Metal Gear Solid V: The Phantom Pain and Project Ogre are one and the same thing. Kojima confirmed this in an interview held during E3.
The first image of Project Ogre from 2011
In 2011, Kojima announced he was working on an ambitious new project, which he referred to as Project Ogre (or Oni in Japan). Kojima now confirmed that Project Ogre was indeed a code name for MGSV, that he used because he couldn’t talk about the game yet.
Snake’s demon-like ‘horn’ in MGSV
There seem to be a lot of references to ‘demons’ in MGSV, all the way up to Snake’s appearance. This will play a role in the story, so that’s how the project received its name.
Also, when still referring to the game as Project Ogre, Kojima said it would tackle taboo subjects, something that’s also the case with MGSV, and that it will be open world and players could spend many hours in the game.