泥质砂岩激发极化弛豫时间谱微观机理

The microscopic mechanisms of induced polarization relaxation time spectra in shaly sandstone

泥质砂岩激发极化弛豫时间谱含有丰富的地层孔隙结构信息。利用串联毛管模型,建立了描述激发极化效应的数学物理模型,数值模拟了激发极化充放电的全过程;利用阻尼最小二乘算法,对理论计算的激发极化衰减谱进行多指数反演,分析了岩石孔隙度、阳离子交换量、溶液浓度、温度、溶液类型和放电时间等因素对激发极化弛豫时间谱的影响。结果表明,弛豫时间谱不仅反映了岩石内部的微观孔隙结构,而且表现了离子扩散迁移恢复平衡的过程。

The relaxation time spectra of induced polarization in shaly sandstone has a wealth of information of formation.This paper established the mathematical-physical model of induced polarization based on serial capillary model,and the charging and discharging processes of induced polarization were simulated by numerical method.Meanwhile,the decay curve of induced polarization was inversed from the multi-exponential inversion by Levenberg-Marquardt.The influences of porosity,cation exchange capacity,concentration of solution,temperature,and discharging time etc.on the induced polarization relaxation time spectrum were analyzed.The result shows that relaxation time spectra is not only the expression of the microscopic pore structure in rock,but also the diffusion process of ion repristination.