塔里木盆地东河砂岩层序地层及沉积演化规律

Sequence stratigraphy and sedimentary evolution of Donghe Sandstone in Tarim Basin

塔里木盆地上泥盆统-下石炭统的东河塘组-巴楚组共同构成"东河砂岩",在盆地范围内对东河砂岩进行追踪和对比,并对其沉积演化规律展开精细研究,是当前盆内油气勘探所关注的重点。以塔里木盆地东河砂岩为研究对象,在层序地层学的理论指导下,利用盆地中大量钻测井、录井、岩心以及地震资料,对东河砂岩层序地层及格架内沉积演化规律进行详细分析。研究认为:东河砂岩共识别出两类层序界面,划分出1个二级层序和6个三级层序(SQ1—SQ6),并建立盆内层序地层格架,发现层序的分布受古地貌影响较大,SQ4—SQ6在全盆保存完整。在层序地层格架内共识别出包括三角洲与滨岸相等5类沉积相,并对层序格架内沉积相的平面演化进行研究,发现SQ1—SQ6时期,东河砂岩沉积面积逐渐扩大,顺南地区的SQ4砂体、顺西SQ5砂体以及顺托地区SQ6砂体都有较好的岩性圈闭发育条件,是下步勘探重点区域。

The Donghe Sandstone is constituted of the Donghetang Formation from the Upper Devonian and the Bachu Formation from the Lower Carboniferous. A basin-wide tracing and correlation of the sandstone combined with a fine study of its sedimentary evolution is currently a major task for further oil and gas exploration in the basin. Guided by sequence stratigraphy theories,we analyzed in detail the sequence stratigraphy and sedimentary evolution of the sandstone based on a wealth of data,including drilling data,mud and wire logging data,cores and seismic data. Two types of sequence boundaries together with two second-order sequences and six third-order sequences( SQ1-SQ6) were recognized in the sandstone and a basin-wide sequence stratigraphy framework was also built. The result showed great influence of palaeogeomorphology upon the distribution of the sequences and an almost intact SQ4 to SQ6 in the whole basin. Within the sequence stratigraphy framework,there were five sedimentary facies,such as delta facies,longshore facies and etc.. A study of plane sedimentary evolution of the sedimentary facies showed that during the deposition of SQ1 to SQ6,the deposition area of the sandstone had gradually enlarged,with favorable conditions for the development of potential lithologic traps in SQ4 sandbody of Shunnan area,in SQ5 sandbody of Shunxi area and in SQ6 sandbody of Shuntuo area. Further exploration shall be focus on these sandbodies.