鄂尔多斯盆地上古生界多藏大气田形成的关键因素及气藏性质的嬗变  

Critical factors for the formation of an Upper Paleozoic giant gas field with multiple gas reservoirs in Ordos Basin and the transmutation of gas reservoir properties

作　　者：胡朝元[1] 钱凯[2] 王秀芹[2] 施振生[2] 张光武[2] 许惠忠[2] 

机构地区：[1]中国石油天然气集团公司咨询中心,北京100724 [2]中国石油勘探开发研究院廊坊分院,河北廊坊065007

出　　处：《石油学报》2010年第6期879-884,共6页Acta Petrolei Sinica

摘　　要：鄂尔多斯盆地上古生界广覆式气源岩与多层砂岩体交互,天然气在自生自储、下生上储等多种组合情况下以及在河口坝砂体、河道充填砂体、辫状河下切谷砂体及地层超覆等多种圈闭条件下成藏。鄂尔多斯盆地上古生界大气田具有大面积产纯气,无明显边水、底水,基本上是低压等特点,这与天然气藏性质由侏罗纪至早白垩世的深盆气嬗变为现今特殊类型的岩性气藏有关。分析计算证明,这种变化可能是通过古深盆气再经砂岩储层扩散运移的天然气,以凝析水的形式将气层内的可动水排出实现的。晚白垩世以来,构造由南低北高转变为西低东高,向东部上倾方向有泥质岩遮挡;由南向北的地层静压力差极小,加上同期生气量大量减少(仅占总生气量的5%),生气超压消失殆尽,早期较弱的渗流动力更趋于零,北部致密带的侧向封堵作用更加凸显等,也是最终形成多藏岩性大气田的客观条件。In Ordos Basin,widely-distributed upper Paleozoic gas source rocks were interbeded with multi-beds of various sandbodies,and natural gases accumulated in various traps including mouth-bar sandbody,filled-channel sandbody,braided-river downcutting-valley sandbody and stratigraphic overlap,with multiple assemblages such as ＂self-generation and self-accumulation＂ or ＂upper-generation and lower-accumulation＂.The upper Paleozoic giant gasfield in Ordos Basin is characterized by pure gas produced in a large area,no edge or basal water in evidence and lower pressure in substance,which are related with the natural gas-reservoir property that transmuted from a deep-basin gas-reservoir in Jurassic and early Cretaceous to a special lithologic gas-reservoir at present.Analyses and calculations showed that this transmutation was realized where the gas generated in a deep paleo-basin reservoir drove the mobile water in a gas-reservoir out in the form of condensed water as it migrated through sandstone reservoirs.The final formation of this giant gasfield with multiple lithologic reservoirs was,of course,resulted from many other objective factors,such as the structure has transmuted from the low in south and high in north to the low in west and high in east since late Cretaceous,a barrier of argillaceous rocks existed in eastward updip,the overpressure by gas generation was exhausted due to a minor difference in reservoir static pressure from south to north and to a massive decrease in amounts of syngenetic gases（only accounting for 5% of the sum）,the early weaker seepage impetus was becoming almost zero,and the lateral blockage by a tight zone in north became more and more significant.

关 键 词：鄂尔多斯盆地 上古生界 多藏大气田 成藏过程 形成条件 

分 类 号：TE112.31[石油与天然气工程—油气勘探]