The over-all apparent single-phase permeability of fracture-rock systems was studied using two different two-dimensional models. In a strict sense the results are applicable only to these models, yet may give some insight into real reservoir behavior.The regular fracture-matrix model can have any number of regular fracture sets. All fractures within each set have the same orientation, width and spacing. The gross behavior is analytically equivalent to that of an anisotropic permeable medium.In the heterogeneous fracture systems, individual fracture conductivities vary within a two-dinensional network pattern. A computer program calculates the overall permeability after the conductivities are randomly placed in the network. The calculated permeability depends upon the distribution of these conductivities and the particular fracture pattern into which they are placed.Although detailed information on actual reservoir fracture systems is not available, this study shows how some of the possible variables may affect observed gross reservoir characteristics.

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I Imbibition Model Studies on Water-Wet Carbonate Rocks MARATHON OIL CO, LITTLETON, COLO. ABSTRACT (M recovery by the imbibition rnecbanism can be ,important in fractured carbonate reservoirs with a bottom water drive. Laboratory experiments were performed on water-wet carbonate rocks to model this process. The results are ifiterpreted in light O! the applicable scaling laws. The imbibition production behavior of cr pillar of rock subjected to a slowly rising water table can be synthesized from data on total immersion experiments on small rock samples. !f the rate of water table r[se is SIOW enough and if tbe physical properties are such that the imbibition zone is of a small vertica[ extent, then only the final oil recovery on tbe small samples need be known.Applying laboratory imbibition data to a reul reservoir, should be done with caution because of possible" nettability problems artd the unknown bebavior of two-phase flow in fractures.

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