation model generated by Tigress Simulation.

Simulation

The Tigress Simulation module takes as its input:

mapping surfaces (for example structural surfaces or thickness surfaces)
reservoir parameter surfaces (for example porosity and permeability).

These data are used to provide a fluid flow model of the reservoir, and a 'snap-shot' (static) of the reservoir at any future time.

The Simulation module has a graphical front-end which allows you to:

enter data
edit or manipulate the data
display and present the data.

Results are fed back into the decision-making process.

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Multi-component interpretation

Multi-component (4C) interpretation is a reservoir characterisation methodology that is primarily used in prospects where traditional compressional wave (p-wave) seismic interpretation does not produce satisfactory results. 4C interpretation uses converted (PS) wave seismic data acquired at the sea floor together with P-wave data and shear-wave log data to provide additional control on reservoir structure and likely pore fluids.

Tigress Geophysics provides a number of tools that complement the multi-component interpretation workflow, including:

multi-volume seismic interpretation capability
support for non-seismic volume types
integration with geology and petrophysical applications for combined interpretation
generation of synthetic traces and gathers based on P-wave (Dt) and S-wave (Dw) sonic log traces
modelling of pore fluid content using Shears and Biot-Gassman methods
crossplot of geophysics data against mapping surfaces and zone parameters.

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