It's certainly possible to refine crude oil without a proper refinery, there's many instances of such things happening in Nigeria and it can be done on a large scale if you have no concern for the health or life of your workers or the environment.
It's also happening in Mexico and a few other places in the world but Nigeria gets the most publicity. It should be noted that with such rough methods of refining, it's possible that up to 80% of heavy crude is rendered unusable - see page 3, 2nd column, 4th paragraph of the following PDF in which Shell Sub-Saharan Africa Vice President Tony Attah, makes reference to this
http://s03.static-shell.com/content/...eft-speech.pdf
http://www.theguardian.com/global-de...ing-stolen-oil news article about stolen oil in Nigeria
http://www.youtube.com/watch?v=jXeTw11fVpU check the section starting at about 1:12 to see the very crude but very simple method for refining.
http://blog.modernmechanix.com/table...-home-chemist/ an article from a 1940s issue of Popular Mechanics discussing simple refining
http://www.youtube.com/watch?v=D4sykoUWZ8g illustrates some of the technology used in the beginnings of the oil trade in the USA (late 1800s)