利用体积分方程的弱化BCGS算法模拟倾斜及层状各向异性地层中井间电磁响应

Simulating Crosswell Electromagnetic Response in Deviated and Stratified Anisotropic Formation by Weak-form BCGS Algorithm for Volume Integral Equations

采用体积分方程的弱化BCGS算法模拟倾斜及层状各向异性地层中的井间电磁响应。在模拟三维异常体产生的散射场时将层状各向异性地层作为背景层,数据点只分布在三维异常体所在的区域,未知量数目和计算量均大大减少。计算结果表明,倾斜井中磁场的轴向分量与倾斜角度及井间距密切相关,且接收井倾角越大其虚分量指示出的地层界面位置就越准确。散射磁场轴向分量的强度相对较大,且受背景层各向异性系数的影响较大,利用该分量可探测电导率异常体的存在。散射磁场水平分量的强度与总磁场的强度相比要小得多,利用该分量不易探测出电导率异常体的存在。不同的各向异性系数对总磁场水平分量影响较大,且利用其实分量可以较准确地识别层状地层界面。

A new method is adopted for simulating cross-well electromagnetic response in deviated and stratified anisotropic formation by weak-form BCGS algorithm for volume integral equations. When simulating the scattered magnetic field generated by three-dimensional anomalies, the stratified anisotropic formation is taken as background formation. The data points are only distributed in anomalous bodies, thus the number of unknowns and the amount of calculation are greatly reduced. The results show that the axial component of the magnetic field is closely related to the inclination angle and the cross-well distance when the wells are inclined, its imaginary part can identify the background formation＇s interface more accurately when the inclination angle of the receiver well increases. The axial component of the scattered magnetic field is relatively large and is greatly influenced by the background formation＇s anisotropy, which can be used in detecting the presence of anomalous conductivities. The horizontal component of the scattered magnetic field is much smaller comparing with the total magnetic field, and it is not easy to detect the presence of anomalous conductivities by this component. Different anisotropy can make a great difference on the horizontal component of the total magnetic field, and its real part can be used to identify the background formation＇s interface accurately.