Abstract
In many rock types, such as shales, elastic parameters vary with
propagation directions, defined as elastic anisotropy. Recent advances
in seismic data acquisition requires the need to include anisotropy
information for imaging and processing. However, anisotropy model
building is not straightforward due to data availability. Here we
present a multi-objective approach to find an optimal solution using
both well logs and seismic data. We use seismic objective as a
constraint to narrow the uncertainty distribution around model
parameters and to ensure that the model is consistent with seismic as
well as well log data. Consequently, the resulting anisotropy model can
be used for both well logs and seismic data analysis. First,
Hudson-Cheng crack model is used to obtain rock matrices properties
(bulk and shear moduli) and aspect ratio of a set of ellipsoidal cracks.
Then, we obtain a set of non-dominated solutions, which minimizes the
RPM (rock-physics model) multi-parameter objective function and the AVO
(Amplitude Versus-Offset) objective function. The approach is applied to
a field data with one vertical well log and pre-stack migrated seismic
data. In spite of the low signal-to-noise ratio of seismic data, the
overall results are consistent with the rock-physics model and fit the
seismic amplitude variations, particularly for the mid-to-far angles of
incidence. Furthermore, we extend the approach to predict seismic
anisotropy away from well log location, to map the occurrence of high
quality organic-rich shales.