Print this pageAbstract: Modeling and prediction
of localized 
flow
in fractured rock masses
SANDERSON, DAVID J. and XING ZHANG
The localization of
fluid flow is of fundamental importance to many aspects of reservoir engineering
as well as in groundwater flow in fractured rock. Numerical modeling of
the coupled mechanical and hydraulic behavior of rock-masses, using distinct
element methods (UDEC), demonstrates that a change in the stress state
can result in a sudden transition from diffuse flow through fracture networks
to highly localized flow generated by the opening up of `pipes' at fracture
intersections. A series of results for selected fracture networks and loading
configurations will be presented. The influence of the 1) fracture network
geometry, (connectivity, fracture density, orientation, distribution, etc.)
and 2) in situ stress on the critical phase boundary between diffuse (plate)
and localized (pipe) flow will be investigated. The geological evidence
for localization of flow in vein systems will also be examined.
Multifractal techniques have
been used to characterize the resulting heterogeneity of the flow in order
to generalize the results of the modeling of discrete systems to a more
continuum-based description of the flow, obviating the need for complete
characterization of the individual `pipes' within specific networks.
Engineering activity (drilling,
fluid extraction, pressure change, etc.) will change the state of stress,
at least locally, and thus effect the deformation and flow in fractures.
The ability to predict if such changes are likely to lead to critical changes
in the flow
characteristics has widespread implications in all forms of
subsurface engineering.
AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria