论文部分内容阅读
实际地层可能出现 2种电阻率的宏观各向异性 :微观的统计平均效应和裂缝走向等因素的构造效应。三分量感应测井方法可能是确定地层电阻率各向异性的最好方法 ,但是 ,该仪器目前在中国还没有应用。已有的数据一般是梯度和双感应曲线 ,梯度和双感应曲线单独使用都难以揭示各向异性 ,但是 ,将二者联合使用则有可能。在反演模型中考虑了电阻率各向异性的存在 ,给出了梯度和双感应曲线联合求地层电阻率各向异性的方法。通过直井水平层的二维人工模型表明 ,用感应方法可确定地层的水平电阻率和厚度。而梯度方法的视电阻率可以近似看作水平电阻率和纵向电阻率的几何平均值 ,梯度方法的视厚度是各向异性参数和真实厚度的乘积。因而不能用梯度方法单独确定各向异性参数和真实厚度 2个参数中的任何 1个。然而 ,联合梯度和双感应的方法则可能确定 3个参数 :各向异性参数 ,水平电阻率和地层厚度。人工数据的例子表明了这种联合的可行性。
There are two types of resistivity macroscopic anisotropy that may occur in the actual formation: the microscopic statistical average effect and the tectonic effect of the fracture trend and other factors. The three-component induction logging method may be the best method to determine the resistivity anisotropy of the formation, however, the instrument is not currently used in China. The existing data are generally gradient and dual-induction curves. The use of gradient and dual-induction curves alone can hardly reveal the anisotropy. However, it is possible to combine the two with each other. In the inversion model, the existence of resistivity anisotropy is considered, and the method of combining gradient and dual-response curves to find the anisotropy of formation resistivity is given. Through the two-dimensional artificial model of horizontal well, it is shown that the horizontal resistivity and thickness of formation can be determined by induction method. The apparent resistivity of the gradient method can be approximated as the geometric mean of the horizontal resistivity and the longitudinal resistivity. The apparent thickness of the gradient method is the product of the anisotropy parameter and the true thickness. Therefore, the gradient method can not be used to determine any one of the two parameters of the anisotropy parameter and the true thickness. However, the combined gradient and dual-sensing approach may determine three parameters: anisotropy, horizontal resistivity and formation thickness. The example of artificial data shows the feasibility of this combination.