摘要
鄂尔多斯盆地在长81期处于浅水湖泊沉积环境,盆地东北部的陕北地区在该期湖盆底部形态相对更加平缓、水体更浅。利用测井、岩心、薄片等资料,从储层类型、时空展布、岩石学特征、物性等方面研究了长81储层特征,认为研究区长81期主要发育水下分流河道砂体和河口坝砂体,砂体单层厚度薄、泥质含量高,具有明显的多旋回性、砂体垂向和纵向上连续性差,但分布范围广;砂体为岩屑长石砂岩和长石岩屑砂岩,属于细砂岩和极细砂岩;物性整体上差,属于典型的低孔特低渗—超低渗储层。分析表明造成该类型砂体形成的主要原因是:①研究区距离物源区远,且供给量不充足;②水体浅、湖盆底部形态平缓,湖岸线波及范围广;③湖水动力和河水动力弱。因此,在上述沉积环境下,在小期次湖平面升降过程中,长81砂体形成了"拉锯"式的砂体沉积模式。
Interval Chang 81 was regarded as shallow lake sedimentary environment in Ordos basin,and the basi~ had a more gentle bottom morphology and more shallow water body in Shanbei area. The Chang 81 reservoir is investigated by means of well-logging, core properties, thin sections for reservoir types, tempo- ral-spaeial distribution,lithology and reservoir physical property. It＇s showed that the area main developed underwater distributary channel sandstone and mouth bar sandstone with thin monolayer,high shale con- tent,significant multiply cyclicity, poor continuity in vertical and longitudinal direction and wide distribu- tion. The sandstones is lithic feldspar and feldspar lithic sandstone, which are regarded as packsand and hone. The reservoir is regarded as low porosity and low-extra-low permeability reservoir as to the poor physical property. Analysis shows that there are 3 reasons why this kind of sand body formed. First, the study area was far away from the provenance, which led to the insufficient supplication. Second, water was shallow, the bottom morphology is gentle and the lake shoreline spread widely. In addition, the water power of lake and river was weak. Therefore,in small times of lake level lifting process, see-saw type sedimenta- tion model was formed in the Chang 81 sandstone.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2013年第1期47-53,共7页
Natural Gas Geoscience
基金
国家科技重大专项(编号:2011ZX05044
2011ZX05001)
中国科学院西部之光项目
中国科学院油气资源研究重点实验室开放基金项目(编号:KFJJ2010-01)联合资助
关键词
浅水缓坡
砂体类型
低孔低渗
成因模式
延长组
鄂尔多斯盆地
Shallow gentle slope
Sand body type
Low porosity and low permeability
Genetic model
Yan-chang Formation
Ordos basin
