Evaluating Fluid Type and GOR in Petroleum Systems Using Headspace Cuttings Gas Data

Headspace cuttings gas data has been recognized as evidence of vertical migration through fine-grained rocks historically thought of as “impermeable”. Therefore, especially in young, cold sedimentary sequences where the mudrocks are well below the thermal stress levels required for significant petroleum generation, headspace gas data are now used to map migration pathways and “fronts”.

When integrated with other available geochemical data, we show that cuttings headspace gas composition and isotope profiles are powerful tools providing important information on the migration style (vertical vs. up-dip migration) providing key data to evaluate charge access and hydrocarbon value. In some cases, where subsurface fluid samples are not collected, and the source rock is not drilled, cuttings headspace gas may be the only geochemical data collected from a well, yet it can provide critical information.

In this paper, we compare headspace gas and flowline data to MDT/DST gas compositional data from several sedimentary basins, including offshore Norway, Nova Scotia, and Gulf of Mexico to demonstrate the application of cuttings headspace gas data. Headspace gas composition and isotopic profiles can be used to directly infer fluid type and GOR. This tool is valuable in both exploration and production.