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天然气组分、碳同位素组成以及气藏储层固体沥青的热变质成因,都说明飞仙关组古油藏确曾存在并发生了裂解,天然气主要为原油裂解气。通过高压封闭体系下的原油热裂解模拟实验,从气态烃组分及产率变化、焦沥青的生成等方面探讨了原油裂解生气特征。结合川东北地区飞仙关组的埋藏史、古地温史、构造演化等地质因素,将实验结果外推至地质条件下,建立了古油藏原油裂解生气的动力学地质模型,指出鲕滩天然气藏的形成经历了古油藏、古气藏和气藏调整定型3个演化阶段。通过动力学计算定量恢复了古油藏裂解生气的成藏过程,揭示出在不同地质年代和地质温度下甲烷(C1)、总烃类气体(C1-5)和焦沥青等原油裂解产物的转化率的变化。取得的动力学地质模型对古油藏原油裂解型天然气的成藏研究具有重要的实用价值。
The composition of natural gas, carbon isotope composition and thermal metamorphism of solid bitumen in gas reservoirs all indicate that the ancient reservoirs of Feixianguan indeed existed and had been cracked, and the natural gas was mainly cracked gas of crude oil. Through the simulation experiment of thermal cracking of crude oil under high pressure closed system, the characteristics of cracked gas generation from crude oil were discussed from the aspects of the composition and yield of gaseous hydrocarbon, the formation of pyrophoric pitch. Combining with the geological factors such as burial history, paleo-geotemperature history and tectonic evolution of Feixianguan Formation in northeastern Sichuan, the experimental results are extrapolated to geological conditions, and a dynamic geological model of pyrolysis of crude oil in ancient reservoirs is established. It is pointed out that oolitic natural gas The formation of the Tibetan reservoir experienced three evolution stages of the ancient reservoir, the ancient gas reservoir and the gas reservoir. The kinetic calculations quantitatively restored the gas accumulation process of paleo-oil cracking and revealed the transformation of crude oil cracking products such as methane (C1), total hydrocarbon gas (C1-5) and pyrophyllite at different geological ages and geologic temperatures Rate changes. The obtained dynamic geological model has important practical value for the study of hydrocarbon accumulation of crude oil cracked natural gas.