各向异性岩石方向渗透率计算模型

Directional Permeability Calculation Model for Anisotropic Rock

岩石颗粒沉积过程中的取向性导致岩石渗透率具有各向异性,各向异性岩石渗透率的确定在油气田开发研究中是一项重要而且基础的工作。首先分析了各向异性岩石的渗流特征,各向异性岩石的渗透率使用张量描述,渗流速度方向与压力梯度方向一般不平行。基于此,分析了原岩石方向渗透率计算模型的不足,指出原模型没有考虑各向异性岩石渗流速度方向与压力梯度方向不一致的特征,进而推导并建立了新的各向异性岩石方向渗透率计算模型。通过新老模型计算得到的方向渗透率与实测渗透率进行对比。结果显示,新的计算模型与实测值更加吻合。计算模型可用于计算油藏不同方向上的传导率以及各向异性油藏中不同方位上的井距设计,相比原模型更加准确。

Anisotropy is generally a result of the orientation and shape of the asymmetric grains making up the porous bed.It is an important and difficult task to determine the directional permeability of rocks in anisotropic media.The seepage features in anisotropic rock are analyzed.The permeability can be expressed as a symmetric second-order tensor with six independent components.The seepage velocity are not parallel to pressure gradient.The method of building the original directional permeability calculation model was discussed,with its shortcomings and limitations indicated.The original model do not consider the feature that seepage velocity are not parallel to pressure gradient in anisotropic rock.A modified model is presented.Experiments show that the modified model results are closer to the measured results compared with the original model.This calculation model of permeability could be used to compute the directional transmissibility in numerical reservoir simulation,and to design the well spaces in different directions for anisotropic reservoir.