Sour crude requires more refining than sweet crude, which is low in sulphur and, as a result, often more valuable.
高硫化油比低硫原油需要更多次提炼，因而低硫原油价值更高。
英语百科
Sour crude oil
Sour crude oil is crude oil containing a high amount of the impurity sulfur. It is common to find crude oil containing some impurities. When the total sulfur level in the oil is more than 0.5% the oil is called "sour".
The impurities need to be removed before this lower-quality crude can be refined into petrol, thereby increasing the cost of processing. This results in a higher-priced gasoline than that made from sweet crude oil.