塔里木盆地库车坳陷中、新生界高蜡凝析油和轻质油形成及其控制因素

大量的原油样品数据表明库车坳陷中、新生界凝析油和轻质油以高含蜡为特征，结合前人的研究成果和现有资料对库车坳陷高蜡凝析油和轻质油的成因和控制因素进行了分析。分析结果表明，烃源岩有机显微组分中部分壳质组和腐泥组形成了高蜡油，镜质组形成了凝析油和轻质油，三者共同决定了库车坳陷高蜡凝析油和轻质油的形成。原油含蜡量主要受3个因素控制：原油成熟度、油气藏类型、气洗作用和原油运移作用。原油成熟度为主要控制因素，库车坳陷原油是烃源岩在成熟阶段下热演化生成的，原油成熟度R_o介于0.8%~1.05%，总体表现为高含蜡的特征，且原油含蜡量随原油成熟度增加而降低；油气藏类型为次要控制因素，干气藏原油含蜡量小于5%，凝析油含量低的凝析气藏原油含蜡量介于5%~10%，凝析油含量高的凝析气藏和油藏原油含蜡量大于10%，且原油含蜡量随生产气/油比对数的减小而增加；气洗作用和原油运移作用影响最小，相同油源条件下，原油受气洗程度越强，原油含蜡量越低，原油运移距离越大，原油含蜡量也越低。

Origin and controlling factors of Mesozoic-Cenozoic gas condensates with high wax content and high-gravity oil in Kuqa Depression

The analysis of a large number of oil samples demonstrates that the Mesozoic-Cenozoic gas condensates and high-gravity oil in Kuqa Depression feature a high wax content.The study discusses the origin and controlling factors of gas condensates with high wax content and high gravity oil in Kuqa Depression based on previous research and available data.The results show that some exinite and sapropelinite of the organic macerals in source rocks are turned into oil with high wax content,whilst vitrinite of the organic macerals produces gas condensates and high-gravity oil.These organic macerals determine the production of gas condensates with a high wax content and high-gravity oil in Kuqa Depression.The wax content in crudes is mainly controlled by three factors: oil maturity,hydrocarbon reservoir type,gas washing and oil migration.Among them,the oil maturity is predominant.The oil in Kuqa Depression is generated by thermal evolution of source rocks during its mature stage,with oil maturity R_o ranging between 0.8%-1.05%,while the crudes as a whole are characterized by a high wax content,and the wax content in crudes decreases with increasing oil maturity.Besides,the hydrocarbon reservoir type plays a secondary role.The wax content of crudes is less than 5% in dry gas reservoirs,ranges between 5%-10% in condensate gas reservoirs with low gas condensates,while is more than 10% in condensate gas reservoirs with high content of gas condensates and oil reservoirs;the wax content of crudes increases with the decrease of lo-garithm of producing gas/oil ratio of hydrocarbon reservoirs.In addition,the effect of gas washing and oil migration ranks last.Under the same oil source conditions,the higher degree of gas washing the crudes undergo,the lower the wax content of crudes will be;meanwhile the farther the crudes migrate,the lower the wax content of crudes will be.