砂岩地层中地层因素表征及其与孔喉比关系分析

Analysis of Formation Factor Expression in Sandstone Formation and Its Relationship with Aspect Ratio

多孔介质的导电特性主要受其孔隙结构的影响,孔隙结构通常用孔隙和喉道尺寸及迂曲度来描述。为简化运算,现有导电模型通常忽略喉道的影响。为准确描述孔隙和喉道在多孔介质中的导电机理,明确孔隙和喉道尺寸及迂曲度对地层因素的影响,提出基于正弦曲线孔隙结构的正弦模型,并通过该模型推导出地层因素的表达式。构建数字岩心,利用数字岩心数值模拟结果,对模型进行验证。结果表明:基于正弦模型的地层因素表达式能准确反映地层的导电特征,地层因素与孔隙度、孔隙形状校正因子、迂曲度和孔喉比有关,当其他因素基本一致时,地层因素随着孔喉比的增大而增大。

The electrical conductivity of porous media mainly depends on the pore structure of the porous media,and the pore structure is traditionally characterized by the pore-throat size and tortuosity.In order to simplify calculation,the existing models usually ignore the influence of throats.In order to accurately describe the conductive mechanism of pores and throats and clarify the influence of pore-throat size and tortuosity on formation factor in porous media,a new model with sinusoidal pore-throat structure is proposed and the expression of formation factor is derived based on this new model.Digital cores are constructed and the numerical simulation results of digital cores are used to verify the expression.The results show that formation factor expression based on sine model can accurately reflect the conductivity characteristics of sandstone formation.The formation factor is related to porosity,pore shape correction factor,tortuosity and aspect ratio,and the formation factor increases with the increase of aspect ratio obviously when other factors are basically the same.