Integrated Characterization Method and Application for Complex Reservoirs Considering Threshold Pressure Gradient

Aiming at the challenges of reservoir quantitative prediction and seepage mechanism characterization in the development of heavy oil reservoirs in the Bohai “Double High” (high water cut and high recovery degree) stage, this study conducts refined characterization method research from two dimensions: 3D architecture modeling and threshold pressure gradient simulation. The integrated modeling-numerical simulation approach is adopted to address key challenges in the refined description of complex reservoirs. The research employs a multi-method integrated technical approach combining dynamic and static data: ①Innovatively proposing a meshfree modeling technique for architectural envelope surfaces to construct a 3D distribution model of architecture interfaces in the target area of S Oilfield;②Employing a small-scale equivalent characterization method to accurately delineate the interfaces of architectural units; ③ Establishing a numerical simulation method considering threshold pressure gradient to quantitatively characterize dynamic behaviors of complex reservoirs; ④ Reducing reservoir model uncertainty through integrated iterative modeling and numerical simulation. The results demonstrate that this methodology effectively resolves the technical challenges in quantitative prediction of inter-well architectural interfaces in S Oilfield, achieving quantitative characterization of 4th-3rd-order architectural units， and breaking through the difficulties in precise characterization of threshold pressure gradient mechanisms. The approach significantly enhances historical matching accuracy, with well-group dynamic matching conformity rate exceeding 90%, while markedly improving the precision of remaining oil distribution predictions. This study innovatively establishes a meshfree architectural envelope surface modeling method and a numerical simulation technique incorporating threshold pressure gradient, while developing an integrated modeling-simulation characterization workflow. The research forms a systematic methodology spanning from architecture delineation to reservoir characterization and ultimately to reservoir simulation. These achievements provide methodological support for fine characterization of complex reservoirs and offer practical guidance for development adjustment in “dual-high” (high water-cut & high recovery degree) oilfields.