Rob
Ansys Employee

In 2d I'd suggest using the sketch tools and create each section as a separate face (sketch) using a combination of sketch & Concept tools. 


The method you describe above is how I've modelled full 3d bores. Create the bore centreline as a sketch line. Then start with the largest diameter & sweep along the path (frozen). Then the next one down & split. Continue until you have the full well. 


Check your sizes too, 10m is an awfully big hole!