A US Department of Energy report found gaps in important crude oil characterization data, uncertainty about how to best sample and analyze crude to ensure its properties are determined accurately, and deficiencies in understanding how a crude’s properties affect its potential to accidentally ignite, combust, and explode.
The Sandia National Laboratories report, Literature Survey of Crude Oil Properties Relevant to Handling and Fire Safety in Transport, recommended that subsequent efforts develop a sampling and analysis plan to close gaps in knowledge of tight crude oil properties.
It also called for an experimental plan to numerically model combustion events and testing from small to large scale to obtain hazard evaluation data.
“The report confirms that while crude composition matters, no single chemical or physical variable—be it flash point, boiling point, ignition temperature, vapor pressure, or the circumstances of an accident—has been proven to act as the sole variable to define the probability or severity of a combustion event,” said Paula Gant, deputy assistant US energy secretary for oil and gas.
“All variables matter,” she said in a Mar. 24 blog posted at DOE’s Fossil Energy Office web site.
In its executive summary, the report said that its key findings included:
• Available data are not of sufficient quality to allow crude oils to be comparable meaningfully—either to each other or against a designated standard—because criteria and procedures used to select, acquire, and analyze crude samples vary significantly.
• Variability also may be introduced through crude conditioning, storage, and transport.
• Current methods to assign crude oil transportation hazard classification and packing group often are inadequate.
• Relationships between crude properties and probability or severity of combustion events in rail car spill scenarios have not been established.
• General lack of uniformity in methods and [quality assurance versus quality control procedures] across industry makes comparison of crude oil vapor pressure difficult.
• Bakken crude is a light, sweet grade which exhibits a statistically higher true vapor pressure than the slightly heavier, blended sweet and sour crudes which are stored at the US Strategic Petroleum Reserve.
• Numerous combustion events can occur from an accident involving hydrocarbons and hydrocarbon mixtures including crude oils, with severity dependent on the amount of fuel involved, surrounding infrastructure, and environment.
• No single parameter defines a fuel’s degree of flammability. Multiple parameters are relevant.
“The report represents the most comprehensive survey of existing, publicly held data and analysis on the chemical and physical properties of tight crude oils completed to date,” Gant said. “This survey helps to inform understanding of these characteristics, and in doing so provide context for ongoing efforts to ensure the safety of crude oil transport.”
An American Petroleum Institute official said the report shows the need to focus more on preventing train derailments as part of a holistic approach to making shipping crude by rail safer. “[DOE] found no data showing correlation between crude oil properties and the likelihood or severity of a fire caused by a derailment,” said Robin Rorick, API midstream director.
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