Abstract
Thirty-two crude oils from five oil fields in the Kosei area, Akita Prefecture, can be classified into five groups based on their API gravity, sulfur content, sulfur isotopic composition and V/Ni ratio. These geochemical characteristics offer important constraints on petroleum migration and accumulation in the area, because they reflect maturity and depositional oxic/anoxic condition of source rock, migration processes, biodegradation and so on.
This study suggests that both sulfur isotopic composition and V/Ni ratio are useful oil classification parameters.
