In many situations, spot sampling provides an economic means by which aliquots of crude oil can be captured from various points in the supply chain for composition, bubble point pressure, density, and sulfur content property analysis. However, inadvertent introduction of N
2 and other gases in sample handling systems during the sampling, transport, and analysis steps can cause difficulties when trying to assess the properties of the parent materials. These difficulties were investigated when compositions of crudes were measured via several analytical methods (ASTM D7169, ASTM D7900, ASTM D8003, GPA 2103, GPA 2177, GOR) on samples obtained from supply chains in North Dakota and Texas using a variety of spot sampling methods/containers (ASTM D3700, GPA 2174, ASTM D8009, ASTM 4057). The N
2 contents were compared to whole oil compositions derived from a tight-line flash gas compositional analysis paired with an Equation of State (EOS) model. The tight-line system was configured so that the pre-conditioning system and analytical equipment were connected directly to the oil process piping in the field. This minimized sample handling and potential for introducing air, and furthermore provided excess volume of oil to purge the pre-conditioning and analytical equipment with parent material. The whole oil compositions resulting from both the spot sampling and tight-line sample collection methods were used as input to a commercially available process simulator to calculate thermophysical properties. The prevalence of N
2 in the spot samples significantly changed calculated thermophysical properties, which can impact process models and classification of materials for transportation.
The Crude Oil Characterization Research Study (funded by US DOE, DOT, and Transport Canada: http://energy.gov/fe/articles/crude-oil-characteristics-research, https://www.theatlantic.com/technology/archive/2018/02/the-great-crude-oil-fireball-test/552029/), seeks to understand the crude oil property differences between conventionally produced and tight oils. Recent activities analyzed the effects of sampling containers/techniques (ASTM D3700, GPA 2174, ASTM D8009, ASTM 4057) and sampling locations (Texas vs. North Dakota) on crude oil thermophysical property measurements. Different compositional measurement techniques (GPA 2103, GPA 2177, ASTM D7900, ASTM D7169, ASTM D8003, GOR flash) have been used to calculate these properties as well, providing insight into the features and limitations of these commercially available methodologies.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.
