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DSS and VSFusion provide
advanced borehole seismic anisotropy modeling for accurate
velocity models and improved subsurface imaging.
Hydrocarbon reservoirs are often buried under an extended
overburden, consisting of shales and thinly-layered
sediments, which are often anisotropic.
Walkaway VSPs are ideal for measuring anisotropy
Records near-vertical to
near-horizontal ray paths
Measures in-situ
anisotropy at seismic frequencies
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Seismic ray paths change
with formation anisotropy. |
Benefits
- Estimate Thomsen
parameters
- Build a complex macro
velocity model
- Image formation with
anisotropy corrections
Repeating the survey along
several walkaway lines having different azimuths allows
the seismic interpreter to estimate azimuthal anisotropy
around the well that may indicate aligned vertical
fractures and anisotropic horizontal stresses. When
integrated with other types of anisotropy measurements,
walkaway VSP data can contribute significantly to an
improved image of the subsurface.
AnisoScape
Today, the most difficult part of a typical anisotropic
imaging task is the determination of the processing
parameters. Most service companies, and many oil
companies, have software to do the forward problem
(imaging); it is the inverse problem (determining the
parameters) that is difficult. Leon Thomsen, 2002
The use of anisotropy in surface-seismic depth imaging
is increasing. Anisotropy parameters are, however,
difficult to obtain from surface data due to limitations
in angular aperture. This limitation can lead to mis-positioning
of structural features and to poor focusing of seismic
anomaly features or faulting.
Borehole seismic data, with a greater angular aperture,
can be used to provide measured and interval anisotropy
parameters at depth. These parameters and controls can
be fed back to the surface-seismic depth model, and
thereby, used to improve the overall depth image.
- Improved structural
imaging
- Better fault focusing
- More accurate
pre-drill geopressure estimation
- Improved AVO results
Walkaway VSP imaged using a
velocity model with and without anisotropic corrections. |
