Properties of Reservoir Fluids

Gas also may appear as a separate phase along with oil. Properties of these fluids are used to determine their amounts in a formation and their fluid flow characteristics. This chapter describes the origin and the common methods for classifying oil and gas resources, introduces keywords and definitions of fluid properties, provides methods for estimating fluid properties, and shows how these properties are measured and used in petroleum engineering. Oils and gases are mixtures of predominantly hydrocarbon molecules with some inorganic molecules, such as nitrogen, carbon dioxide, and hydrogen sulfide. The chapter provides brief definitions and units for many of the fluid properties encountered in the oil and gas industry. It includes examples of correlations for the fluid properties most often needed by petroleum engineers. Examples of correlations for estimating three properties of oils are provided in the chapter: Bubble‐point (BP) pressure, formation volume factor (FVF), and viscosity.