What is the difference between live oil and dead oil ?
Oil can be classified as 'live' or 'dead' depending on the presence or absence of gas (basically CH4) or the volatile hydrocarbons dissolved in the oil.
Crude Oil typically has a carbon chain length ranging from C5 to C20. The gaseous hydrocarbons are mainly methane, ethane, propane, and butane (C1, C2, C3 and C4). The boiling point of methane, ethane, propane and butane are -161°c, -89°c, -42°c, and -0.5°c respectively. What this means is that at standard surface conditions of temperature and pressure (60°F or 15.5°c and 14.7 psi), if the oil is left exposed in an open container, the volatile hydrocarbons will certainly evaporate, simply because 15.5°c (surface) is already too 'hot' for these components of the liquid to remain at rest in the liquid. The intermolecular forces of attraction has already been exceeded and thus they evaporate. The closest neighbour to these volatile components-pentane- has a boiling point of +36°c, meaning that pentane and longer carbon chain components of crude oil remain liquid at surface conditions of 15.5°c, they also remain liquid at room temperature of 25°c.
Imagine a situation where crude oil is placed in a special container, say (PVT cell), then subjected to the original pressure it existed in the reservoir, this pressure is gradually reduced until surface pressure is reached, at this time all the solution gas and volatile components are expected to have been released because of the reduction in the intermolecular forces of attraction existing between the molecules of the crude oil,which happens to be a function of pressure. The oil that remains at this point is actually 'dead' having being stripped of its dissolved gases and other volatile components.
Heavy oil, tar, and bitumen are perfect examples of oil that already exists in 'dead oil' condition. This is because heavy oil, tar and bitumen have little or no gas that may be released on the surface under separator conditions.
Live oil, on the other hand, contains sufficient dissolved gas that may be released from the oil at separator conditions. Examples include normal black oil, near critical oil, high shrinkage oil.
The truth is, at the surface both live and dead oil alike will have no dissolved gas present. Dead oil, therefore, refers to the state of produced crude oil at atmospheric condition.
Typically, when crude oil is produced, at the surface it is passed through one or more separators where the solution gas (C1 and some C2) is separated from the crude oil. Furthermore, the other lighter components (C3, C4 and some C5) may also be stripped off from the crude oil through other means of NGL recovery. C2-C5 are collectively referred to as natural gas liquids (NGLs). The now dead crude oil is then transported through pipelines or tankers to terminals for sales or for further refining.
