Print this page ABSTRACT: An integrated approach to pressure prediction from 3D seismic 
data
French, Mike1, and Dr. Nader Dutta2
(1) Baker
Hughes, Western Geophysical, Middlesex, United Kingdom
(2) Baker Hughes, Houston, TX
The capability of predicting subsurface pressure regimes prior to drilling can
significantly influence a drilling program from safety issues to well planning and
control. In rapid sedimentation areas the prime mechanism for developing overpressure is
disequilibrium compaction. This overpressure class influences seismic velocity and density
by differences in porosity between normal and overpressured shales and is acoustically
measurable. Traditionally pressure prediction is attempted utilising seismic NMO
velocities. Seismic NMO velocities suffer from poor temporal resolution and are optimised
for stacking. Dix Interval velocity conversion does not correctly handle lateral velocity
variations. However, picking velocities with criterion other than stacking can yield
valuable low frequency trends. These trends have been found useful for pressure prediction
purpose. Seismic data, however, contains two sources of velocity information, reflector
traveltime and reflector amplitudes. The procedure described utilises high quality seismic
processing to both correctly image reflectors and preserve amplitudes. This enables the
use of poststack and prestack seismic inversion techniques so both sources of velocity
information can be fully integrated to derive a detailed 3D interval velocity field
suitable for pressure prediction work. Calibration from velocity to effective stress and
pore pressure is derived by detailed geostatistical analysis of well logs and seismic
pseudo-logs. The relationships are then applied to the inverted seismic data to derive a
'volume' of predicted pressure from 3D seismic data
. The procedure also has the benefit
that the pressure 'volume' can be recalibrated and updated in 'near time' as future wells
are drilled and new logging information becomes available.
AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia