I am not sure for quite understanding your question. From my point of view, if you extract impedance attributes in 2D profile or in 3D volume via HRS. you can export it using Segy
(Sgy) format. then you can load it into Petrel by selecting SEG-Y Import with preset paramters in Input file parameters. If you extract impedance in 2D Map, you can export it by using Ascii format like horizon interpretation file format, then you can load it into petrel by choosing 2D interpretation format( a quite few format for that). hope this can give some help.