Petroleum Testing - A Comprehensive Guide

From physical characteristics such as viscosity and density to concentration of chemical elements like sulphur content, petroleum testing offers deep insight into the unique properties of crude oil, refined fuels and other petroleum-derived products. As well as physical and chemical properties, petroleum testing is used to determine characteristics such as purity and country of origin.

Testing is the backbone of the oil industry, with producers, refiners and buyers relying on advanced methods to analyse petroleum at the atomic level. Analysis is carried out at all stages of the production process, including upstream, midstream, and downstream operations. Insight helps inform and educate decision makers when determining variables such as cost and suitability for applications.

Petroleum testing is a complex field with a myriad of moving parts. Read on to find out more about the multifaceted industry and the different methods used.

Why is Petroleum Testing Important?

Before we get stuck into the specifics of petroleum testing methods, let’s take a moment to explore why analysis is so important.

• Setting price

The physical and chemical characteristics of petroleum play a major role in determining price. Of all the properties assessed, sulphur content and weight are two of the most important. Light petroleum with low sulphur content is generally considered high quality and is priced accordingly. In comparison, heavier oils with high sulphur content are cheaper and less desirable.

• Sweet vs sour

As mentioned above, chemical characteristics have a big impact on price. Sulphur content is a major concern as high concentrations can impair emission control systems in engines and increase the amount of particulate matter released into the atmosphere. Petroleum with a low-sulphur content is classed as “sweet”. According to the New York Mercantile Exchange, sweet oil must contain less than 0.5% sulphur. Petroleum with high-sulphur content is classed as “sour” and is generally less valuable. For example, West Texas Intermediate (WTI) is classified as a sweet oil with a low percentage of sulphur. This makes it more valuable than oil produced by OPEC, which is generally rich in sulphur and considered sour.

• Determining suitability for engines

A one-size-fits-all approach can’t be applied to engines and heavy machinery. Choosing the wrong type of fuel can not only compromise mechanical efficiency but damage sensitive components and moving parts. Petroleum testing helps decision match the right fuels to engines.

• Maximising mechanical efficiency

Fuel characteristics can have a big impact on the performance of engines and machinery. Advanced testing methods allow operators to scrutinise the chemical and physical properties of petroleum. Data can be used to select fuels that maximise mechanical efficiency and reduce operating costs. A sharp increase in petroleum prices over the past year has made petroleum testing a priority for operators looking to maximise yield and minimise fuel spends.  

• Extending the longevity of components

Choosing fuel with optimal physical and chemical characteristics can significantly extend the longevity of sensitive components in engines and machines.

• Assessing quality of stored fuel

Petroleum is often stored for months before reaching its final destination. Over time, certain characteristics can deteriorate and change the quality and suitability of the oil. Petroleum testing makes it easy to assess the quality of stored fuel and determine condition.

Best-in-class methods from ASTM International

Now we know more about why petroleum testing is important, let’s take a look at some of the different methods used to analyse oil. Around the world, petroleum testing methods published by ASTM International are considered gold-standard. Formerly known as the American Society for Testing and Materials, the organisation publishes technical standards for a myriad of industries, including oil and gas.

Below, we spotlight some of the most widely used ASTM methods:

ASTM D5185-18

Additive elements, contaminants and wear metals can hinder the performance of petroleum products. This is a particular concern for lubricants, which form a protective barrier between moving parts and prevent engines from seizing.  

The ASTM D5185-18 Standard Test Method for Multielement Determination of Used and Unused Lubricating Oils and Base Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) is used to calculate concentrations of contaminants such as calcium, sulphur and zinc in samples. It can be used to analyse both used and unused lubricating oils, as well as base oils. The method relies on a spectral method called Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) to measure the elemental composition of oil.

ASTM D2887-19ae2 

Boiling range distribution is an important parameter used to determine the quality of petroleum. During the refining process it’s used to estimate variables such as potential yield and profitability. The ASTM D2887-19ae2 Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography is used to calculate the boiling range distribution of petroleum products with a maximum boiling point of 538 °C or lower.

