# Quantitative Scale Analysis of the Channel Bar in a Braided River and Its Internal Architecture
## 3 Results
### Study on the Architecture Elements of Channel Bar  
(1) The Identification Method for Single Channel Bar  
The identification of a single channel bar is the top priority of the quantitative study on the inner architecture of the channel bar. Due to the complex underground structural conditions, the diverse types of sand, the short formation duration of the beach sedimentation driven by the tide, and the limited observation view, this method cannot help achieve an accurate understanding of the sedimentation process of the single underground channel bar. Therefore, in order to accurately depict the spatial distribution characteristics of channel bar, combined with the inter-well comparison of the dense well pattern of oilfields, the PI3 sublayer of Putaohua in the Nanwu area of Daqing Oilfield in Songliao Basin, located in northeast China, is selected as a typical area for the comprehensive depiction of the scale of single channel bar. The common method is to use the difference in elevation of the channel bar and the sandstone top depth microstructure map to calculate the scale of the single channel bar, because the sandstone top depth and high value area usually indicate a complete channel bar development area [34]. In general, the bottom of the channel bar is flat while the top is convex. The bottom of the braided river channel is convex while the top is flat. The thickness of the channel bar is obviously greater than the thickness of the river channel, which causes h1, the elevation between the top surface of the channel bar sand body and the top surface of the layer, to be smaller than h2, the elevation between the top surface of the braided river sand body and the top surface of the sublayer. Therefore, the elevation difference between the sand body of the channel bar and the sand body of the river channel is formed (Figure 3). Through leveling the sandstone top structure, the microstructure of the sandstone top surface as well as the sand body of the same channel bar can be identified. (2) Quantitative Analysis of Single Channel Bar  
In order to more clearly and quantitatively study the scale of the single channel bar, the single channel bar dam is divided into several parts horizontally, including the head, the main body, the wing, and the tail. The head is the upstream face. Affected by the erosion of the water current, the steep erosion surfaces are likely to develop in the head area (Figure 4a). The end of single channel bar is gentle, while the wings on both sides are tangent to the direction of the current, and they are generally symmetrically developed [35]. This study measured the width and length of the eight selected channel bar sand bodies (Figure 4b-d), and recorded the corresponding data in sheets. In order to better characterize  
Figure 3: Identification method of a single channel bar based on the elevation difference of a sand body. the characteristics of channel bar sand bodies, the length of the channel bar L\({}_{\rm b}\) is defined as the longest distance along the long axis of the dam body in the downstream direction, i.e., L\({}_{\rm b}\) = L3 + L4 + L5. The width of the single channel bar W\({}_{\rm b}\) is defined as the longest distance in the transverse direction of the braided flow; that is, W\({}_{\rm b}\) = 2L1 + L2. Similarly, for a single braided river sand body, the length of the braided river is defined as \(L_{h}\), which is the length along the long axis of the channel bar from the top to the bottom. The width of the single braided river sand body is defined as \(W_{h}\), which is the maximum width between the embankment and the center of the channel bar in the cross-cutting direction of the flowing water. The actual measurement area is bounded by the line when the river bank suddenly becomes steep [36]. According to the length and width of the selected eight single channel bar sand bodies, this study establishes the relevant function relationship.