Mechanisms of CO2 flooding front migration and injection-production regulation in heterogeneous reservoirs: A large-scale visual physical simulation study

The unclear migration mechanisms of CO 2 flooding fronts in heterogeneous reservoirs significantly constrain the efficiency enhancement of CCUS-EOR technology. This study, employing a self-designed large-scale two-dimensional visual physical model, systematically reveals for the first time the dominant control mechanism of interlayer spatial configuration on channeling pathways and the laws of injection-production regulation. Experiments demonstrate that when gas is injected on the side with a developed interlayer, CO 2 preferentially migrates horizontally along the high-permeability layer and, after breakthrough, channels laterally into the low-permeability layer through the non-interlayer interface. Conversely, gas injection on the non-interlayer side induces vertical channeling. The mode of “gas injection at the non-interlayer end + oil production at the interlayer end” coupled with early soaking expanded the miscible zone by 29.81 % and achieved a total recovery factor of 91.04 %. Although increasing the pressure difference in the low-permeability layer by 1.5 times can forcibly initiate oil mobilization, channeling must be suppressed to avoid inter-layer imbalance. The evolution of the miscible zone exhibits a two-stage characteristic of “synergistic growth - competitive substitution”: dominated by mass transfer-displacement synergy before breakthrough, and by gas channeling and phase competition afterwards. The high-permeability layer readily forms an arc-shaped miscible enrichment zone, while the low-permeability layer exhibits narrow, strip-like expansion limited by mass transfer. Future work needs to focus on enhancing dynamic identification of the miscible zone, optimizing soaking timing, and combining numerical simulation to study the influence of interlayer spatial configuration on inter-layer channeling. These results provide key experimental evidence for CCUS-EOR development in heterogeneous reservoirs, promoting the advancement of inter-layer conflict regulation from mechanistic understanding to engineering optimization. • A large-scale 2D visual physical model reveals that interlayer barrier configuration controls CO 2 crossflow paths: CO 2 preferentially migrates horizontally along high-permeability layers before breaking through into low-permeability layers via barrier-free interfaces. • Optimal injection-production strategy (“barrier-free injection + barrier-side production + early shut-in”) enhances oil recovery to 91.04 %, expanding the miscible zone by 29.81 % and delaying gas channeling. • Miscible zone evolution follows a two-stage “synergistic growth–competitive replacement” pattern, with high-permeability layers forming arc-shaped enrichment zones and low-permeability layers exhibiting narrow strip-like expansion due to mass transfer limitations.