Abstract: Integrated Carbonate Reservoir
Characterization and Modeling
Using Outcrop, Subsurface and
Seismic
Data
and Technologies: An Example from the Permian Basin, U.S.A.
Fitchen, W. M., Drexler, C. W., Frantes, T. J., Helwick, S. J., Kozar, M. G., Mitchell, J. C., Rankey, E. C., and Schroeder, F. W. - Exxon Production Research Company
A fundamental challenge in characterizing
carbonate reservoir properties and undertaking 3-D geologic modeling
of
facies and porosity is the prediction of property continuity and associated
uncertainty away from the wellbore. ?Successful? prediction, i.e., accurate
prediction of pore volume within the reservoir, depends on (1) data availability
(type, spacing, quality and resolution), (2) the quality of the structural,
sequence stratigraphic, and facies frameworks, which requires appropriate
models and concepts as well as innovative model-building procedures, (3)
the degree to which different data types are integrated and interpretations
are cross-checked for consistency, and (4) the
modeling
techniques used
to predict property continuity while incorporating and/or subsequently
quantifying uncertainty. The different stages of exploration, field appraisal,
development, and enhanced recovery witness changes in data, time and cost
budgets, and objectives (e.g., assessment, flow simulation, production
optimization); these factors exert a major influence on the scope of the
reservoir characterization and model construction and thus also influence
the relative success of property prediction. In this study, we quantify
the value of integrating outcrop analogs and 3D
seismic
data - two data
types that provide measures of property continuity - into the reservoir
characterization and 3D geologic model construction process.
The oil field studied, complemented by nearby
world-class outcrop analogs in the Guadalupe Mountains, provides an exceptional
proprietary database to examine the role of outcrop analogs and 3D seismic
data in reservoir characterization and 3D geologic model construction.
The producing formation in the field, the San Andres Formation (Middle
Permian), is a heterogeneous restricted platform carbonate reservoir with
over 950 wells on 10 to 20 acre spacing; a recent full-field, high effort
3-D
seismic
survey; over 13,000 ft of calibrated core data; oil, water
and CO2 production and injection data; and a suite of engineering
test data (injection profiles, production surveys, buildup tests).
Outcrop analogs and seismic
attributes provide
critical data to appraisal and development stage descriptive and
modeling
efforts. Outcrop analogs were used to develop regional to flow-unit scale
sequence stratigraphic models for prediction of sequence and systems tract-keyed
facies architecture, continuity and connectivity (e.g., stacking patterns,
N/G, facies object dimensions, directional variograms).
Seismic
attributes
were used to predict facies and porosity continuity away from calibration
wells in seismically-integrated cell-based models. Calibration models relating
seismic
response to porosity changes were developed utilizing 1) traditional,
amplitude-based
seismic
attributes, 2) proprietary principle component
attributes, 3) proprietary inflection segment attributes, and 4) total
impedance inversion (the preferred approach).
A seismically-integrated cell-based model using
a small subset of calibration wells was built in an effort to simulate
an assessment project during field appraisal. Subsequently, conventional
cell-based models were built using ranges of wellsets, ranges of sequence-specific
facies proportions, and ranges of variogram models for SISIM stochastic
facies modeling
to simulate 40-, 20-, and 10-acre development drilling.
These models highlight the importance of 3D
seismic
integration in the
absence of wells early in field development, followed by outcrop analog
integration as development proceeds.
AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil