Fault
Characterization and Reservoir Development
at Kuparuk River Field, Part 2: Understanding
Fault
Zones and Predicting
Fault
Seal
By
R.W. Krantz and M.R Longden (Phillips Alaska, Inc.)
The production
history at Kuparuk provides evidence of sealing or baffling faults. Some faults
separate pressure cells, offset fault
blocks with distinct oil-water contacts,
and create barriers to effective EOR processes. Other faults with similar throw
show little impact on fluids. At many drill-sites producing wells receive no
support from adjacent injectors. Optimizing further development requires
confident prediction of sealing faults.
Past efforts that focused on sand juxtaposition
achieved only partial success. Evidence from core helps explain why. Core
through fault
zones shows both small faults with clay smear and larger
fault
zones with clay-rich gouge. These and other
fault
zone lithologies result in
greatly reduced permeability. Thus even where sands may be present on either
side of a
fault
, the intervening
fault
zone may itself create a barrier to fluid
flow.
Fault
zone width increases with greater
fault
throw, and also contributes
to
fault
seal probability. Our new characterization of faults begins with
detailed
fault
mapping, especially
fault
continuity in three dimensions.
Fault
style models help guide the interpretation. We then integrate local stratigraphy
and rock properties adjacent to the faults. Multiple techniques (shale gouge
ratio, clay smear potential) determine the distribution of low permeability
zones within the
fault
zones. Some of these are keyed to the deformation style
differences between the early and later
fault
sets. Several case studies
demonstrate this approach, and show more effective results in matching observed
reservoir performance. These results can be applied at the scale of individual
patterns or regional simulations.
AAPG Search and Discovery Article #90008©2002 AAPG Pacific Section/SPE Western Region Joint Conference of Geoscientists and Petroleum Engineers, Anchorage, Alaska, May 18–23, 2002.