致密砂岩分形渗透率模型构建及关键分形参数计算方法

针对现有渗透率分形模型关键参数计算方法与渗透率相关性较差、迂曲度分形维数不能反映三维特征,造成致密砂岩渗透率预测困难的问题,基于致密砂岩孔隙结构分形特征及迂曲毛管束模型,构建了一种致密砂岩渗透率预测模型,提出了分形维数、迂曲度分形维数、特征长度的有效计算方法,并探讨了不同迂曲度计算方法对致密砂岩渗透率预测的影响。研究表明:构建的渗透率模型可以有效预测致密砂岩渗透率,更接近于实测值,计算得到分形维数与岩心渗透率相关性更强;不同迂曲度计算方法得到的致密砂岩迂曲度值差异较大,选取合适的迂曲度计算方法可以提高致密砂岩渗透率预测精度。研究成果可以准确、快速地预测渗透率,对致密砂岩油藏储层评价与有效开发具有重要意义。

Tight Sandstone Fractal Permeability Model and Key Fractal Parameter Calculation

In order to improve the tight sandstone permeability prediction challenges result from the poor correlation between fractal permeability model parameters and permeability and the poor 3D structure characterization with tortuosity fractal dimension, a tight sandstone permeability prediction model was established based on the fractal patterns of tight sandstone pore structure and tortuous capillary bundle model. The calculation methods of fractal dimension, tortuosity fractal dimension and characteristic length were proposed to discuss the influence of different tortuosity calculation methods on the tight sandstone permeability prediction. Research indicates that this model can effectively predict tight sandstone permeability, and the prediction is closer to that of tested value. The calculated fractal dimension shows a favorable correlation with core permeability. There is a significant difference in the tight sandstone tortuosity for different calculation methods, and appropriate tortuosity calculation method could improve the prediction accuracy of tight sandstone permeability. This research could accurately and quickly predict permeability, which will provide certain guidance for the evaluation and efficient development of tight sandstone reservoir.