STUDY ON GEOCHEMICAL TRACKING FOR THE PERIODS OF RESERVOIR-FORMING OF OIL AND GAS IN THE TAHE OILFIELD

The geochemical characteristics of oil and natural gas contain a lot of information on organic matter of source rocks,evolution of hydrocarbon generation,hydrocarbon migration direction and hydrocarbon reservoir-forming stages.Based on systematic research of the geochemical characteristics of crude oil and natural gas from the Tahe Oilfield,the reservoir-forming stages of the Tahe Oilfield was discussed.The geochemical characteristics of the crude oils from the Tahe Oilfield are very similar,which imply that the oils are derived from the same source.The characteristics of the oil from the Tahe Oilfield reveal that it had been underwent two oil infilling stages of which the former infilling oil had relative lower maturity and was strongly biodegraded and the later infilling oil had high maturity.The natural gas from the Tahe Oilfield belongs to the typical petroliferous gas with high maturity,which falls into mature to overmature.The geochemical characteristics of natural gas from the Tahe Oilfield reveals that it had two stages of charging.The first was gas associated with crude oil and the second was pyrolysis dry gas.So there at least exists 3 times of hydrocarbon charging in the Tahe Oilfield.