1ARCO International Oil and Gas Company
2ARCO Exploration and Production Technology
3ARCO Alaska, Inc.
Abstract: Integrated Reservoir
Study Case History: Application of
Levy-stable Random Fractal Simulation Techniques for
Understanding
Reservoir
Mechanisms
in the Kuparuk River Field,
North Slope, Alaska
Incorporating a suitable level of heterogeneity into reservoir
simulation models is a key prerequisite for accurate prediction of
production rates and final recoveries. Commonly-used numerical
techniques impose Gaussian models for spatial and multivariate
statistics in the well conditioning data and in the undrilled
reservoir
volume. These methods often require complex variographic
procedures in order to quantify the spatial heterogeneity of a
given
reservoir
attribute. Such Gaussian-based approaches have
inadequately characterized permeability extrema that dominate flow
behavoir in certain reservoirs.
This study utilizes a newly introduced method,
Levy-stable fractal simulation, for the distribution of
reservoir
properties at a former gas storage area in the Kuparuk
River Field. The main
reservoir
zone in the gas injection region is
a diagenetically and mineralogically complex clastic unit (C-sand).
Because of these complexities, the C-sand unit presents
difficulties in the lateral modeling of large changes in
petrophysical properties observed in near-vertical wells. Prior
efforts at modeling the movement of
reservoir
fluids, particularly
gas, in the C-sand have met with limited success. Previous
reservoir
descriptions have been insufficiently detailed to
adequately represent the inherent heterogeneity. The
Levy-stable technique employs automatic calibration with log
and core data for the interwell modeling of the complex spatial
characteristics of
reservoir
properties within the C-sand.
Levy-stable fractal simulations preserve the sharp jumps in
reservoir
properties observed at stratigraphic boundaries and
within
reservoir
sub-zones.
An upscaled dynamic simulation model built to test reservoir
mechanisms
predicts gas movement out of the injection area along
layers with correlated high permeabilities. This predicted gas
movement is consistent with offset well behavior and historic
reservoir
pressure data. Thus, areas in the former gas injection
region are predicted to have zones of relatively high oil
saturation that have been bypassed by migrating gas, representing
potential targets. Wells drilled in areas immediately adjacent to
the modeled region support the predictions of the detailed geologic
description and provide confirmation of simulated dynamic
behavior.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas