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2D & 3D VSP Inversion |
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2D VSP Inversion
VSFusion’s Sparse Spike Inversion application estimates the
impedance profile, velocity, density and depths. Sparse
spike inversion mixes a seismic wave field with the low
frequency components of a reflectance series generated from
an input model. The input model can be developed from VSP
first break time-depth of receiver pairs, TD-pairs or from a
VSP checkshot survey. Models developed using this
application initially consist of horizontal plane layers.
Dipping and nonplanar layers are then added through the
interactive editor.
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The available outputs consist of
the input data, and various model parameter images presented
as time images, spike images, and the derived images of
impedance, velocity and density. For quality control, the
solution can band limited to match filtering applied to the
input surface seismic data. |
3D
VSP Inversion
VSFusion performs 3D VSP using the TDROV 3D technique, the
only 3D layer-based inversion service available on the
market. It features a new multi-volume capability for 4-D,
4-C and AVO processing. The TDROV technique derives a finely
layered impedance model, giving access to the architecture
of the reservoir. Elastic impedance is estimated from the
3D seismic (surface or borehole derived), using well data
as calibration for the wavelet and for obtaining the
low-frequency component of elastic impedance. TDROV
technique follows a model-based approach where the model
parameters are sparse and constrained. The key advantage of
the layering approach is improved vertical resolution. In
addition, the layered impedance model allows a quick QC of
the inversion, mapping of impedances along the stratigraphy,
and an easy description of reservoir properties.
Prediction of Events and
Pressures Ahead of the Bit
While prediction ahead of the bit is not a new technique,
advances through VSFusion’s inversion method and processing
software are achieving improved accuracy. The VSP trace at
the borehole is inverted to generate an acoustic impedance
log below TD. Acoustic impedance changes on the log can
provide indications of rock type and properties such as
reservoir sands and over pressured zones. VSP imaging can
also be used for visualizing formations in front of the bit. |
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