Constant producing pressure solutions that define declining production rates with time for a naturally fractured reservoir are presented. The solutions for the dimensionless flow rate are based on a model presented by Warren and Root.1  The model was extended to include constant producing pressure in both infinite and finite systems. The results obtained for a finite no-flow outer boundary are new and surprising. It was found that the flow rate shows a rapid decline initially, becomes nearly constant for a period, and then a final decline in rate takes place.

A striking result of the present study is that ignoring the presence of a constant flow rate period in a type-curve match can lead to erroneous estimates of the dimensionless outer radius of a reservoir. An example is presented to illustrate the method of type-curve matching for a naturally fractured system.

Keywords:
drillstem testing, two-porosity system, approximation, permeability, fractured reservoir, type curve, initial decline, upstream oil & gas, flow rate, equation
Subjects:
Drillstem/well testing, Flow in porous media, Formation Evaluation & Management, Pressure transient analysis, Reservoir Fluid Dynamics
Copyright 1981, Society of Petroleum Engineers
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