A question about oil futures

[Value Buy]

Can anyone tell me what percent of our oil useage is bought thru the Future's Markets, and what percent is actually bought through longterm contracts that are negotiated with the production companies?
Or is everything now based in contracts on the prevailing Future contract?
I am assuming some refiners who are not producers, must have some longterm contracts at a set price per barrel.
Of course, longterm, may only consist of a year due to volitility....
Government agencies, many times lock in gasoline costs for a whole year, so I am assuming some refiners must have that capability also.

[clarkrl2]

I know from reading the quarterly and yearly report they use some futures contracts but they also have some other arrangements. I copied a part of Valero's (VLO) 10k but I doubt it will read very well in this format since it was copied from a PDF. Valero uses a lot of sour crude that will generally be cheaper that the sweet crude and wti front month prices.

Purchase Obligations
A purchase obligation is an enforceable and legally binding agreement to purchase goods or services that specifies significant terms, including (i) fixed or
minimum quantities to be purchased, (ii) fixed, minimum, or variable price provisions, and (iii) the approximate timing of the transaction. We have various
purchase obligations including industrial gas and chemical supply arrangements (such as hydrogen supply arrangements), crude oil and other feedstock
supply arrangements, and various throughput and terminalling agreements. We enter into these contracts to ensure an adequate supply of utilities and
feedstock and adequate storage capacity to operate our refineries. Substantially all of our purchase obligations are based on market prices or adjustments
based on market indices. Certain of these purchase obligations include fixed or minimum volume requirements, while others are based on our usage
requirements. The purchase obligation amounts included in the table above include both short-term and long- term obligations and are based on (a) fixed or
minimum quantities to be purchased and (b) fixed or estimated prices to be paid based on current market conditions. As of December 31, 2010 , our shortterm
and long-term purchase obligations increased by $6.4 billion from the amount reported as of December 31, 2009
. The increase is primarily
attributable to higher crude oil and other feedstock prices at December 31, 2010 compared to December 31, 2009 .