Identification of Water-Flooded Layers and Evaluation of Flooded Levels in Fractured Tight Sand Oil Reservoir

Owing to the heterogeneity of tight reservoirs, the development of fractures, and the unreasonable water injection development method, the logging response characteristics of water-flooded layers in fractured tight sandstone reservoirs in the H oilfield in the Junggar Basin are complex, making it difficult to identify and evaluate them quantitatively. This has severely restricted the treatment of water-flooded layers and the optimization of development methods. This study calibrates logging data with dynamic production data and experimental analysis data. Based on clarifying the logging response characteristics of the water-flooded layers, these layers were qualitatively identified through radial resistivity differences and original resistivity recovery methods. By constructing models for the water cut and extraction index, which reflect water flooding characteristics, quantitative evaluations of water flooding levels can be conducted on the basis of consistency principles. Furthermore, the impacts of structural location, sedimentary environment, and fracture development on the water-flooded layers were analyzed. The results suggest that the radial resistivity difference method, along with the original resistivity recovery approach, can effectively identify water-flooded layers. By integrating the water cut, the extraction index, and the radial resistivity difference chart, the influence of reservoir heterogeneity is mitigated, resulting in improved quantitative characterization accuracy and efficiency for water-flooded layers in fractured tight sandstone reservoirs. There are two primary mechanisms for the formation of water-flooded layers in the H oilfield: matrix pore infiltration and differential water drive through fractures. The lower parts of the structure and areas with developed channel sedimentary microfacies are more susceptible to the formation of water-flooded layers, and the remaining oil potential in the matrix pores of the fracture development zone in the northeast of the oilfield is objective.