when a copmany like "Royal Dutch Shell" finds oil feild do they get there revenue from selling the oil or ...?

Answer 1

They will usually be exploring on land they have a lease to. After paying any required royalties to the lease holder and/or government (sometimes the lease holder is the government) they get the money from the oil produced from that field. They may sell it on the open market for cash or (in the case of a major like Shell) they can send it to one of their refineries to process and sell the refined gasoline, jet fuel, etc.

So, short answer to your question is yes, but they can also process it and get more money from selling the refined petroleum products.