泌阳凹陷北部斜坡带三角洲沉积与油气成藏研究

A STUDY ON DELTA DEPOSITS AND RESERVOIR FORMING IN THE NORTHERN SLOPE OF BIYANG DEPRESSION

泌阳凹陷北部斜坡带发育有两种类型的三角洲。辫状河三角洲位于东北部缓坡带,离物源区相对较近,其面积最大,为整个凹陷提供了广泛的储集层。沿盆地长轴方向,在坡降缓、斜坡长的古地形等条件下,源远流长地巨大的定向曲流河携带大量的泥沙进入湖盆,在河湖作用过渡带形成曲流河三角洲沉积体。辫状河三角洲的油层主要分布于河口坝微相中,其次为远砂坝微相,水下分流河道则以油水同层和水层居多。本区张厂、古城曲流河三角洲平原相大部分已被剥蚀,埋藏浅(<500m),储层曾遭受过表层后生作用的改造,因此非常疏松,岩性主要为细砂岩和粉砂岩,只有少量含砾砂岩。

There are two kinds of deltas in the Northern Slope of Biyang Depression.The braided deltas are located in the northeastern gentle slope of the Depression,which is relatively close to the provenance and the largest kind in area, so they provide extensive reservoir strata for the whole depression.The immense oriented meandering river,along the long axis of the depression and with the gentle declivity and long slope,carried a large amount of mud and sand into the lake basin.Then,the meandering river delta deposit mainly lies in the mouth bar facies and secondly the distal sand bank facies,while the oil-water and aqueous layers are the major ones in the underground distributary channel.The plain facies of Zhangchang and Gucheng meandering deltas are denudated largely,together with the shallow burial(<500m) and the catagenesis,so the reservoir are loose and composed of packsands,siltstones and few pebbled sandstones.