Evolution of Reservoir
Models Incorporating Different Recovery
Mechanisms
and 4-D Seismic – Implications for CO2 Sequestration Assurances
Alan P. Byrnes, Richard D. Miller, and Abdelmoneam E. Raef
Kansas
Geological Survey ,University of Kansas, Lawrence, KS
CO2 sequestration in aquifers and oil reservoirs requires reservoir
modeling to predict the nature of gas distribution, its transport paths, and its
long-term fate. The process of
reservoir
modeling is constrained by the nature
and volume of the information available at the time of model construction.
Reservoir
models almost invariably increase in complexity with each recovery
process. Simple
reservoir
models that accurately represent primary recovery
usually must increase in complexity to accurately model
reservoir
response to
waterflood. With CO2 tertiary recovery, and associated three-phase flow and
mobility ratio differences, further increases in
reservoir
model complexity are
usually required. Understanding this evolution permits the necessary advancement
in the complexity of
reservoir
models prior to or contemporaneously with
injection providing improvement of injection and recovery processes.
The DOE-sponsored CO2 enhanced recovery project in central Kansas
illustrates this evolution of reservoir
modeling and the role 4-D seismic can
play in accelerating model development. One- and two-layer models adequately
predicted primary production. Subsequent waterflooding required the introduction
of more layers and lateral heterogeneity. Injection of CO2 for enhanced
recovery, begun in December 2003, exhibited delayed breakthrough response and
different well response than predicted by models. 3-D seismic revealed lateral
heterogeneities that were also indicated by well interference testing but not
fully quantified. 4-D seismic revealed that injected CO2 was constrained in its
motion both in response to the observed heterogeneities and the interaction of
pressures generated by water containment injectors. Information provided by 4-D
seismic can play a key role in developing accurate
reservoir
models.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005