吐哈盆地天然气成藏地质条件与富集因素分析

Natural Gas Accumulation Conditions and Controlled Factors in Turpan-Hami Basin

吐哈盆地是我国西北主要的侏罗系含煤盆地,近年来不仅在天然气勘探上迟迟未能取得重大突破,而且发现的天然气田数量及储量规模均远小于油田的数量及储量规模,明显有悖于"含煤盆地贫油富气"的地质规律。为此通过对吐哈盆地天然气成藏地质特征及油气分布规律的解剖分析和探讨,认为煤系源岩成熟度相对较低,天然气转化率较小且明显滞后于液态烃的生成,是造成吐哈盆地"油气共生、油多气少"的主要原因;煤系源岩的热演化程度及油气藏后期的保存条件是盆地大、中型气田形成、富集的关键因素;台北凹陷中部的胜北、丘东和小草湖等地区,煤系源岩发育、热演化程度较高、且后期构造活动相对较弱,应是盆地下一步天然气勘探的最有利地区。

Turpan-Hami （Tuha） basin is a typical Jurrassic coal measure basin located in northwest of China, Middle or large scale gas fields are not only undiscoveried in recent years, but also the quantities and the reserves of discoveried gas fields are much less than those of oil fields, which is different from other coal measure basins that are usually prone to generate and accumulate natural gas. This paper analyzed natural gas petroleum geological conditions and natural gas accumulation controlled factors of known gas fields. The results indicate that the low maturity of the coal-measures source and low gas generation rates are the major reasons for poor gas discoveries~ Maturity of the coal-measures source and preservation of oil ＆ gas pools are the key control factors for the formation and accumulation of middle or large scale gas fields; The areas surrounding Shenbei, Qiudong and Xiaocaohu are the potential domains for further natu- ral gas exploration.