The existence of natural fractures and their effects on the wellbore storage vanishing time and the onset of the outer boundary in a tight gas reservoir are examined. The so called pre- and post-fracture test design is used for both linear and radial flow type to investigate the effect of different values of ω and λf on the time needed for the wellbore storage to disappear and for the outer boundary to be reached.
It was found that for a constant hydraulic fracture conductivity, decreasing the ω value causes the wellbore storage to vanish earlier. Conversely, increasing the value of λf, with omega constant, causes the wellbore storage to vanish earlier. These changes have no effect on the time to reach outer boundary, which can be sealed or at constant pressure.
Commercial production from a tight gas reservoir seems to be a function of effectiveness of the natural fractures, and the hydraulic fractures. Applying the concept of dual porosity behaviour to a tight gas reservoir, as opposed to the single porosity behaviour that is considered by several other researchers, seems to be a promising idea for better understanding of these reservoirs.