Naturl fractures are comonly encountered in several Oil Industry related activities: one has to think, for example, to mud losses or lost circulation problems when drilling fractured formations. In the same way the characterization of porosity and permeability is one of the most difficult task when dealing with naturally fractured reservoirs. In fact these properties depend on parameters which cannot be known with direct measurements, such as the geometric characteristics of the single fractures, their density, the extension of the networks they form, etc. Moreover, the conductivity of natural fractures depends on the physical mechanisms whgich govern the flow within them and, during the exploitation of the reservoirs, can diminish due to the increase of the effective stresses which tend to close the fractures. Recently Eni/Agip has presented a methodology which characterizes the conductivity of the open fractures using real time monitoring of mud loss data while drilling. Starting from this previous work, a detailed characterization of single-phase flow within natural fractures has been performed via numerical simulations and analytical models. In particular, the effect of the geometric properties of the fractures (aperture, tortuosity and roughness) on the flow pattern and on the average conductivity have been investigated.
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