Abstract
Crude oils and condensates from two sedimentary basins in Northeast Japan were analyzed for steroid and triterpenoid hydrocarbon biomarkers. Based on the biomarker parameters, the following conclusions were drawn concerning their maturities and sources:
(1) The condensates are distinctly more mature than the crude oils. Some crude oils from the Akita-Yamagata basin are more immature than any of the oils from the Niigata basin. The stage of primary migration of petroleum in the former basin was possibly earlier than in the latter.
(2) The source material for the oils from the Niigata basin is more terrigenous than that for the oils from the Akita-Yamagata basin. No systematic difference exists between the source material for the oils and that for the condensates from the Niigata basin.
