Cracking crude's tantalizing secrets

Inside Aramco’s crude assay characterization


  • A crude oil assay is an extensive chemical analysis
  • Knowing chemical intricacies help prevent environmental issues
  • Exceptional Arabian crude oil has high gravity scales and low upstream carbon intensity

Janet E. Pinheiro |


No two samples of crude oil are identical. Similar to how every sand grain is different, each crude oil type has its own exclusive chemical and molecular characteristics.

Oil and gas reservoirs — just like desert winds move and shape sand dunes — impulsively alter the composition of their fluids. The process of unlocking oil’s tempestuous mysteries is known as a “crude oil assay.”


Preventing environmental
issues with knowledge

A crude oil assay is the chemical evaluation of crude oil feedstocks by petroleum testing labs. Understanding crude oil’s intricacies helps prevent yield, quality, and more importantly, environmental issues.

The assay reveals extensive hydrocarbon analysis for refiners, oil traders, and producers. Its data helps refiners determine if an oil feedstock is suitable for a particular refinery.

Under production, hydrocarbons are fickle. Discovering crude oil’s composition secrets is also fundamental work toward maintaining oil and gas production value chains. 

Hydrocarbons may be sweet one day, and the next day sour with sulfur. Or, they may emulsify, and block the flow in a pipeline.

Aramco’s crude assay is a detailed analysis of a crude oil sample used to market Arabian oils to the market.

Cutting out crude’s secrets

For decades, Aramco’s science labs have cut precisely into the deep secrets of Arabian oils. About every six weeks, from any one of Aramco’s reservoirs, 15 liters of oil arrives at the Aramco Research and Development Center in the company’s Dhahran headquarters.

Within the center’s walls, Technical Services Division (TSD) scientists test the lustrous liquid’s tantalizing characteristics. Testing commences inside the second-floor distillation lab, where the crude oil is poured into a fractional distiller — akin to a miniature processing and refining facility.

Techniques like gravity, heat, and cooling, see the distiller meticulously separate the dynamic oil into various hydrocarbon products, known as fractions. Included in up to 13 cut fractions is gasoline, diesel, kerosene, and bitumen.

Within the Research and Development Center at Aramco’s Dhahran headquarters, scientists evaluate crude oil feedstocks to help prevent yield, quality, and more importantly, environmental issues.

Marketing Arabian oils to
the world

Turn the handles on the long corridor of doors adjacent to the distillation lab, and behind each door is an imposing purpose-built testing lab to test each fraction. Every lab treats its fraction to extensive methodical analysis of its exclusive molecular, physical, and chemical characteristics.

Collectively, the results build Aramco’s comprehensive crude assay — the all-important intricate chemical analysis relied upon for marketing crude oil. TSD Crude and Product Characterization unit supervisor Amani H. Musharah explains that assay data determines a feedstock’s use, “Feedstock assay data is important for decision making about the refining process.”


“Using the wrong feedstock in a particular refinery can cause production, quality, and environmental problems.”

Amani H. Musharah, Aramco Crude and Product Characterization unit supervisor

Musharah says products ordered by customers need to meet their needs, “Using the wrong feedstock in a particular refinery can cause production, quality, and environmental problems.”



Low upstream carbon intensity

Aramco, with a history dating back to 1933, is one of the world’s largest integrated energy and chemicals companies. Its upstream operations are based in the Kingdom of Saudi Arabia.

The Kingdom has a small number of large and productive oil reservoirs, low per barrel gas flaring rates and low water production. This results in less mass lifted per unit of oil produced, and less energy used for fluid separation, handling, treatment, and reinjection.

All of which contribute to Aramco having one of the lowest upstream carbon intensities in the industry. For 2020, the upstream carbon intensity of Aramco’s domestic wholly owned and operated assets was 10.5 kilograms of carbon dioxide equivalent per barrel of oil equivalent.

Five Arabian crude oil grades

Aramco produces some of the world’s finest crude oils — Arabian Heavy, Arabian Medium, Arabian Light, Arabian Extra Light, and Arabian Super Light. All Arabian grades, including the wide range of blends produced from them, are highly compatible with most refineries globally.

Five Arabian crude oil grades

Arabian crude oils, with their high gravity scales and low upstream carbon intensity, are an exceptional product.

The largest determinant of crude oil market value is gravity.

Higher gravity — a lighter hydrocarbon liquid — is worth more as it enables production of a greater percentage of high-margin products.

The “lights” are the star products, with Arabian Super Light, Arabian Extra Light and Arabian Light accounting for approximately 69% of the total Aramco crude oil production in 2020.