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Okavango delta is a typical distributive fluvial system, which is composed of a series of sand island-river-swamp networks. River migration in the Okavango delta is analyzed by using satellite images from Google Earth and Alaska Satellite Facility (ASF). Four configuration characterization parameters are selected to depict and measure the meandering river. These four parameters are sinuosity index (S), curvature (C), the difference of along-current deflection angle (Δθ) and expansion coefficient (Km). In the fan, the channel migration is mainly asymmetric. According to geomorphic elements and associated features, Okavango Delta can be subdivided into three zones: axial zone, median zone and distal zone. Under the influence of slope, climate and vegetation, different migration modes are developed in different zones. As the river moves downstream, the sinuosity index of the river on the Okavango Delta decreases downstream. Based on the characteristics of different zones, the sedimentary facies model of a single source distributive fluvial system of a meandering river is proposed. The models of channel migration and sedimentary facies have wide application. This research will not only provide a basis for the prediction of future river channels but will also provide important theoretical guidance for the study of the sedimentary morphology of underground reservoirs.

Although a large number of meandering rivers have been studied by means of modern sedimentation, instrument detection, numerical simulation, flume experiment and field outcrop, and a lot of achievements have been made, there are not many fine anatomical examples of deep buried ancient rivers, which is a situation that still needs to be improved. The main difficulties in the research of deep, ancient meandering rivers are the acquisition of data and the incompleteness of structure, which are both difficulties and challenges. Under the guidance of the modern meandering river fan sedimentary model and migration law, we established the scheme of meandering river geomorphology and structure. In the process of river migration, a variety of single migration models (expansion, contraction, rotation, and translation) and composite migration models can be distinguished. By analyzing the distribution structure characteristics of channel configuration elements in different migration modes, the coupled model of the meandering channel plane and profile structure is established by systematically constructing plane and profile combined with a three-dimensional channel configuration model. Based on the data of the dense well, taking the Shan 11 sublayer in the Su-x block of the Sulige gas field as an example, the reservoir structure of the deep, ancient meandering channel is dissected. In order to reconstruct the evolution of the deep, ancient channel and make it more consistent with the real laws of river migration and evolution, the morphological migration law of the modern river is applied to the ancient sedimentation, and the migration configuration is dissected by combining with the plane-profile structure coupled model. It further reveals the heterogeneity, the vertical distribution and the superposition form of the channel sand, and enriches the theory of the reservoir configuration of underground fluvial facies, all of which are significant for oil and gas exploration and development.

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