琼东南盆地深水区中央峡谷沉积微相特征

Characteristics of Sedimentary Microfacies in the Central Canyon Within the Deep Water Area,Qiongdongnan Basin

／中央峡谷位于南海北部琼东南盆地深水区，是琼东南盆地深水区油气勘探的重点区域。迄今为止，对于峡谷的成因及沉积微相的认识，不同学者有不同的观点。近来，峡谷内又新增了多口钻井，系统的分析总结峡谷的充填期次、沉积微相的划分及骨架砂体的展布意义重大，将直接影响到峡谷下一步的勘探部署。因此，本文以钻井资料为基础，通过岩矿特征、粒度分析、沉积构造、古生物特征、测井相等的分析，再结合高分辨率三维地震资料，综合分析了地震剖面、均方根振幅属性、多种切片技术等地震相特征，根据从点到面的研究思路对黄流组时期（S40-S10）中央峡谷发育的沉积微相进行了精细研究，研究表明琼东南盆地中央峡谷为大型侵蚀型水道，具有曲流水道特征，类似陆上曲流河沉积，发育点砂坝、天然堤复合体、泥质水道等沉积微相；综合构造背景、古地貌及古地貌与平面沉积相叠合图的研究表明，点砂坝主要发育于峡谷古地形的弯曲处，系水道不断迁移摆动而形成的侧向加积体，地震剖面上表现为强振幅叠瓦状前积型特征，岩性为块状细砂岩夹薄层泥岩，测井曲线GR呈中一高幅箱形夹薄层低幅齿形，为正旋回沉积特征。点砂坝规模不等，面积约8～20．5k㎡；天然堤复合体范围较窄，这可能受峡谷壁的限制作用影响。已钻井也证实，点砂坝作为峡谷水道的骨架砂体，储层物性好，具有良好的勘探前景。

Central canyon is located in Qiongdongnan Basin deep water area of the northern South China Sea, and is key areas in oil and gas exploration. So far, canyon about the microfacies, causes and sandbody distribution rule are still in dispute. Therefore, based on the new drilled well, high-resolution 3-D data, we carried out a series of work, such as technical analysis for the rock and mineral characteristics, particle size analysis, sedimentary structures, pale ontological features, well logging facies, and using the RMS amplitude attribute, a variety of slicing technology, etc. The results show that the canyon is the deeper downcutting and scours to the older strata eastwards within the Huang Liu group （T40 - T30）. The three genetic facies are included in the Central canyon channel system： muddy chan nel, point bar, and levee complex. Integration of tectonic setting, ancient landforms and planar deposition facies su perimposed map indicates that point bar developed in the bend of the canyon pale-topography and interpreted to be as sociated to continuous lateral migration during channel evolution, resulting in the deposition of lateral accretion packa ges in the inner side of the channel and erosion at the outer side of the channel. Characteristics of lithology and log in the well drilling through the Central canyon contain sets of sand bodies, named point bar in this paper, and thin mud stones. Point bar can form sizable reservoir elements as much as 8 ～ 20.5 km： in the central canyon.