Calculation and Characteristics of Array Laterlog Responses

To study the characteristics of new array laterolog tools, the finite element method in a steady current field is used for calculating the responses of an array laterolog tool for the formation model composing of borehole, invaded zone, surrounding rock and target zone. The theoretical results are helpful to the design of an array laterolog tool. The influences of radial invasion characteristics, borehole effect and bed thickness on array laterolog tool are studied. The pseudegeometrical factor is calculated. The characteristics of logging response in array electrodes are discussed according to the calculation of tool factor. The calculation results are compared with the responses of a dual laterolog tool. The array laterolog tool can provide six apparent resistivities in different radial investigation depth. The new tool has advantages of high vertical resolution and wide radial investigation depth. It is a developing reasonable log tool especially in thin bed logging and the heterogeneous formation measurement around borehole.