Determining the presence or absence of hydrocarbons in an area is an easy process. But when attributing the source of hydrocarbon contamination is critical, standard testing methods can fall short.
Whether faced with a possible accidental release or simply monitoring the impact of operations, source attribution is important for oil and gas developers. It’s not enough to know that hydrocarbons are present. In order to determine responsibility and liability, companies need to be able to determine whether the hydrocarbons come from their operations, those of a competitor or simply from natural sources.
See chart for more information on EPA standard methods and their limitations.
The Limitations of EPA Required Testing
The Environmental Protection Agency (EPA) has outlined specific required tests for oil and gas developers and operators. These minimum testing requirements are geared towards safety and environmental compliance, with a goal of determining whether toxic substances are present and in what quantities. They are generalized testing requirements that have not been optimized for hydrocarbons specifically; the tests simply allow the EPA to determine whether contaminants in an area present risks for human health and safety or for the environment. Designed to support compliance with the Resource Conservation and Recovery Act (RCRA), the battery of required tests are applied to all hazardous wastes, including wastewater and sludge from a variety of industrial processes.
When it comes to source attribution for the oil and gas industry, these tests have significant limitations. First and foremost, they were not designed specifically for hydrocarbon chemistry. While they are useful for initial screening, they miss some of the most abundant (and toxic) components of petroleum products. As a result, these tests are often subject to false positives or negatives and lack valuable quantitative information.
Secondly, they provide little or no diagnostic source identification. They simply do not have the precision and level of detail necessary to accurately determine what type of product is present (e.g. heavy crude vs. light crude vs. heavy fuel oil) or characterize the exact chemical makeup of a sample. This means that they are subject to interference from naturally occurring hydrocarbons and are not able to distinguish between petroleum products originating from different sources.
Analysis for Accurate Source Identification
These distinctions become critical in the case of forensic investigations. Crude oils and refined petroleum products are complex mixtures that can contain hundreds or thousands of organic compounds. Each petroleum product will have its own unique chemical “fingerprint” depending on its exact composition, meaning that physical and chemical properties of oil from the North Slope can be very different from oil from the Gulf of Mexico. Refining methods and chemical additives lead to even more chemical differentiation between finished products.
Petroleum chemists quantify the presence of hydrocarbon chains of different lengths as well as key biomarkers, polycyclic aromatic hydrocarbons, and other chemicals and additives in order to develop a fingerprint for a specific sample. Chemists can compare the fingerprints of different samples for highly accurate product identification and differentiation. This allows them to determine appropriate source attribution and model the fate and transport of different petroleum products in the environment.
Source attribution must also take factors such as weathering, water-washing and biodegradation into account when comparing fresh samples from a source to samples collected from the environment. An understanding of how hydrocarbons weather and degrade over time and under different conditions is necessary for accurate product comparison and attribution.
Selecting the Right Tests for Forensic Investigation
Determining which tests are required for a particular project requires an in-depth understanding of petroleum chemistry. There is no “one size fits all” analytical method that is universally appropriate for all types of crude oils and refined products. The mix of analytical methods used will depend on the types of contaminants present (e.g., light distillates vs. heavy crudes) and the ultimate goals of the investigation. In cases where the types of hydrocarbon compounds present are unknown, a tiered approach that starts with basic screening before moving into more sophisticated tests may be the most cost-effective way to discover or eliminate potential contaminants from consideration.
For spill response and forensic investigations, companies need highly accurate and defensible data. Battelle has developed modified methods that improve the accuracy and precision of EPA required tests for hydrocarbon forensics. These methods are specific to petroleum chemistry and address the limitations of the standard EPA methods. Petroleum chemists at Battelle work with oil & gas customers to develop a testing protocol that meets the specific needs of the investigation.
Many companies waste time and resources by engaging in analytical tests that will not meet their ultimate needs and requirements. By understanding the strengths and limitations of different analytical methods, and selecting the right methods to meet their goals from the start, companies can control costs and speed up investigation time.