Interlayer Interference Analysis and Layered Development Strategy in CO₂ Miscible Flooding of Reverse-Rhythm...

To address the severe interlayer interference and insufficient sweep efficiency during CO₂ flooding in reverse-rhythm reservoirs, this study conducted miscible CO₂ flooding experiments using a self-designed three-layer heterogeneous two-dimensional (2D) visual physical model under two production schemes: sequential layered production and simultaneous layered production. Through image monitoring and a gas/oil ratio control system, the evolution characteristics of displacement front advancement, miscible layer expansion, and interlayer interference under different schemes were revealed. The results indicate that high-permeability layers tend to form gas channeling paths and exhibit a gravity override, which significantly suppresses oil recovery from medium- and low-permeability layers. In contrast, the simultaneous layered production scheme enables collaborative exploitation of multiple layers, significantly improving sweep efficiency and miscible layer continuity in lower-permeability layers and effectively mitigating interlayer interference. The overall oil recovery factor increased from 68.63 to 79.24%. Further analysis shows that shutting the production end of the high-permeability layer enhances vertical mass transfer of CO₂ and delays gas breakthrough, making the medium-permeability layer the dominant contributor to recovery. This study clarifies the controlling mechanisms of permeability contrast and gravitational differentiation on interlayer interference, confirms the crucial role of layered production in controlling displacement paths and enhancing oil recovery, and provides theoretical insights and engineering guidance for the development of CO₂-EOR in reverse-rhythm reservoirs.