A quantitative coupling degree model for source-to-sink (S2S) system through entropy weight-coupling theory: A case study of the Chengbei Low Uplift area, offshore Bohai Bay Basin, eastern China

Xinyuan Ji ^* Chunqiang Xu Wenrui Li Qiming Wang Hewei Hu

• China National Offshore Oil Corporation Limited, Tianjin Branch, Tianjin, China

Source-to-sink (S2S) analysis plays a crucial role in sedimentological studies, serving as an effective tool for reconstructing sediment-routing processes and guiding hydrocarbon exploration. Most S2S system studies rely on multivariate nonlinear or correlation analysis using S2S system parameters. However, few studies focus on quantifying the degree of interaction (i.e., the coupling degree) between multiple sub-S2S systems, leading to a biased understanding of coupling mechanisms, S2S processes, and exploration potential. To address this gap, a quantitative model for coupling degree was developed using entropy weight-coupling theory (EW-CT). Based on key S2S system parameters, this model quantitatively measures the coupling degree of S2S systems and successfully reveals correlations between EW-CT values and coupling degree. The Paleogene Chengbei Low Uplift (CBLU) in the Bozhong Sag, offshore Bohai Bay Basin (OBBB) in eastern China, serves as a case study to validate the model and examine the multi-hierarchy S2S coupling mechanisms as well as the exploration potential in an ancient uplift system. The main findings are: (1) the CBLU is divided into five second-level S2S systems (P/Q/R/S/T), with the study area (S) further subdivided into six third-level sub-S2S systems (S1–S6); (2) there is a positive correlation between EW-CT values and coupling degree in the S2S systems; (3) the coupling degree of the eastern braided-delta S2S systems (S4–S6) exceeds that of the northern fan-delta S2S systems (S1–S3); and (4) among the braided-delta S2S systems, the S5 system shows the highest exploration potential.