oa Unexpected 2H-CSIA Signals in a Mature Petroleum System – Unlocking New Fluid Insights?

The large relative mass difference between deuterium and protium explains why the variability in d2H values of long chain hydrocarbons is much larger than variability observed in the d13C values of the respective compounds. As such, 2H-compound specific isotope analysis (CSIA) of hydrocarbons is a potential powerful tool to deconvolute complex petroleum systems. However, to date this technology is not as widely applied to petroleum system analysis as 13C-CSIA. In part this could be due to the analyses being technically more challenging than for d13C, but also to the difficulty in explaining d2H data derived from petroleum hydrocarbons, e.g., what degree, if any, of hydrogen exchange occurs between water and oil during generation, migration and/or reservoir entrapment? In this study the 2H-CSIA data of fluids from various petroleum systems with differing source, maturity and biodegradation levels, as well as d2H values of several associated reservoir water samples, have been analysed. Furthermore, the technology has been applied to oils from different fields with the same source and compared to other geochemical data types to determine what additional information 2H-CSIA may provide. This includes improved insights into the petroleum system and/or possible value as additional reservoir geochemical fingerprinting tool.