Technical
Publications:
reservoir characterization
petrophysical
seismic
Seismic Attributes Consortium
Definition of Seismic Attributes
All measured quantities obtained from seismic data are called 'Seismic
Attributes'. These include complex trace attributes, velocities, offset-varying
attributes, bedding patterns, their continuity characteristics, etc.
Historically these attributes have been used at various stages of processing
and interpretation. The Computation and Interpretive use of Seismic Attribute
Consortium investigates their quantitative use in the interpretation
process.
Objectives:
- To generate new seismic attributes to improve the interpretability of seismic data from structural and stratigraphic points of view
- To provide physical and geometrical measurements to allow a more accurate extrapolation of lithology, porosity and permeability away from the well bore
- To provide sufficient evidence to allow more accurate prediction of lithology, porosity and permeability in new areas
- To develop pattern-recognition techniques that will delineate discontinuities such as faults, on-lap, off-lap, down-lap, etc. that will classify bedding patterns such as parallel, diverging, etc. to aid in stratigraphic interpretation
Present State of the Art
Since the introduction of seismic attributes in the early 1970's, most
of the published articles have emphasized their geometrical aspects in
interpretation. Lithological implications were confined to only a few
papers giving results of some limited investigation. A number of different
attributes were introduced, however, no attempt was made to organize
all of the attributes in a logical manner. In our present approach we
have developed an attribute classification scheme and are in the process
of developing their quantitative use in lithological prediction and pattern
classification.
Approach
At the present time Attrib3D generates attributes divided into 5 classes.
The first two classes are instantaneous complex trace attributes, which
are computed sample by sample. The second two classes are wavelet attributes.
The first of these two classes is computed from original trace data,
and the second set is computed from signal-to-noise improved traces.
The fifth class is the geometrical attributes, which are computed from
the time/space relationship of the wavelets.
We will continue to define and classify new attributes based on their utilization. In addition to the current list of 2-D and 3-D poststack attributes we plan to develop new prestack attributes.
The Seismic Attribute Consortium has adopted the following approach:
- Select seismic lines representing various lithological settings and generate corresponding attributes to investigate any visible indications
- Select pre-processed seismic lines according to the stratigraphic processing guide-lines, investigate effectiveness of geometric attributes
- Generate seismic attributes and analyze their inter-relations by cross plots and cluster analyses
- Generate seismic attributes and clusters for specific attribute combinations by various clustering techniques including the self-organizing maps
- Generate seismic attributes and train Neural Networks with interpreted well logs for predicting lithology away from the training area
- Develop pattern recognition techniques for various stratigraphic settings
Deliverables
In Phases I and II of the consortium a number of sub-programs and some
interactive procedures have produced which can be used in either a stand-alone
mode or integrated within a more extensive analysis and interpretation
system. Following is a list of the products that have been developed
thus far:
- Post stack attributes with physical characteristics, such as amplitudes, frequency, velocity, Q, etc. (Note that all routines are amenable to integration within different processing systems)
- Attributes with geometrical characteristics, e.g. depositional bedding geometries such as parallel, diverging or converging beds, chaotic patterns, event tracking, event termination detection, termination modes, etc.
- Interactive generation and display of 2-D attributes
- Attributes extended to 3-D
- Interactive generation and display of 3-D attributes
- Associated n-dimensional clustering by Self-Organizing Feature Maps and other clustering techniques
- Provision of 4 output options for the computed 3-D attribute volume:
- Conventional 32-bit floating-point SEG-Y data.
- 16-bit fixed-point data
- 8-bit fixed-point data
- .VOL format for export to interpretation packages
- Neural Network training with interpreted well logs (LogANN®)
- Pre-stack attributes with physical characteristics, e.g. most of the post stack attributes including those attributes computed using trace offset as one of the variables such as NMO or imaging, group and phase velocities, etc
- Interactive event picking and picked event attribute display and transfer and store for further computations
- Interpreted well log or synthetic seismogram overlay on attributes
- Extrapolation of lithology away from wells and display projected lithology
The current release of the Attributes Suite of software is Attrib3D 2.8 and LithANN® 2.8 supported on SUNOS 5.5.1+ and IRIX 6.2 +
Consortium Sponsors:
Anadarko
Petroleum Corporation
BHP
Petroleum Company
ChevronTexaco
Technical University
of Delft
ExxonMobil
Norsk
Hydro ASA
PEMEX
RWE-DEA
Aktiengesellschaft f�r Mineraloel und Chemie
Saudi
Arabian Oil Company
Shell EPTC Company
Sonatach
