Jerosch-Herold M, Thomann H, Thompson A H
Corporate Research Laboratory, Exxon Research and Engineering Company, Annandale, NJ 08801.
Magn Reson Imaging. 1994;12(2):369-73. doi: 10.1016/0730-725x(94)91558-x.
Diffusion dynamics for water in a series of sandstone core plugs with a broad range of permeabilities was studied using both the Carr-Purcell-Meiboom-Gill (CPMG) and inversion recovery experiments. Both the transverse and longitudinal magnetization curves were found to fit well to stretched exponential relaxation kinetics. At short times, the transverse magnetization is well described by an expression for free diffusion averaged over a distribution of pore sizes. The stretch exponents for the transverse and longitudinal magnetization are shown to be simply related to the width of the pore size distribution. A cross over from free to restricted diffusion is evident in the dependence of T2 with increasing diffusion time set by the interpulse spacing tau in the CPMG experiment. The T2(tau) data is fit to a model which interpolates between the limits of free and restricted diffusion. A length derived from this model is shown to provide a simple estimate of the absolute fluid flow permeability.
利用 Carr-Purcell-Meiboom-Gill（CPMG）和反转恢复实验研究了一系列渗透率范围广泛的砂岩岩心塞中水分子的扩散动力学。发现横向和纵向磁化曲线都能很好地拟合拉伸指数弛豫动力学。在短时间内，横向磁化可以用一个在孔径分布上平均的自由扩散表达式很好地描述。横向和纵向磁化的拉伸指数被证明与孔径分布的宽度有简单的关系。在 CPMG 实验中，随着由脉冲间隔 tau 设置的扩散时间增加，T2 的依赖性表明从自由扩散到受限扩散的转变是明显的。T2(tau)数据拟合到一个在自由扩散和受限扩散极限之间进行插值的模型。从该模型得出的一个长度被证明可以提供绝对流体流动渗透率的简单估计。
