Abstract
<title>Abstract</title> <p>Offshore strongly heterogeneous heavy oil reservoirs generally suffer from severe development imbalance during the ultra-high water cut stage, characterized by preferential flow in high-permeability layers, insufficient utilization of medium- and low-permeability layers, and significant remaining oil accumulation between wells. To address these challenges, this study focuses on the progressive adjustment of well patterns based on the existing row well pattern in a typical offshore heavy oil reservoir in the Bohai Sea, rather than evaluating the initial well pattern itself. A combination of three-dimensional physical simulation experiments and numerical simulations with consistent experimental parameters was employed to investigate the effects of different well pattern adjustment schemes. Recovery factor, interlayer interference coefficient, and remaining oil distribution were selected as evaluation criteria to analyze the development performance and interlayer flow characteristics. The results show that introducing horizontal wells into high-permeability thick layers can effectively improve overall oil recovery; however, the increased recovery is mainly contributed by high-permeability layers, while the improvement of medium- and low-permeability layers remains limited due to intensified preferential flow. After shutting down production wells in high-permeability layers, the recovery factor increased by 0.20 and 1.27 percentage points in physical experiments and numerical simulations, respectively, accompanied by reductions of 0.02 and 0.01 in the overall interlayer interference coefficient. However, the imbalance between different permeability layers was not fundamentally alleviated because the dominant flow behavior in high-permeability layers persisted. Compared with the production shutdown scheme, the staggered well pattern combined with separate-layer injection–production increased the recovery factor by 19.37 and 19.27 percentage points in physical experiments and numerical simulations, respectively, while reducing the interlayer interference coefficient by 0.27 and 0.37, leading to a more uniform remaining oil distribution and improved mobilization of medium- and low-permeability layers. The results indicate that the combination of well pattern adjustment and separate-layer injection–production can effectively regulate interlayer fluid allocation, weaken preferential flow in high-permeability layers, and improve the coordinated development of strongly heterogeneous heavy oil reservoirs during the ultra-high water cut stage.</p>