Abstract
In tight carbonate and clastic reservoirs, log interpreted saturation is often challenging. Archie derived Sw values involve “a”, “m” and “n” factors which are measured on samples that are quite variable within a core. Nevertheless, typically a constant “a”, “m” and “n” factor values are assumed for saturation measurements for the whole reservoir section or for a given rock type of a reservoir section which may still yield inaccurate hydrocarbon saturation having an impact on volume estimation among others. We propose an alternative solution that is real time, cost-effective and provides high confidence sweet spot identification for the selection of perforation zones in a vertical well and plugging of high water saturation zones in a horizontal well. The modified pyrolysis technique we present here and term “Sh_Pyroil” can provide high confidence direct hydrocarbon saturation rapidly (3 minutes) at a very low cost. Sh_Pyroil, measured in miligram HC per gram of rock weight (mg HC/g rock), can be conveniently converted into hydrocarbon saturation in percentage. We used modified pyrolysis on 90 core plugs, at one foot interval, from the dense and oil bearing zones. The objective of this study was to compare the thermally extracted core hydrocarbon saturation “Sh_Pyroil” to the log derived (Archie) saturation in order to assess its applicability as a rapid, cost-effective and high confidence direct hydrocarbon saturation tool that can assist in:
Time sensitive drilling and completion decisions (e.g. selection of optimal perforation zones and plugging of high water saturation zones),
Keeping the horizontal well in sweet spots and,
In-Place hydrocarbon volume estimations, in conventional and unconventional reservoirs.
