The thing that most attracts me to historical fiction is taking the factual record as far as it is known using that as scaffolding and then letting imagination build the structure that fills in those things we can never find out for sure.
Like any business the oil industry runs on the basic premise of supply and demand. The more supply - the lower the price. The higher the demand - the higher price. In other words the more people who can buy oil the higher the price of oil.