A majority of the world's oil and gas reserves are locked in tight, "unconventional", reservoirs. Without the presence of fractures (natural or hydraulic), these tight reservoirs with matrix permeabilities, usually less than 0.1md and porosities between 3-10PU, do not produce commercially. While hydraulic fracturing is widely used to improve the economic viability of wells, and fields to that matter, the presence of natural fractures plays the same role in improving the flow mechanics.

As an industry, there are many tools available which characterize the properties of a created hydraulic fracture from both the predictive and evaluative standpoint. This is important in understanding the impact these properties have in increasing the production from a specific wellbore. Typically, we characterize these hydraulically induced fractures in terms of fracture height, length, width, and conductivity.

These fracture characteristics are estimated using a variety of techniques including, pressure transients, production transients, micro-seismic, and various other techniques. However the ability to fully characterize natural fractures in terms other than pure qualitative (number of fractures observed, open or closed) has been limited in application and often only address conductivity.

Based on case studies from Cambro-Ordovician tight sandstone reservoirs of the Hassi Messaoud field in Algeria, this paper describes methods that can be used to fully characterize natural fractures in terms commonly used for hydraulic fractures. With the application of combined imagery packages along with analyses of both pressure and production transient data, we now have the means to both understand the long-term impact of natural fracturing by associating quantitative properties that characterize both their locally observed (in-well) and far-field properties.

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