# Quantitative Scale Analysis of the Channel Bar in a Braided River and Its Internal Architecture
## 1 Introduction  
Reservoir architecture refers to the shape, scale, direction, and spatial superposition relationship of reservoir units and interbeds at different levels. For mature oil fields that have entered the stage of a high water cut and ultra-high water cut, reservoir architecture analysis is one of the keys to achieve a fine reservoir description [1], aiming at enhancing the stable production, tapping potential, and oil recovery technology of the oil field. In a braided river reservoir, the braided river and channel bar are essential sand bodies in reserving oil and gas, but the internal architecture of a braided river reservoir is very complex due to the frequent overlapping of the river channel and channel bar in different developing stages of the reservoir, as well as the mud deposits, such as the silting layer of the channel bar, in the reservoir. Since the last century, in response to current reports on reservoir architecture of braided rivers, scholars all over the world have achieved great results in the methodology for the architecture of river reservoirs [2, 3, 4, 5]. Benefiting from the application of data and technology such as high-precision, ground-penetrating radar, and shallow seismic and dense well patterns, the study of braided river sedimentation (architecture) has transited from one-dimensional lithofacies combination models (such as trench) and two-dimensional architecture unit combination relationships (such as outcrop profile) to three-dimensional space distribution models (such as ground-penetrating radar) [6, 7, 8]. Based on high-resolution satellite photos, the spatial observation scale of rivers has increased, and the study of rivergeomorphological characteristics has developed from local to overall [9; 10; 11; 12; 13]. In general, a lot of research has been carried out on braided river sedimentation, and the sedimentary architecture patterns of several braided river examples have been established [7; 14; 15; 16; 17; 18; 19]. However, many research cases show that the sedimentary architecture models of braided rivers established by different scholars or based on different cases are significantly different. Due to the lack of a systematic study on the formation mechanism and applicable conditions of differential sedimentary models, it is difficult to select a suitable braided river type and matching sedimentary architecture model in the prediction of underground braided river reservoirs [9; 12; 18; 19]. Other methodologies have different limitations. Field outcrop observation is the most intuitive way and also the closest way to approach the actual underground river landform [20]. However, due to the limitation of outcrop data on the earth's surface, this method can only showcase a certain geological information point, which lacks comprehensiveness. The qualitative and quantitative characterization of interlayer thickness, dip angle, and distribution range is performed through the comparison of small well-spacing wells, combined with the dynamic data of injection production wells [21; 22]. The architectural structure of braided river reservoirs is still in the qualitative and quantitative exploration stage. Physical experiment simulation is a commonly used research method for river sedimentation, which is simple and not restricted by climate or season [23], but this method tends to be greatly influenced by human factors. Moreover, underground river sedimentation is a long historical process, while simulation based on sedimentation experiments is a short process, which means that the time scales of the two processes are asymmetric and cannot truly reflect the long reconstruction process of braided river reservoirs. Satellite photos of modern rivers can reflect the river sedimentation process at different times [24], but due to space-time and human factors, and the same asymmetry issue as with the physical experiment simulation method, it is also difficult to truly reflect the long reconstruction process of braided river reservoirs.