Recent advances on the inversion of deep directional borehole resistivity measurements

Summary

We describe our latest developments on the inversion of subsurface electrical resistivity from deep directional borehole resistivity measurements. Two different methods are introduced for fast inversion of tri-axial induction measurements with multiple transmitter-receiver positions. The first one approximates transversely isotropic (TI) formations with a sequence of “stitched” 1D planarly layered TI sections, which efficiently approximates the solution via 1.5D simulations. The second method uses a pixel-based inversion approach and employs full 3D modelling of borehole EM induction with either an iterative or a direct solver. This enables the inversion of spatial distributions of electrical resistivity of any complexity without restrictions on the symmetry of the models. Numerical examples for several challenging synthetic conditions confirm the accuracy and efficiency of the developed algorithms.

• electromagnetic methods
• tri-axial induction
• logging while drilling
• inversion