Advanced Analytical Tools for Fingerprinting, Production Allocation, & Improved/Enhanced Oil Recovery Monitoring

Abstract

Demands are being placed on service companies to provide non-evasive analytical solutions that measure the contribution of individual hydrocarbon streams in a commingled system. This often involves being able to differentiate fluids which have similar compositions. An advanced analytical workflow has been developed which includes chromatographic techniques along with a suite of stable isotope ratio analyses that look at unique Natural Tracers/Markers in individual hydrocarbon or brine streams. This paper will look at how the Natural Tracer methodology can be applied to fingerprinting, production allocation and IOR/EOR projects. A variety of laboratory-based techniques were used to evaluate end member fluids, commingled fluids, and various synthetic blends. Gaseous streams were analyzed using compound specific stable isotope ratio mass spectrometry systems (CS-IRMS) looking at carbon and hydrogen isotopes of the carbon dioxide, methane, ethane, etc. present. Aqueous streams were analyzed using a combination of conventional physiochemical (complete water) and water oxygen and hydrogen stable isotope analysis. Liquid hydrocarbon systems were assessed using conventional high-resolution gas chromatography and 2-dimentional gas chromatography (GCxGC). Analysis of the data includes simple plots to visualize differences between fluid sources and a linear regression analysis to look at the mixing relationships between synthetic blends and commingled field samples. The advanced analytical workflow allowed for the allocation determination of hydrocarbon systems with both similar and contrasting compositions. The GCxGC method, for hydrocarbon liquids, allows for a higher resolution separation where a single peak using conventional gas chromatography can be composed of multiple types of compounds. In this instance the conventional GC and GCxGC yielded comparable allocation results. For gas phase allocation, using carbon and hydrogen isotope ratios (δ13C and δ2H) of methane and ethane yielded linear mixing relationships in the two-production systems that were analyzed. Allocation values were successfully calculated for these binary systems with an outlying datapoint resulting in the client initiating an investigation to confirm flow meter readings. For an IOR/EOR application, the δ13C of methane show sufficient contrast between injected and produced gases that were sampled from a variety of wells. In this instance the gas molar compositions were similar so the only means to identify injection gas breakthrough in producing wells was by the CS-IRMS analysis technique. Complete physiochemical and water isotope ratio (δ18O and δ2H) analysis also show contrasting signatures between injection and produced water. An advanced analytic workflow was developed to incorporate commercially available, non-evasive techniques to production allocation and IOR/EOR projects. For production allocation, this technique will not replace traditional metering but can be used as a tool to identify problems with the metering/monitoring systems in the field.