ABSTRACT
Petroleum reservoir fluids are multicomponent mixtures consisting primarily of hydrocarbons. Methane (CH4) is the simplest of all hydrocarbons, and also the most common component in petroleum reservoir fluids. Because methane contains one carbon atom, it is often referred to as C1. Similarly, the term C2 is used for ethane (C2H6), C3 for propane (C3H8), and so on. Hydrocarbons with seven and more carbon atoms are called C7+ components, and the entity of all C7+ components is called the C7+ fraction. Petroleum reservoir fluids may contain hydrocarbons as heavy as C200. A particular C7+ component will belong to one of the following component classes:
Paraffins: A paraffinic compound consists of hydrocarbon segments of the type C, CH, CH2, or CH3. The carbon atoms are connected by single bonds. Paraffins are divided into normal paraffins (n-paraffins) and iso-paraffins (i-paraffins). In an n-paraffin, the carbon atoms form straight chains, whereas an i-paraffin contains at least one side chain. Paraffins are sometimes also referred to as alkanes. Figure 1.1 shows the structure of methane (C1), ethane (C2), and n-hexane (nC6), which are all examples of paraffinic compounds.
