In-situ API gravity prediction using polars
Predicting API gravity ahead of drilling especially in unconventional settings is still a challenge because produced fluids are highly fractionated with respect to the dispersed in-situ fluids. Because the NSO-fraction (resins and asphaltenes) is preferentially retained during expulsion it plays a crucial role in governing in-source fluids physical properties.
We rapidly assess in-situ and produced fluids API gravity using targeted NSO-compounds of bitumen extracts or pyrolysates detected by ultra-high resolution mass spectrometry (FT-ICR MS). Momentarily, a heavy over medium molecular weight cut ratio of N-containing compounds from the carbazoles family works best for siliciclastic, marine source rocks, whereas calculated API values of extracted bitumen directly resemble API values of fluids produced from unconventional plays. Pyrolysate APIs are inbetween conventional and unconventional oils sourced from a given rock and can be used for tuning.
Due to the relative novelty of the overall approach, calibration of predicted and encountered field APIs is not yet fully completed and optimisation ongoing.
We rapidly provide API values which wil be encountered during production.
Full geochemical screening is offered in order to select key areas and key samples for regional or prospect scale evaluations.