Methods and systems employing look-around and look-ahead inversion of downhole measurements

A method of characterizing a geological formation traversed by a wellbore while drilling the wellbore using a resistivity tool in combination with a directional electromagnetic (EM) tool, the method comprising:

• operating the resistivity tool to acquire non-directional resistivity measurements of a look-around zone of the formation, and operating the directional electromagnetic tool to acquire directional EM measurements of the look-around zone of the formation and a look-ahead zone of the formation, wherein the electromagnetic tool comprises a transmitter subassembly that has a triaxial set of antennas comprising axial, tilted, and transverse antennas,
• determining a profile of the look-around zone by interpreting the non-directional resistivity measurements of the look-around zone and the directional EM measurements of the look-around zone, wherein the profile of the look-around zone characterizes at least formation dip as well as horizontal resistivity and vertical resistivity or resistivity anisotropy of one or more formation layers of the look-around zone;
• and
• determining a profile of the look-ahead zone by interpreting the directional EM measurements of the look-ahead zone, wherein the profile of the look-ahead zone characterizes at least formation dip as well as horizontal resistivity and vertical resistivity or resistivity anisotropy of one or more formation layers of the look-ahead zone, wherein interpretation of the directional EM measurements uses a formation model that is initialized according to values from the profile of the interpretation of the non-directional resistivity measurements.