Over the past several months, you may have noticed that gas prices have been relatively stable. Unfortunately, that stability can’t last forever. It is estimated that petroleum (link to product page) is being depleted three times as fast as it is being discovered. With the supply of sweet (low sulfur) light crude oil diminishing, the industry is shifting to heavy sour crude with higher sulfur content in new well sites, and re-evaluating the economics of activating existing wells to meet global demand. A particular concern in refining sour crude is the proportion of heteroatoms (N, S, and O) as they contribute to deposition, catalyst deactivation, equipment corrosion, and storage instability. As a result, oil producers are looking at applying enhanced analytical methodologies to better estimate the economic value of crude oils in exploration and production processes. This rapidly growing field is known as petroleomics.
Characterization of Petroleum
Petroleomics is the characterization (molecular fingerprinting) of petroleum in crude oils and distillates using mass spectrometry. Developments in high resolution mass spectrometry (link to product page) have enhanced our understanding of the chemical composition of crude oils. However, a number of analytical challenges still remain before the technique reaches its full potential. Crude oils include more than 20,000 compounds of varying elemental composition (number of heteroatoms), type (aromatics and aliphatics), and carbon number (extent of alkylation). Identification and chemical composition of crude oil components is still largely unknown. A direct quantitative correlation between ions found in gas phase analysis and all compounds that exist in crude oils is incomplete. In turn, the extent to which the correlation of data can be relied upon as an accurate assessment of crude oil valuation is unclear.
The Role of Biomarkers
A growing imperative to make more informed decisions on the economics of crude oils is driving a need to understand the origin of petroleum. Biomarkers (geochemical fossils found in oils and rock extracts) are used to extract genetic information about the types of organisms contributing to the organic matter in the crude oil and source rock. Biomarkers are structurally similar to specific natural products produced by living organisms, and they typically retain all or most of the carbon skeleton of the original natural product. This means biomarkers can be used to make oil-source rock correlations, such as the age of the oil source rock, the extent of biodegradation, and whether a field is composed of multiple distinct pools of oil or a single large one.
The most important biomarkers known today are hydrocarbons. Their resistance to biodegradation depends largely on their chemical structure. Figure 1 below is of a full scan analysis of terpanes (link to application note), a class of source and maturity biomarkers that are more degradation-resistant to the environment. The chromatogram below displays the distribution of terpanes in the aliphatic hydrocarbon fraction of crude oil sample. Analysis was performed using a DFS high resolution GC-MS (link to product brochure) equipped with an MID detector.
Are you or your lab working with petroleomics? If so, I'd like to hear your thoughts and experiences.