深水重力流沉积机理新认识及其在北海G油田发现中的应用

基于野外露头、岩心和已发现油田实例分析,对传统深水重力流沉积进行了厘定,认为深水重力流沉积可划分为分异好的浊流沉积和分异差的块体流沉积,前者中富砂浊积体是有利的勘探目标。富砂浊积体由水基的浊流砂(砾)、泥基的碎屑流沉积和牵引流沉积组成。从汇水区到盆地中心,一次浊流沉积可分为4个阶段:即路过沉积、限制性浊积沟道、沟道和朵叶结合部及朵体边缘和远缘,其中沟道和朵叶结合部是储层发育最佳部位。物源区岩性是控制富砂浊积体的决定性因素,三角洲前缘砂、滨面砂等是最好的物源;构造运动和断裂亦是关键性因素,靠近物源区的断阶区最富砂。在新认识指导下成功预测了北海G油田砂岩储层,取得了较好的勘探效果。

New understanding of deep-water gravity flow deposition mechanism and its application in the discovery of G oilfield in North Sea

Based on the analysis of field outcrops,cores and discovered oilfields,the traditional deep-water gravity flow deposits are determined.It is proposed that the deep-water gravity flow deposits can be divided into well differentiated turbidity current deposits and poorly differentiated mass transport deposits,and sand-rich turbidite in the former one is a favorable exploration target.The sand rich turbidite is composed of water-based turbidity sand(gravel),mud based debris flow deposit and tractive current deposit.From collection area to basin center,the primary turbidite deposition can be divided into four stages:by-pass deposition,restricted turbidite channel,channel-lobe junction and lobe margin-far margin.Among them,the channel-lobe junction is the best place for reservoir development.The lithology of provenance area is a decisive factor for sand rich turbidites,while delta front sand and shoreface sand are the best provenance.Tectonic movements and faults are also key factors,and the fault terrace zone near the provenance area is the most sand rich area.Under the guidance of the new understanding,the sandstone reservoir of G oilfield in North Sea has been successfully predicted,and good exploration results have been achieved.