A method for characterizing a subterranean formation traversed by a wellbore, the method comprising: collecting data from the subterranean formation using a nuclear density tool , wherein the nuclear density tool is configured to collect data to form azimuthal images representative of a density and photoelectric factor of the formation; characterizing a section of the subterranean formation based on the azimuthal images acquired in said section, wherein the section includes a high angle wellbore section, a horizontal wellbore section, or a combination thereof; and performing a parallel inversion using the azimuthal apparent densities and volumetric photoelectric factor images to build a formation model, wherein the parallel inversion comprises a high angle workflow that models the high angle wellbore section and a horizontal workflow that models the horizontal wellbore section, wherein performing the horizontal workflow comprises performing a horizontal well pre-processing workflow on the horizontal wellbore section, wherein the pre-processing workflow comprises: obtaining a curtain-section model from azimuthal squaring compensated density image data; identifying points defining a formation boundary of the subterranean formation by comparing boundary true vertical depths (TVDs) and density contrast in adjacent sections of data sequentially; filtering out hanging points; sampling formation boundaries within a predefined interval; and building up a topological model for each of the horizontal wellbore sections by identifying geometry and zones of the formation model. collecting data from the subterranean formation using a nuclear density tool , wherein the nuclear density tool is configured to collect data to form azimuthal images representative of a density and photoelectric factor of the formation; characterizing a section of the subterranean formation based on the azimuthal images acquired in said section, wherein the section includes a high angle wellbore section, a horizontal wellbore section, or a combination thereof; and performing a parallel inversion using the azimuthal apparent densities and volumetric photoelectric factor images to build a formation model, wherein the parallel inversion comprises a high angle workflow that models the high angle wellbore section and a horizontal workflow that models the horizontal wellbore section, wherein performing the horizontal workflow comprises performing a horizontal well pre-processing workflow on the horizontal wellbore section, wherein the pre-processing workflow comprises: obtaining a curtain-section model from azimuthal squaring compensated density image data; identifying points defining a formation boundary of the subterranean formation by comparing boundary true vertical depths (TVDs) and density contrast in adjacent sections of data sequentially; filtering out hanging points; sampling formation boundaries within a predefined interval; and building up a topological model for each of the horizontal wellbore sections by identifying geometry and zones of the formation model. obtaining a curtain-section model from azimuthal squaring compensated density image data; identifying points defining a formation boundary of the subterranean formation by comparing boundary true vertical depths (TVDs) and density contrast in adjacent sections of data sequentially; filtering out hanging points; sampling formation boundaries within a predefined interval; and building up a topological model for each of the horizontal wellbore sections by identifying geometry and zones of the formation model. <EOS>