海拉尔盆地贝尔凹陷南屯组扇三角洲沉积特征及模式

扇三角洲是陆相断陷盆地内重要的油气汇聚场所,建立准确并可靠的扇三角洲沉积模式,对预测优势储集体具有重大意义。综合应用岩心、地震、测井等资料,对扇体内部沉积单元及相特征进行了精细刻画。研究表明:贝尔凹陷南屯组发育有典型的扇三角洲沉积体系,可细分为3类亚相和11类微相,其中扇三角洲平原亚相发育平原分流河道、平原分流河道间、平原天然堤3类微相,扇三角洲前缘亚相发育前缘水下主河道、前缘水下分流河道、前缘席状砂、河口坝、远砂坝以及前缘水下分流间6类微相,前三角洲亚相发育前三角洲粉砂岩和前三角洲泥岩2类微相;贝尔凹陷南屯组扇三角洲主要发育在贝西斜坡带、霍多莫尔构造带、苏德尔特构造带等靠近盆缘或控陷断裂的陡坡地带,可划分为断坡型、断阶型2种扇三角洲沉积模式。

Sedimentary characteristics and model for the fan delta in Nantun Formation of Beier Sag in Hailar Basin

Fan delta is a very important oil and gas accumulating place in continental faulted basin, so the establishment of the accurate and reliable fan delta depositional model is of great significance to predict the dominant reservoir group. With the help of the comprehensive application of the core, seismic and well logging data, the fine characterization of the internal sedimentary units and facies features of the fan delta was conducted. The study shows that the typical fan-delta depositional system is developed in Nantun Formation of Beier Sag, which can be subdivided into 3 subfacies and 11 microfacies, among them, the fan-delta plain subfacies can be further divided into plain distributary channel, plain distributary interchannel and plain natural dyke microfacies;there are 6 types of the microfacies developed in the fan delta front subfacies i.e. main front-edge underwater channel, front-edge underwater distributary channel,front-edge sand sheet, mouth bar sandstone, far sand bar and front-edge underwater distributary interchannel;there are 2 kinds of microfacies developed in the front delta subfacies, namely, the front delta siltstone and front delta mudstone;the fan delta deposited in Nantun Formation of Beier Sag is mainly developed in West Beier Slope, Huoduomoer Structural Belt, Sudeerte Structural Belt and so on, which is close to the basin margin or the steep slope of the sag-controlling fault, and furthermore is can be divided into the following 2 kinds of fan-delta sedimentary models: fault slope and fault step.