Chapter One - Oil and Gas Properties and Correlations

Abstract

Crude oil and gas are naturally occurring mixtures composed of mainly hydrocarbons and small amounts of nonhydrocarbon compounds such as sulfur, oxygen, and nitrogen. Crude oil and gas samples are characterized in petroleum engineering by their different physical properties. The composition of reservoir fluid is known as the most significant factor, which affects its PVT behavior. The phase behavior of the reservoir fluid and reservoir temperature are two important factors; the type of reservoir fluid is determined based on them. Crude oil and gas properties are used in various steps of petroleum engineering in order to evaluate oil and gas reserves, recovery efficiency, production optimization, etc. More particularly, the phase behavior of natural gas should be addressed precisely not only for gas reservoirs, but also for oil reservoirs, due to its substantial role in oil production mechanisms of saturated oil reservoirs. Therefore, an accurate evaluation of reservoir fluid properties is required for prediction of oil and gas production during the life time of a hydrocarbon reservoir. Obviously, the best source for description of properties is laboratory experiments of actual reservoir fluid sample. However, there are many correlations that can be used in lack of experimental data for prediction of oil and gas properties. In this chapter, the most physical and thermodynamic properties of crude oil (oil density, oil gravity, compressibility, bubble point pressure, solution gas ratio, oil formation volume factor, and viscosity) and gas (gas density, gas compressibility, gas formation volume factor, and viscosity) are defined, and the corresponding correlations are presented.