准噶尔盆地西北缘五八开发区二叠系原油特征与成藏关系探讨

Research on Relation between Oil Properties and Petroleum Pool Formation of Permian in the 5^(th) & 8^(th) Districts,Northwestern Margin of Junggar Basin

对准噶尔盆地西北缘勘探五、八开发区二叠系原油地球化学与物理性质特征的研究表明,研究区原油具有早期成藏、早期稠化破坏、中晚期连续成藏与保存的特点。二叠系原油的总体地球化学特征相似,主要来自二叠系风城组湖相烃源岩,但由于成藏时期与次生改造作用的不同,可以把原油分为A1和A2两类。A1类原油生成、运移、聚集成藏时间早,经历了早期的生物降解、水洗、氧化等次生改造作用,原油密度和粘度普遍较高,成藏期主要在海西中晚期,原油稠化时间主要在海西末期—印支早期,分布范围不大。A2类原油生成时间晚,运移、成藏时间主要应在中生代及其以后,分布广,目前所发现的多数二叠系油藏都属于该类原油。

By analysis of oil physical properties and organic geochemical features of the Permian System in the 5^th and 8^th districts, northwestern margin of Jungar basin, the authors come to a conclusion that the initial oil pools here were formed in an earlier stage, and afterwards they were viscosified and destroyed. At the middle and later stages the oil pools were formed again and preserved. The total organic geochemical characteristics of different generations of oil were similar and mainly originated from the Fengcheng Formation. Because of difference of reservoir formation times and secondary recreation roles, the crude oil can be divided into A1 and A2 types. The type A1 oil is of limited distribution. It was generated, migrated and accumulated in the earlier stage, and the oil pool formation time was early too. Afterwards, the oil pools were destroyed, and the crude oil was biodegradated and experienced water washing and oxidation, and therefore its density and viscosity are higher. The type A1 crude oil pools were formed in the middle to late Hercynian time, and its densification time was chiefly in the late Hercynian to early Indosinian time. The type A2 crude oil is of wide distribution in this area. Its generation, migration, accumulation and pool formation time was later, chiefly in the Mesozoic and even still later time. Most oil pools found in the Permian sediments in this area belong to this type.