VERTICAL 1-D INVERSION WITH THIN LAYERS OF EQUAL THICKNESS

摘要

Measurements made by a multicomponent logging tool (12) in a borehole (2) ar e inverted to obtain horizontal and vertical resistivities of a formation (4) traversed by the borehole. For a vertical borehole, the inversion is done by first iteratively obtaining the horizontal resistivities (353) of the layer using the Hzz component of the data. The vertical resistivity model (361) is set equal to the derived horizontal resistivities and the iterative process is repeated using the ratio (363) of the model Hxx output to the measured Hxx. A similar process is used for boreholes with a known inclination. No Jacobians or gradients are necessary in the method, so that computational times are small relative to prior art gradient methods.