Compositional analysis generally refers to the measurement of the distribution of hydrocarbons and other components
present in oil and gas samples. Using modern chromatography techniques samples are analyzed to determine the
breakdown of the components in the sample. The analysis can be used to determine the value of a sales gas, it
can be calculated to determine emissions. Compositional analysis can be used to assess the quality of samples,
it can also help determine resevoir continuty and investigate leakage.
The composition of the gas and oil samples taken from a surface separator can be used as a quality check. Once
the compositions of the separator products are determined, the K-values of those equilibrium products are calculated
The values, when plotted alongside theoretical values based on separator conditions, help reinforce
the confidence of the validity of the samples.
Drilling Mud Contamination
A sample of circulated oil-base mud is squeezed in a mud press and the collected filtrate is
also injected onto a gas chromatograph column to be used as a reference.
Once both the reservoir
fluid and oil-base compositions have been determined, the resulting molar compositions are input
into proprietary software that determines the level of contamination of oil-base mud in the stock tank liquid.
In some cases there is a need to profile or "fingerprint" a petroleum sample to determine whether
two hydrocarbons have come from a common source.
This technique can also be used to check for lubricants and other refined products.
Another specialized chromatography analysis is the C60 paraffin analysis. This analysis is used to determine
the distribution of the paraffin components of a hydrocarbon system. A sample of stock tank liquid is injected
onto a capillary column of a high temperature chromatograph and the normal paraffin components from Heptadecanes
(C17) through Pentacontanes (C60) are identified and quantified.
Distillation, or volatility characteristics, of petroleum products are an indication of their
performance in their intended applications.
Petroleum product specifications generally include
distillation limits to assure products of suitable volatility performance