Is it possible to reach master level without studying theory? Wikipedia page for GM Granda from Peru says:

Julio Granda does not study opening theory. He has said that he has
only read a chess book, the third volume of the General Chess Treaty
of Roberto Grau. Anyway, he admits reading magazines and reviewing the
Informant, which together with his excellent memory and assimilation
capacity, has allowed him to win important tournaments and titles.
Google translation from spanish wikipedia.

Is this possible? Can one become a master without studying theory at all?
Anything is possible.  The real question is how likely are you and most people to do it that way.

And it depends on what you call 'theory'.  

I read NO theory. But I read a lot of practical books on openings, tactics, end games, pawn structure, positional play, yada yada.  

They claim that an AI program learned to play Go by playing itself.  I do not know anyone humans that have done that.  We might if we lived millions of years but in reality humans can't do it that way.  Most humans learn by seeing how others,  who win doing it, have done it;  and try to improve on that if possible using the basic tools they learned from practical books.