横向电阻率测井反演计算

利用有限元方法建立了包含井眼、侵入带、上下围岩和目的层的横向测井电阻率响应数值计算模型，利用阻尼最小二乘法建立了相应的快捷、有效的反演算法，根据横向测井的电阻率响应同时反演地层电阻率、侵入带电阻率和侵入带半径。该算法对于３个或４个梯度电极系（或电位一电极系）的测井结果均适用。讨论了模型算法对初值的依赖性，当初值在较大范围内变化时，反结果均能在真值或真值附近收敛。

Inversion of Departure Resistivity Log

Numerical calculation of departure resistivity log responses is modeled using finite element method. Wellbore, invasion zone, shoulder bed and formation of interest are included in the present model. A rapid and efficient invasion algorithm is programmed using damping least square method. True formation resistivity, invasion zone resistivity and invasion depth can be obtained by the present inversion technique from the responses of departure log. The present algorithm is suitable to both three or four lateral sondes and normal sondes. The dependence of the algorithm on initial values is discussed. Even though the initial values vary within a large range, the inversion results converge to the true value.