Comparison of Pressure-Transient Response in Intensely and Sparsely Fractured Reservoirs

Abstract

Summary A comprehensive analytical model is presented to quantify the pressure-transient behavior of a naturally fractured reservoir with a continuous matrix-block-size distribution and interporosity skin. Geologically realistic probability density functions of matrix block size are used to represent reservoirs of varying fracture intensity and uniformity. Drawdown and interference type curves are developed with rectangular probability density functions. The results obtained extend previous dual-porosity models by incorporating fracture spacing variability. In the absence of interporosity skin, intensely and sparsely fractured reservoirs show distinctions in the pressure response. Uniformity of a fractured reservoir also significantly affects pressure responses, irrespective of the degree of fracture intensity. The pressure response in a nonuniformly fractured reservoir with large block-size variability, for example, can exhibit a nonfractured (homogeneous) reservoir response. The results may be used to estimate matrix-block-size variability and the degree of fracture intensity from drawdown and interference well tests.