Transient pressure analysis of pressure-dependent naturally fractured reservoirs

This paper presents the results of a study that investigates the effect of the pressure sensitivity of the natural fractures of a fissured formation on the transient pressure analysis of well tests. Two motivations for this study were as follows. First, many (or most in some cases) of the producing reservoirs (geothermal and petroleum) are naturally fractured, showing a stress sensitivity behavior of the fractures. Second, some reservoir simulators consider the option of varying the fractured media properties with the exploitation time. This work discusses a mathematical model for the radial flow of a fluid through a pressure sensitive naturally fractured formation, with pseudosteady state matrix-fracture flow as described by Warren and Root. This model includes the effects of wellbore storage, a finite skin (damage) around the wellbore and high-velocity flow. A finite difference solution for this model is also described. A discussion is also presented regarding the determination of the pressure sensitive characteristics of a producing formation. Simulated and field tests are discussed.