陕甘宁盆地姬塬地区三叠系延长组三角洲前缘的微相组合及特征

以陕甘宁盆地姬塬地区晚三叠系延长统为例,将该区的三角洲前缘划分为“台型前缘”和“坡型前缘”两部分,其识别标志是以水下分流河道、复合河口坝(坝上河)和河口坝三种主要沉积微相为主导的多种微相的不同组合。文中对三角洲前缘中的沉积微相组合进行了精细划分和描述,例如,将水下分流河道划分为截削式和叠加式2种,将河口坝划分为完整式和复合式两大类,其中复合式河口坝(坝上河)还可划分为下残坝上河、完整坝上河和上残坝上河三种亚类型。这种对三角洲前缘的详细解释以及对其沉积微相的精细描述有助于优质储层的鉴别和分布预测,对油藏开发中的细分流动单元也有所帮助。

The Microfacies Combination and Characteristics of Delta Front in Yanchang Formation (Triassic) of Jiyuan Area Shaanxi-Gansu-Ningxia Basin

A series of gentle slope delta are developed in Yanchang Formation in Jiyuan Area of Shaanxi-Gansu-Ningxia Basin. The delta front in this area can be divided into mesa delta front and sloping delta front. The deposition models of delta along gentle slop are proposed based on the strength of the current in distributary channel and the depth of water in the lake. According to the research of underwater distributary channel, recombination bars and mouth bar, we can establish the assorted scheme and discriminating characteristics. For example, the distributary channels are composed of truncated underwater distributary channels and underwater superposition channels. The river mouth bars are composed of the integrated mouth bars and recombination bars. The recombination bars consist of mouse bars at the bottom and underwater distributary channels at the top, and it can be subdivide into upside deformity recombination bars, integral recombination bars and downside recombination bars. This type of compartmentation scheme can be helpful to identify and distributing prognosticate of high quality reservoir, and it can also serve to subdivide the flow unit in oil exploitation.