Numerical modeling of multiphase and nonisothermal flow in fractured media
Approaches for modeling of coupled multiphase fluid and heat flow in fractured media include ``explicit`` modeling of fractures, which are represented as domains with small spatial scale and large permeability: effective continuum approximations, in which one attempts to model the composite behavior of a fractured porous medium in terms of a single effective continuum; and ``hybrid`` models such as double- or multiple-porosity techniques which combine features of the explicit fracture and effective continuum approaches. We present examples of each of these approaches. The explicit fracture approach has been applied to investigate thermohydrologic conditions near high-level nuclear waste packages emplaced in partially saturated fractured tuffs. Besides providing some useful insight into multiphase flow processes this approach substantiates an effective continuum approximation, which leads to a drastic simplification in the modeling of fractured flow systems. A consideration of diffusive processes in rock matrix and fractures provides criteria for the validity of the effective continuum approximation; these have been verified by means of numerical experiments. Flow studies using the method of ``multiple interacting continua`` have demonstrated how effects of global flow tend to diminish sensitivity to individual matrix block response in enhanced oil recovery and in heat mining in geothermal systems. In some cases simple semi-analytical techniques are found to provide an adequate approximation to the complexities of multiple-continua behavior. 25 refs., 4 figs., 4 tabs.
- Research Organization:
- Lawrence Berkeley Lab., CA (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 60472
- Report Number(s):
- LBL--25547; CONF-880583--3; ON: DE88014855
- Country of Publication:
- United States
- Language:
- English
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