What Does Crude Oil Quality Mean?

When liquid petroleum is extracted from the Earth in its raw state, it is referred to as crude oil. Deposits of crude oil are found throughout the world, with much of the world’s oil wealth concentrated in the Middle East and other parts of Asia. The last 12 months have seen several developments in the crude oil market as it relates to this particular market, with prices largely dropping due to a lack of demand.

But while the cost of crude oil fell almost everywhere around the globe as a result of the coronavirus, not all crude oil varieties are priced at the same level. That’s because different samples have different qualities, based upon the specific characteristics of the oil in question, which will have a knock-on effect on their price tag.

Density and sulphur content

The principal ingredient in crude oil is carbon, which can comprise up to 87% of the substance’s overall composition. Hydrogen is another major ingredient, accounting for as much as 15% of the total volume of the oil, while helium, nitrogen, oxygen and sulphur are other naturally occurring components.

What’s more, there are often other chemicals and elements present, such as organic chlorides. These can damage refinery equipment if left unchecked, so must be quantified using ASTM technology. For more information on how this process works, please check out the article Detailed How to Measure Chlorides in Crude Oil by ASTM D4929C & Water Extraction.

The exact concentrations of each of these substances will affect the oil’s density, while its sulphuric content is another chief characteristic that determines its quality. In the industry, an oil’s density is defined as either light or heavy, while its sulphur content is discussed in terms of sweetness or sourness.

How does that affect the price tag?

Generally speaking, the lighter and sweeter a crude oil sample is, the more desirable it is – and therefore the more expensive it is. That’s because oil with a higher API gravity (lower density) and a lower sulphur concentration can be processed using less complex and less costly techniques, which also consume less energy in the process.

That means that they can be converted into the final end product (generally petrol and diesel used in vehicular combustion engines, but also for a variety of other applications) without as much expense. Therefore, lighter, sweeter oils are regarded as having a high quality, which is reflected in their price. Heavier, sourer oils are regarded as being “bottom of the barrel” and sell for less on the international market.