不平坦的三角洲前缘席状砂--来自露头和地下的证据

延长剖面发育的三叠系延长统三角洲前缘席状砂．平面上呈席状，垂向上表现为砂泥岩互层，剖面上可见不同规模的水下分流河道砂岩透镜体。大庆油田三角洲前缘席状砂解剖发现．即使在外前缘相带．席状砂仍然具明显的水道特征。由于湖盆三角洲受波浪和潮汐的作用较小，受河漉作用较强，分流河道向前延伸直至三角洲的前端，貌似平坦的席状砂前缘实际上分布着大大小小的分流河道，河道的迁移就形成了由多个宽厚比极大的对称或不对称的透镜状单元叠加而成的三角洲前缘席状砂。三角洲前缘席状砂的建筑结构分析表明，貌似平坦简单的席状砂实际上是一个复杂的非均质体．储层物性的非均质变化受砂体建筑结构的控制具有明显的层次性规律。

Non-flattening Delta Front Sheet Sand--Evidence from Outcrops and Subsurface

Delta front sheet sand on Yanchang profiles is a sheet on a plane, it is a sand-shale interlayer vertically. Sandstone lenticular bodies of different sizes in distributary channels can be seen on the profiles. It is found by dissecting the delta front sheet sands in Daqing Oilfield that though it is at outer front facies belt, there exists obvious characteristics of a water course in sheet sands. Because lake basin delta is slightly influenced by waves and tides and is strongly influenced by rivers, thus the distributary channel is extended forward to the front end of delta, it looks like a flattening sheet sand, but actually different sizes of distributary channels are arranged on it. Delta front sheet sands superposed by symmetric or non-symmetric lenticular units with great wide-thick ratio are formed by the migration of the channels. The architectural analysis of the delta front sheet sands shows that a looking-like flattening and simple sheet sand are actually a complicated heterogeneous body, the heterogeneous changes of reservoir physical properties are controlled by the architectural structures of sandbodies with obvious hierarchical rules.