Abstract: The formation of coal measure-derived oil ggs fields in NW China is the product of the assemblage in spatial and temporal domains of certain tectonic conditions,sedimentology and the accumulation of oil-prone organic materials as well as the effective expulsion of oil gas from the coal measures.The study made by this paper shows that the following.conditionsare necessary for the formation of coal measure-derived oil gas fields in Jurassic sequence of NW China The Jurassic original basin,which was occupied by lake water or low-positional swamp during the most Jurassic time,should exist,so that the complete association of source rock,reservoir and caprock was well developed;The original depositional environment was characterized with low and gentle depression and humid climate which are favorable for the development of low-positional marshland and lake where the oil-prone organic materials were accumulated with large volume;The sequent basin should occur on the Jurassic original basin which is necessary to keep the coal measure source rocks in the condition of progressive mat uration,and certain degree of tectonic compression taking place soon after the maturation of source rocks can provide the driving force for the effective expulsion of oil gas from the coal measures.Coal measure-derived oil gas fields is horizontally distributed along the inner side of lake strandline depositing with source-rock and vertically occured above or below the thresh old of maturity.Owing to the sharp variation of lithology and facies in coal measures,the lithological and composite types of oil gas pools play a big role in the petroleum accumula tions of coal measure sequence.

Key words: NW area, jurassic system, coal measures, oil and gas fields, condition, oil and gas distribution

摘要： 煤系油气田的形成是一定的构造、沉积与生烃母质富集、成熟与油气有效排出等因素在时空间配置组合而形成的产物.西北地区侏罗系煤系油气田形成必不可少的条件是：①侏罗系原盆地应存在,发育有完整的生储盖组合;②原始沉积环境呈低缓洼地,并具备潮湿气候,有利于近湖低位沼泽与大量易生烃母质的发育和堆积;③后续盆地要继承发展,以保持源岩递进性受热并熟化;④源岩成熟后的构造挤压是油气有效排驱的主要动力.煤系油气田在平面上沿着与源岩同期的湖岸线内侧分布,位于有油源断层切割,收缩量适中,破坏较弱的区带.剖面上则集中于生烃门限上下.其中构造-岩性与岩性型油气藏占有重要比例.

关键词: 西北地区, 侏罗系, 煤系, 油气田, 条件, 油气分布