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.