Joint inversion of HRDL and HRDI with site applications at the Qaidam Basin of western China

A joint inversion algorithm was suggested for high-resolution dual induction device and a new high-resolution dual laterolog tool. The combination log using these high-resolution logging devices not only modifies the behaviors of conventional logging tools and provides much reliable information of reservoirs for inversion techniques, but also makes the joint inversion possible. Generalized inversion method was used to construct the present three-parameter joint inversion algorithm to obtain true-formation resistivity, depth of invaded zone, and resistivity of invaded zone simultaneously. The joint inversion introduced less deviation than single high-resolution dual laterolog inversion or single high-resolution dual induction inversion. Joint inversion also enhanced the accuracy and stability of inversion results so that the joint inversion results are much more helpful for log analysts to evaluate reservoirs. The present algorithm has been successfully applied for the site logging interpretation at Qaidam Basin in western China.

► High-resolution dual laterolog device improved the vertical resolution.
► Joint inversion uses four logging curves from HDRL and HDRI tool simultaneously.
► Three unknown formation parameters were estimated simultaneously by joint inversion.
► Joint inversion enhances the stability and the accuracy, reduced the iteration times.
► The present algorithm was successfully applied at Qaidam Basin in western China.