Salting-out of Organics from Oilfield Brines to Supercritical Carbon Dioxide: Validating the Use of Setschenow Constants for Modeling Partitioning Behavior
EMSL Project ID
47864
Abstract
The partitioning of organic compounds from brines to supercritical carbon dioxide (sc-CO2) in depleted oil reservoirs is one of the targets of research by the Department of Energy’s National Risk Assessment Partnership (NRAP); which is assessing the risks associated with the injection of CO2 into geologic formations for utilization and storage. In regards to organic compound mobility, this risk assessment requires partitioning coefficients from brines to sc-CO2. These partitioning coefficients for compounds of interest, such as polycyclic aromatic hydrocarbons (PAHs), vary over temperature, pressure, and brine composition (TPX) and therefore will require thousands of data points to develop appropriate equations of state for predicting partitioning. The objective of the experiments at PNNL and EMSL is to validate whether existing Setschenow constants can be used to predict the salting-out effect of organic compounds from brines to sc-CO2 over the TPX range of interest. If Setschenow constants are valid, they will reduce the number of experiments needed to predict risk associated with organic compound mobility. These experiments will measure the partitioning coefficients of selected PAHs, nitrogen-containing organics and organosulfur compounds over a TPX range. PNNL and EMSL have developed a specialized apparatus that allows for in-situ online and simultaneous measurements of the organic compounds in the sc-CO2 and aqueous phases by Near Infrared Spectroscopy (NIRS) and UV detection. This apparatus, which is only available at PNNL and EMSL, will provide for the most accurate measurements of the organics in each phase. The partitioning coefficients measured through these experiments will be compared to partitioning coefficients predicted by the Setschenow constants using the partitioning coefficient measured with no salt content. If Setschenow constants are valid, in addition to saving time and resources, they can be incorporated into an existing linear solvation energy relationship (LSER), which predicts the partitioning coefficients of organic compounds between water (no electrolytes) and sc-CO2. The data from these experiments and modeling efforts can be incorporated into comprehensive risk assessment models used by NRAP.Project Details
Start Date
2013-10-01
End Date
2014-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Bryce D A,Shao H ,Cantrell K J,Thompson C J 2016. "Determination of Organic Partitioning Coefficients in Water-Supercritical CO2 Systems by Simultaneous In Situ UV and Near-Infrared Spectroscopies" Environmental Science & Technology
Burant A S,Thompson C J,Lowry G ,Karamalidis A 2016. "New Linear Partitioning Models based on Experimental Water – Supercritical CO2 Partitioning Data of Selected Organic Compounds" Environmental Science & Technology