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西湖凹陷曾发生过大规模的气侵分馏作用,但目前仅局限于定性描述。以平湖构造带孔雀亭气区为研究对象,利用流体包裹体和原油正构烷烃测试等手段,结合该区油气地球化学性质和断裂构造特征,研究了孔雀亭气区气侵条件及主控因素,并讨论了气侵分馏作用对油气藏的影响。结果表明,该区高有机质丰度、生气持续的煤系源岩提供了充足气源,数量众多的断裂发育以及油气充注时间的良好匹配等地质条件,使得孔雀亭气区能够大规模发生气侵分馏作用。气侵分馏定量计算表明研究区各井原油的正构烷烃损失率Q值介于35.3%~97.1%之间,折点碳数介于18~27之间。气源距离和垂向深度共同控制了气侵分馏的强度,而且前者比后者表现出更强力的控制。气侵分馏不仅使得孔雀亭气区各井沿着气侵方向其含气层数和凝析气层数比值逐渐减小,而且导致该区呈现出“上油下气”的垂向分布样式以及低蜡质凝析油与伴生的高蜡质油等复杂原油类型的形成。
West Lake depression has occurred in large-scale gas-intrusion fractionation, but only confined to the qualitative description. Taking the peacock karst area in Pinghu structural belt as the research object, this paper studied the gas invasion conditions and main controlling factors in the peacock kiting area by means of fluid inclusions and crude n-alkanes test, combined with the geochemical characteristics and structural features of the faults in the area. , And discussed the effect of gas invasion and fractionation on the reservoir. The results show that the coal source rocks with high abundance of organic matter and sustained gas generation in the area provide sufficient gas source, numerous fracture development and good matching of oil and gas filling time and other geological conditions, enabling the peacock gas zone to generate large-scale gas Invasion Fractional role. The gas invasion fractionation quantitative calculation shows that the Q value of n-paraffin loss of crude oil in each well of study area ranges from 35.3% to 97.1%, and the carbon number of breakpoints is between 18-27. Gas source distance and vertical depth together control the intensity of gas intrusion fractionation, and the former shows stronger control than the latter. The gas-in-fractionation not only reduces the ratio of gas-bearing and gas-condensing gas layers in each well of the peacock pavilion along the gas invagination direction, but also results in the vertical distribution of the oil-gas in the area Patterns and the formation of complex crude types such as low-wax condensates and associated waxy oils.