西藏南羌塘盆地达卓玛地区油气地质条件研究

Study on petroleum geological conditions in Dazhuom area of Southern Qiangtang Basin of Tibet

前人在南羌塘达卓玛地区零星发现了一些地表油气显示并采集了少量的烃源岩进行分析,但勘查程度总体较低,未开展系统的生、储、盖研究。结合前人资料,通过野外石油地质调查、样品采集、室内分析、对比研究等手段,对南羌塘盆地达卓玛地区的烃源岩、储集岩、盖层等油气地质条件进行了分析,认为研究区阿堵拉组泥岩、页岩为好烃源岩,色哇组泥岩、粉砂质泥岩为差—中等烃源岩,布曲组、夏里组和索瓦组发育差烃源岩;储集岩主要为阿堵拉组砂岩和布曲组白云岩;盖层有泥质岩、灰岩和石膏,以Ⅰ、Ⅱ类盖层为主。野外调查中发现了大量地表油气显示,盆地经历了油气生成、运移、聚集和散失的过程,具有油气生成的物质基础和成藏的油气地质条件。建议在油气存储条件良好的达卓玛背斜布置钻井,进一步开展深部研究,力争实现该地区油气突破。

Previous researchers in Dazhuoma area of Southern Qiangtang Basin have found some sporadic oil and gas on the surface and collected a small amount of source rocks for analysis,but the exploration degree was generally low and they have not carried out systematic analysis of the generation,storage and cap of oil and gas.Based on the previous data,the authors in this paper have studied the characteristics of the source rocks,reservoir rocks and cap rocks in Dazhuoma area of Southern Qiangtang Basin by means of field petroleum geological survey,sample collection,indoor analysis and comparative research.The results suggest that the mudstone and shale of Adula Formation in the study area are considered as good source rocks,and the mudstone and silty mudstone of Sewa Formation are poor-medium source rocks,while Buqu Formation,Shari Formation and Suowa Formation are poor source rocks.The main reservoir rocks are the sandstone of Adula Formation and the dolomite of Buqu Formation.The cap rocks are argillaceous rocks,limestone and gypsum,and are mainlyⅠandⅡcap rocks.Furthermore,the discovery of oil exposure shows that this basin has underwent the process of oil and gas generation,migration,gathering and losing,which builds the material foundation of oil and gas generation and the petroleum geological conditions of hydrocarbon accumulation.It is suggested that more drilling should be arranged in Darzhuoma anticline with good oil and gas storage conditions,and further deep research should be carried out to achieve oil and gas breakthrough in this area.