受潮汐影响的缓坡三角洲有利砂体叠置样式——以塔河油田石炭系卡拉沙依组为例

Superimposition patterns of favorable sandbodies in gentle-slope delta affected by tides:a case study of the Carboniferous Karashayi Formation in Tahe Oilfield

塔河油田石炭系卡拉沙依组地层埋深大,砂体厚度薄,横向变化快。基于岩心观察、野外露头、薄片鉴定、测井和录井资料等,分析研究区砂体的成因及叠置样式;采用野外砂体构型及密井网区精细砂体解剖的方法,识别受潮汐影响的缓坡三角洲沉积模式。结果表明:研究区卡拉沙依组成因砂体主要包括水上分流河道、水下分流河道、潮汐改造分流河道、砂坪和砂泥混合坪5种类型,其中水上分流河道和水下分流河道砂体物性相对较好,是有利砂体;有利砂体叠置样式包括冲刷式、互层式和夹层式等垂向叠置样式,以及连片式、斜切式、对接式和孤立式等侧向展布样式。研究区北部靠近物源方向,为有利砂体分布区。

Carboniferous Karashayi Formation in the Tahe Oilfield is characterized by large buried depth,thin sandbody and fast lateral change.Using core observation,outcrops,slice identification,etc.,combined with logging data,we analyzed the genesis and superimposition patterns of the sandbodies in the study area;identified the gentle slope-delta sedimentary model affected by tides using sandbody architecture in the outcrops and fine sandbody anatomy in the dense well area.The research shows that the types of genesis sandbodies in the study area mainly include water diversion channel,underwater distributary channel,tidal diversion channel,sand flat and sand-mud mixed flat.The sandbodies of water diversion channel and underwater distributary channel are favorable sandbodies.The results also show that superimposition patterns of the favorable sandbodies include vertical stacking styles such as scoured type,inter-layer type and sandwich type,as well as lateral spreading styles such as vast type,slanting type,butt-joint type and isolated type.The northern part of the study area is close to the source and is a favorable sandbody distribution area.