Natural gas is often found with crude oil, and has in the past just been flared off. I don't think oil is turned into gas though.
The Omnibus Budget Reconciliation Act of 1993 (or OBRA-93 ), passed by the 103rd United States Congress and signed into law by President Bill Clinton
From fossils like old plants and animals breaking down and becoming a gas or liquid. This process can take up to thousands and millions of years.
Natural gas is natural gas. It is not made from crude oil or anything else. Thus the name.