ASTM D93-20

Flash point describes the minimum temperature at which enough fluid evaporates from petroleum to create combustible levels of gas. The parameter is used to assess the performance and efficiency of petroleum products, as well as safety. The ASTM D93-20 Standard Test Methods for Flash Point by Pensky-Martens Closed Cup Tester is a useful tool for petroleum analysis. A manual or automatic closed-cup apparatus is used to determine the flash point of petroleum products at temperatures of between 40 °C to 370 °C.

ASTM D287-12b

The Standard Test Method for API Gravity of Crude Petroleum and Petroleum Products (Hydrometer Method) measures how light or heavy petroleum is compared to water. The method was developed by the American Petroleum Institute and is used to determine the density of products, relative to water.

Petroleum with API gravity of more than 10 will float on water and is considered light. High concentrations of light hydrocarbon fractions allow products such as West Texas Intermediate (WTI) to flow freely at room temperature. WTI has a high API gravity, which contributes to its higher price point on commodity markets. This is because oil with high API gravity can be used to make more valuable finished products, such as gasoline.

Petroleum with API gravity of less than 10 will sink and is considered heavy. Examples of heavy petroleum include bitumen extracted from the Athabasca oil sands deposits in Canada. These ultra-heavy oils have an API gravity of around 8, which makes them unsuitable for most Canadian refineries. Instead, the product is sent to heavy-duty refineries in the United States. Hydrometer instruments are used to measure API gravity and assign petroleum products a rating.

Choosing the right petroleum analysis methods

With more than 12,000 technical standards currently available on the ASTM website, industry-specific guides are a helpful way of narrowing down test methods. The Guide to ASTM Test Methods for the Analysis of Petroleum Products, Liquid Fuels, and Lubricants – 3rd Edition written by R.A. Kishore Nadkarni is a valuable tool for any decision maker looking to explore ASTM methods.

“Featuring the essential elements of all standard analytical tests used to characterise petroleum products and lubricants, this book is a useful tool for oil industry researchers, analysts, marketers, and regulators,” reads the guide.

First published in 2000, this latest edition of the guide features more than 130 new petroleum test methods, as well as 75 revised methods. In total, Nadkarni offers short descriptions of more than 600 petroleum testing methods. Each description covers key principles, as well as advantages, limitations and accuracy. Some descriptions also cover equivalent tests from organisations such as the International Organization for Standardisation (ISO), Deutsches Institut für Normung (DIN), Association Française de Normalisation (AFNOR) and Japanese Industrial Standards (JIS).

“The test methods covered involve a variety of analytical techniques to identify and/or quantify over 220 chemical and physical properties of crude oils, gasoline, reformulated gasoline, lubricating oils, additives, transmission fluids, lubricating greases, gear oils, aviation fuels, diesel and heating fuels, petroleum waxes, marine fuels, and other specialty petroleum products,” writes Nadkarni.

Nadkarni stresses that it’s important for laboratory personnel to be well acquainted with all tests available, as well as the unique details and methods associated with each. This includes a good understanding of the advantages, limitations and accuracy of different petroleum testing methods.

“Only by understanding the pros and cons of these tests can both suppliers and customers reach sound conclusions and agree on the appropriate quality and performance of a product,” adds Nadkarni.

Tackling climate change with petroleum testing

Petroleum testing isn’t just about maximising profits. Methods such as the ASTM D2622 Standard Test Method for Sulphur in Petroleum are used to assess concentrations of the chemical element and reduce amounts of harmful pollutants released into the atmosphere.

In a recent article published by UK-based global gas analysis expert Servomex, Karen Gargallo explores how combustion control strategies can be used to slash industrial carbon emissions. Find out more about how the techniques are helping countries reach goals set at events such as the 2021 United Nations Climate Change Conference and COP26 in ‘The role of combustion in decarbonization strategies’.