Basics of Oil and Gas Flow in Reservoirs

Abstract

This chapter deals with basic concepts of oil and gas flow in porous media. In the first section (oil flow), the basics of oil flow in porous media and different flow equations, including viscous, Darcy, and Brinkman flow are introduced. Then, based on a new work the boundary between these kinds of flow are reported. Then, the well-known diffusivity equation, combination of continuity equation and Darcy velocity, is introduced. The relative permeability as an important concept in two-phase flow through porous media is described as well. After that, the forces affecting oil flow in porous media are introduced as well as different dimensionless numbers which reflect the relative importance of forces during oil flow. The gas flow through porous reservoir can occur as single or multiphase. A second phase releases as a result of pressure decline in reservoir and starts flowing when its saturation exceeds a minimum value, known as critical saturation. At these conditions, the relative permeability concept applies to take into account the multiphase flow. Also, the classic Darcy’s law equation for flow in porous media may fail in certain flowing conditions, and the non-Darcy flow equations need to be studied and applied for proper modelling of gas flow in porous medium. In addition, the role of wettability alteration on production enhancement of gas condensate reservoirs is a novel approach in gas reservoir performance. Also, the active forces during CO2 storage and the challenges of gas flow in unconventional gas reservoirs are two important subjects. These subjects will be covered in the second section (gas flow) of this chapter.