Acoustic Non-Linear Full-Waveform Inversion Application on an Outcrop-Based High-Resolution Geological and Petrophysical Model (Book Cliffs, Utah)
Geological outcrops are often used to develop predictive
models and provide quantitative parameters that describe the architecture and
facies distribution at a sub-seismic
scale, which is used in the development of
exploration and production strategies. In the oil- and gas-industry, the
inversion of
seismic
data is well-known technique used for obtaining the
reservoir geometries and properties. It often uses well data and external
knowledge such as outcrop analogues as guiding constraints. The goal of this
study is to build a synthetic
seismic
data-set that provides detailed,
realistic geological and petrophysical reservoir information and use these data
for a multi-parameter (P-wave velocity (compressibility) and bulk density)
acoustic full-waveform inversion.
As a basis
for the geological and petrophysical modeling
we used published work of a
regional section of the Book Cliffs outcrops (Utah, USA) with a continuous
exposure of mostly shallow-marine deposits over 120 km. A subset of this data
set is used and populated with representative layer properties. The so-called
‘Kennett invariant embedding method’ was used for the forward
modeling
of a synthetic acoustic full wavefield. We apply the recently
introduced target-oriented non-linear full-waveform acoustic inversion
technique (Gisolf and Van den Berg, 2010) on the resulting synthetic pre-stack
seismic
data set. This approach keeps the acoustic inversions to a manageable
size and therefore looks promising for commercial implementation.
The main
result is that the two media parameters (P-velocity and bulk density) could be
successfully recovered from the seismic
synthetic data set that provides
detailed reservoir information at a resolution higher than the shortest
seismic
wavelength. In addition, a wide band reconstruction of the compressibility was
achieved, well outside the spatial bandwidth commensurate with the
seismic
temporal bandwidth. These were possible because the inversion exploits the
non-linear nature of the relationship between recorded data and the medium
contrast properties. Non-linear inversion is taking full advantage of this by
which meaningful density information can be extracted. The quality of fit
between the broadband predictions and the actual model is outstanding for the
compressibility, and good for the bulk density. Moreover, the inversion results
make it possible to understand and interpret which geological features can be
resolved from
seismic
data.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California