浅水型三角洲前缘砂体叠加样式——以鄂尔多斯盆地姬源地区长9油层组为例

为研究砂体叠加样式对浅水型三角洲前缘砂体发育规模及程度的影响，利用鄂尔多斯盆地姬源地区长9油层组沉积构造、测井相等分析浅水型三角洲特征，刻画浅水型三角洲前缘砂体叠加样式及分布规律。研究认为姬源地区发育平行层理、槽状交错层理、板状交错层理等层理构造及垂直虫孔、碳化植物茎干等生物标志，测井曲线多见顶底突变的单个或叠合“箱型”。识别出均质叠合厚层砂体、向上变细中厚层砂体及向上变粗复合砂体3种砂体叠加样式。浅水三角洲前缘水下分流河道单砂体在垂向上由下到上由数量少、厚度小到数量多、厚度大再到数量少、厚度小的演化特点，在平面上砂体分布受控于湖盆水位线的高低变化，低水位期受湖水顶托作用砂体快速堆积，砂厚域广，高水位期砂体的规模明显变小，与鄂尔多斯盆地由初次湖泛到第一次大型湖泛之间的沉积演化密切相关。

Superposed sand style of shallow lacustrine delta front: A case of Yanchang Formation in Jiyuan area,Ordos Basin

In order to study the influence of superposed sand style on the development scale in shallow lacustrine delta front, analyzed characteristics of shallow water delta using sedimentary structure and logging facies of Chang9 Formation in Jiyuan area, and described the superposed sand style and distribution of sand body in shallow lacustrine delta front. It shows that sedimentary beddings such as parallel bedding, trough cross-bedding, tabular cross-bedding and vertical wormhole, carbonized plant stem are developed in the Jiyuan area. The logging shows single or superimposed box models with abrupt top and bottom. Identified three superposed sand style such as homogeneous laminated thick sand body, medium-thick sand body up to fine and roughened upward composite sand body. Single sand body of underwater distributary channel in shallow lacustrine delta front from bottom to upper have less quantity, small thickness in bottom, the middle on the contrary compared with the bottom, meanwhile the upper same as bottom. The distribution of the sand body is controlled by the change of the basin waterline, thick and wide sand body supported by lake water in the lowstand period, the size of sand body decreases obviously in highstand period. This situation is closely related sedimentary evolution from the first lake flood to the first large lake flood.