Chapter 3 - Porosity and Permeability

Abstract

The nature of reservoir rocks containing oil and gas dictates the quantities of fluids trapped within the void space of these rocks, the ability of these fluids to flow through the rocks, and other related physical properties. Undoubtedly, the two most important petrophysical parameters that have dominated the petroleum engineering literature since the first well was drilled are porosity and permeability. Porosity allows us to estimate oil and gas in place and reserves, while permeability makes it possible to determine production rate and predict reservoir performance. This chapter is completely dedicated to identifying rock properties that influence, qualitatively and quantitatively, these two parameters. Several methods for determining permeability are discussed, including core analysis, NMR, and well test analysis. Statistical, as well as analytical, permeability-porosity relationships are investigated. The Kozeny equation and the Leverett J-function are used as the primary tools to develop the theory of flow units and introduce new concepts of the flow zone index (FZI) and reservoir quality index (RQI). Dykstra-Parsons and Lorenz coefficients are used to characterize reservoir heterogeneity. Most concepts are illustrated with numerical examples. Many exercises are included at the end of the chapter.