Study on forward and inversion modeling of array laterolog logging in a horizontal/highly deviated well

Electric field synthesis was carried out using the multi-field superposition method according to the working principle of the array laterolog electrode system. The field distribution of each subfield was simulated with the 3D finite element method, and the laterolog response of the array was obtained using the linear superposition principle of electric field. The detection depth and thin layer response at different angles of the array laterolog were analyzed. The forward response calculation shows that the radial detection depth of the array laterolog is smaller than the deep laterolog detection depth. When the inclination angle of the well is less than 15°, the logging response of the array laterolog is less affected by the well inclination, and the well inclination correction need not be performed. The logging response values of highly deviated wells with inclination angles exceeding 60° and horizontal wells are quite different from those of vertical wells; thus, well deviation correction must be performed. To improve the stability of array laterolog logging inversion using the accurate forward response, a Newton–singular value decomposition method based on particle swarm optimization is proposed to realize inversion of array laterolog logging, and the stability and reliability of logging inversion are greatly improved. Thus, application of the theoretical model and actual data processing and analysis show that the proposed method can effectively and accurately eliminate the influence of a complex logging environment and obtain real formation parameters.