Representation of Fault Zone Permeability in Reservoir Flow Models
Eric A. Flodin, A. Aydın, Louis J. Durlofsky, Burak Yeten · SPE Annual Technical Conference and Exhibition · 2001
Abstract Faults can act as fluid flow barriers, conduits, or barrier/conduit systems in reservoirs. Their accurate representation in reservoir flow simulations is essential if realistic predictions are to be attained. In this work we compute the effective flow characteristics of faults using fine-scale field-based data. The faults we focus on are in porous aeolian sandstone and were formed by shearing along pre-existing joint zones. To find the bulk flow characteristics of the fault zones, we develop a computationally efficient upscaling methodology that combines numerical flow modeling and power averaging. By analyzing faults with different slip magnitudes, we are able to produce a relationship between fault permeability and fault slip. Slip magnitude is one of the few fault parameters that can be measured remotely in the subsurface and we show how it can be used to estimate the variation in permeability along a fault. We present three different flow simulation scenarios using variable fault properties derived using our new procedure. For each scenario, we present a second fitunedfl case where we replace our variable fault-zone permeability by a fault with a constant permeability and width. In one case, we find no significant difference in flow response between the variable and constant permeability faults. The other two cases display differences, mostly with regard to breakthrough time and liquid production rates. Because the reservoir flows considered here are relatively simple, we postulate that the differences between the variable and constant permeability fault descriptions will become greater for more complex systems.