A New Model for Pressure Transient Analysis in Stress Sensitive Naturally Fractured Reservoirs

Abstract

ABSTRACT The most commonly used methods to describe the transient flow behavior in porous media are based on the assumption of constant rock properties. Nevertheless, these methods are not strictly applicable to reservoirs that undergo changes in the rock properties due to variation in pore pressure. A frequent characteristic of fractured reservoirs is sensitivity of permeability and porosity to effective stress. This paper presents a new analytical model, for interpreting pressure transient test. The model considers the flow in a naturally fractured stress sensitive reservoir, that is to say, the dependency of rock properties on pressure is established (dependency of permeability on pore pressure is measured by the permeability modulus parameter), and makes that the flow equation be strongly non linear. Likewise, the theory is developed under unsteady- state or pseudosteady-state conditions, and considers that the fracture is uniformly distributed, matrix geometry is the so called stratum and flow contribution from the matrix to the fracture is described by the term source proposed by De Swaan. The problem stated is solved through an analytical approach for different boundary conditions and different permeability modulus values, thus obtaining type curves that can be used for the analysis of pressure buildup and drawdown tests.