塔里木盆地志留系成藏条件与勘探方向探讨

Discussion on oil reservoir forming conditions and exploration targets of the Silurian in Talimu Basin

志留系是塔里木盆地油气勘探的重要目的层系之一,主要为一套滨岸或潮坪、滨外陆棚相沉积,在沙雅隆起、北部坳陷和塔中低凸起均有较广泛的分布,其沉积中心位于满加尔坳陷的草1井区,自西向东、自南向北地层由薄变厚,岩性由粗变细,泥岩颜色由紫变灰,笔石化石增多.志留系自下而上分为4个岩性段,下砂岩段是盆地内著名的沥青砂分布层位,构成三套储盖组合.志留系具有近源聚集油气的优越条件、良好的储集岩发育背景、多种圈闭类型和多期成藏的特征.志留系油气勘探的主攻领域应在轮南地区、环哈拉哈塘周缘地区、塔河油田南部、孔雀河斜坡、塔中隆起北斜坡以及巴楚隆起南缘地区.加强海西期古构造研究,寻找海西期以前形成的型圈闭是志留系大中型油气藏勘探的方向.

The Silurian is one of the interest intervals in oil-gas exploration in Talimu Basin. It is mainly a set of shore, tidal-flat or offshore continental-shelf deposit, and the deposition widely distributes in Shaya uplift, the depression in the north of the basin and low prominence in the middle part of the basin. The depocenter locates in Cao-1 wellblock of Manjiaer Depression. From west to east and from south to north, the deposit thickens, its lithology varies from coarse to fine, the color of shale varies from violet to gray, and traptolite fossil gradually increases. The Silurian can be divided into 4 lithologic layers from down to up, the first layer is asphaltic sand layer and it has 3 sets of reservoir--cap assembles. The Silurian has the favorable condition of proximate accumulating oil-gas, good reservoir-rock development setting, many types of traps and multistage oil-gas accumulation characteristic. The target regions for the oil-gas exploration of the Silurian are Lunnan area, the border of Huanhalahatang, the southern part of Tahe oilfield, Kongquehe slope, the northern slope of Tazhong uplift and the southern border of Bachu uplift. Hercynian palaeostructures should be studied and the traps formed before Hercynian should be seek in the exploration of the large-middle scale oilfields of the Silurian.