We have developed a new method for the fast inversion of
borehole resistivity measurements acquired in multiple wells
using logging-while-drilling instruments. There are two key
novel contributions. First, we approximate general 3D transversely
isotropic (TI) formations with a sequence of several
“stitched” 1D planarly layered TI sections. This allows us to
approximate the solution of rather complex 3D formations
using only 1.5D simulations. Second, the developed method
supports the simultaneous inversion of measurements acquired
in different neighboring wells and/or with different logging
instruments. Numerical experiments performed with
realistic 3D synthetic formations confirm the flexibility of the
method and the reliability of the inversion products. The
method yields relative errors of less than 5% on the model
space, and it enables the interpretation of resistivity measurements
acquired in multiple wells (e.g., an exploratory, an offset,
and a geosteering well) and with any combination of
coaxial and/or triaxial commercial logging measurements acquired
with known antennae configurations. Numerical results
also indicate that thinly bedded resistive formations are very
sensitive to the presence of noise on the measurements and/or
to possible errors on bed-boundary locations, whereas conductive
layers are only weakly sensitive to those effects.