Use of Seismic-Derived Attribute for Internal Reservoir Description: A Case History
Sala, Claudio, Luca Baruffini, Fabio Luoni, Anna Pizzo, Marco Rovellini, ENI -Exploration & Production, San Donato Milanese, Italy
The opening of the deep-water frontier highlights the importance
of integrating well data with the information coming from different sources, to
reduce the appraisal costs and improve the reservoir knowledge. The presented
case history illustrates a semi-quantitative approach for integrating seismic
information for the internal reservoir description.
The reservoir is characterised by deep-water channel-lobe
systems. The complex internal architecture reflects the coexistence of surge-type
gravity flow and sustained currents. These two mechanisms, together with the
channel system evolution have a big impact in the facies distribution and, in
the view of reservoir management, in the geometry and in the quality of the
sands.
In this perspective, a reliable and constrained distribution of
the heterogeneity in the reservoir levels is a basic factor to optimise the
development, reducing uncertainties and minimizing risk.
The applied approach uses the seismic information for facies
distribution, integrating data at the well and seismic scale, also accounting
for the peculiar sand deposition mechanisms of the current sedimentary
environment.
Using a statistical methodology, well logs and core data are
used to define a very detailed facies distribution at the well (well-facies).
In parallel, the seismic volume has been inverted to elastic
attribute and
calibrated to acoustic facies (seis-facies) defined by petroacoustic
elastic
modelling using well data.
Next, a quantitative
relationship has been found between well-facies and seis-facies. The final
distribution of well-facies has been obtained using the 3D seis-facies volume
to steer the geostatistical simulations, capturing the depositional system
heterogeneity and evolution. Petrophysical
properties are finally simulated inside each facies according with the core
analysis and the log interpretation.
At the end, a
series of reliable pictures of the reservoir obtained with this methodology has
been successfully used for a trustworthy reserves risk assesment and for the
well plan optimisation.