塔里木盆地顺北油田油气来源研究

基于塔里木盆地顺北地区原油和天然气样品的地球化学特征分析,研究了顺北地区奥陶系中下统油气来源。通过饱和烃色谱及饱和烃、芳烃色谱—质谱、全油及族组分碳同位素检测,发现原油样品中C23三环萜烷占优势,伽马蜡烷含量低,C27-C28-C29ααα20R规则甾烷表现为不规则的"V"字形分布,规则甾烷相对重排甾烷含量高,原油碳同位素偏轻,与柯坪露头及孔探1井等下寒武统烃源岩有很好的亲缘性;天然气δ13C1值为-50.7‰^-44.7‰,天然气δ13C2值为-36.1‰^-33.1‰,干燥系数为0.520~0.883,为原油伴生气,油气同源,判断顺北油田油气主要来源于下寒武统烃源岩。通过已钻井岩相、沉积相和全盆地地震相资料,预测下寒武统烃源岩在塔里木盆地广泛分布,厚度在30 m左右,有机碳含量高,生烃潜力大,具有长期生烃、多期供烃的特点,能提供充足的油气资源,是塔里木盆地台盆区最主要的烃源岩。

Oil and gas sources in Shunbei Oilfield,Tarim Basin

The hydrocarbon sources in the Middle and Lower Ordovician in the Shunbei area of the Tarim Basin were studied based on the geochemical characteristics of oil and gas samples. The saturated hydrocarbon gas chromatography, mass spectrometry of crude oil and natural gas, and the carbon isotope distribution of whole oil and group components were used. The C₂₃ tricyclic terpane is dominant in crude oil samples from the Shunbei area, with a low content of gammacerane. The C₂₇-C₂₈-C₂₉ααα20R regular steranes show an irregular "V" shape distribution. The regular steranes account for a larger amount than the rearranged steranes, and the carbon isotope of the crude oils is light. The geochemical characteristics of crude oil samples from the Middle and Lower Ordovician in the Shunbei area have a good affinity with those from the Lower Cambrian in the Keping outcrop and the well KT1. The δ13C₁ and δ13C₂ values of natural gas samples are -50.7‰ to -44.7‰ and -36.1‰ to -33.1‰, respectively. The gas dryness coefficient ranges from 0.520 to 0.883. The oil and natural gas in the Shunbei Oilfield have the same source, that is, the Lower Cambrian source rocks. The distribution of source rocks in the Lower Cambrian of the Tarim Basin was predicted by means of drilled lithofacies, sedimentary facies and seismic facies of the whole basin. The source rocks are about 30 m thick. They have a high TOC content and show a great hydrocarbon generation potential. They have experienced a long term of hydrocarbon generation and multiple stages of hydrocarbon supply, providing significant oil and gas resources for the Tarim Basin.