Introduction

The material balance equations for each of the four reservoir types defined in were developed. These material balance equations may be used to calculate the production of oil and/or gas as a function of reservoir pressure. The reservoir engineer, however, would like to know the production as a function of time. To learn this, it is necessary to develop a model containing time or some related property, such as flow rate.

The contains a detailed discussion of Darcy’s law as it applies to hydrocarbon reservoirs. The discussion will consider four major influences on fluid flow, their effect on the reservoir fluid, and the manipulation of Darcy’s law to account for these influences. The first major influence is the number of phases present. The will consider only single-phase flow regimes. Subsequent will investigate specific applications of multiphase flow. The second major influence is the compressibility of the fluid. Third is the geometry of the flow system, namely linear, radial, or spherical flow. Fourth is the time dependence of the flow system. Steady state will be considered first, followed by transient, late-transient, and pseudosteady state. The concludes with an introduction to pressure transient testing methods that aid the reservoir engineer in getting information such as average permeability, damage around a wellbore, and drainage area of a particular production well.