The objective of this study is to delineate the characteristics of a well flowing at a constant pressure in a naturally fractured reservoir. Methods are suggested to determine system parameters. We consider both pseudosteady state and unsteady state fluid transfer from the matrix system to the fracture system. If pseudo steady state flow governs the transfer of fluids, then the rate data exhibit an initial period of decline indicating the depletion of the fracture, followed by a period in which the rate is nearly constant and finally a rapid decline in rate. The period of constant rate reflects replenishment of the fracture by the matrix. If unsteady state flow in the matrix governs the well response, then the constant rate period does not exist. Instead, the rate vs. time graph is a straight line on log-log coordinates with slope equal to 0.5. That is, a linear period is evident. This characteristic response is evident in all the unsteady state flow models discussed in the literature. Thus, it is possible to determine the flow regime in the matrix by analyzing rate data.

The flow periods described above will be evident if αkm/kf ≤ C/A. Here,k is the permeability, A is the drainage area, α is a parameter which depends on the characteristic length of the matrix element (block) and C is a constant which also depends on the shape of the matrix element. The symbols m and f represent the matrix and fracture, respectively.

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