Print this page ABSTRACT: A case study on using 
seismic
inversion, 90 degree phase shifted seismic
data and geostatistical simulation in the Bayu-Undan Field
Gallagher, Joseph, M. J. Raymondi, and D. Mayo , Phillips Petroleum Co, Bartlesville, OK
A measure of the impedance variation can be obtained from the negative first derivative
of the seismic trace or by applying to the zero phase seismic section, a phase shift of
-90 degrees. In this paper, it is shown that this process can provide a quantitative
measure of the high and low values of impedance along a seismic trace. Peaks on seismic
trace processed in this way can be associated with intervals of increases in impedance
while toughs on the trace can be associated with intervals of decreases in impedance.
Seismic sections processed in this manner are compared to a sparse spike
geostatistical-based inversion performed on the 3-D seismic data acquired over the
Bayu-Undan field in the Timor Sea. The inversion encompassed the entire reservoir
interval. Sonic and density logs from seven wells were used to geostatistically build a
low frequency impedance model and an amplitude balance model. These models were applied to
the sparse spike inversion in the frequency domain to generate absolute impedances for the
inverted seismic traces. From the impedance and -90 phase shifted seismic section and
using gamma ray log calibration, it is shown that peaks in the seismic trace are
associated with higher impedance values and shale intervals while troughs are associated
with lower impedance and sand intervals. The estimation of porosity in the sands using
impedance/porosity correlation as soft data
in a geostatistical simulation are also
discussed.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia