一个典型的水下分流河道砂体展布与油气富集规律

三角洲一般位于海(湖)陆之间的过渡地带,是海(湖)陆相的重要组成部分。鄂尔多斯盆地三叠系延长组储层,由于其特殊的沉积环境,湖底坡降小,河控占主导地位,水下分流河道极为发育,最典型的是白120井区长33储层,由一个单一的水下分流河道组成。该区沉积规律强,各沉积单元发育,中间为河道沉积区,两侧为高于河道的天然堤,外部为漫溢沉积区,末端有4个朵体,中部发育一个小型决口水道。砂体呈指状展布,左右对称,具有三角洲水下分流河道典型的双凸特点。该区的沉积环境控制了砂体的展布和油气的富集程度。通过对该区块的研究,建立了一个完整的水下分流河道的沉积模式,这对于丰富三角洲沉积相的内容具有一定的意义。

A typical case study on the sand body to subaqueous distribution river course and its oil enrichment

Delta lies in the intermediate zone between the sea and land or lake and land,and it is also a very important part of them. Because the slope of lake bottom is low, it is the channel which plays a leading role to the formation of rather long sub-sea distributary chinnel. Chang 33 reservoir of Bai 120 tract is a typical example. Bai 120 tract has intact sedimentary unit. There is a channel deposit zone in the middle of Bai120 tract, two natural barriers which are higher than channel outside, and there are four sand lobes in the end;a small creva sse channel being in the middle of that. The sand bodies distribute like a bar-finger, symmertrizing on the right and left sides,having typical biconvex of a delta sub-sea distributary. chinnel. The channel deposit cross flow in the west,three lobes in the end and parts of natural barries in the west are the good reservoirs because of better physical properties. Natural barriers in the east,parts of the west and cross flow zones are dry because of the poor physical properities. Among these rservoirs,natural barriers in the east are the seal to the up-dip direction of south and north. The author builds up a perfect model of sub-sea distributary chinnel deposit,which willen rich deposit theory on delta.