DISSOLVED ORGANIC CARBON IN PRODUCED WATER: TRACING CHEMICAL COMPONENTS WITH CARBON ISOTOPIC ANALYSIS BY CAVITY RING-DOWN SPECTROSCOPY

We describe the performance and limitations of a method for the dissolved organic carbon isotopic analysis in saline waters via wet chemical oxidation and cavity ring-down spectroscopy. his work evaluates the effectiveness of silver ion exchange cartridges for pretreatment of samples and the inclusion of a carbon oxidation module following the wet chemical oxidation step. This described method is appropriate for WCO-CRDS analysis for samples greater than seawater salinity and we evaluate the performance on samples from 0 to 10 wt% chloride (equivalent to 5.6x seawater). Our results suggest that this WCO-C-CRDS technique adequately resolves natural abundance measurements of carbon isotopes in brines and seawater. In addition, following a single 50% dilution of seawater we estimate that this method can analyze seawater directly with minimal isotopic effects of the chloride interference given approximately 22.5 μg of carbon (equivalent to 2.5mg/L in a 9mL seawater salinity sample). In addition, we have performed a suite of isotopic analyses on industrywide common chemical additives to production fluids and flowback waters and demonstrate the carbon isotope mixing curves that might be useful to identify and trace produced waters in groud and surface waters.