Abstract
Reconstructing meandering paleo-channels is attracting global research attention. We implemented a novel method by comprehensively integrating migration models and sedimentary structures. Firstly, the migration architectures of the corresponding characteristics in planform and cross-sectional models were summarised as expansion, translation, expansion and translation, expansion and downstream rotation, constriction and downstream rotation, and expansion and countercurrent rotation models. Secondly, full continuous core data from 270 dense drilling wells were collected from the Daqing Oil Field in the Songliao Basin, China, providing information on rock textures, sedimentary cycles, and boundary information for the two layers being studied. Through a comprehensive analysis of dense drill cores and logging data, the abandoned channels and the initial and final channel centrelines were identified. Consequently, four profiles, including one longitudinal and three transverse sections, were constructed to reveal the cross-sectional structures and planform migration architecture. Profile interpretation revealed the evolution from the initial channel centreline to the final centreline. Using a method of rational interpolation, we were able to reconstruct the migration architecture of the meandering channels. The results showed that the average ancient bankfull width (Wc) was approximately 100 m, a single meandering belt was 800 m, the radius of the curvature was 250 m, the length of the channel bend was 700 m, the average meander wavelength was 1300 m, the sinuosity was 3.0, and the annual average discharge rate was 450 m3/s. Furthermore, we compared the results from empirical equations, which verified that our reconstruction is both feasible and potentially widely applicable.
Highlights
Meandering rivers are ubiquitous, dynamic earth surface systems (Seminara 2006, 2010; Abad and Garcia 2009; Guneralp and Rhoads 2011; Abad et al 2013; GutierrezEdited by Jie HaoKey Laboratory of Exploration Technologies for Oil and Gas Resources, Ministry of Education, Yangtze University, Wuhan 430100, ChinaSchool of Geosciences, Yangtze University, Caidian, Wuhan 430100, China and Abad 2014; Lin et al 2017)
We compared the results from empirical equations, which verified that our reconstruction is both feasible and potentially widely applicable
The different planform migration modes for modern bends may be associated with soil properties (Guneralp and Rhoads 2011; Motta et al 2012a, b), vegetation, and riverbed material (Abad and Garcia 2009; Abad et al 2013), and bend migration patterns may be associated with floodplain- rather than channel-dominated controls (Motta et al 2012a)
Summary
Meandering rivers are ubiquitous, dynamic earth surface systems The research methods and sedimentary environments differ between ancient and modern fluvial deposition, the evolutionary mechanisms and characteristics of river planform dynamics might follow similar hydrodynamic and sediment transport processes (Hubbard et al 2011; Ielpi and Ghinassi 2014). It is difficult to analyse ancient meandering dynamics based only on logging and seismic data, considering that most reservoirs are buried several thousands of metres deep. It can be effective when dense drilling well data are available, as in the case of the Daqing Oil Field in China. The study area is located in the northern part of the central basin (Fig. 1b), and the study strata belong to the Coniacian-aged Yaojia Formation (K2y1)
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