Although crude oil assays evaluate various chemical properties...

Although crude oil assays evaluate various chemical properties of the oil, the two most important properties determining a crude's value are its density (measured as API specific gravity) and its sulphur content (measured per mass). Crude oil is considered "heavy" if it is high in wax content, or "light" if low in wax content: an API gravity of 34 or higher is "light", between 31-33 is "medium", and 30 or below is "heavy". Crude is considered "sweet" if it is low in sulphur content (< 0.5%/weight), or "sour" if high (> 1.0%/weight). Generally, the higher the API gravity (the "lighter" it is), the more valuable the crude!

This list of the worlds oil products, showing specific gravity and sulphur content

Galeota Mix 37.8? 0.19% Trinidad
http://en.wikipedia.org/wiki/List_of_crude_oil_products

What RRL have so far encountered in Trinidad is high quality with a low sulphur content. I suspect the crew are 'very excited' indeed, taking one step at a time..expect a quick revision of oil bopd soon as they increase the flow rates!