Publications

In this paper, improved models for the analysis of pressure transient tests in naturally fractured reservoirs are proposed. The development of the models was prompted by observations of actual well tests which showed anomalous dope changes during the transition period and where the behavior could not be explained by existing models such as dual porosity models.Consider a system where fractures have homogeneous properties throughout and interact with two groups of separate matrix blocks which have distinclty different permeabilities and porosities. This system reierred here as a ",Triple porosity System",,is in all likelihood a more realistic representation of naturally fractured reservoirs than the traditionally used dual porosity models.Two geometrical configurations that have widely used, namely, the uniformly distributed blocks separated by an orthogonal set of fractures and the horizontal matrix layers separated by fractures are choosen for investigation. Both systems were assumed to be under gradient flow conditions and included were the early time effects of skin and wellbore storage.The unsteady state solution for both systems were semi analitically derived by using the numerical Laplace inverter.Significant observations made from the theoretical predictions are that the fracture-controlled early times and portions of the transition period will resemble the behavior of a dual porosity system. The latter part of transition zone, however, exhibits slope changes, durations of which are a function of XI/% (ratio of interporosity flow coefficients for the two matrix types) and ol/q (ratio of fluid capacitance coefficients).Correlations developed based on numerous sensitivity runs allow one to estimate wl/w2 and Xl/h The recognition of the various matrix properties emphasized in this study will also safeguard againts extrapolation of incorrect late time curves.Some published field data were used to demonstrate of finding reservoir parameters mentioned above and to test the validity of the proposed models.