Oil is a valuable commodity and the subject of a great deal of panic right now. The panic is based on ill-informed doom-mongering, with little basis in reality. Some long term perspective might be useful.
By about 2030, as a result of technology development, stimulated at least in part by high oil prices today, solar energy farming will be a big business. Already, work is under way to start building solar farms in the Sahara, where suitable land is both plentiful and cheap.
The staring point for a calculation must be the energy equivalent of a barrel of oil, since that is the prime purpose of oil today. Each barrel contains approximately 6 gigajoules of energy.
Assuming that solar panels can be mass-produced, with a sunlight conversion efficiency of about 12%, at a cost of $200 per sq metre, in today's money, a 1 sq metre panel will generate approximately 8.5kwh of energy per day, equating to 1 barrel of oil every 6 months. The land also needs to produce a good income for its developer, who would presumably be happy with a return of $50,000 per hectare for otherwise worthless land, i.e. $5 per sq m per year, and assuming that 50% of the land is covered by panel, that translates into $10 per panel + depreciation costs, of say $50 per year for a 4 year write-off. With total revenue of $60 per panel per year, 6 months is $30.
If the energy equivalent of a barrel of oil can be generated for $30, it is reasonable to set this as an upper limit on the market value of oil, when used for fuel. Prices of oil for other purposes such as plastics manufacture or specialist industries may be higher.
However, since oil is mainly used for fuel, substitution in this market by cheaper alternatives such as solar power will lead to a gradual collapse in the oil market as supply far outstrips demand. Therefore, most oil will probably be left in the ground, and it will be much cheaper than today in real terms.