塔河油田成藏期次的地球化学示踪研究

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

应用油藏地球化学的方法对塔河油田的成藏期次进行了探讨。塔河油田稠油正构烷烃分布完整,但色谱基线不同程度抬升;原油非烃和沥青质碳同位素偏轻,族组成碳同位素发生倒转;原油中普遍含有25-降藿烷。这些特征表明该区油藏经历了至少两期成藏过程,早期充注原油遭受生物降解作用后又受到高成熟原油充注。塔河油田天然气为典型的油型气,成熟度较高,为成熟—过成熟阶段产物,亦显示了两期充注的特征:早期充注的为典型的原油伴生气,充注时间与后期原油的充注时间相同;晚期充注的为高温裂解气,充注方向为自东向西。因此,塔河油田至少存在着3次油气充注过程。

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.