Part partionning in ABAQUS
Partitioning is mainly done to improve the mesh quality, by partitioning one can hope to get "hex" element type to "tet". In abaqus partition can be made by using datum planes, sketches and using the geometry of the part itself and so on. Note that only one type of partition techniques might be applicable to your model, hence choose carefully on how to partition the part to get a maximum benefit.
As for your query, there's no such thing called spherical partitioning as far as I know, if you can post the picture of your part, I can tell the procedures by which you might able to successfully partition the block.